Sharks of Onslow County

Category: Other Marine Species

When Every Bird Looks Like a Hawk: Reading the Raptors of Onslow County
A reader recently asked me about five birds he had seen over the sounds of Surf City last weekend. He was convinced they were five different kinds of “sea hawks.”

At first glance, it was an understandable conclusion.

Each bird was large. Each spent time soaring overhead or hesitating up high over the water. Each occupied the same stretch of coastal North Carolina sky.

Yet every photograph and description reflected the same species: an osprey.

Distance has a way of simplifying wildlife. Colors disappear. Markings fade. Details are lost. What remains is a silhouette against the sky.

Most of us learn to recognize birds by their appearance. Raptors are often easier to understand by their behavior.
- What is the bird doing?
- Is it hovering over the water?
- Circling without flapping?
- Perched motionless on a fence post?
- Drifting above a marsh?
- Crossing silently through the trees after sunset?
The answer often reveals more than the feathers.

The skies above Onslow County are shared by a community of predators. Some hunt fish. Some hunt rodents. Some hunt insects. Some hunt other birds. Some hunt only at night. Others serve as nature’s cleanup crew.

At a distance they may look similar.

Spend enough time watching them, however, and the differences become impossible to miss.

Following the Fish

Osprey: The Fisherman

If there is a signature bird of the coast, it may be the osprey (Pandion haliaetus).

You notice one long before you identify it. The bird appears above a creek, river, or stretch of open water, turns into the wind, and suddenly seems to stop moving. For a few seconds it hangs there, suspended above the surface before plunging feet-first toward the water below.

That moment of hesitation is not hesitation at all.

The bird is making a final decision.

Water distorts light. Fish change direction. Wind roughens the surface. What appears obvious from a dock or kayak becomes much more complicated from above. The osprey’s brief hover allows it to judge distance, depth, and movement before committing to the dive (Poole, 1989; Bierregaard et al., 2020).

The splash usually draws everyone’s attention.

The fish often draws the next question.

Watch an osprey leave the water carrying a mullet or menhaden and it is difficult not to wonder how the bird manages to hold onto it. Fish are essentially living bars of soap wrapped in muscle, built to slip through water and escape predators. Osprey solve that problem with feet lined by tiny backward-facing spicules and a reversible outer toe that help secure slippery prey (Poole, 1989; Bierregaard et al., 2020).

Then, almost as soon as the bird becomes airborne, something else happens.

The fish turns.

Within seconds the osprey has repositioned its catch so the fish faces forward. What looks like a small adjustment saves energy over the course of the flight. A fish carried sideways catches air. A fish carried headfirst moves through it. Often the bird gives its catch a vigorous shake as it climbs away from the water, shedding excess water before continuing on its way. Together, these adjustments reduce drag and make transporting a heavy, slippery meal through the air more efficient (Allen et al., 2018; Poole, 1989; Bierregaard et al., 2020).

Around nesting season, however, it is often the noise rather than the fishing that gets people’s attention.

Osprey rarely seem quiet.

Calls echo from nesting platforms, channel markers, dead trees, and utility poles throughout the breeding season. Adults announce arrivals. Mates communicate with one another. Young birds call constantly whenever food appears nearby. What sounds chaotic from a distance is often a family carrying on a conversation (Bierregaard et al., 2020).

By late summer, that family becomes easier to see.

Several birds may gather near a nest, perched along the same stretch of water where they have spent months raising young. Then, without warning, they take to the air together. The younger birds follow the adults across creeks, marshes, and open water, practicing turns, landings, and the flight skills that will eventually carry them south. What appears at first to be a loose gathering of osprey is often a family still learning from one another long after the young birds have left the nest (Poole, 1989; Bierregaard et al., 2020).

To boaters, it is a channel marker in the New River in Jacksonville, NC. To an osprey, it is home. Many coastal nests are rebuilt and expanded year after year, becoming landmarks visible across the water. | Image credit: A. Mitchell

The nests themselves remain long after the birds have departed.

Many osprey return to the same sites year after year, adding sticks, repairing damage, and expanding structures that can eventually become enormous. What begins as a modest nest slowly grows into a landmark visible from hundreds of yards away (Poole, 1989; Bierregaard et al., 2020).

For many coastal residents, those nests become part of the landscape.

And when spring returns, so do the birds that built them.

Bald Eagle: The Opportunist

If you spend enough time around the water, eventually you’ll see it happen.

An osprey leaves the surface carrying a fish. For a few moments, everything appears normal. Then a second bird enters the scene.

Larger.

Heavier.

Built on an entirely different scale.

The bald eagle (Haliaeetus leucocephalus) begins to follow.

What started as a successful fishing trip suddenly becomes a chase.

From below, the interaction can look almost personal. The osprey twists and climbs. The eagle closes the distance. Sometimes the osprey escapes. Sometimes it drops the fish. The eagle wheels downward after the falling meal while the osprey continues on empty-taloned.

Why go through all that trouble?

Because catching a fish requires energy.

An osprey may spend considerable time searching the water, hovering above the surface, adjusting for currents, and committing to a dive before finally securing a meal. An eagle watching from a nearby perch can recognize that success immediately. From the eagle’s perspective, the fish has already been found. The difficult part of the hunt is over (Buehler, 2020).

This often leads people to wonder whether bald eagles are better fishermen than osprey.

The answer depends on how you define fishing.

If the goal is catching fish, the osprey remains the specialist. Nearly every aspect of its anatomy is designed around that task. Its feet grip slippery prey with remarkable efficiency, and its entire hunting strategy revolves around locating fish beneath the water’s surface.

A bald eagle approaches the world differently.

Rather than specializing in a single food source, eagles take advantage of opportunities wherever they find them. Fish remain important, particularly along the New River, Stump Sound, the Intracoastal Waterway, and the countless creeks that thread through coastal marshes. Yet waterfowl, mammals, reptiles, and carrion can also become part of the menu (Buehler, 2020).

A closer look at their feet reveals those differences. Osprey feet are designed to hold fish. Eagle talons are designed to seize and restrain a wider variety of prey. One bird is built around precision. The other is built around versatility (Buehler, 2020).

That versatility helps explain why bald eagles have become increasingly common sights along the Onslow County coast. Open water, abundant prey, expansive marshes, and large trees provide everything they need. Whether soaring above an estuary, perched along a creek, or watching from a pine overlooking the water, eagles occupy a position near the top of the coastal food web (Buehler, 2020).

And every so often, that position allows them to let someone else do the fishing.

The Hunters of Marsh and Forest

Red-shouldered Hawk: The Watcher on the Fence

Not every raptor announces itself from the sky.

Some introduce themselves by showing up in the yard.

You glance out the window and notice a hawk perched on the fence. Hours later it seems to be in exactly the same place. The next morning it is back again.

Eventually curiosity takes over.

What is it watching?

Perched above a yard in Jacksonville, NC, a red-shouldered hawk waits for movement. From elevated vantage points, these woodland hunters watch patiently for opportunities hidden within the landscape below. | Image credit: A. Mitchell

Many people assume the hawk is focused on the house, the dog, or the family moving through the yard.

In reality, the bird is usually paying attention to everything else.

A well-maintained yard often provides excellent hunting habitat. Frogs move through flower beds. Lizards bask along retaining walls. Small snakes hunt beneath shrubs. Mice travel fence lines and wood piles. The red-shouldered hawk watches for movement, waiting for the landscape to reveal itself (Dykstra et al., 2020).

That patient approach reflects the habitats these birds prefer.

Unlike the open-country red-tailed hawk, red-shouldered hawks (Buteo lineatus) are closely tied to places where woods and water meet. Creek corridors, swamp edges, ponds, marshes, and bottomland forests provide the cover and diversity of prey they rely upon (Dykstra et al., 2020).

A red-shouldered hawk feeds on captured prey in a parking lot. While often associated with swamps and wooded wetlands, these adaptable hunters frequently take advantage of opportunities in suburban landscapes. | Image credit: A. Mitchell

Along the coast, those habitats frequently overlap with where people live.

The fence post is simply the best seat in the house.

From there, the hawk can watch an entire ecosystem unfold beneath it.

Red-tailed Hawk: Master of the Open Sky

A red-tailed hawk (Buteo jamaicensis) – and my personal favorite bird – often attracts attention by doing remarkably little.

You notice one circling high above a field.

Several minutes later it is still there.

The wings barely move.

At first, most people wonder how the bird can remain in the air for so long without flapping. The answer lies in the atmosphere itself. As the ground warms, pockets of heated air rise into the sky. Red-tailed hawks locate these invisible thermals and circle within them, gaining altitude while expending very little energy (Kerlinger, 1989; Preston & Beane, 2024).

But staying aloft is only part of the story.

The real question is why the bird wants to be up there in the first place.

The answer becomes clearer when compared to the red-shouldered hawk.

A red-shouldered hawk often hunts by focusing on a particular place. A pond edge. A marsh creek. A backyard. It watches patiently from a perch, waiting for the landscape to reveal movement (Dykstra et al., 2020).

A red-tailed hawk takes the opposite approach.

Rather than concentrating on one corner of the landscape, it climbs high enough to see how all of those pieces connect. Fields blend into hedgerows. Roadsides meet forest edges. Open ground transitions into cover. From above, what appear to be separate places from the ground become a single hunting landscape.

That broader view is the red-tail’s specialty.

What appears to us as an empty field is filled with clues. A rabbit pauses along a fence line. A squirrel breaks from cover. A mouse rustles through the grass. The bird is not searching for a specific animal. It is searching for movement, patterns, and opportunities spread across hundreds of acres (Preston & Beane, 2024).

The thermal keeps the hawk aloft long enough to gather that information. Height becomes an advantage. Distance becomes information.

The bird is not circling because it has nowhere else to be.

It is circling because the sky offers the best view.

And from that vantage point, one movement in the wrong place at the wrong time is often all it takes.

Cooper’s Hawk: The Pursuit Hunter

If you maintain a bird feeder long enough, sooner or later the yard will go silent.

One moment cardinals, doves, and finches are moving between the feeder and nearby trees.

The next, everything disappears.

Then a gray blur streaks through the yard.

The first time you see it happen, it feels almost impossible that a bird that large could move that quickly through such a cluttered space.

Unlike the red-tailed hawk searching from hundreds of feet above the landscape or the red-shouldered hawk watching patiently from a perch, the Cooper’s hawk (Astur cooperii) hunts in motion. It is built for pursuit (Rosenfield et al., 2025).

Its long tail acts like a rudder while relatively short wings allow it to twist, turn, and accelerate through spaces that would seem impossible for most raptors. Branches, fences, shrubs, and backyard obstacles that slow other birds become part of the chase (Rosenfield et al., 2025).

That agility allows the hawk to exploit something many predators cannot.

Confusion.

A flock of birds startled into flight rarely moves in a straight line. Individuals scatter in different directions, darting through vegetation and searching for cover. The Cooper’s hawk follows.

What appears chaotic to us is a hunting opportunity to the hawk.

Yet not every backyard attracts a Cooper’s hawk.

If you’ve ever noticed that these birds seem more common in some neighborhoods than others, the surrounding landscape is often the reason. Cooper’s hawks favor places where trees, forest edges, wooded corridors, and open spaces meet. Those transitions provide both cover and opportunity, allowing the bird to move quickly between concealment and pursuit (Rosenfield et al., 2025).

A bird feeder placed within that landscape can become part of the story, not because the feeder attracts the hawk, but because it concentrates movement. Birds travel between the feeder and nearby cover. The hawk is already watching the area. The feeder simply makes activity easier to find.

Which is why the sudden silence is often the first clue.

Long before most people see the hawk, the birds have already noticed it.

For a few moments, the yard belongs to the fastest hunter in the neighborhood.

The Hunters of the Air

Mississippi Kite: Catching the Wind

At first glance, a Mississippi kite (Ictinia mississippiensis) looks like it should behave like any other hawk.

It drifts overhead with long, pointed wings, barely moving as it rides the summer air. Then it suddenly changes direction, banking sharply, twisting through the sky, and accelerating after something too small for most people to see.

The first time you notice it, the behavior feels strange.

What is that hawk chasing? Is it chasing dragonflies?

The bird banks again, then again, each turn seeming impossibly precise. Whatever it is pursuing appears far too small to interest a raptor. Yet the longer you watch, the clearer the answer becomes.

While many hawks spend their time searching the ground for prey, Mississippi kites have turned the air itself into a hunting ground. Dragonflies, cicadas, beetles, and other flying insects become meals captured directly on the wing. What appears to be effortless wandering is often an active hunt unfolding overhead (Parker, 2020).

That hunting style explains why they seem so different from other raptors.

The red-shouldered hawk watches a particular place. The red-tailed hawk surveys an entire landscape. The Cooper’s hawk chases prey through trees and backyards. The Mississippi kite is hunting somewhere entirely different.

Its long wings and graceful flight allow it to maneuver with remarkable precision, changing direction quickly as insects dart, climb, and shift with the wind (Parker, 2020).

The same warm air currents that help other raptors gain altitude also gather flying insects into concentrated pockets, creating opportunities for a predator adapted to exploit them (Parker, 2020).

The result is a bird that often feels more like a swallow than a hawk.

An osprey may be hunting fish below. A red-tailed hawk may be watching a field nearby. A Cooper’s hawk may be moving along a forest edge. Above them all, a Mississippi kite may be feeding on insects carried by the same air currents that support the rest of the ecosystem.

The bird is not ignoring the landscape beneath it.

It has simply found opportunity in a place most predators never think to look.

For the Mississippi kite, the sky is not a pathway.

It is habitat.

The Cleanup Crew

Turkey Vulture: Death Becomes Renewal

A turkey vulture (Cathartes aura) lands on your roof and suddenly everyone becomes concerned.

To us, it looks like a warning. To the vulture, it is simply another perch from which to read the landscape. | Image credit: A. Mitchell

Some people take it as a bad omen. Others wonder if something nearby has died. Before long, the bird becomes the center of attention despite doing little more than sitting still.

The turkey vulture, meanwhile, is completely unaware of the stories being told about it.

Most of the time, something far less dramatic is happening.

A rooftop provides warmth on a cool morning, a place to dry rain-soaked feathers, or a convenient perch where rising air currents can be reached without much effort. The bird is not predicting death. It is simply taking advantage of the landscape (Kirk & Mossman, 2020).

Yet the association exists for a reason.

Unlike the hawks and eagles we have encountered so far, turkey vultures are searching for something very different. They are not looking for prey. They are looking for what remains after life has already moved on.

A dead fish along the shoreline.

A raccoon hidden in roadside vegetation.

A deer beyond the edge of a forest.

But how do they find it?

Part of the answer can be seen on the bird’s face. If you are fortunate enough to observe a turkey vulture through binoculars or at close range, you may notice something unusual about its nostrils, or nares. Unlike our own noses, the openings pass completely through the beak. In the right light, you can literally see from one side of the nostril to the other (Kirk & Mossman, 2020).

A close comparison of a turkey vulture (top) and black vulture (bottom) reveals one clue to how they read the landscape differently. Turkey vultures use an exceptional sense of smell to locate carrion, while black vultures depend more on vision and the behavior of other vultures. Arrows highlight differences in the nostril openings of the two species. | Image credit: T. Lisney

That adaptation supports one of the most powerful senses of smell in the bird world. While many raptors rely primarily on vision, turkey vultures are able to detect the scent of carrion from remarkable distances, allowing them to locate food sources hidden beneath vegetation and, in some cases, even beneath the soil itself (Grigg et al., 2017; Kirk & Mossman, 2020).

Finding carrion, however, is only part of the challenge.

Consuming it presents an entirely different set of problems.

The turkey vulture’s bald head, which many people find unsettling, is actually an important adaptation. Unlike a feathered head that could trap blood, bacteria, and other organic material, the bare skin can be cleaned much more easily after feeding. What gives the bird its ominous appearance also helps protect it from the very things it eats (Roggenbuck et al., 2018).

The same is true inside the bird.

Turkey vultures possess an extraordinarily acidic digestive system capable of destroying many of the bacteria and pathogens that would make other animals sick. Organisms responsible for diseases such as anthrax, botulism, cholera, and salmonella are often neutralized during digestion, allowing the vulture to safely consume material that would be dangerous for most scavengers (DeVault et al., 2016; Kirk & Mossman, 2020).

Even their hygiene is unusual.

Turkey vultures practice a behavior known as urohidrosis, in which they defecate on their own legs. While it may seem unpleasant from a human perspective, the highly acidic waste helps kill bacteria picked up while walking on carcasses and also provides a cooling effect during hot weather (Arad et al., 1989; Kirk & Mossman, 2020).

Taken together, these adaptations solve a difficult ecological problem. Dead animals can become reservoirs for bacteria, disease, and decay. Turkey vultures have evolved to exploit that resource while avoiding many of the risks associated with it.

Black vultures, which are often seen alongside them, approach the problem differently. Their nostrils are narrower and not open from side to side. Rather than relying so heavily on smell, they depend more on vision and often watch the movements of turkey vultures to help locate food (Buckley et al., 2020).

That relationship creates an interesting partnership. Turkey vultures are often the first to detect a carcass hidden beneath vegetation, while black vultures are quick to notice where the turkey vultures are gathering. One species excels at finding the scent. The other excels at finding the finder (Buckley et al., 2020; Kirk & Mossman, 2020.

Together, the two species accomplish something few other animals can.

They return nutrients to the landscape.

What appears to be an ending becomes the beginning of something else. Energy stored within a fish, a raccoon, or a deer does not simply disappear. Vultures help move those nutrients back into the ecosystem where they become available to countless other organisms (DeVault et al., 2016) .

The bird on your roof is not waiting for something bad to happen.

More often than not, it is part of the reason the landscape remains healthy after it does.

Black Vulture: Following the Leader

A single turkey vulture on a rooftop often attracts attention.

Ten vultures attract concern.

What appears to be a crowd is often an information network. Black vultures frequently roost together, sharing a landscape where opportunities can appear and disappear without warning. | Image credit: jspruill, iNaturalist

Unlike turkey vultures, which are frequently seen soaring alone or in small numbers, black vultures (Coragyps atratus) often seem to arrive as a group, called a committee. One bird becomes five. Five become ten. Before long, an entire rooftop, parking lot, or dead tree appears covered in vultures (Buckley et al., 2020).

The first question is usually the same.

Why are there so many?

Part of the answer lies in how black vultures find food.

While turkey vultures rely heavily on their extraordinary sense of smell, black vultures depend much more on vision and on one another. They watch the landscape, but they also watch other vultures. A turkey vulture dropping toward a hidden carcass can reveal an opportunity that a black vulture might never have discovered on its own (Buckley et al., 2020).

That difference creates an unusual relationship between the two species.

Turkey vultures are often the first to locate carrion concealed beneath vegetation or hidden from view. Black vultures are often the first to notice that the turkey vultures have found something worth investigating (Buckley et al., 2020).

One species excels at finding the scent.

The other excels at finding the finder.

Their social nature extends beyond feeding. Black vultures frequently roost together, travel together, and gather in numbers that can seem surprising to people unfamiliar with them. What appears to be a crowd is often a network of birds sharing information about a landscape filled with unpredictable opportunities (Buckley et al., 2020).

That strategy has served them well.

A dead fish washed onto a shoreline, a raccoon along a roadside, or a deer hidden beyond the edge of a forest represents a resource that appears without warning and disappears quickly. By paying attention to one another, black vultures can exploit those opportunities efficiently.

To most people, the meal is something to avoid. To a black vulture, it is an opportunity. By consuming carrion that would otherwise decay on the landscape, vultures help return nutrients to the ecosystem while reducing the spread of disease. | Image credit: A. Mitchell

Like the turkey vulture, the black vulture plays an important role in returning nutrients to the ecosystem.

It simply approaches the problem differently.

Where the turkey vulture trusts its nose, the black vulture trusts its neighbors.

The Night Shift

As daylight fades, a different group of predators takes over.

The thermals weaken. The soaring hawks settle. Shadows lengthen across marshes and forests.

Then the owls emerge.

Eastern Screech-Owl: Master of Camouflage

Many people have an eastern screech-owl (Megascops asio) living in their neighborhood and never realize it.

Not because the owl is rare.

Because it is exceptionally good at remaining unnoticed.

You might spend years walking past the same tree without ever seeing this small bird tucked inside a cavity or pressed against the bark. Then one evening, just after sunset, a soft trill or whinny drifts through the yard and suddenly you realize there has been an owl nearby the entire time (Gehlbach, 2009; Ritchison et al., 2020).

The discovery often raises an interesting question.

If eastern screech-owls feed on many of the same insects, rodents, reptiles, and amphibians as some daytime raptors, why don’t we see them more often? (Gehlbach, 2009; Ritchison et al., 2020)

Part of the answer is timing.

While hawks spend the day watching fields, marshes, forests, and backyards, the eastern screech-owl waits for darkness. As daylight fades and the daytime hunters settle into roosts, the owl begins its own shift (Ritchison et al., 2020).

But timing alone does not explain its success.

The owl’s real advantage is concealment.

Its mottled gray and brown feathers blend remarkably well with tree bark, allowing it to disappear into the landscape even when it is in plain sight. During the day, many spend hours motionless inside tree cavities or against trunks where they become nearly impossible to detect (Gehlbach, 2009; Ritchison et al., 2020).

That camouflage allows the owl to remain close to people while largely escaping notice.

Neighborhoods, wooded lots, parks, forest edges, and suburban backyards can all provide suitable habitat. The insects drawn to porch lights, the rodents moving along fence lines, and the small reptiles hiding among shrubs create hunting opportunities throughout the night (Gehlbach, 2009; Ritchison et al., 2020).

By the time most people realize an eastern screech-owl is nearby, it has often been there all along.

Its success does not come from being the largest predator in the landscape.

It comes from being the one you never knew was watching.

Barn Owl: Sound Becomes Sight

A pale shape crosses a field at dusk.

For a moment it hardly seems real. The bird appears almost white against the fading light, gliding silently above the grass before disappearing into the darkness beyond.

The first question is often simple.

What did I just see?

For centuries, encounters like that have inspired stories of ghosts, spirits, and things that move through the night unseen. The barn owl’s piercing scream has only reinforced that reputation. Unlike the familiar hoots people associate with owls, barn owls produce calls that can sound startlingly human, often described as shrieks, screams, or cries drifting through the darkness. Heard for the first time from a forest edge or old barn, it is easy to understand how the bird became woven into folklore (Marti et al., 2024).

Yet the call serves a practical purpose.

In darkness, sound becomes one of the most effective ways for American barn owls (Tyto alba pratincola) to communicate with mates, defend territories, and maintain contact with one another. What sounds eerie to us is simply part of life for an owl that spends most of its time hunting when the rest of the landscape is asleep (Marti et al., 2024).

The hunt itself is equally remarkable.

Barn owls are among the most specialized rodent hunters in North America. Their heart-shaped facial disks act like satellite dishes, funneling sound toward asymmetrical ears capable of pinpointing prey with astonishing precision. A mouse rustling through grass can reveal its location long before the owl ever sees it (Payne, 1971; Marti et al., 2024).

That adaptation helps explain another common experience.

Step quietly into an old barn, abandoned building, or large outbuilding and you may discover one or more barn owls perched overhead. They often watch intruders with an intense stare, swaying and bobbing from side to side as they study the unfamiliar visitor below (Marti et al., 2024).

At first glance, the behavior appears nervous or even strange.

In reality, the owl is gathering information. The subtle movements help it judge distance, depth, and position before deciding whether to remain still or slip silently into the darkness.

Fields, agricultural landscapes, marsh edges, and open grasslands provide ideal hunting habitat (Marti et al., 2024). Every mouse captured represents energy transferred from one part of the ecosystem to another, helping regulate populations that might otherwise grow unchecked.

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The pale bird crossing the field is not a ghost.

It is one of the most effective hunters the night shift has to offer.

For the barn owl, sound does not simply reveal the landscape.

It becomes a way of seeing it.

Barred Owl: The Voice of the Swamp

“Who cooks for you? Who cooks for you-all?”

Once you hear it, you rarely forget it.

The call drifts through wooded neighborhoods, swamp edges, and forested wetlands after sunset, often carrying much farther than people expect. Many coastal residents know the sound long before they ever see the bird responsible for making it (Bierregaard et al., 2025).

The question naturally follows.

Who is calling from the darkness?

More often than not, it is a barred owl.

Unlike the barn owl crossing open fields or the eastern screech-owl disappearing into a backyard tree, barred owls (Strix varia) are closely tied to forests and wetlands. Swamps, creek corridors, bottomland hardwoods, and wooded neighborhoods provide the cover, water, and diversity of prey they need (Bierregaard et al., 2025).

The call itself serves several purposes. Barred owls use it to communicate with mates, establish territories, and maintain contact across dense forests where visibility is limited. What sounds like a conversation to us is often exactly that (Bierregaard et al., 2025).

Those forests and wetlands provide hunting opportunities throughout the year. Frogs call from wetland edges. Crayfish move through shallow water. Rodents travel beneath fallen leaves. Snakes, insects, and small birds all become potential prey. Rather than specializing in a single food source, barred owls have learned to take advantage of whatever the swamp provides (Bierregaard et al., 2025).

The swamp, however, does not make hunting easy.

Prey hides beneath vegetation, beneath water, and beneath layers of leaf litter. Fallen logs, tangled branches, and dense understory create countless places to disappear.

Barred owls overcome many of those challenges through silence.

The leading edges of their feathers are specially adapted to break up airflow, reducing the sound of flight to nearly nothing. A mouse rustling beneath leaves, a frog moving along a wetland edge, or a crayfish crossing shallow water may never hear the owl approaching (Bachmann & Wagner, 2016).

For prey, the danger often arrives without warning.

By the time a barred owl commits to an attack, silence has already done much of the work.

That ability helps explain why barred owls are among the most successful predators in the region.

It also reveals something many people do not realize.

Hunting is not simply a switch that turns on when a young owl leaves the nest.

Juvenile barred owls must learn. They practice. They miss opportunities. They refine the skills needed to locate, pursue, and capture prey in a complex environment. In wildlife rehabilitation settings, young barred owls that fail to develop those hunting skills cannot be successfully returned to the wild (Watson et al., 2023).

Instinct provides the foundation.

Experience builds the hunter.

Perhaps that is why barred owls have become such a familiar voice in the coastal night. Their success comes not from mastering a single prey species or hunting strategy, but from learning to adapt to whatever the swamp provides.

For the barred owl, the swamp is more than habitat.

It is a hunting ground, a classroom, and a home.

Great Horned Owl: Ruler of the Night

The night can be surprisingly noisy.

A barred owl calls from the swamp.

Tree frogs answer from the wetlands.

Crickets fill the spaces in between.

Then, sometimes, the woods erupt with alarm calls.

Crows mob during the day. Smaller birds call from hidden roosts after sunset. Even other predators seem suddenly aware that something has changed.

What happened?

Often, a great horned owl (Bubo virginianus) has arrived.

While many predators spend their lives worrying about what might hunt them, the great horned owl occupies a different position in the food web. Rabbits, squirrels, rodents, reptiles, birds, and even other predators can become prey. Where great horned owls occur, few animals completely ignore them (Artuso et al., 2020).

That includes other owls.

Barred owls, screech-owls, and other nocturnal hunters may alter their behavior when a great horned owl is nearby (Artuso et al., 2020). The question is not simply what the owl is hunting.

The question is whether anything wants to become its next opportunity.

Part of that success comes from versatility. Great horned owls hunt forests, wetlands, agricultural fields, suburban neighborhoods, and coastal habitats with equal confidence. Rather than specializing in a single prey species, they take advantage of whatever opportunities the landscape provides (Artuso et al., 2020).

Yet versatility alone does not explain why other animals react when one arrives.

Power does.

A great horned owl’s grip rivals that of a bald eagle. The force generated by its talons can exceed 270 newtons, allowing it to seize and control prey with remarkable efficiency (Ward et al., 2002). Those feet are capable of exerting tremendous force once they close around a target (Ward et al., 2002; Lingham-Soliar, 2014).

Combined with a wingspan approaching five feet, the result is a predator that commands attention even before it leaves the ground (Artuso et al., 2020).

Yet perhaps the most remarkable thing about a great horned owl is how quietly all of that power moves through the landscape.

Like other owls, the leading edges of their feathers break up airflow, reducing the sound of flight to nearly nothing. A bird carrying a wingspan wider than many people are tall can pass overhead with little more than a faint rush of air (Bachmann & Wagner, 2016).

Sometimes not even that.

The first indication that a great horned owl is nearby is often the reaction of everything else around it.

That silence becomes even more effective when paired with another adaptation.

Many people believe owls can rotate their heads completely around.

They cannot.

A great horned owl can rotate its head roughly 270 degrees, allowing it to scan much of the landscape without moving its body (Ward et al., 2002). Unlike our eyes, an owl’s eyes are largely fixed within the skull. To change its view, it must move its head (Ward et al., 2002; Lingham-Soliar, 2014).

For an ambush predator, that matters.

Every movement risks revealing its position. The ability to gather information while remaining nearly motionless allows the owl to watch far more than most animals realize.

And that may be the real reason so many creatures react when one arrives.

The great horned owl combines strength, silence, patience, and awareness in a way few predators can. By the time a rabbit, squirrel, snake, or even another owl realizes it is being watched, the great horned owl has often been watching for quite some time.

Perhaps that is why other animals seem to know when one is nearby.

The great horned owl is not simply another hunter in the night.

It is often the hunter watching the hunters.

Reading the Sky

At first glance, they all appear similar.

Large birds.

Broad wings.

Silhouettes against the sky.

Yet an osprey hovering above the water, a red-shouldered hawk watching from a fence post, a Mississippi kite chasing dragonflies, a vulture riding a thermal, and a barred owl moving through the darkness are not performing the same job.

They are reading the landscape in different ways.

The osprey watches the water.

The red-tailed hawk watches entire fields.

The Cooper’s hawk watches movement between trees.

The Mississippi kite watches the air itself.

Even the vultures, often dismissed as scavengers, are searching for clues that most of us never notice.

The next time a large bird catches your attention, resist the urge to identify it immediately.

Instead, watch what it does.

Does it hover?

Circle?

Perch?

Glide?

Disappear into the trees?

The answer often tells you as much as the feathers.

Because the sky is not filled with birds doing the same thing.

It is filled with specialists solving different problems.

And once you begin to notice those differences, the sky becomes a little easier to read.

At a distance, every raptor can seem like little more than a shape against the clouds. Spend enough time watching, however, and the sky becomes easier to read. | Image credit: A. Mitchell

References

Allen, L. L., Morrison, K. L., Scott, W. A., Shinn, S., Haltiner, A. M., & Doherty, M. J. (2018). Differences between stance and foot preference evident in osprey (Pandion haliaetus) fish holding during movement. Brain and Behavior, 8(11). https://doi.org/10.1002/brb3.1126

Arad, Z., Midtgard, U., & Bernstein, M. H. (1989). Thermoregulation in Turkey vultures. Vascular anatomy, arteriovenous heat exchange, and behavior. The Condor, 91(3), 505. https://doi.org/10.2307/1368103

Artuso, C., Houston, C. S., Smith, D. G., & Rohner, C. (2020). Great Horned Owl (Bubo virginianus). In Birds of the World (1.0th ed.). Cornell Lab of Ornithology.

Bachmann, T., & Wagner, H. (2016). Silent owl wings. Encyclopedia of Nanotechnology, 3659-3669. https://doi.org/10.1007/978-94-017-9780-1_267

Bierregaard, R. O., Livezey, K. B., Pyle, P., Mazur, K. M., & James, P. C. (2025). Barred Owl (Strix varia). In Birds of the World (2.1st ed.). Cornell Lab of Ornithology.

Bierregaard, R. O., Poole, A. F., Martell, M. S., Pyle, P., & Patten, M. A. (2020). Osprey (Pandion haliaetus). In Birds of the World (1.0th ed.). Cornell Lab of Ornithology.

Buckley, N. J., Kluever, B. M., Driver, R., & Rush, S. A. (2020). Black Vulture (Coragyps atratus). In Birds of the World (2.0th ed.). Cornell Lab of Ornithology.

Buehler, D. A. (2022). Bald Eagle (Haliaeetus leucocephalus). In Birds of the World (2.0th ed.). Cornell Lab of Ornithology.

DeVault, T. L., Beasley, J. C., Olson, Z. H., Moleón, M., Carrete, M., Margalida, A., & Sánchez-Zapata, J. A. (2016). Ecosystem Services Provided by Avian Scavengers. In Why Birds Matter: Avian Ecological Function and Ecosystem Services (pp. 235-270). University of Chicago Press.

Dykstra, C. R., Hays, J. L., & Crocoll, S. T. (2020). Red-shouldered Hawk (Buteo lineatus). In Birds of the World (1.0th ed.). Cornell Lab of Ornithology.

Ferguson-Lees, J., & Christie, D. A. (2001). Raptors of the world. Houghton Mifflin Harcourt.

Gehlbach, F. R. (2009). The eastern screech owl: Life history, ecology, and behavior in the suburbs and countryside. Texas A&M University Press.

Grigg, N. P., Krilow, J. M., Gutierrez-Ibanez, C., Wylie, D. R., Graves, G. R., & Iwaniuk, A. N. (2017). Anatomical evidence for scent guided foraging in the Turkey vulture. Scientific Reports, 7(1). https://doi.org/10.1038/s41598-017-17794-0

Kerlinger, P. (1989). Flight strategies of migrating hawks.

Kirk, D. A., Mossman, M. J., Bildstein, K. L., Naveda-Rodríguez, A., & Mallon, J. M. (2024). Turkey Vulture (Cathartes aura). In Birds of the World (2.0th ed.). Cornell Lab of Ornithology.

Lingham-Soliar, T. (2014). Feather structure, biomechanics and biomimetics: The incredible lightness of being. Journal of Ornithology, 155(2), 323-336. https://doi.org/10.1007/s10336-013-1038-0

Marti, C. D., Poole, A. F., Bevier, L. R., Bruce, M. D., Christie, D., Kirwan, G. M., Marks, J. S., & Pyle, P. (2024). American Barn Owl (Tyto furcata). In Birds of the World (1.1st ed.). Cornell Lab of Ornithology.

Odum, E. P., & Barrett, G. W. (2005). Fundamentals of ecology. Cengage Learning.

Parker, J. W. (2020). Mississippi Kite (Ictinia mississippiensis). In Birds of the World (1.0th ed.). Cornell Lab of Ornithology.

Payne, R. S. (1971). Acoustic location of prey by barn owls (Tyto Alba). Journal of Experimental Biology, 54(3), 535-573. https://doi.org/10.1242/jeb.54.3.535

Poole, A. F. (1989). Ospreys: A natural and unnatural history. Cambridge University Press.

Preston, C. R., & Beane, R. D. (2024). Red-tailed Hawk (Buteo jamaicensis). In Birds of the World (1.0th ed.). Cornell Lab of Ornithology.

Ritchison, G., Gehlbach, F. R., & Patten, M. A. (2020). Eastern Screech-Owl (Megascops asio). In Birds of the World (1.0th ed.). Cornell Lab of Ornithology.

Rosenfield, R. N., Madden, K. K., Bielefeldt, J., & Curtis, O. E. (2025). Cooper’s Hawk (Accipiter cooperii). In Birds of the World (1.2nd ed.). Cornell Lab of Ornithology.

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Watson, W. A., Hofstadter, D. F., Jones, G. M., Kramer, H. A., Kryshak, N. F., Zulla, C. J.,

Whitmore, S. A., O’Rourke, V., Keane, J. J., Gutiérrez, R. J., & Peery, M. Z. (2023). Characterizing juvenile dispersal dynamics of invasive barred owls: Implications for management. Ornithological Applications, 126(1). https://doi.org/10.1093/ornithapp/duad061
June 20, 2026
Where the Sand Breathes: Life Beneath the Tide Line in Onslow County

Most beachgoers look across the shoreline and see a boundary.

The ocean ends. The land begins.

But the strip of sand where waves wash ashore and slide back toward the sea is not really either one. It is a threshold—a place that becomes ocean and land again with every passing wave.

At first glance, this narrow band of wet sand appears empty. There are no marsh grasses, no oyster reefs, and no obvious schools of fish. Yet beneath the surface, the sand is alive with animals digging, filtering, feeding, hunting, and breathing.

This is the swash zone: the constantly shifting seam between ocean and land.

It is one of the most overlooked ecosystems on the North Carolina coast.

The swash zone is the narrow strip of shoreline where waves wash ashore and then retreat back toward the sea. Though it may appear to be little more than wet sand, it supports a diverse community of animals adapted to life between ocean and land. | Image credit: J. Morales

The Beach That Never Stops Moving

Unlike a marsh, oyster reef, or seagrass meadow, the swash zone never stays still.

Each wave pushes seawater into the sand and then pulls it back out again. Water moves through the spaces between sand grains, carrying oxygen, microscopic algae, bacteria, and organic matter. The sand itself acts almost like a living filter, supporting communities of organisms adapted to conditions that change minute by minute (Brown & McLachlan, 2018; McLachlan & Defeo, 2018).

To survive here, animals must tolerate burial, shifting sediments, crashing waves, changing salinity, and predators arriving from both land and sea.

Few species can endure such instability.

Those that do are specialists (Defeo et al., 2009).

The Living Wave Riders: Mole Crabs and Coquina Clams

If you’ve ever noticed the wet sand suddenly shimmer or seem to move as a wave retreats, you’ve likely witnessed two of the swash zone’s most abundant residents.

Atlantic Mole Crabs (Emerita talpoida)

An Atlantic mole crab, in Surf City, NC, briefly exposed at the surface of the swash zone. Within seconds, these specialized crustaceans can bury themselves beneath the sand, where they spend most of their lives filtering food from the surf. | Image credit: johnnybirder, iNaturalist

Known locally as sand fleas, Atlantic mole crabs spend nearly their entire lives buried beneath the surface of the swash zone.

They are not true crabs. Instead, they belong to a group of highly specialized crustaceans adapted for life where waves break on the shore. Their bodies are smooth, streamlined, and shaped almost like a small bean. Using powerful rear legs, they can bury themselves in saturated sand in seconds (Abude et al., 2024).

When waves wash overhead, they extend feathery antennae into the water and filter microscopic plankton and organic particles from the surf (Abude et al., 2024).

Rather than remaining stationary, mole crabs occupy the constantly shifting swash zone, where food and oxygen are delivered by breaking waves. Their abundance makes them one of the most important food sources for shorebirds, fish, and ghost crabs (Abude et al., 2024).

Coquina Clams (Donax variabilis)

Sharing the same habitat is one of the most recognizable shells on Atlantic beaches.

Coquina clams are the tiny, brightly colored shells scattered across the tide line in shades of pink, yellow, purple, blue, orange, and white.

Most people only notice the shells.

The living animal beneath them is remarkably adapted to life in moving sand.

Coquinas live just beneath the surface of the swash zone where they filter microscopic algae and suspended particles from the water. As waves advance and retreat, they repeatedly rebury themselves, using a muscular foot to dig into the sand with astonishing speed (Ellers, 1995).

Like mole crabs, coquinas are adapted to the dynamic conditions of the swash zone. Their abundance provides food for fish, crabs, and shorebirds, making them a critical link between microscopic plankton and larger coastal predators (Wilson, 1999).

Standing at the water’s edge, it is easy to think the beach is motionless.

In reality, thousands of coquinas and mole crabs may be moving beneath your feet with every wave.

The Night Shift: Atlantic Ghost Crabs (Ocypode quadrata)

Higher on the beach, above the reach of most waves, another resident waits.

Atlantic ghost crabs spend daylight hours hidden inside deep burrows excavated into the sand. Their pale coloration blends almost perfectly with the beach, making them difficult to see unless they move.

Atlantic ghost crabs spend daylight hours hidden in burrows above the tide line. Their pale coloration provides excellent camouflage against the sand, making them surprisingly difficult to spot until they move. | Image credit: A. Mitchell

While the swash zone below is dominated by animals filtering food from the surf, ghost crabs are hunters and scavengers.

After sunset, they emerge to patrol the shoreline, feeding on mole crabs, coquina clams, stranded marine organisms, insects, carrion, and whatever other opportunities the beach provides (Wolcott, 1978).

Many beachgoers never see them at all. Instead, they notice the evidence they leave behind. Round burrow openings dot the upper beach. Fresh tracks crisscross the sand overnight and disappear with the next tide. Occasionally, a pale shape darts sideways through the beam of a flashlight before vanishing into darkness.

Those burrows tell a story of their own. Beaches with abundant ghost crab burrows often support richer communities of animals living both above and below the sand, which is why scientists sometimes use ghost crabs as one way of assessing beach condition and disturbance (Schlacher et al., 2016).

The next time you notice a round hole in the upper beach with a pile of freshly excavated sand nearby, you are likely looking at the entrance to a ghost crab burrow—and evidence that the beach is still very much alive after dark.

Between the Grains

The largest residents of the swash zone are only part of the story.

Beneath the surface lies an even larger community that most beachgoers never see. Between individual grains of sand are tiny water-filled spaces that form a hidden habitat known as the interstitial zone. To us, a handful of wet sand looks solid. To these organisms, it is an underwater landscape of tunnels, chambers, and passageways (Higgins & Thiel, 1988).

The beach is layered with hidden communities. From amphipods and ghost crabs higher on the shore to coquina clams and mole crabs at the water’s edge, different species occupy distinct zones shaped by waves, moisture, food availability, and shifting sand. | Image credit: Michel et al., 2016

Amphipods: The Cleanup Crew

The line of seaweed, shells, and debris left behind by the tide may look messy, but it is often one of the busiest places on the beach.

Hidden among the wrack, in the upper intertidal zone, are amphipods, small crustaceans often called Atlantic beach hoppers (Americorchestia longicornis). If you sift through a pile of damp seaweed or drift algae, you may catch a glimpse of them springing away before disappearing back into cover.

Much of what washes ashore eventually becomes food for something else. Amphipods feed on decaying seaweed, dead animals, and other organic material stranded by the tide. In doing so, they help break down material that would otherwise accumulate along the shoreline. They also become food themselves, supporting shorebirds, fish, and other invertebrates that forage along the beach (Dugan et al., 2003).

Polychaete Worms: Engineers Beneath the Sand

Most beachgoers never see the worms living beneath the tide line, but their work is happening constantly beneath the surface.

As polychaete worms burrow through the sand, they create tiny pathways that allow water and oxygen to penetrate deeper into the sediment. In many ways, they perform the same role that earthworms do in a garden, except their garden is the beach itself.

Some species spend their lives feeding on organic material trapped between the sand grains, such as Lugworms (Arenicolidae). Others hunt small crustaceans and worms moving through the sediment such as Bloodworms (Glyceridae) and Paddle Worms / Shimmy Worms (Nephtyidae). As they burrow, feed, and move through the beach, they continually mix the sand and help create conditions that allow countless other organisms to survive there (McLachlan & Defeo, 2018).

Ribbon Worms: Hidden Predators

Not every animal beneath the sand is feeding on algae, bacteria, or decaying material.

Ribbon worms (Nemertea) are predators, though few people ever realize they are there. Hidden beneath the surface, they hunt some of the same tiny animals that share the spaces between the sand grains, including small worms, crustaceans, and other invertebrates moving through the sediment (Thiel & Kruse, 2001).

Many possess a remarkable feeding structure called a proboscis that can be rapidly extended to capture prey (Thiel & Kruse, 2001).

Most beachgoers will never see a ribbon worm, yet they are part of the same hidden food web as the amphipods, copepods, and nematodes surrounding them. Even beneath a seemingly empty stretch of sand, animals are feeding, avoiding predators, and competing for resources every hour of the day.

Nematodes: Life at Microscopic Scale

If you could shrink yourself down and explore a handful of wet sand, the landscape would look very different.

What appears solid to us is actually filled with tiny spaces between the grains. Moving through those water-filled passages are microscopic animals called nematodes (phylum Nematoda).

These tiny roundworms feed on bacteria, algae, fungi, and organic matter coating the sand. Though nearly invisible, they are among the most abundant animals on many beaches and play an important role in breaking down organic material and recycling nutrients throughout the sediment (Coull, 1999; Schratzberger & Ingels, 2018).

Harpacticoid Copepods: Tiny Links in the Food Web

Sharing those same microscopic spaces are harpacticoid copepods (Paraleptastacus wilsoni), tiny crustaceans that spend their lives moving between individual sand grains.

They graze on algae and microbial films coating the sediment, feeding on resources too small for larger animals to use directly. In turn, they become prey for larger invertebrates and juvenile fishes.

Most beachgoers will never see a harpacticoid copepod. Yet every handful of wet sand may contain a community of animals like these, quietly connecting the microscopic world to the larger food web of the beach (Schratzberger & Ingels, 2018).

Individually, these animals are easy to overlook.

Collectively, they form much of the living foundation of the tide line. The coquinas, mole crabs, ghost crabs, fishes, and shorebirds visible along the shoreline all depend, directly or indirectly, on countless small interactions taking place beneath the sand.

Following the Birds

One of the easiest ways to observe this hidden ecosystem is not by looking down.

It is by looking up.Anyone who spends time on the beach has likely watched sanderlings (Calidris alba) racing along the edge of the surf. They dart forward as a wave retreats, stop suddenly to probe the sand, and then sprint away from the next incoming wave. A little farther up the beach, ruddy turnstones (Arenaria interpres) pick through wrack lines left behind by the tide. Along the surf edge, Eastern willets (Tringa semipalmata semipalmata) walk deliberately through the shallows, searching for movement beneath the water.

To many beachgoers, they are simply birds feeding along the shoreline.

What they are actually doing is reading the beach.

Each probe into the sand is a search for prey hidden beneath the surface. Mole crabs, small worms, amphipods, coquinas, and other invertebrates living within the tide line provide food for these birds (Dugan et al., 2003; Hubbard & Dugan, 2003).

The birds go where the food is.

When shorebirds gather along a stretch of beach, they are often revealing an ecosystem that would otherwise remain invisible. Their presence tells us that the sand beneath them is alive with prey, even if we cannot see it ourselves.

In many ways, shorebirds act as interpreters of the tide line. By watching where they feed, pause, and congregate, we gain a glimpse into the hidden community supporting them below.

Reading the Beach

From a distance, the tide line can seem almost empty. A narrow strip of wet sand separates the ocean from the rest of the beach. Waves arrive, waves leave, and little appears to change.

Spend a few minutes watching, however, and a different picture begins to emerge.

Shorebirds gather where the surf is most active. Tiny shells appear and disappear with the retreating waves. Fresh ghost crab burrows punctuate the upper beach. Even the wrack line left behind by the tide becomes a gathering place for scavengers and foraging birds.

What first appears to be a simple boundary between land and sea begins to look more like a busy shoreline neighborhood.

At first glance, the tide line can appear almost empty. Look a little longer, however, and the clues begin to emerge—feeding shorebirds, scattered shells, and the constant movement of the surf all hint at the hidden community living beneath the sand. | Image credit: A. Mitchell

The animals living here are responding to the same thing: the constant movement of the tide. Food arrives with the surf, becomes available for a brief moment, and is quickly claimed by whatever creature is best adapted to find it. Some filter it from the water. Some collect it from the sand. Others hunt the animals already feeding there.

Because these organisms live so closely tied to the conditions of the beach, changes in their numbers can provide clues about the habitat itself (Defeo et al., 2009). A shoreline where birds are feeding, ghost crab burrows remain active, and life continues to reveal itself at the edge of the surf is often a sign that this narrow strip of beach is supporting the community that depends upon it.

When those communities decline, the change may not be immediately obvious. Yet over time the beach can begin to feel quieter. Fewer birds stop to feed. Fewer burrows appear in the sand. The signs become harder to find. Those changes can ripple outward through the food web, affecting species both on the beach and beyond it (Peterson et al., 2006).

The Threshold

The next time you stand at the edge of the surf, watch where the waves pause before sliding back toward the sea.

It is easy to see this narrow strip of shoreline as a boundary. Ocean on one side. Land on the other.

But the tide line is not really a dividing line at all.

It is a place where both worlds meet.

With every passing wave, food, oxygen, and life arrive from the ocean. Beneath the sand, animals capture it, consume it, recycle it, and pass it on. Shorebirds search for it. Ghost crabs emerge after dark to hunt it. Countless organisms spend their entire lives within a space that is neither fully ocean nor fully land.

Most people walk across this strip of beach without ever noticing it.

Yet it is one of the busiest places along the coast.

The next time you see shells appearing and disappearing in the surf, a flock of sanderlings racing the tide, or ghost crab burrows scattered across the upper beach, remember that these are not separate observations. They are pieces of the same story.

What appears to be an empty stretch of wet sand is actually a living threshold—a place where ocean and land remain connected through countless interactions happening beneath every step.

And once you see it, it becomes difficult to look at the shoreline the same way again.

The tide line in Surf City, NC may appear to be little more than wet sand. Yet beneath every retreating wave lies a hidden community connecting ocean and land through countless interactions, most of them unseen. | Image credit: A. Mitchell

References

Abude, R. R., Lôbo-Hajdu, G., Moreira, D. A., & Cabrini, T. M. (2024). Sandy beach mole crabs (Decapoda: Hippidae: Emerita): A systematic review of the anthropic impacts, populations density, and conservation strategies. Marine Environmental Research, 202, 106745. https://doi.org/10.1016/j.marenvres.2024.106745

Coull, B. C. (1999). Role of meiofauna in estuarine soft‐bottom habitats. Australian Journal of Ecology, 24(4), 327-343. https://doi.org/10.1046/j.1442-9993.1999.00979.x

Defeo, O., McLachlan, A., Schoeman, D. S., Schlacher, T. A., Dugan, J., Jones, A., Lastra, M., & Scapini, F. (2009). Threats to sandy beach ecosystems: A review. Estuarine, Coastal and Shelf Science, 81(1), 1-12. https://doi.org/10.1016/j.ecss.2008.09.022

Dugan, J. E., Hubbard, D. M., McCrary, M. D., & Pierson, M. O. (2003). The response of macrofauna communities and shorebirds to macrophyte wrack subsidies on exposed sandy beaches of Southern California. Estuarine, Coastal and Shelf Science, 58, 25-40. https://doi.org/10.1016/s0272-7714(03)00045-3

Ellers, O. (1995). Behavioral control of swash-riding in the clam Donax variabilis. The Biological Bulletin, 189(2), 120-127. https://doi.org/10.2307/1542462

Hubbard, D. M., & Dugan, J. E. (2003). Shorebird use of an exposed sandy beach in Southern California. Estuarine, Coastal and Shelf Science, 58, 41-54. https://doi.org/10.1016/s0272-7714(03)00048-9

McLachlan, A., & Defeo, O. (2018). The ecology of sandy shores (3rd ed.). Academic Press.

P, H. R., & Thiel, H. (1988). Intro study meiofauna. Smithsonian Books (DC).

Peterson, C. H., Bishop, M. J., Johnson, G. A., D’Anna, L. M., & Manning, L. M. (2006). Exploiting beach filling as an unaffordable experiment: Benthic intertidal impacts propagating upwards to shorebirds. Journal of Experimental Marine Biology and Ecology, 338(2), 205-221. https://doi.org/10.1016/j.jembe.2006.06.021

Pilkey, O. H., Rice, T. M., & Neal, W. J. (2014). How to read a North Carolina beach: Bubble holes, Barking sands, and rippled Runnels. UNC Press Books.

Schlacher, T. A., Lucrezi, S., Connolly, R. M., Peterson, C. H., Gilby, B. L., Maslo, B., Olds, A. D., Walker, S. J., Leon, J. X., Huijbers, C. M., Weston, M. A., Turra, A., Hyndes, G. A., Holt, R. A., & Schoeman, D. S. (2016). Human threats to sandy beaches: A meta-analysis of ghost crabs illustrates global anthropogenic impacts. Estuarine, Coastal and Shelf Science, 169, 56-73. https://doi.org/10.1016/j.ecss.2015.11.025

Schratzberger, M., & Ingels, J. (2018). Meiofauna matters: The roles of meiofauna in benthic ecosystems. Journal of Experimental Marine Biology and Ecology, 502, 12-25. https://doi.org/10.1016/j.jembe.2017.01.007

Thiel, M., & Kruse, I. (2001). Status of the nemertea as predators in marine ecosystems. Hydrobiologia, 456(1-3), 21-32. https://doi.org/10.1023/a:1013005814145

Wilson, J. G. (1999). Population dynamics and energy budget for a population of Donax variabilis (Say) on an exposed South Carolina beach. Journal of Experimental Marine Biology and Ecology, 239(1), 61-83. https://doi.org/10.1016/s0022-0981(99)00027-1

Wolcott, T. G. (1978). Ecological role of ghost crabs, Ocypode quadrata (Fabricius) on an ocean beach: Scavengers or predators? Journal of Experimental Marine Biology and Ecology, 31(1), 67-82. https://doi.org/10.1016/0022-0981(78)90137-5

June 5, 2026
The Fish That Follows the Tide: American Eels Along the Waters of Onslow County

Most people who see an American eel (Anguilla rostrata) for the first time do not think they are looking at a fish at all.

They appear suddenly in shallow blackwater creeks, beneath dock lights, beside culverts after rain, or slipping through spartina grass at dusk. Long and muscular, they move more like a snake than something belonging to a river. In muddy water they are usually seen only in fragments — a curve disappearing beneath tannin-dark current, or a ripple crossing the surface where something alive passed moments earlier.

Along the coast of Onslow County, American eels have likely moved through these waters longer than the marshes themselves have held their present shape. They pass through tidal creeks, estuaries, freshwater streams, flooded ditches, cypress swamps, and inland rivers, connecting habitats that often seem separate to us but function together as one living system.

And almost no one realizes that every eel seen here began life far out at sea.

Born Beyond the Horizon

The American eel’s life cycle spans thousands of miles, linking the Sargasso Sea, Atlantic coast, estuaries, marshes, rivers, and inland lakes through a single migration that can last decades. | Image credit: U. S. Fish and Wildlife Service

Far offshore, beyond the continental shelf and beyond the visible horizon of North Carolina’s beaches, lies the Sargasso Sea — a warm, rotating gyre of Atlantic water bordered by ocean currents rather than land. This is where American eels spawn, though much of their reproduction still remains one of the great biological mysteries of the Atlantic Ocean (Béguer‐Pon et al., 2015).After hatching, eel larvae drift for months within the Gulf Stream. At this stage they do not yet resemble eels. They are thin, transparent, leaf-shaped organisms called leptocephali, nearly invisible against the open ocean (Wang & Tzeng, 2000).

Leptocephali, the larval stage of the American eel, drift within the Atlantic Ocean currents for months before transforming into glass eels and entering coastal estuaries. | Image credit: hunterefs, iNaturalist

As they approach the coastline, their bodies begin to transform. The broad leaf-like shape narrows into the familiar eel form. Their organs reorganize. Their muscles strengthen. By the time they arrive in estuaries along the Atlantic coast, they have become what scientists call glass eels — small, transparent juveniles that move into tidal rivers and marshes under the cover of darkness (Starks, 2026).

Glass eels, the transparent juvenile stage of the American eel, gather along coastlines before moving inland through estuaries, marshes, and rivers. | Image credit: W. O’Connor

At night in late winter and spring, these glass eels enter coastal waters by the thousands. Most people never notice them. But beneath bridge lights and along quiet marsh edges, tiny transparent bodies gather against the current, moving inland on tides that have repeated for thousands of years.

Some settle into estuaries. Others continue far upriver into freshwater creeks and reservoirs. A single eel may spend decades there before returning once again to the open Atlantic.

As they continue growing, American eels pass through a series of color changes that reflect different stages of their life cycle. Newly arrived glass eels are nearly transparent. Within months they develop pigmentation and become elvers, often showing olive, brown, or yellowish coloration. During the longest phase of their lives they are known as yellow eels, displaying yellow-brown to olive sides with lighter undersides while feeding and growing in estuaries, rivers, and wetlands for years or even decades (ASMFC, 2017; Haro et al., 2000). As they mature and prepare for their return migration to the Sargasso Sea, they transform into silver eels. Their bodies darken along the back, their sides become silvery, and their eyes enlarge — adaptations that help prepare them for life in the open ocean and their final spawning migration (Haro et al., 2000; Tesch & White, 2008).

American eels change dramatically throughout their lives, from transparent leptocephali and glass eels to yellow eels in estuaries and rivers before developing the silver coloration of spawning adults returning to the Sargasso Sea. | Image credit: C. Bowser & R. Papish

The Marsh at Night

American eels are largely nocturnal, which means many people living along the coast rarely realize how common they are.

After sunset, they emerge from submerged roots, oyster reefs, marsh undercuts, rock piles, and mud-bottom channels to feed. In tidal creeks around Onslow County, they move through habitats that shift constantly with salinity, rainfall, temperature, and tide.

Unlike many fish that specialize in one narrow environment, eels are remarkably flexible. They can tolerate freshwater, brackish estuaries, and saltwater marsh systems throughout different stages of life (Able, 2005).

This flexibility makes them important ecological connectors between habitats.

An eel feeding in an estuary may consume shrimp, small fish, crabs, worms, insect larvae, and carrion. Larger eels become predators capable of feeding on nearly anything they can overpower. In turn, they become prey themselves for river otters, wading birds, striped bass, sharks, alligators, ospreys, and larger coastal predators (MacGregor et al., 2009).

What appears at first to be a strange solitary fish is actually woven through multiple levels of the food web.

American eels help transfer energy through the ecosystem, linking marsh invertebrates, small fish, and larger predators with the waters of Onslow County. | Image credit: A. Mitchell

Ancient Currents and Modern Coastlines

And in a much deeper sense, eels also connect modern coastal ecosystems to ancient worlds that existed long before humans reshaped shorelines. Their lineage stretches back tens of millions of years, surviving repeated shifts in sea level, climate, and continental geography. Long before beach renourishment projects, before the Outer Banks existed in their present form, and even before many modern mammals evolved, ancestral eels were already moving between oceans and coastal rivers (Inoue et al., 2010).

That timeline overlaps surprisingly well with the broader environmental history explored in my earlier posts. During the Carboniferous Period over 300 million years ago, vast swamp forests covered portions of what would eventually become eastern North America, laying down the organic material that later formed coal deposits (Sahney et al., 2010). The world looked entirely different then, but the shallow coastal environments that support migratory fish today evolved from ancient marine systems shaped across those immense spans of geologic time.

By 66 million years ago — around the end-Cretaceous extinction that eliminated non-avian dinosaurs — early eel relatives already existed in ancient seas (Near et al., 2012). Modern American eels evolved much later, but their migratory strategy reflects something extraordinarily old: the continual exchange between ocean currents, estuaries, rivers, and wetlands.

Fossil eels resembling modern species appear in the geologic record tens of millions of years ago, reflecting a lineage that has persisted through changing oceans, shifting coastlines, and repeated cycles of environmental change. | Image credit: Fossil Forum

Beach renourishment, by contrast, exists on an almost microscopic timescale geologically. Most projects reshape shorelines over years or decades, temporarily altering sediment movement, inlet dynamics, turbidity, and nearshore habitat. Eels are resilient enough to survive natural coastal change — hurricanes, shifting barrier islands, overwash events, and migrating inlets that have continually transformed the Atlantic coast. But human-driven shoreline modification can compress those disturbances into shorter, more frequent intervals that affect how juvenile eels enter estuaries and move inland.

So while beach renourishment itself is modern, the habitats it alters are part of a coastal system assembled over millions of years — one that species like the American eel have been navigating since long before the present coastline existed.

Their ecological importance is recognized even within local fisheries. In many areas, crab pots are now designed with eel escapement openings that allow smaller American eels to exit traps rather than become unintended bycatch. These modifications help reduce eel mortality while acknowledging the species’ role in maintaining healthy estuarine ecosystems.

The Animal That Connects Rivers

Many coastal species remain tied to a single environment. Oyster reefs remain fixed in estuaries. Marsh periwinkle snails cling to grass stems. Flounder shift between nearshore and estuarine waters but remain marine fish.

American eels move between worlds.

A juvenile eel may travel from offshore Atlantic currents into a coastal marsh creek, then into freshwater rivers hundreds of miles inland before eventually returning to the Sargasso Sea years later to spawn. Very few animals along the Atlantic coast connect ecosystems across such enormous distances.

American eels connect ecosystems across the Atlantic Ocean, beginning life in the Sargasso Sea before dispersing into estuaries, rivers, lakes, and wetlands throughout eastern North America. } Image credit: L. Poirier

Because of this, eels transport energy and nutrients between habitats that otherwise remain loosely connected. Predators feeding on eels receive marine-derived nutrients that originated far offshore. When adult eels migrate back toward the Atlantic, they carry inland energy back toward the ocean system (Jessop et al., 2020).

Even freshwater mussels depend upon them.

Several mussel species release microscopic larvae called glochidia that temporarily attach to fish hosts while developing. Research in Mid-Atlantic rivers has shown that American eels are one of the most successful hosts for some native mussel species, helping sustain mussel populations throughout eastern river systems (Schwalb et al., 2013).

So beneath the surface, the eel is doing more than surviving for itself. It is helping move life through the watershed.

What Happens When Eels Decline

Globally, the American eel is listed as “endangered, but stable” on the IUCN Red List because of long-term population declines across much of its range (IUCN, 2023). In the United States, however, the U. S. Fish and Wildlife Service has concluded the species does not currently require federal protection under the Endangered Species Act. The Atlantic States Marine Fisheries Commission determined that their populations are largely depleted in U. S. waters and have recommended continued monitoring of their populations because their life cycle depends upon the health and connectivity of both freshwater and marine environments (ASMFC, 2026).

For centuries, rivers along the Atlantic coast held far larger eel populations than they do today.

In many parts of the eastern United States, dams and hydroelectric turbines block migration routes and kill adults moving back downstream toward the ocean. Those barriers have severely reduced eel access to inland habitat across major river systems (Haro et al., 2000).

Onslow County is different.

The New River estuary is not fed by large mountain rivers or controlled by dams upstream. It is a relatively closed coastal watershed shaped instead by rainfall, groundwater springs, blackwater creeks, tidal exchange, runoff, and low-gradient streams winding through wetlands and forests. Here, eel movement depends less on navigating massive river barriers and more on the health and connectivity of marshes, culverts, floodplains, tidal creeks, and shallow estuarine habitat.

That makes local environmental changes especially important.

Wetland loss, shoreline hardening, stormwater runoff, dredging, declining water quality, and altered tidal flow can fragment the smaller pathways eels rely upon throughout the watershed. Even undersized culverts or poorly designed drainage structures can interrupt movement between creeks and flooded wetlands during critical migration periods.

Barrier islands also shape the system eels enter.

Along the Onslow coast, shifting inlets, overwash events, and beach renourishment projects continually reshape the boundary between ocean and estuary. In some cases, renourishment can temporarily increase turbidity, bury nearshore habitat, or alter tidal exchange patterns affecting juvenile eel recruitment into estuarine creeks. At the same time, healthy barrier islands and functioning marsh systems help buffer salinity extremes, reduce erosion, and maintain the sheltered estuarine habitat young eels depend upon once they arrive from the Atlantic.

Because eels use so many habitats, their decline spreads outward through the ecosystem in ways people may not immediately notice.

River otters lose an important prey source in some waterways. Mussel reproduction declines where host fish disappear. Predators that once relied seasonally on eels shift toward other prey. The disappearance of a species that connects marshes, rivers, estuaries, and offshore currents weakens the ecological ties between those environments.

And unlike species that reproduce quickly, eels recover slowly.

An eel living beneath a dock in coastal North Carolina may already be older than the child fishing above it. Some females remain inland for decades before ever returning to spawn (Haro et al., 2000). Every interruption between inland waters and the sea disrupts a migration pattern older than modern coastlines themselves.

The Fish Most People Never See

On warm summer nights in coastal North Carolina, much of the estuary moves unseen.

Shrimp rise into the water column. Rays cross shallow mudflats beneath darkness. Juvenile fish gather around dock lights. Crabs emerge from oyster beds to forage with the tide.

And somewhere below that shifting water, an eel moves silently between habitats, carrying the Atlantic inland and returning inland waters back toward the sea.

Most people standing along the shoreline will never know it is there.

But the marsh still holds the traces of its passage. So do the river otters weaving through flooded reeds and the herons stalking the quiet creek edges at dusk.

The tidal creeks of Onslow County continue shaping themselves around an animal whose life still stretches beyond much of human observation — from blackwater rivers to the open Atlantic, and back again.

Hidden beneath dark water and shifting tides, American eels remain one of the Atlantic coast’s most remarkable connections between ocean, estuary, and river. | Image credit: E. Smith, iNaturalist

References

Able, K. W. (2005). A re-examination of fish estuarine dependence: Evidence for connectivity between estuarine and ocean habitats. Estuarine, Coastal and Shelf Science, 64(1), 5-17. https://doi.org/10.1016/j.ecss.2005.02.002

ASMFC. (2026). American Eel. Atlantic States Marine Fisheries Commission. https://asmfc.org/species/american-eel/

Béguer-Pon, M., Castonguay, M., Shan, S., Benchetrit, J., & Dodson, J. J. (2015). Direct observations of American eels migrating across the continental shelf to the Sargasso Sea. Nature Communications, 6(1). https://doi.org/10.1038/ncomms9705

Haro, A., Richkus, W., Whalen, K., Hoar, A., Busch, W., Lary, S., Brush, T., & Dixon, D. (2000). Population decline of the American eel: Implications for research and management. Fisheries, 25(9), 7-16. https://doi.org/10.1577/1548-8446(2000)025<0007:pdotae>2.0.co;2

Inoue, J. G., Miya, M., Miller, M. J., Sado, T., Hanel, R., Hatooka, K., Aoyama, J., Minegishi, Y., Nishida, M., & Tsukamoto, K. (2010). Deep-ocean origin of the freshwater eels. Biology Letters, 6(3), 363-366. https://doi.org/10.1098/rsbl.2009.0989

Jessop, B. M. (2020). Oceanic environmental effects on American eel recruitment to the east river, Chester, Nova Scotia. Marine and Coastal Fisheries, 12(4), 222-237. https://doi.org/10.1002/mcf2.10121

MacGregor, R., Casselman, J. M., Allen, W. A., Haxton, T., Dettmers, J. M., Mathers, A., LaPan, S., Pratt, T. C., Thompson, P., Stanfield, M., Marcogliese, L., & Dutil, J. D. (2009). Natural Heritage, Anthropogenic Impacts, and Biopolitical Issues Related to the Status and Sustainable Management of American Eel: A Retrospective Analysis and Management Perspective at the Population Level. American Fisheries Society Symposium, 69, 713-740. https://www.thelandbetween.ca/wp-content/uploads/2014/06/Anacat_Final_Final-reprint_-macgregor.pdf

Near, T. J., Eytan, R. I., Dornburg, A., Kuhn, K. L., Moore, J. A., Davis, M. P., Wainwright, P. C., Friedman, M., & Smith, W. L. (2012). Resolution of ray-finned fish phylogeny and timing of diversification. Proceedings of the National Academy of Sciences, 109(34), 13698-13703. https://doi.org/10.1073/pnas.1206625109

Pike, C., Casselman, J., Crook, V., DeLucia, M. B., Jacoby, D., & Gollock, M. (2023). Anguilla rostrata. The IUCN Red List of Threatened Species. https://dx.doi.org/10.2305/IUCN.UK.2023-1.RLTS.T191108A129638652

Sahney, S., Benton, M. J., & Falcon-Lang, H. J. (2010). Rainforest collapse triggered Carboniferous tetrapod diversification in Euramerica. Geology, 38(12), 1079-1082. https://doi.org/10.1130/g31182.1

Schwalb, A. N., Cottenie, K., Poos, M. S., & Ackerman, J. D. (2011). Dispersal limitation of unionid mussels and implications for their conservation. Freshwater Biology, 56(8), 1509-1518. https://doi.org/10.1111/j.1365-2427.2011.02587.x

Starks, C. (2026). Interstate Fisheries Management Program Overview: American Eel (May 2026). Atlantic States Marine Fisheries Commission. https://asmfc.org/wp-content/uploads/2025/11/4.AmericanEel_May-2026.pdf

Tesch, F. W., & White, R. J. (2008). The eel (5th ed.). John Wiley & Sons.

Wang, C., & Tzeng, W. (2000). The timing of metamorphosis and growth rates of American and European eel leptocephali: A mechanism of larval segregative migration. Fisheries Research, 46(1-3), 191-205. https://doi.org/10.1016/s0165-7836(00)00146-6

May 29, 2026
When the Water Turns Gelatinous: The Hidden Filter Feeders of Onslow County

Sometimes the estuary changes before people notice why.

The water may look normal from shore, but drifting just beneath the surface are long ribbons of translucent gelatin — soft strands that gather along marsh edges, collect in eddies, or drift through the current like mucus suspended in the tide. In Surf City this week, people described them as “whale snot.”

Gelatinous material collected from Murrells Inlet, South Carolina at the low tide edge. Such suspended material may include colonial tunicates, salps, mucus-rich plankton aggregates, and other organic matter associated with productive estuarine conditions. | Image credit: J. Mattevi

They are more likely colonial tunicates or salps, gelatinous filter-feeders that can appear suddenly when conditions in the water favor rapid plankton growth (Bone, 1998; Madin & Deibel, 1998).

What matters is not only the organisms themselves, but what their appearance says about the estuary around them.

The drifting forms

These blooms often form when the water column becomes temporarily stable and productive (Madin, 1982). Warmer temperatures, calmer conditions, reduced wave turbulence, and elevated plankton concentrations create an environment where filter-feeding gelatinous organisms can reproduce rapidly. Water moving through the inlets may also transport offshore plankton communities into the estuary, concentrating them in tidal creeks and slower-moving surface water (Bone, 1998; Madin, 1982).

In these calmer stretches, the water column begins separating into layers. Suspended plankton remains concentrated near the surface while weaker turbulence allows fragile gelatinous colonies to persist long enough for blooms to form. What would normally disperse through wave action instead remains suspended within the estuary itself (Madin, 1982).

To most people, they look like debris.

Ecologically, they are processing the estuary in real time.

Salps and colonial tunicates continuously pump water through their bodies, removing suspended phytoplankton, bacteria, and organic particles from the water column. During bloom periods, enormous volumes of water can be filtered each day (Madin, 1982; Sutherland et al., 2010). In effect, the estuary briefly develops a drifting layer of living filtration suspended between the surface and the bottom.

Each colony filters continuously. Thousands moving through a tidal creek or marsh edge at once can collectively filter enormous volumes of suspended material over short periods of time, temporarily altering the clarity and composition of the surrounding water (Riisgård & Larsen, 2010).

That shift affects everything around them.

When these blooms are abundant, water clarity can temporarily improve as suspended particles are removed. Organic material becomes concentrated into mucus-rich waste pellets and decaying gelatinous tissue that sink toward the bottom, transferring energy from the surface into benthic food webs below (Madin & Deibel, 1998). Microbes, worms, crustaceans, and scavengers begin responding almost immediately (Madin, 1982; Madin & Deibel, 1998).

Instead of remaining suspended near the surface, nutrients and organic matter begin settling downward through the water column. What had been dispersed through open water becomes concentrated along the bottom, where deposit-feeding worms, small crustaceans, microbes, and scavengers begin incorporating that material into the estuary below (Madin, 1982).

The bloom itself becomes food.

The drifting masses also create temporary structure within otherwise open water. Small fish gather along their edges. Tiny invertebrates gather within folds and strands of gelatinous tissue. Predators begin responding not only to the bloom itself, but to the concentration of life forming around it (Bone, 1998; Madin & Deibel, 1998).

Small fish and invertebrates feed around the edges of these drifting masses. Juvenile fishes may remain near these drifting masses as food becomes concentrated around them. Sea turtles, some fishes, and other gelatinous predators may increase feeding activity where blooms become dense enough to concentrate prey (Bone, 1998).

But like many ecological events, balance matters.

If too few filter-feeders are present during periods of elevated nutrients, water grows murkier and oxygen conditions become less stable, particularly during heat and nighttime respiration. But filtration at the opposite extreme can also reshape the food web. Too many gelatinous filter-feeders, however, may strip large amounts of plankton from the water column, altering food availability for larval fishes and other plankton-dependent organisms higher in the food web (Petersen & Riisgård, 1992).

Most blooms are temporary.

Currents disperse them. Heat and bacteria break them apart. Waves fragment the colonies into nearly invisible strands that disappear back into the system as quickly as they arrived. Even in collapse, the bloom continues feeding the estuary. Decaying tissue is broken apart by bacteria, consumed by scavengers, and recycled back into the same nutrient pathways that allowed the bloom to form in the first place (Madin, 1982).

But for a short period, the estuary reveals something normally hidden: the water between the marsh and the bottom is not empty space. It is an active habitat, filled with organisms that filter, recycle, transport, and redistribute energy through the coastal ecosystem (Bone, 1998; Madin, 1982).

The attached forms

Not all tunicates remain suspended in the water column. Some attach themselves directly to the surfaces that hold still long enough for life to accumulate—dock pilings, oyster shell, ropes, marsh grass roots, floats, and the shaded undersides of piers where current continues moving but turbulence drops away.

Along the estuaries of Onslow County, these attached forms become part of what looks, at first glance, like simple buildup.

The surfaces beneath docks rarely stay bare for long (Wahl, 1989; Lindeyer & Gittenberger, 2011). Marine scientists often describe these layered growths as fouling communities, but along the estuary they appear simply as the layer of life that forms on anything left in the water long enough. First comes a film too thin to notice, then algae, then colonies of organisms layered over one another until wood, shell, and rope begin carrying part of the estuary itself.

Sea squirts and other attached filter-feeders beneath a dock in Surf City, North Carolina. | Image credit: A. Mitchell

Tunicates are part of that layer.

Along this coast, attached tunicates can include solitary species like the pleated sea squirt (Styela plicata) and the sea grape (Molgula manhattensis), as well as colonial species such as Clavelina oblonga and sea pork (Aplidium stellatum) (Van Name, 1945; Lambert, 2007).

Some grow individually, attached like soft sacs with openings at the top. Others spread as colonial sheets or clustered lobes, sharing a common outer covering while continuously filtering water moving past them. Around pilings and floating docks, entire communities can form this way—sponges beside hydroids, bryozoans layered against tunicates, all responding to current, salinity, temperature, and suspended food moving through the tide (Wahl, 1989).

To most people, these surfaces register as slime.

Ecologically, they are filtration, habitat, and nutrient transfer occurring simultaneously (Wahl, 1989).

Sea squirts

The organisms most people recognize first are usually sea squirts. They appear as rubbery sacs attached beneath docks or clustered along ropes, and shell. Press one accidentally and water jets outward through small siphons near the top of the body, giving rise to the common name.

A sea squirt partially coated in algae and sediment beneath shallow estuarine water in Surf City, North Carolina. The two siphon openings are part of the continuous filtration process occurring beneath docks and marsh edges. | Image credit: A. Mitchell

Species such as the pleated sea squirt (Styela plicata) often develop thick, wrinkled outer coverings ranging from tan and off-white to purple, while the sea grape (Molgula manhattensis) forms smaller rounded bodies attached within the layered communities growing beneath docks and along estuarine structure — what marine scientists often call fouling communities (Van Name, 1945).

What looks like a reaction is actually the visible end of a process already underway.

Sea squirts continuously pull water inward through one siphon, filter out phytoplankton, bacteria, and suspended particles from the water, then expel the filtered water back into the estuary through another opening. The animal does not begin filtering when disturbed. It has been filtering the entire time (Riisgård & Larsen, 2010).

In productive estuarine water, thousands of these organisms may be pumping simultaneously (Riisgård & Larsen, 2010).

That filtration matters.

As suspended particles are removed, nutrients become concentrated into waste and biomass that can be transferred downward into bottom communities. Water clarity may improve locally (Riisgård & Larsen, 2010). Microbial activity shifts around them. Small invertebrates begin using the folds and surfaces their bodies create.

Their presence also signals something about the surrounding water.

Sea squirts tend to cluster where flow remains steady enough to deliver oxygen and suspended food continuously, but not so violent that colonies are torn free. Around tidal creeks, dock edges, and quieter stretches of the Intracoastal Waterway, their abundance often reflects a system carrying enough suspended productivity to sustain constant filtration (Barros, 2009).

Sea pork

Some tunicates take a different form entirely.

One of these is sea pork, commonly associated with colonial tunicates such as Aplidium stellatum, which spread outward as shared gelatinous colonies rather than isolated individuals (Van Name, 1945).

Sea pork, a colonial tunicate, washed ashore along Surf City, North Carolina. Though it appears as a single gelatinous mass, it is made up of thousands of tiny filter-feeding animals embedded within a shared outer layer. | Image credit: D. Miles

Sea pork spreads across submerged surfaces in thick, rubbery colonies that look less like individual animals and more like flesh-colored mats attached beneath floats and pilings. Depending on the species and age of the colony, the surface may appear muted pink, tan, orange, or almost translucent beneath the waterline.

Most people don’t realize they are looking at colonies made up of thousands of tiny individual filter-feeding bodies embedded together within a shared outer layer.

The colony functions collectively (Van Name, 1945).

Water moves continuously through countless small openings across the surface, carrying suspended plankton and organic particles into the colony while waste and filtered water move back outward into the surrounding estuary (Riisgård & Larsen, 2010).

That structure changes the surface around it.

Sea pork colonies trap sediment and create small protected surfaces where microorganisms and invertebrates begin to accumulate between folds and protected edges. Tiny crustaceans move across them. Worms and microbial films develop within the folds and protected spaces between colonies. What appears smooth from above becomes, at smaller scales, complex terrain (Wahl, 1989).

Like other filter-feeding communities along this coast, sea pork helps transfer suspended energy from the water column into the attached world beneath docks and marsh edges.

And once that layered habitat forms, other organisms begin responding to it—including the nudibranchs moving slowly across its surface.

Nudibranchs

At low tide along the edges of the sound—where pilings hold a thin skin of life and oyster shells stack into uneven ridges—the water sometimes carries color that doesn’t belong to the sand or the grass. It moves slowly, almost deliberately, across surfaces that most people step over without noticing. What looks like a fragment of drifting algae or a soft piece of shell resolves, if you stop long enough, into something alive.

These are nudibranchs.

They are not fish, not worms, not plants. They are marine gastropods—relatives of snails—but without shells (Valdés et al., 2006). Along the coast of Onslow County, they appear in the quiet places: beneath docks in the Intracoastal Waterway, along the edges of Topsail Island marsh creeks, and on the submerged surfaces where current slows just enough for growth to take hold.

Along shallow estuarine structure in this region—beneath docks, across pilings, and within the layered growth attached to ropes and shell—nudibranchs may include species such as the striped nudibranch (Cratena pilata), the Brazilian aeolid sea slug (Spurilla braziliana), the fringeback dondice (Dondice occidentalis), Thecacera pennigera, Berghia rissodominguezi, and the brackish-water species Tenellia adspersa (Marcus, 1972; Valdés et al., 2006).

Most people never see them. But they are there, working through the same system that shapes everything else along this coast.

A nudibranch collected near Morehead City, North Carolina, viewed under magnification. The cerata along its back increase surface area for respiration and, in some species, store defensive stinging cells obtained from prey. | Image credit: marineinvertgirl, iNaturalist

Built for sensing, not speed

A nudibranch’s body is built for sensing and feeding, not speed. The two structures at the front—rhinophores—sample the water chemically, reading it the way a shoreline bird reads the wind. Along their backs, many species carry cerata, small extensions that look ornamental but function as both respiration and defense.

In aeolid nudibranchs like Spurilla braziliana, Cratena pilata, and Berghia rissodominguezi, these cerata become important sites for both respiration and defensive storage of stinging cells obtained from prey (Goodheart et al., 2018).

The Brazilian aeolid sea slug (Spurilla braziliana) moving across submerged structure near Morehead City, North Carolina. The cerata lining its back function in respiration and can store defensive stinging cells obtained from prey such as anemones and hydroids. | Image credit: wonglab, iNaturalist

They move slowly because they can afford to. Their food doesn’t run.

Sponges, hydroids, bryozoans—these are the surfaces most people would describe as “growth” on docks or shells. To a nudibranch, those surfaces are structure, habitat, and food all at once (Valdés et al., 2006).

The work they do (even when no one’s watching)

Along this coastline, growth is constant. Give any hard surface—an old piling, a piece of shell, a boat hull—enough time in the water and it becomes layered. First a film, then algae, then invertebrates. The system builds upward and outward, creating what scientists call structural complexity, but what you actually see is texture: roughness where there used to be smoothness (Wahl, 1989).

Along shallow estuarine bottoms, algae, shell, and attached growth begin forming the layered habitat that supports juvenile fish, crabs, filter-feeders, and the organisms moving through the estuary food web. | Image credit: A. Mitchell

Nudibranchs move through that texture selectively.

Many species feed on a single type of prey. One may specialize in a particular sponge. Another tracks hydroids, those delicate branching animals that resemble tiny underwater ferns. Species such as Dondice occidentalis, Cratena pilata, and Tenellia adspersa are commonly associated with hydroids and other organisms growing across submerged pilings, docks, ropes and shell in shallow coastal environments (Marcus, 1972; Valdés et al., 2006). This selectivity matters more than their size suggests. They are not removing everything. They are removing specific pieces of the system.

That kind of feeding does not flatten the landscape—it shapes it.

Where one organism begins to dominate, nudibranchs can limit its spread. Where surfaces would otherwise become uniform, their grazing introduces variation. Over time, this helps maintain the uneven habitat small fish, shrimp, and juvenile invertebrates depend on (Wahl, 1989).

Growth that begins as algae quickly becomes habitat. Along shallow estuarine edges, layered vegetation and attached organisms create shelter for crabs, juvenile fish, shrimp, and other small life moving through the system. | Image credit: A. Mitchell

It’s easy to miss because nothing dramatic happens. There’s no visible clearing, no sudden absence. But the balance of what grows, and where, shifts quietly in response to their presence.

Borrowed defenses, redistributed energy

Some nudibranchs do something that seems improbable until you see it up close: they take the defenses of what they eat and keep them.

Hydroids and certain cnidarians carry stinging cells—nematocysts—that function as protection. When a nudibranch feeds on them, those cells pass through the digestive system intact and are stored within the cerata along its back. The nudibranch doesn’t just consume its prey; it incorporates part of its defense (Goodheart et al., 2018).

This changes how energy moves through the system.

Instead of defenses being lost when prey is consumed, they are transferred upward. The nudibranch becomes both grazer and deterrent, a small organism that is less likely to be eaten because of what it has already eaten.

You can see the result in their coloration. Many are bright, almost out of place against the muted tones of sand and shell. That color is not decoration—it’s a signal (Avila, 1995). Along this coast, where predation pressure is constant, visibility can function as warning rather than risk.

Where they sit in the trophic cascade

They are not apex predators. They don’t regulate fish populations or move through the system in ways that draw attention. But they occupy a position that connects the base of the food web to everything above it.

They feed on organisms that build habitat.

Those organisms—sponges, hydroids, bryozoans—form the living surface that supports small invertebrates and juvenile fish. Those smaller organisms, in turn, become prey for larger fish, which then connect to the predators people are more familiar with along this coast—species like blacktip shark (Carcharhinus limbatus) and Atlantic sharpnose shark (Rhizopriodion terranovae) that move along the breakers and through the sounds.

Remove the visible predators, and people notice quickly.

Remove something like a nudibranch, and what changes is slower, but it moves in the same direction. Surfaces become dominated by fewer species. Habitat becomes more uniform. The small organisms that rely on variation lose space. That change works its way upward, not as a single event, but as a shift in the system’s capacity to support diversity.

Even small organisms attached to pilings and submerged structure become part of much larger coastal food webs. Scientific food-web models show nudibranchs, hydroids, bryozoans, worms, shrimp, and fishes linked together through the transfer of energy across the ecosystem.

Generalized food web showing how organisms associated with sponge and attached invertebrate communities connect upward through coastal ecosystems. Nudibranchs, hydroids, bryozoans, worms, shrimp, and fishes all participate in the transfer of energy through these layered habitats. Adapted from Archer et al. (2020).

Why they stay hidden

There’s a reason most beachgoers never encounter them.

They live where water movement slows just enough to allow growth to accumulate, but not so still that oxygen drops away. Around docks, inside creeks, along the quieter edges of the New River estuary, they remain attached to the surfaces that feed them.

Out in the open surf, where sand shifts constantly and hard structure is buried and exposed with each change in wind and tide, there’s less for them to hold onto and less for them to eat. The breakers are a moving environment (Wahl, 1989). Nudibranchs belong to the places that hold still just long enough for complexity to form.

What changes if they’re gone

Nothing you would notice in a single afternoon at the beach.

But over time, the surfaces beneath the waterline would begin to simplify. One or two fast-growing organisms would spread further, covering space that would otherwise remain shared. The small sheltered spaces used by larval fish, juvenile shrimp, and small crabs would begin to thin out.

That loss doesn’t stay at the bottom.

It moves upward, changing how much life the system can support, and how evenly that life is distributed. By the time it reaches the fish people see from the shore, the cause is no longer visible. But it started here, in the slow movement of something small across a surface most people never look at twice.

Nudibranchs don’t reshape the coastline in ways that draw attention. They don’t mark their presence with absence or disturbance. Instead, they work within what’s already there—adjusting, redistributing, and maintaining the uneven structure that makes this coast function.

If you happen to see one, it won’t be moving fast. It won’t need to.

What they’re feeding on (and why it looks familiar)

Along the docks and pilings of Onslow County, the surfaces most people notice first aren’t fish at all. They’re the things attached to everything.

The branching, plant-like fuzz that brushes your hand when you reach into the water—those are hydroids. The firm, uneven coatings that look like they’re part of the structure itself are often sponges or bryozoans.

It’s easy to group all of it together as buildup. Something slimy, something in the way.

But that “squirt” people laugh about isn’t random. A tunicate pulls water in, filters out plankton and suspended particles, and then expels that water back out. What looks like a reaction is just the visible end of constant filtration. They are processing the water column—removing particles, cycling nutrients, and clarifying the water in small, continuous ways (Riisgård & Larsen, 2010).

Hydroids are doing something different. They are predators at a scale most people don’t consider, capturing microscopic prey drifting past. Sponges filter continuously as well, pulling bacteria and organic matter from the water and converting it into biomass that other organisms can use.

A sea anemone beneath shallow estuarine water in Surf City, North Carolina. Organisms like these become part of the layered communities that nudibranchs, tunicates, hydroids, and other invertebrates move through beneath the surface. | Image credit: A. Mitchell

This is the surface layer of the ecosystem.
And it doesn’t stay unchecked.

The ones moving across the surface

Species like the Brazilian aeolid sea slug (Spurilla braziliana) often feed directly on anemones associated with these same submerged communities, while smaller species such as Tenellia adspersa are frequently associated with hydroids in brackish and estuarine waters (Valdés et al., 2006).

The nudibranchs moving across these surfaces are not all the same, and what they eat tells you what role they’re playing.

Some of the small, leaf-like sea slugs in this region—species in the genus Elysia—feed on algae and can even retain the chloroplasts from what they consume, briefly using sunlight as part of their energy system. They blur the line between grazing and something closer to plant-like function (Valdés et al., 2006).

Others, like Cratena pilata and Dondice occidentalis, track hydroids specifically. Where hydroids begin to spread across a piling, these nudibranchs follow, feeding in a way that limits how dense those colonies can become (Marcus, 1972).

Species such as Thecacera pennigera are often associated with the layered communities growing beneath docks and harbor structure, while Berghia rissodominguezi and Spurilla braziliana move through shallow cnidarian-rich habitat where anemones and hydroids provide both food and defensive material (Valdés et al., 2006).

Heavier-bodied nudibranchs—often in groups like Doris—tend to feed on sponges. Not all sponges, and not everywhere, but selectively enough that no single form easily dominates a surface for long.

Even their eggs reflect this connection. The ribbon-like spirals sometimes seen attached to docks are laid directly where food is available. The next generation doesn’t disperse randomly—it begins where the system is already functioning.

Beneath the surface layer

Most of the time, these organisms go unnoticed.

People see the drifting ribbons and call them whale snot. They scrape tunicates from pilings without thinking about what those colonies were filtering from the water. They brush past hydroids and sponges growing beneath docks without realizing those surfaces are part of the estuary’s food web just as much as the fish moving above them.

But the water between the marsh and the bottom is never empty.

It carries suspended plankton, drifting larvae, dissolved nutrients, bacteria, predators, scavengers, and colonies of organisms filtering continuously through the tide. Along the quieter edges of Onslow County—beneath floats, around oyster shells, beside marsh grass roots, and inside the slower water of creeks and sounds—entire communities form within that suspended layer (Wahl, 1989; Lindeyer & Gittenberger, 2011).

Some drift. Some attach. Some graze slowly across the surface consuming the organisms beneath them.

Together, they reshape the estuary constantly.

The gelatinous ribbons appearing this week are not separate from the rest of the system. They are one visible moment in a larger cycle of filtration, growth, decay, grazing, and redistribution that normally happens out of sight (Bone, 1998; Madin, 1982). For a short time, the estuary simply becomes easier to see.

What appears empty from above often contains layered communities of algae, filter-feeders, invertebrates, and microorganisms quietly redistributing energy through the estuary. Surf City, North Carolina. | Image credit: A. Mitchell

References

Avila, C. (1995). Natural products of opisthobranch molluscs: A biological review. In Oceanography and marine biology: An annual review (33rd ed., pp. 487-559). UCL Press.

Barros, R. (2009). Human-mediated global dispersion of Styela plicata (Tunicata, Ascidiacea). Aquatic Invasions, 4(1), 45-57. https://doi.org/10.3391/ai.2009.4.1.4

Bone, Q. (1998). The biology of pelagic tunicates. Oxford University Press on Demand.

Encarnação, J., Seyer, T., Teodósio, M. A., & Leitão, F. (2020). First record of the nudibranch Tenellia adspersa (Nordmann, 1845) in Portugal, associated with the invasive hydrozoan Cordylophora caspia (Pallas, 1771). Diversity, 12(6), 214. https://doi.org/10.3390/d12060214

Goodheart, J. A., Bleidißel, S., Schillo, D., Strong, E. E., Ayres, D. L., Preisfeld, A., Collins, A. G., Cummings, M. P., & Wägele, H. (2018). Comparative morphology and evolution of the cnidosac in Cladobranchia (Gastropoda: Heterobranchia: Nudibranchia). Frontiers in Zoology, 15(1). https://doi.org/10.1186/s12983-018-0289-2

Korshunova, T., Lundin, K., Malmberg, K., Picton, B., & Martynov, A. (2018). First true brackish-water nudibranch mollusc provides new insights for phylogeny and biogeography and reveals paedomorphosis-driven evolution. PLOS ONE, 13(3), e0192177. https://doi.org/10.1371/journal.pone.0192177

Lambert, G. (2007). Invasive sea squirts: A growing global problem. Journal of Experimental Marine Biology and Ecology, 342(1), 3-4. https://doi.org/10.1016/j.jembe.2006.10.009

Lindeyer, F., & Gittenberger, A. (2011). Ascidians in the succession of marine fouling communities. Aquatic Invasions, 6(4), 421-434. https://doi.org/10.3391/ai.2011.6.4.07

Madin, L. P. (1982). Production, composition and sedimentation of salp fecal pellets in oceanic waters. Marine Biology, 67(1), 39-45. https://doi.org/10.1007/bf00397092

Madin, L. P., & Deibel, D. (1998). Feeding and energetics of Thaliacea. The Biology of Pelagic Tunicates, 81-104. https://doi.org/10.1093/oso/9780198540243.003.0005

Marcus, E. D. (1972). On Some Opisthobranchs from Florida. Bulletin of Marine Science, 22(2), 284-308. https://www.ingentaconnect.com/content/umrsmas/bullmar/1972/00000022/00000002/art00002

Petersen, J., & Riisgard, H. (1992). Filtration capacity of the ascidian Ciona intestinalis and its grazing impact in a shallow fjord. Marine Ecology Progress Series, 88, 9-17. https://doi.org/10.3354/meps088009

Riisgård, H., & Larsen, P. (2010). Particle capture mechanisms in suspension-feeding invertebrates. Marine Ecology Progress Series, 418, 255-293. https://doi.org/10.3354/meps08755

Sutherland, K. R., Madin, L. P., & Stocker, R. (2010). Filtration of submicrometer particles by pelagic tunicates. Proceedings of the National Academy of Sciences, 107(34), 15129-15134. https://doi.org/10.1073/pnas.1003599107

Valdés, Á., Behrens, D. W., & DuPont, A. (2006). Caribbean Sea slugs: A Field guide to the opisthobranch mollusks from the tropical Nortwestern Atlantic. Sea Challengers Natural History Books.

Van Name, W. G. (1945). The North and South American Ascidians. Bulletin of American Museum of Natural History, 84, 1-476. http://hdl.handle.net/2246/1186

Wahl, M. (1989). Marine epibiosis. I. Fouling and antifouling: Some basic aspects. Marine Ecology Progress Series, 58, 175-189. https://doi.org/10.3354/meps058175

May 16, 2026
Where Wings Meet Water: Reading Birds Along the Edges of Onslow County

At the Line Where Air Meets Water

On a late spring morning along Surf City, the first movement is often above the water, not within it. Brown pelicans travel low and steady just beyond the breakers, their wingtips nearly touching the surface as they follow a line that seems invisible from shore. Farther out, a group of terns holds in place against the wind, hovering, adjusting, then dropping sharply into the water before rising again. Closer to the sound side of Topsail Island, an osprey circles once, then folds into a dive toward a channel edge that looks, at first glance, no different than the water around it.

Nothing about these movements is random. They are responses to structure that exists beneath the surface—structure shaped by tide, wind, and the movement of other organisms. What appears as scattered bird activity is, in practice, a map of where the water is concentrating life.

For someone standing at the edge of it, that movement is one of the most accessible ways to read what cannot be seen directly.

What Birds Are Following Beneath the Surface

The birds that move along this stretch of coast are not searching broadly; they are tracking concentration. Along barrier island systems like those in Onslow County, physical processes—tidal exchange through inlets, wind-driven surface currents, and subtle differences in bottom shape—create zones where small fish, shrimp, and other prey accumulate (Peterson & Peterson, 1979; Piersma, 1997).

When the tide moves through places like New River Inlet, water does not flow evenly across the landscape. It accelerates through constrictions, slows along marsh edges, and bends around sandbars and channels. These shifts in speed and direction compress organisms into tighter spaces, particularly along boundaries where moving water meets something that resists it—an edge, a drop-off, or a change in depth (Wright et al., 1985).

Small schooling fish respond to that compression by tightening their formation. In doing so, they become more visible and more vulnerable. Larger fish—bluefish, Spanish mackerel, and juvenile coastal sharks—often move in from below, using that same concentration to feed. The pressure from below pushes prey upward, sometimes all the way to the surface.

Coastal birds feeding where prey has been concentrated near the surface along the breakers. | Image credit: A. Mitchell

What appears overhead depends on which part of that concentration each species is built to exploit.

Terns hovering and diving are often responding to prey that has been driven upward by predatory fish (Safina & Burger, 1985). Brown pelicans, which rely on plunge-diving, tend to follow more stable schools of fish that remain near the surface for longer periods (Shields, 2014). Ospreys, in contrast, depend on clear water and individual fish they can visually isolate, which is why their activity often aligns with calmer conditions and defined channel edges (Poole et al., 2002).

Each species is not simply feeding in the same place; each is reading a different layer of the same system.

When Surface Activity Signals Pressure Below

From the shoreline, bird activity can appear as isolated events—one dive, then another, then a sudden shift down the beach. Watched over time, a pattern emerges. A cluster of terns may concentrate in one location for several minutes, then disperse abruptly, reforming farther along the shoreline. Pelicans may align along a narrow band just beyond the breakers, following it as it drifts.

These shifts often reflect changes in how prey is being compressed and released beneath the surface. When predatory fish move through a bait school, the school tightens, rises, and becomes briefly accessible from above. When that pressure dissipates, the school spreads out again, and the birds move on.

This movement of energy—from smaller organisms to larger predators, and upward through the water column—is one visible expression of a trophic cascade. The term itself is often used to describe longer chains of ecological influence, but along the coast it can be observed in compressed moments, where the effects of predation become visible within seconds (Heithaus et al., 2008).

Birds do not initiate this process. They respond to it. Their presence marks where the system has already intensified.

Indicator Species at the Water’s Edge

From the beach, the difference is subtle. The water does not change color dramatically, and the waves continue to break as they did before. The level of activity shifts within that band—first visible in the air, then inferred below– marking places where the system has tightened, energy is moving through multiple layers at once, and the distance between surface and depth has, for a time, narrowed (Heithaus et al., 2008; Estes et al., 2011).

For someone entering the water, these differences in bird behavior can offer practical information, not in a predictive or absolute sense, but as indicators of what is happening just below the surface.

Brown pelicans traveling low in a consistent line often indicate schools of fish moving parallel to shore. Terns repeatedly diving in a tight area suggest smaller prey being pushed upward, frequently by larger fish feeding below. Ospreys focusing on a specific channel edge reflect clearer water and individual prey availability, rather than broad schooling events. Along the shoreline, shorebirds probing the sand at low tide are responding to invertebrates exposed by receding water, signaling a different layer of the system entirely—one tied to sediment and tidal timing rather than active predation (Colwell, 2010; Piersma, 1997).

None of these signals point directly to a specific species beneath the surface. What they indicate is concentration, and concentration is what draws larger predators closer to shore.

Along the coast of North Carolina, nearshore and juvenile shark presence is often associated with areas of high prey density, particularly where schooling fish aggregate (Heupel & Hueter, 2002). These conditions are not constant, and they shift with tide, temperature, and time of day. Birds make those shifts visible in real time.

At times, that activity stretches into lines that run the length of the breakers.

For someone stepping into the water, that narrowing matters. Not as a warning in the abstract, but as a recognition that the conditions supporting visible feeding above often extend below, linking organisms that are rarely seen together into the same moving structure.

Where the System Tightens

The patterns become easier to see near places where the water is forced to narrow, turn, or accelerate. The most consistent bird activity along this coast tends to occur where water movement is constrained and redirected. Inlets, marsh edges, sandbars, and the transitions between the Intracoastal Waterway and adjacent sounds create these zones (Wright et al., 1985).

At New River and its inlet, tidal flow compresses water into narrow channels before releasing it into broader areas, creating gradients in speed and depth. Along these gradients, prey accumulates, predators follow, and birds gather above.

These are not fixed points. As tide rises and falls, and as wind reshapes surface conditions, the locations of these compression zones shift. The birds move with them, tracing patterns that are constantly changing but not random.

For someone watching from shore, these movements can be read as lines, clusters, and absences—places where activity intensifies, and places where it suddenly drops away.

Standing Within It

Entering the water along this coast means stepping into a system already in motion. The surface may appear uniform, but the activity above it often reveals where that motion is focused.

Birds diving repeatedly in a confined area, or tracking a narrow band just beyond the breakers, indicate where prey is concentrated. Those same conditions are what draw larger predators into closer proximity to shore, not as an anomaly, but as part of the same process.

Watching the birds does not eliminate risk, and it does not provide certainty about what is beneath the surface. What it offers is context—a way to recognize when the water is more active, more compressed, and more connected across its layers.

What appears as feeding from above is part of a larger structure moving through the water. The birds do not create it, and they do not remain once it passes. They mark it, briefly, making visible what is otherwise difficult to see.

Bird movement along the shoreline often draws attention toward activity that remains unseen beneath the surface. | Image credit: A. Mitchell

References

Castro, J. I. (1993). The shark nursery of bulls Bay, South Carolina, with a review of the shark nurseries of the southeastern coast of the United States. Environmental Biology of Fishes, 38(1-3), 37-48. https://doi.org/10.1007/bf00842902

Colwell, M. A. (2010). Shorebird ecology, conservation, and management. University of California Press.

Estes, J. A., Terborgh, J., Brashares, J. S., Power, M. E., Berger, J., Bond, W. J., Carpenter, S. R., Essington, T. E., Holt, R. D., C. Jackson, J. B., Marquis, R. J., Oksanen, L., Oksanen, T., Paine, R. T., Pikitch, E. K., Ripple, W. J., Sandin, S. A., Scheffer, M., Schoener, T. W., & Wardle, D. A. (2011). Trophic downgrading of planet Earth. Science, 33(6040), 301-306. https://doi.org/10.1126/science.1205106

Heithaus, M. R., Frid, A., Wirsing, A. J., & Worm, B. (2008). Predicting ecological consequences of marine top predator declines. Trends in Ecology & Evolution, 23(4), 202-210. https://doi.org/10.1016/j.tree.2008.01.003

Heupel, M. R., & Hueter, R. E. (2002). Importance of prey density in relation to the movement patterns of juvenile blacktip sharks ( Carcharhinus limbatus ) within a coastal nursery area. Marine and Freshwater Research, 53(2), 543-550. https://doi.org/10.1071/mf01132

Peterson, C. H., & Peterson, N. M. (1979). Ecology of intertidal flats of North Carolina: A community profile (79/39). FWS/OBS. https://pubs.usgs.gov/publication/fwsobs79_39

Piersma, T. (1997). Do global patterns of habitat use and migration strategies Co-evolve with relative investments in Immunocompetence due to spatial variation in parasite pressure? Oikos, 80(3), 623-631. https://doi.org/10.2307/3546640

Poole, A. F., Bierregaard, R. O., & Martell, M. S. (2002). Osprey (Pandion haliaetus). In The Birds of North America (1st ed.). Cornell Lab of Ornithology.

Safina, C., & Burger, J. (1985). Common tern foraging: Seasonal trends in prey fish densities and competition with bluefish. Ecology, 66(5), 1457-1463. https://doi.org/10.2307/1938008

Shields, M. (2014). Brown Pelican (Pelecanus occidentalis). In Birds of North America (1st ed.). Cornell Lab of Ornithology.

Wright, L., Short, A., & Green, M. (1985). Short-term changes in the morphodynamic states of beaches and surf zones: An empirical predictive model. Marine Geology, 62(3-4), 339-364. https://doi.org/10.1016/0025-3227(85)90123-9

May 9, 2026
Slough Mud: The Gooey, Stinking Ecosystem Beneath Onslow County’s Shoreline

Where the Ground Doesn’t Hold

There are places along the edges of the water in Onslow County where the ground stops behaving like ground.

You find them along the sound side, at the margins of tidal creeks, and in the quieter edges of channels that drain toward New River Inlet. Places like the shallows near Soundside Park or the creek edges around Kenneth D. Batts Family Park look ordinary when the tide is in—flat water, sometimes with a darker tone beneath the surface, but otherwise unremarkable.

As the tide pulls away, that surface is left behind, exposed in a way that suggests continuity, as though it will hold underfoot the same way sand does along the open beach.

It holds just long enough to believe that.

Then it gives way.

A step sinks past the ankle before there is time to adjust, and the next carries deeper, the sediment tightening around your leg—not suddenly, but with a steady resistance that makes each movement slower than expected, until pulling free requires more effort than the surface first suggested and the footing you thought you had no longer offers anything solid to push against.

Sometimes the mud keeps what you brought with you.

It holds—until it doesn’t. | Image credit: Florida Tech

Each step releases a faint, unmistakable sulfur smell from below, brief but distinct, rising as the sediment shifts and settling again as it closes around the space you’ve displaced.

Nothing about it suggests stability, and yet nothing about it is still.

Where It Forms: Water That Slows Down

If you step back—onto firmer ground, where your footing holds—the pattern begins to show itself.

These places gather along edges where water loses momentum. Along the sound side, there are no breaking waves to constantly overturn the bottom. Water moves in, spreads thin across the flats, and then drains back through the same narrow paths, slowing as it goes.

When that movement slows, what the water was carrying no longer stays suspended.

Fine silts and clays begin to settle. Fragments of marsh grass drift down. Microscopic shells and organic particles—too small to notice while they are moving—collect layer by layer until the bottom changes character (Folk, 1980; Riggs et al., 2008).

Much of that material begins only a few feet away.

Where the water slows, what it carries begins to settle. | Image credit: A. Mitchell

Along the edges of these creeks, smooth cordgrass—Spartina alterniflora—holds the shoreline in place. When it dies back, it doesn’t disappear. It breaks apart, and with each tide, that material moves outward. What looks like loss becomes movement—organic matter carried away from the marsh and into these quieter edges (Odum, 1980).

Where the water lingers, that material accumulates.

And over time, accumulation becomes something you can step into.

The Surface: What Almost Holds

From above, it can look continuous.

In certain light—especially when the sun is low—there is a faint sheen across the surface, something smoother and more uniform than water alone would create. It can appear firm enough to cross, at least for a step or two.

That thin layer is not just sediment.

It settles just enough to look stable—until the weight shifts. | Image credit: A. Mitchell

Microscopic organisms—diatoms and cyanobacteria—spread across the surface, forming a film that binds particles together. They produce substances that hold grains in place, creating a surface that can briefly support weight before it gives way beneath it (Rimmer et al., 2025).

It is just enough structure to mislead you.

Just enough to suggest that what lies beneath it will behave the same way.

Why It Gives Way: Structure Without Support

Once that surface breaks, the difference becomes immediate.

The particles here are small enough to trap water between them, and once that water is there, it does not drain the way it does through sand. The sediment remains saturated, and when pressure is applied, the water has nowhere to go.

Instead of holding its shape, the ground shifts.

There is a way to describe how well a surface resists that kind of movement—shear strength. Sand has enough of it to support your weight.

This does not (Folk, 1980).

There’s form here, but no support—only water and loosened sediment. | Image credit: A. Mitchell

And beneath the surface, the structure is already interrupted. Burrows open and collapse. Small voids form and disappear. Gas collects in pockets that shift when disturbed. What looks continuous from above is already moving below.

So when your foot sinks, it is not breaking through something solid.

It is entering something that was never still to begin with.

Below the Surface: Where the Air Runs Out

The smell arrives as soon as the surface opens.

It rises quickly, sharp and distinct, and then fades again as the mud closes.

Just beneath the surface, oxygen is used up rapidly by microorganisms breaking down the organic material that has accumulated there. Below that thin layer, the sediment becomes anoxic—oxygen is no longer present (Fenchel & Riedl, 1970; Jørgensen & Nelson, 2004).

But the process doesn’t stop.

Bacteria continue to break material down, using sulfate from seawater instead of oxygen. That shift produces hydrogen sulfide gas, which remains trapped until the sediment is disturbed (Kasten & Jørgensen, 2000).

Each step releases it.

The smell is not separate from the system. It is evidence that the breakdown is still happening—just without air.

And because it is happening without oxygen, it happens more slowly.

What Stays Behind

If that same plant material were left exposed to air, it would break down quickly. Most of what it contains would return to the atmosphere as carbon dioxide.

Here, much of it does not.

The organic material that settles into this mud—marsh grass, algae, microscopic debris—is buried into a system where oxygen disappears almost immediately. Without that oxygen, decomposition slows, and a portion of that carbon remains stored in the sediment instead of returning to the air (Chmura et al., 2003).

It does not stop changing.

It is broken down, reworked, and shifted. But it is not fully released.

Layer after layer builds beneath the surface—material that was once living, now held within the mud you step into.

What smells like decay is also storage.

The Surface Is Breathing

Even without oxygen below, the surface is not sealed.

If you stand still long enough, you begin to see small openings, slight movements, places where the mud seems to shift or pulse.

Water moves in and out with the tide. Burrows connect the surface to what lies below. Worms, shrimp, and crabs pull oxygenated water downward as they move through the sediment (Aller, 1982; McCave, 1976).

And the plants at the edge are part of it too.

Marsh grasses do not just sit in the mud. They move oxygen from the air above down into their roots. Some of that oxygen leaks into the surrounding sediment, creating small zones where oxygen briefly exists before it is used up again.

It is uneven. Temporary. Constantly shifting.

At the surface, gases move both ways.

Oxygen enters. Carbon dioxide leaves. Small amounts of other gases—products of what is happening below—escape when the sediment is disturbed or when pressure changes with the tide.

The boundary is thin.

But it is active.

Movement You Don’t See

If you stop looking for stable ground and begin watching the surface itself, other patterns start to emerge.

What looks still is already in use. | Image credit: A. Mitchell

Small openings appear—round, spaced in ways that suggest something below rather than something left behind. Around them, slight mounds form and disappear as the mud dries and softens again.

These are not marks left on the surface. They are the surface expression of what is moving through it.

Polychaete worms pass through the sediment, ingesting it and depositing what remains behind them (Rhoads, 1974). Burrowing shrimp and amphipods maintain tunnels that allow water—and with it, oxygen—to move deeper into the mud than it otherwise could (Aller, 1982).

Crabs hold the edges.

Fiddler crabs open and close their burrows with the tide. Blue crabs move through when water returns, feeding within the same soft substrate that gives way underfoot. Mud crabs remain within it, emerging only when conditions allow.

Bivalves stay buried beneath it all, filtering water when submerged, holding position when exposed.

Sometimes you don’t see them until you feel them.

A sharp edge beneath your foot where the mud shifted just moments before.

The surface does not tell you everything that is there.

When the Water Returns

Then the water comes back.

It fills the same space that resisted your footing, covering the surface without changing what lies beneath it. The ground that gave way becomes part of a shallow, moving system again.

Fish arrive with the water.

Killifish move into these margins first, tolerating the low oxygen conditions that remain in the sediment. Flounder settle directly onto the bottom, their bodies flattening, their coloration shifting until they disappear against it.

Juvenile blue crabs move through these same areas, using them as nursery habitat—protected, shallow, and full of food (Bilkovic et al., 2020).

They are not just using the space. They are feeding on what the mud is processing.

Detritus, microbes, and organic material move through the system below the surface, supporting what arrives above it.

Other species follow.

Stingrays glide over the surface, feeding on what is buried below. Croaker move through slightly deeper channels. Along exposed flats near The Point at Topsail Beach, shorebirds track the retreating tide—probing, picking, following the movement of water as it exposes and covers the same ground again.

As the water returns, the surface changes—and life moves with it. | Image credit: A. Mitchell

What looked still becomes active.

Not because it changed.

But because the conditions around it did.

What Comes From the Marsh

At the edge where your footing gave way, the connection is already there.

The marsh does not end where the grass stops. It extends outward through what it releases.

This isn’t separate from the marsh—it’s what the marsh leaves behind. | Image credit: A. Mitchell

The grasses along the shoreline slow the water, trapping sediment and holding the edge in place. During storms, they absorb energy that would otherwise move inland, reducing erosion and limiting how much material is carried away (Barbier, 2012).

But they also export material.

As grasses break down, they move with the tide—out of the marsh, into the creeks, and into these quieter margins where the water slows again.

What settles here is not separate from the marsh.

It is what the marsh becomes once it begins to move—and what it leaves behind when it does.

What Changes, and What Doesn’t

The ground beneath you is not fixed.

Periods of calm allow fine sediments to build, thickening the layer and increasing the amount of organic material held within it. Warmer temperatures increase microbial activity, accelerating what is happening below the surface.

A storm can undo that quickly.

Sediment lifts back into the water, moves elsewhere, and settles in new places. Edges shift. Channels deepen or fill. What held you in place one week may not exist in the same way the next (Pilkey et al., 2014).

Other changes move more slowly.

Development alters how water flows. Marsh edges are reduced or hardened. Invasive plants like Vitex rotundifolia change how sediment is captured and released.

The system continues.

But the way it moves through the landscape can change.

Standing at the Edge of It

Standing at the edge of one of these places, it is easy to focus on the moment your footing failed—the way the ground gave way when it seemed like it shouldn’t.

But nothing about it failed.

What felt unstable is a working layer—one that gathers what the marsh releases, slows its return to the air, supports what can move within it, and disappears beneath the water as the tide returns.

The same ground that held you in place becomes part of something continuous again, connected to marsh, creek, sound, and ocean.

It does not hold because it is not meant to.

It holds because it is already in motion.

Nothing here failed—it’s doing exactly what it’s meant to do. | Image credit: A. Mitchell

References

Able, K., Manderson, J., & Studholme, A. (1999). Habitat quality for shallow water fishes in an urban estuary:the effects of man-made structures on growth. Marine Ecology Progress Series, 187, 227-235. https://doi.org/10.3354/meps187227

Aller, R. C. (1982). The effects of Macrobenthos on chemical properties of marine sediment and overlying water. Topics in Geobiology, 53-102. https://doi.org/10.1007/978-1-4757-1317-6_2

Barbier, E. B. (2012). Progress and challenges in valuing coastal and marine ecosystem services. Review of Environmental Economics and Policy, 6(1), 1-19. https://doi.org/10.1093/reep/rer017

Bilkovic, D., Isdell, R., Stanhope, D., Angstadt, K., Havens, K., & Chambers, R. (2021). Nursery habitat use by juvenile blue crabs in created and natural marshes. Ecological Engineering, 170(106333). https://doi.org/10.1016/j.ecoleng.2021.106333

Chmura, G. L., Anisfeld, S. C., Cahoon, D. R., & Lynch, J. C. (2003). Global carbon sequestration in tidal, saline wetland soils. Global Biogeochemical Cycles, 17(4). https://doi.org/10.1029/2002gb001917

Fenchel, T. M., & Riedl, R. J. (1970). The sulfide system: A new biotic community underneath the oxidized layer of marine sand bottoms. Marine Biology, 7(3), 255-268. https://doi.org/10.1007/bf00367496

Folk, R. L. (1980). Petrology of sedimentary rocks (2nd ed.). Hemphill Publishing Company.

Jørgensen, B. B., & Nelson, D. C. (2004). Sulfide oxidation in marine sediments: Geochemistry meets microbiology. Sulfur Biogeochemistry – Past and Present. https://doi.org/10.1130/0-8137-2379-5.63

Kasten, S., & Jørgensen, B. B. (2000). Sulfate Reduction in Marine Sediments. In Marine Geochemistry (pp. 263-264). Springer, Berlin, Heidelberg.
https://doi.org/10.1007/978-3-662-04242-7_8

McCave, I. N. (1976). Organism-Sediment Relationships. In The Benthic Boundary Layer (pp. 273-295). Plenum Press.

Odum, E. P. (1980). The status of three ecosystem-level hypotheses regarding salt marsh estuaries: Tidal subsidy, outwelling, and detritus-based food chains. Estuarine Perspectives, 485-495. https://doi.org/10.1016/b978-0-12-404060-1.50045-9

Pilkey, O. H., Rice, T. M., & Neal, W. J. (2014). How to read a North Carolina beach: Bubble holes, Barking sands, and rippled Runnels. UNC Press Books.

Riggs, S. R., Ames, D. V., & Dawkins, K. R. (2008). Coastal processes and conflicts: North Carolina’s Outer Banks: A curriculum for middle and high school students (NCU-E-08-002). NOAA Oceanic and Atmospheric Research; Sea Grant. https://repository.library.noaa.gov/view/noaa/46454/noaa_46454_DS1.pdf

Rimmer, J., Blight, A., Chocholek, M., & Paterson, D. (2025). Response of natural estuarine Microphytobenthic Biofilms to multiple anthropogenic stressors. Environmental Pollution, 387(127285). https://doi.org/10.1016/j.envpol.2025.127285

April 25, 2026
When the Bottom Moves: Rays in the Shallows of Onslow County

What People Are Seeing

In the last few weeks, the water along the edges of Onslow County has felt different.

Not because the water itself has changed—but because something beneath it has become harder to ignore.

Schools of cownose ray (Rhinoptera bonasus) move just below the surface nearshore, their wingbeats lifting faint clouds from the bottom as they pass. In the soundside shallows, where the water thins over sand and mud, Atlantic stingray (Hypanus sabinus) settle into the substrate, half-buried and nearly invisible until a step comes too close and the outline breaks.

People are seeing them more often now—but they’re also reacting to them.

A pause mid-step in shallow water.
A quick shift backward when something moves.
Fishermen lifting a line and stopping for a second longer than usual—not what they expected to find.

There is awe in it.

And sometimes hesitation.

Because the same thing that makes them easy to notice now also makes them easy to miss.

The question follows quickly:

Are there more of them this year?

Maybe.

But that question lingers longer than the answer.

Cownose rays migrating in Swansboro, NC. | Image credit: Pogie’s Academy

What Brings Them Here

As spring settles in along the North Carolina coast, the system begins to reorganize.

Water temperatures rise, and with that rise comes a shift in metabolism. Rays—like many coastal species—become more active as conditions move into a narrower range that supports feeding and movement (Smith & Merriner, 1987; Schwartz & Dahlberg, 1978).

For cownose rays, this seasonal transition includes a northward migration along the Atlantic coast, bringing large groups into nearshore and estuarine waters (Smith & Merriner, 1987).

Large groups of cownose rays like these move north along our coast each season, arriving together in shallow water. | Image credit: Vidyacharan A. Alchi

But movement alone does not explain what people are seeing.

What matters is where that movement meets the structure of the environment.

The water does not always look the same—some days it is flat and clear enough to see straight to the bottom, and other days the slightest movement turns it cloudy, changing what can be seen and what remains hidden (Peterson et al., 2001).

And beneath all of it is food.

Cownose rays move through the shallows, sweeping across the bottom and disrupting what lies beneath them, crushing clams, oysters, and other shelled invertebrates with broad, flattened tooth plates (Collins et al., 2007; Fisher, 2010).

Atlantic stingrays hold low against the bottom, burying into the sand as they feed and working within the sediment itself—not moving across it—uncovering and drawing in small invertebrates hidden below (Snelson et al., 1988; Schwartz & Dahlberg, 1978).

Atlantic stingrays hold close to the bottom, often blending in until something shifts and gives them away. | Image credit: Andy Murch

Where prey is accessible, rays follow.

Where prey is concentrated in shallow, warming water, rays do not just pass through—they stay, turn, feed, and linger.

And in doing so, they cross into the same narrow band of space where people enter the water (Bangley et al., 2018).

They are not simply “here more.”

They are here in ways—and in places—that make them visible.

What Happens When They Feed

When a ray feeds, the bottom does not remain the same.

A cownose ray moving across a flat is not just searching—it is actively restructuring the surface beneath it. As it passes, the bottom is turned over behind it, patches of sand and mud disturbed where clams and other buried life have just been uncovered and crushed (Peterson et al., 2001; Smith & Merriner, 1985).

Feeding pits left behind by rays. Easy to mistake for crab holes at first—until you start to recognize the pattern and what’s actually shaping the bottom. | Image credit: Giaroli et al., 2024

Atlantic stingrays leave a different kind of trace. Where they settle, the surface shifts more subtly—small depressions, softened patches, places where the sediment has been worked rather than overturned, as buried invertebrates are uncovered and drawn in (Snelson et al., 1988; Schwartz & Dahlberg, 1978).

This is bioturbation—the bottom being reworked by the animals moving through it and within it (Thrush & Dayton, 2002).

As they feed, the bottom lifts into the water—fine particles rising and hanging there, turning clear water slightly cloudy (Thrush & Dayton, 2002).

The water does not stay still—the bottom here is constantly shifting, the way much of this coastline does, even when it appears unchanged.

And neither does the system.

Oysters and clams quietly filter the water as they feed, and when their numbers shift—even in small areas—the water and everything moving through it begins to change with them (Newell, 2004; zu Ermgassen et al., 2013).

In places where rays have been feeding, those filtering communities can be reduced or redistributed (Peterson et al., 2001).

Not removed entirely—but changed.

And that change does not stay in one place.

It moves outward, carried in the way the water looks, the way it settles, and what it can hold.

Layers of the Food Web

Rays do not sit at the top of the system, and they are not at the bottom of it.

As mesopredators, they feed on what is buried in the sediment, but they are also available to what moves through the water above. That position—between—links parts of the system that do not often meet directly (Myers et al., 2007; Heithaus et al., 2008).

What they do in that space matters.

As cownose rays move through andAtlantic stingrays work within the bottom, they are not just feeding—they are shaping what persists there. Clams, oysters, and other invertebrates do not simply accumulate unchecked. Their numbers are reduced, redistributed, and in some places kept from becoming dominant (Peterson et al., 2001).

Movement like this doesn’t stay in one place for long.

That pressure shapes the bottom itself.

Bivalves filter the water. Invertebrates stabilize sediment. When their abundance shifts, the system responds—sometimes toward clearer water, sometimes toward more suspended material, depending on what remains and where (Newell, 2004; zu Ermgassen et al., 2013).

Rays do not create those conditions alone—but they influence which direction the system moves.

At the same time, they carry that energy upward.

Juvenile sharks moving through these shallow waters encounter not just prey, but a system already in motion—areas where the bottom has been disturbed, where feeding has recently occurred, where something has been uncovered or displaced (Bangley et al., 2018).

And in some cases, the rays themselves become part of that exchange.

This is what it means to sit in the middle.

Not just connecting layers—but regulating how energy and movement pass between them.

If that middle shifts, the balance does not disappear.

It changes direction.

Why It Feels Sudden

There is a moment, standing in shallow water, when the bottom stops feeling like something you can trust.

What looked like sand shifts.
What felt still is no longer still.

Sometimes you notice it in time—a shape lifting away, a shadow moving just beneath the surface. A plume of fine sediment rising to the surface under a paddleboard with a trail following it.

The moment when the bottom stops looking empty. | Image credit: iStock

Sometimes you don’t.

A step comes down where something is already settled.
Hidden in the sand.
Working within it.

The reaction is immediate.
Surprise first. Then pain. Then the realization of what was there all along.

It is easy, in that moment, to think something unexpected has happened—the same kind of sudden awareness that comes when something just beneath the surface reveals itself.

But what you are stepping into is not a single event.

It is a convergence.

Water temperatures have risen, bringing rays into the shallows as they feed and move through these systems (Smith & Merriner, 1987; Schwartz & Dahlberg, 1978).

Tides narrow the space, concentrating movement into a thinner band of water.

The bottom has already been worked—turned by cownose rays moving through, disturbed by Atlantic stingrays holding within it.

And at the same time, people have returned to the water.

For a brief window, all of it overlaps.

Not more.
But more visible.

It feels sudden because you are standing at the point where all of these things meet.

And for a moment, the system lets you see it.

References

Bangley, C. W., Paramore, L., Dedman, S., & Rulifson, R. A. (2018). Delineation and mapping of coastal shark habitat within a shallow lagoonal Estuary. PLOS ONE, 13(4), e0195221. https://doi.org/10.1371/journal.pone.0195221

Giaroli, M. L., Byrne, I., Gilby, B. L., Taylor, M., Chargulaf, C. A., & Tibbetts, I. R. (2024). The distribution and significance of stingray feeding pits in Quandamooka (Moreton Bay), Australia. Marine and Freshwater Research, 75(18). https://doi.org/10.1071/mf23247

Heithaus, M. R., Frid, A., Wirsing, A. J., & Worm, B. (2008). Predicting ecological consequences of marine top predator declines. Trends in Ecology & Evolution, 23(4), 202-210. https://doi.org/10.1016/j.tree.2008.01.003

Kolmann, M. A., Huber, D. R., Motta, P. J., & Grubbs, R. D. (2015). Feeding biomechanics of the cownose ray, Rhinoptera bonasus, over ontogeny. Journal of Anatomy, 227(3), 341-351. https://onlinelibrary.wiley.com/doi/full/10.1111/joa.12342

Myers, R. A., Baum, J. K., Shepherd, T. D., Powers, S. P., & Peterson, C. H. (2007). Cascading effects of the loss of APEX predatory sharks from a coastal ocean. Science, 315(5820), 1846-1850. https://doi.org/10.1126/science.1138657

Newell, R. I. (2004). Ecosystem influences of natural and cultivated populations of suspension-feeding bivalve molluscs: A review. 23(1), 51–61. Journal of Shellfish Research, 23(1), 51-61. https://go.gale.com/ps/i.do?id=GALE%7CA118543914

Peterson, C. H., Fodrie, J. F., Summerson, H. C., & Powers, S. P. (2001). Site-specific and density-dependent extinction of prey by schooling rays: generation of a population sink in top-quality habitat for bay scallops. Oecologia, 129, 349-356. https://link.springer.com/article/10.1007/s004420100742

Schwartz, F. J., & Dahlberg, M. D. (1978). Biology and ecology of the Atlantic Stingray, Dasyatis Sabina (Pisces: Dasyatidae) in North Carolina and Georgia. Northeast Gulf Science, 2(1). https://doi.org/10.18785/negs.0201.01

Smith, J. W., & Merriner, J. V. (1985). Food habits and feeding behavior of the Cownose ray, Rhinoptera bonasus, in lower Chesapeake Bay. Estuaries, 8(3), 305. https://doi.org/10.2307/1351491

Smith, J. W., & Merriner, J. V. (1987). Age and growth, movements and distribution of the Cownose ray, Rhinoptera bonasus, in Chesapeake Bay. Estuaries, 10(2), 153. https://doi.org/10.2307/1352180

Snelson, F. F., Williams-Hooper, S. E., & Schmid, T. H. (1988). Reproduction and ecology of the Atlantic Stingray, Dasyatis Sabina, in Florida coastal lagoons. Copeia, 1988(3), 729. https://doi.org/10.2307/1445395

Thrush, S. F., & Dayton, P. K. (2002). Disturbance to marine benthic habitats by trawling and dredging: Implications for marine biodiversity. Annual Review of Ecology and Systematics, 33(1), 449-473. https://doi.org/10.1146/annurev.ecolsys.33.010802.150515

Zu Ermgassen, P. S., Spalding, M. D., Blake, B., Coen, L. D., Dumbauld, B., Geiger, S., Grabowski, J. H., Grizzle, R., Luckenbach, M., McGraw, K., Rodney, W., Ruesink, J. L., Powers, S. P., & Brumbaugh, R. (2012). Historical ecology with real numbers: Past and present extent and biomass of an imperilled estuarine habitat. Proceedings of the Royal Society B: Biological Sciences, 279(1742), 3393-3400. https://doi.org/10.1098/rspb.2012.0313

April 11, 2026
Alligators in North Carolina Coastal Waters: What Their Presence Really Means

The Surface That Holds

There are mornings along the edges of the water in Onslow County when the surface looks still enough to trust.

The marsh grass has not yet reached its summer height. What stands there leaves more water exposed between the stems, and without sustained wind, the surface holds its shape. You can see farther into it now than you will in a few weeks, before suspended sediment and constant movement return it to opacity. The water carries less of the season, and because of that, more of what moves beneath it becomes visible—if you are willing to wait long enough to see the difference between movement and reflection.

This is when people begin to notice them again.

Not all at once. Not everywhere. Just a change that does not follow wind or tide. A line that holds where the rest of the surface releases. Something that holds its position in a system that is always adjusting.

An alligator does not arrive in that moment.

It becomes visible.

Alligator emerging from the mud. | Photo credit: Gilbert Grant, iNaturalist

Seasonal Absence Is Not Absence

Through winter, they remain within these same creeks, marsh edges, and quieter channels. What changes is not location, but how they occupy it. As temperatures fall, activity narrows. Movement slows, and the need for it slows with it. Energy is conserved, not spent. And the surface carries fewer signs of what lies beneath it. Individuals hold in deeper water or along softer margins where mud retains heat longer than the surrounding water column, remaining within conditions that allow them to persist without constant movement (Nifong et al., 2014; Rosenblatt & Heithaus, 2011).

The same stretch of water that in spring will hold a visible form can pass through winter without interruption, its stillness mistaken for absence.

But the system does not empty.

It compresses.

The System Wakes in Layers

By early spring, that compression begins to release—not all at once, but in layers that build on each other before they are recognized. Shallow water warms first, taking in solar heat more quickly than deeper channels. Along these edges, fish begin to hold longer. Movements that in winter passed through quickly begin to extend into areas that had remained quiet. Invertebrates return to the sediment surface, and the water column begins to carry more suspended life, even before it becomes visible as turbidity.

Birds respond to this before most other changes are noticed. Their movements tighten. Landings become more frequent, departures more abrupt. What they are tracking is not random. It is the redistribution of energy into places where it can be accessed.

The alligator moves within that shift.

Not as a trigger. Not as something layered on top. But as part of a system reorganizing itself across temperature, light, and movement at the same time.

Great blue heron and alligator are part of an interconnected system. | Photo credit: Audubon North Carolina

Reading What It Is Responding To

When one becomes visible along the edge of a creek or marsh, it is easy to reduce that moment to temperature alone. Warmer water allows for more activity.

But what draws it into that position is more specific than warmth.

It is the arrangement of prey.

Along the margins where water meets land, movement compresses. Fish traveling with the tide encounter shallow gradients that limit how long they can remain. Small mammals moving between marsh and upland must cross exposed edges. Birds landing to feed do so in places where depth and access align for only short intervals.

These are not isolated events. They are recurring patterns shaped by tidal cycles, substrate, and seasonal change.

The alligator positions itself within those patterns.

Its diet reflects that flexibility, spanning invertebrates, fish, birds, reptiles, and mammals depending on size and availability (Nifong, 2016). But the diet alone does not explain its placement. What matters is where energy becomes concentrated, even briefly.

That concentration is not constant. It forms and dissolves with tide, with light, with movement.

And the predator tracks that.

And what appears as a single movement—a fish turning, a bird lifting, something crossing the edge of the marsh—is part of a larger structure that holds only briefly before dissolving again.

The alligator does not respond to the individual movement.

It responds to the pattern that produces it.

Where Freshwater Meets Salt

These are not just places where water mixes.

They are places where movement is forced—and where that movement becomes available to something waiting at the top of it.

There are places along this coastline where those changes concentrate.

At the mouths of creeks, along the edges of the Intracoastal Waterway, and near the shifting bars of New River Inlet, the water does not settle into a single condition. Freshwater moves outward with tide and rainfall, meeting saltwater pressing back in with tidal exchange. The result is not a fixed boundary, but a gradient that shifts continuously—sometimes visible as a faint line, sometimes only detectable in how the surface moves differently from one side to the other.

This is where alligators are most often encountered—because this is where the system compresses into something they can use.

They are not marine animals. They do not possess the specialized salt glands that allow for extended life in high salinity environments. Over time, saltwater carries a physiological cost, requiring a return to freshwater to restore balance (Rosenblatt & Heithaus, 2011; Fujisaki et al., 2014).

But that limitation does not exclude them.

It defines how they move through them.

In these mixing zones, salinity is not constant. It rises and falls with tide, with rainfall, with wind direction. A location that carries higher salinity at one stage may shift toward fresher conditions hours later. What appears to be a boundary is, in practice, a moving field.

Within that field, movement compresses.

Fish traveling with the tide are funneled into narrower pathways. Shallow gradients limit how long they can remain in deeper water. Schools tighten. Individuals encounter edges that restrict escape. The system concentrates energy into space.

The predator does not need to range widely in these conditions.

It needs to hold where movement is forced.

And so it does.

An alligator near the tall grass near Marine Corps Air Station New River | Photo credit: Martin Egnash

At the Edge of the Open Water

There are moments when that pattern extends beyond the mixing zones, into places that appear, at first, outside of where an alligator belongs.

Along the shoreline, in the breaking waves where the ocean meets sand, one will sometimes appear—rising and falling with the swell, holding position just beyond where the water turns over onto the beach. It looks misplaced, as though it has moved beyond the system that defines it.

It has not.

The surf zone is one of the most compressed environments along the coast. Waves reduce depth, disrupt orientation, and concentrate movement into a narrow band where escape is limited. Fish pushed into breaking water lose some ability to maintain direction. Schools fragment. Individuals become briefly exposed in ways that do not occur in deeper, more stable water.

For a predator capable of stillness followed by short bursts of movement, that compression creates opportunity.

But the cost is higher.

Salinity is elevated. The water is in constant motion. There is no stable refuge within immediate reach. Time in this environment cannot be extended indefinitely.

And so it does not.

Movements into higher salinity water tend to be brief—extensions outward, followed by a return to freshwater or lower salinity conditions where balance can be restored (Nifong et al., 2014).

What appears as an anomaly is part of a larger pattern.

The predator crosses the boundary not to remain, but to use it, moving where the system briefly offers more than it costs.

The same forces that shape the marsh edge—compression, constraint, and brief exposure—are recreated here, just for a moment, in a different place.

An alligator rests at the ocean’s edge in North Topsail. | Photo credit: Fox8 Digital Desk

What Its Presence Changes

Most of what that presence changes cannot be seen when it is observed.

Long before any direct interaction occurs, it is already altering how other organisms use space.

Fish moving along the edge do not simply pass through. They adjust their depth, their speed, the amount of time they remain exposed. Birds land with shorter intervals between contact and departure. Mammals approaching the water shift their paths or their timing. These changes are not dramatic in isolation. But they are continuous.

Over time, they accumulate into structure—the kind that determines who feeds, where they feed, and how long they remain.

The influence of a predator at this level extends beyond what it consumes. It shapes behavior across multiple species, redistributing where and how energy moves through the system. The possibility of predation—present even when not observed—alters interactions in ways that regulate access to habitat and resources (Heithaus et al., 2008; Ripple et al., 2014; Estes et al., 2011).

What holds the system in place is not removal alone.

It is pressure.

What is being shaped is not just movement, but access—and access is what determines how energy moves through the system.

More Than Predation

The influence of the alligator does not end with what it hunts, but extends beyond those interactions.

As it moves through shallow systems, it disturbs sediment, creating depressions and pathways that alter how water is retained and how nutrients are redistributed. These small changes in physical structure create conditions that other species use—temporary refuges, feeding areas, and zones where organic material accumulates (Eversole et al., 2018; Subalusky et al., 2009).

In wetland systems, these disturbances have been linked to broader effects, including nutrient cycling and carbon storage, where the presence of large predators contributes to the retention of organic material within the system rather than its export (Murray et al., 2025; Atwood et al., 2015).

These processes do not occur in isolation.

They intersect with the same patterns of movement, feeding, and behavior that define the system at larger scales.

Seeing the Surface, Reading the System

When one becomes visible along the surface, it is easy to treat the moment as singular.

A sighting. An encounter. Something separate from everything around it.

But that form at the surface is supported by layers extending beyond what can be seen.

It reflects water temperatures crossing into ranges that support sustained activity. It reflects prey moving into positions where access becomes possible. It reflects a system where behavior is still shaped by the presence of something at the top.

The alligator is not an interruption to that system.

It is an expression of it.

What Becomes Visible

Seeing one does not indicate that something has entered the water.

It indicates that enough beneath the surface is functioning to hold it.

Not in a static sense. Not as balance in the way it is often described. But as a set of interactions that remain connected—movement, response, pressure—each shaping the others even when they are not directly observed.

What becomes visible at the surface is only a fraction of that structure.

But it is enough to know that the rest is still in place.

An alligator in Onslow County sits at the edge of the saltmarsh. |Photo credit: Gilbert Grant, iNaturalist

When That Pressure Is Reduced

If that pressure is reduced, the system does not leave an obvious gap.

It shifts.

Movements that were once constrained begin to extend. Species that passed quickly through exposed areas begin to remain longer. Edges that functioned as transition zones become used differently—not because the physical environment has changed, but because the conditions that shaped behavior within it have relaxed.

Mid-level predators expand their activity under these conditions, increasing their access to prey and space when not constrained from above (Nifong et al., 2013).

The change is subtle.

It appears in how long something stays. In how often it returns. In where it lingers. In how quietly the structure of behavior begins to loosen.

The food web and trophic cascade of the American alligator in the Florida Everglades.

A System Written Into Temperature

There is another layer to this that does not show itself at the surface.

The structure of that presence is set years earlier, in a place that can be overlooked when standing at the water’s edge. Along the margins of marsh and wetland, slightly above the reach of regular water movement, nests are built from vegetation and sediment, forming mounds that hold heat as they decompose.

Within those mounds, temperature determines something that will not be visible for much later.

Sex is not fixed at fertilization. It emerges during incubation, shaped by the thermal conditions held within the nest. A difference of only a few degrees is enough to shift the outcome, producing more males or more females depending on where within that range the nest remains (Lang & Andrews, 1994; Janzen, 1994).

Under variable conditions—differences in shading, rainfall, timing, and placement—those outcomes are distributed across the landscape. Some nests produce more females, others more males. That variability holds the population in a form that can sustain itself over time.

When conditions become more consistent, that variation narrows.

Warmer nights hold heat longer within the nest. Seasonal transitions extend. The range of outcomes compresses. What was once distributed begins to align.

And that alignment carries forward into the structure of the population—into how individuals occupy space, into how pressure is applied across the system, into what will eventually be visible at the surface.

Alligator eggs hatch after 65 days of incubation in the fall. The babies will chirp to alert their mom, who then digs out the nest while the babies use their egg tooth to hatch from their eggs. Their mom will then safely carry them to the water.

Where the Next Generation Is Set

The placement of those nests depends on something even more constrained.

A narrow band of land that remains above water just long enough to hold them.

That band is not fixed.

It shifts with tide, with rainfall, with the gradual reworking of shoreline that occurs across seasons and years. With rising sea levels, water reaches farther into areas that once remained above it. Flooding becomes more frequent, not always through singular events, but through repeated intrusions that saturate and destabilize what had previously held (Joanen & McNease, 1989; Sweet et al., 2022).

Human alteration compresses this space further.

Hardened shorelines, dredging, and development reduce the gradual transition between land and water. Where there was once a slope capable of holding multiple elevations, there becomes a defined edge. That edge does not provide the same range of conditions required for successful nesting.

The number of suitable sites decreases.

More importantly, the variability between them narrows.

And with that, the system loses one of the mechanisms that allowed it to absorb change.

Alligator on her nest that can hold up to 60 eggs. | Photo credit: National Park Service (NPS)

What Its Presence Means

When an alligator becomes visible along the surface, it reflects conditions that have aligned across multiple layers.

Temperature has reached a range that supports activity. Prey has moved into positions where access becomes possible. Behavioral pressure remains in place across the system. Reproduction has held across enough years, in enough suitable places, to sustain what is now present.

What is seen at the surface is not separate from them.

It is supported by them.

Seeing one does not signal that something has entered the water.

It signals that enough of what lies beneath it—movement, pressure, response, and continuity—remains intact.

And that—even when most of it is not visible—the system is still holding together.

And that is what becomes visible—just long enough to be seen, before the system closes back over it again.

The system does not end at the water’s edge.

Epilogue: Chicken Nugget

We came across him along the New River, near the courthouse in Jacksonville.

We were there to clear what had been left behind—fishing line caught along the walkways, hooks, and the overflow from a trash can that had spilled out onto the edge. Fast food containers, grocery store chicken trays, scattered along the bank. The signs were clear enough. People had been there for a while—crabbing, fishing, eating, leaving what remained.

He was directly below us.

Small enough to miss at first. Still enough to blend into the water until you stopped looking for movement and started noticing what held its position.

A juvenile alligator, watching.

He stayed there while we worked, then slipped beneath the surface and crossed the small bay. On the opposite side, someone tossed a piece of food into the water. He surfaced almost immediately, took it, and remained.

Waiting.

I came back later and stayed longer.

The pattern repeated. He would disappear until footsteps approached, then return to the same place along the edge. Holding position. Watching. Waiting for something to fall.

No fishermen or crabbers passed through while I was there, but the behavior was consistent with what happens when food becomes predictable. Bait, catch, scraps—anything that can be taken without the cost of searching or pursuing.

Energy, without effort.

It is easy to see something like that and respond to what it looks like in that moment. A small animal. Still. Attentive. Something that feels close enough to interact with.

But what is being shaped there is not just a single interaction.

It is behavior.

A shift away from the conditions that formed it—toward something more efficient, more immediate, and less stable over time. The system that once required movement, patience, and response begins to narrow into expectation.

And expectation changes how an animal uses space.

What happens when that animal is no longer small is not a separate question.

It is the continuation of the same pattern.

Alligators do not forget where food has been easy to obtain. They return to it. They hold in those places. They begin to associate presence—human presence—with opportunity.

What begins as something that feels harmless becomes something that alters how the system functions around it.

Not just for the animal, but for everything that responds to it.

There are instincts at work here that were shaped long before any walkway, any dock, any place where food might be dropped from above. Those instincts are not just about survival in isolation. They are part of how pressure is applied, how movement is shaped, how the system holds.

When those instincts are replaced with something easier, the effect does not remain contained.

It carries outward.

He stayed there while I watched. Returning to the same place. Holding the same position. Waiting for something to fall.

There is a kind of kindness in wanting to give something to an animal like that.

But there is another kind in leaving it as it is.

Not interrupting the conditions that shape it. Not narrowing what it has learned to expect. Not replacing a system built on movement and response with one built on waiting.

Let it remember the water as it is.

And you, only as something that passed through it.

We affectionately named this juvenile alligator in the New River in Jacksonville, NC “Chicken Nugget” for all of the chicken nugget boxes left behind on the walkway from an overflowing trash can. | Photo credit: A. Mitchell

References

Atwood, T. B., Connolly, R. M., Ritchie, E. G., Lovelock, C. E., Heithaus, M. R., Hays, G. C., Fourqurean, J. W., & Macreadie, P. I. (2015). Predators help protect carbon stocks in blue carbon ecosystems. Nature Climate Change, 5(12), 1038-1045. https://doi.org/10.1038/nclimate2763

Estes, J. A., Terbough, J., Brashares, J. S., Power, M. E., Berger, J., Bond, W. J., Carpenter, S. R., Essington, T. E., Holt, R. D., & Wardle, D. A. (2011). Trophic Downgrading of Planet Earth. Science, 333(604), 301-306. https://www.science.org/doi/abs/10.1126/science.1205106

Fujisaki, I., Hart, K. M., Mazzotti, F. J., Cherkiss, M. S., Sartain, A. R., Jeffery, B. M., Beauchamp, J. S., & Denton, M. (2014). Home range and movements of American alligators (Alligator mississippiensis) in an Estuary habitat. Animal Biotelemetry, 2(1), 8. https://doi.org/10.1186/2050-3385-2-8

Heithaus, M. R., Frid, A., Wirsing, A. J., & Worm, B. (2008). Predicting ecological consequences of marine top predator declines. Trends in Ecology & Evolution, 23(4), 202-210. https://doi.org/10.1016/j.tree.2008.01.003

Janzen, F. J. (1994). Climate change and temperature-dependent sex determination in reptiles. PNAS, 91(16), 7487-7490. https://doi.org/10.1073/pnas.91.16.7487

Joanen, T., & McNease, L. L. (1989). Ecology and physiology of nesting and early development of the American alligator. American Zoologist, 29(3), 987-998. https://doi.org/10.1093/icb/29.3.987

Lang, J. W., & Andrews, H. V. (1994). Temperature‐dependent sex determination in crocodilians. Journal of Experimental Zoology, 270(1), 28-44. https://doi.org/10.1002/jez.1402700105

Nifong, J. C. (2016). Living on the edge: Trophic ecology of alligator mississippiensis (American alligator) with access to a shallow estuarine impoundment. Bulletin of the Florida Museum of Natural History, 54(2), 13-49. https://doi.org/10.58782/flmnh.xkdw7119

Nifong, J. C., Nifong, R. L., Silliman, B. R., Lowers, R. H., Guillette, L. J., Ferguson, J. M., Welsh, M., Abernathy, K., & Marshall, G. (2014). Animal-borne imaging reveals novel insights into the foraging behaviors and Diel activity of a large-bodied APEX predator, the American alligator (Alligator mississippiensis). PLoS ONE, 9(1), e83953. https://doi.org/10.1371/journal.pone.0083953

Nifong, J. C., & Silliman, B. R. (2013). Impacts of a large-bodied, APEX predator (Alligator mississippiensis Daudin 1801) on salt marsh food webs. Journal of Experimental Marine Biology and Ecology, 440, 185-191. https://doi.org/10.1016/j.jembe.2013.01.002

Ripple, W. J., Estes, J. A., Beschta, R. L., Wilmers, C. C., Ritchie, E. G., Hebblewhite, M., Berger, J., Elmhagen, B., Letnic, M., Nelson, M. P., Schmitz, O. J., Smith, D. W., Wallach, A. D., & Wirsing, A. J. (2014). Status and ecological effects of the world’s largest carnivores. Science, 343(6167). https://doi.org/10.1126/science.1241484

Rosenblatt, A. E., & Heithaus, M. R. (2011). Does variation in movement tactics and trophic interactions among American alligators create habitat linkages? Journal of Animal Ecology, 80(4), 786-798. https://doi.org/10.1111/j.1365-2656.2011.01830.x

Sweet, W. V., Hamlington, B. D., Kopp, R. E., Weaver, C. P., Barnard, P. L., Bekaert, D., Brooks, W., Craghan, M., Dusek, G., Frederickse, T., Garner, G., Genz, A. S., Krasting, J. P., Larour, E., Marcy, D., Marra, J. J., Obeysekera, J., Osler, M., Pendleton, M., … Zuzak, C. (2022). Global and regional sea level rise scenarios for the United States: Updated mean projections and extreme water level probabilities along U.S. coastlines (Technical Report NOS 01). National Oceanic and Atmospheric Administration, National Ocean Service. https://earth.gov/sealevel/us/internal_resources/756/noaa-nos-techrpt01-global-regional-SLR-scenarios-US.pdf

April 3, 2026
Fish That Break the Rules: Unusual Anatomy Along the Edge of Onslow County

Where Expectations Begin to Slip

There are stretches of shoreline in Onslow County where the water looks simple.

A low wind flattens the surface just beyond the breakers. The sand underfoot is firm, packed by a falling tide. Small schools of baitfish turn in unison at the edge of visibility, their bodies catching light and then disappearing again as if nothing had moved at all.

From here, fish seem predictable. They swim. They are streamlined. They slip through water in ways that feel consistent, almost mechanical.

A school of juvenile fish swim in the Surf City sound. | Photo credit: A. Mitchell

But that impression doesn’t hold for long.

A few steps into the surf, something crunches beneath your heel—a shell, or what remains of one.. Offshore, a shape drifts that doesn’t seem built for movement at all. In the shallows, something settles to the bottom and then, impossibly, walks.

The closer you look, the more the pattern breaks apart. Along this stretch of coast—from the swash zone to the deeper water of Onslow Bay—some fish are not built like fish are “supposed” to be.

And once you notice them, the rules start to feel less like rules at all.

Teeth built for stone: Sheepshead

The rule broken: fish are supposed to have simple teeth

On calm mornings near New River Inlet, when the tide is just beginning to push in, the water around pilings and rock edges clears enough to see movement below the surface. Dark vertical bands appear and disappear as fish turn sideways to feed, their bodies angled tightly against pilings and rock.

If you get a close look—often only when one is caught—you notice the teeth.

Flat. Squared. Set in rows that look more like something borrowed from a mammal than a fish.

Sheepshead fish have mammal-like teeth used for scraping and crushing hard shells and barnacles. | Photo credit: Jeannette’s PIer

The sheepshead (Archosargus probatocephalus) feeds primarily on hard-shelled organisms—barnacles, oysters, mussels, and crabs attached to pilings, jetties, and natural hardbottom (Sedberry, 1987). These prey items are abundant in estuarine and nearshore environments where salinity fluctuates and structure concentrates life.

Instead of pointed, uniform teeth, sheepshead possess incisiform front teeth for scraping and strong molariform teeth set further back for crushing (Deang et al., 2018; Hernandez & Motta, 1997). Bite force measurements and stomach content analyses show they are capable of breaking calcareous shells that would resist most coastal fishes (Hernandez & Motta, 1997).

They are most active in waters typically ranging from 60–80°F (15–27°C), often within just a few feet of structure in depths from less than a meter to roughly 10 meters (Sedberry, 1987).

Fish are often imagined as generalized swimmers feeding on soft prey. But along the Onslow coast, hard surfaces—oyster beds, submerged debris, pilings—create entire microhabitats built on calcium carbonate (Grabowski & Peterson, 2007).

Sheepshead are not exceptions to the system; they are shaped by it. Their teeth are a direct response to a landscape where food remains locked inside a shell.

Most fish don’t have teeth like this because most environments don’t require it. Here, where geology and biology meet in layers of shell and structure, the rule changes.

The fish that walks: Bluespotted and Northern searobin

The rule broken: fish move by swimming

On a falling tide along the edges of Topsail Island, the water pulls thin over the sand flats. What remains is a shifting surface—ripples, shadows, and the occasional sudden burst of motion.

Then something moves without swimming.

It doesn’t dart or glide. It advances in short, deliberate steps, stopping and starting again, as if testing the ground before each movement.

For a moment, it looks wrong—like something moving through air instead of water.

The bluespotted searobin (Prionotus roseus) and the Northern searobin (Prionotus carolinus) do not rely on their fins for propulsion in the way most fish do. Instead, three detached rays from each pectoral fin extend downward, contacting the bottom and supporting the body as it moves. These rays function both as supports and as sensory structures, probing the sediment and detecting chemical cues—effectively allowing the fish to “taste” the seafloor as it moves (Bardach & Case, 1965).

Across these shallow flats, often just inches to a few feet deep, the water warms into the upper 60s and 70s as the tide recedes. Prey is rarely exposed. Worms, small crustaceans, and buried mollusks remain hidden beneath the surface. Vision alone is not enough here. The searobin moves slowly, stepping and pausing, tracing the bottom until something beneath the sand gives itself away.

Movement in water is usually about efficiency—minimizing drag, maximizing speed.

But the seafloor is a different environment entirely.

Here, visibility narrows, prey disappears beneath the surface, and swimming can carry you past what you’re trying to find. Walking—slow, deliberate, sensory-driven—becomes the better strategy.

Most fish don’t have “legs” because most fish don’t live where walking is more useful than swimming. Along the shallow bottoms of Onslow waters, this rule no longer applies.

The fish that swells: Northern puffer

The rule broken: fish don’t change shape

In late summer, when the water just beyond the breakers settles into the upper 70s, small shapes begin to move just offshore—slow, almost indifferent to the motion around them.

One drifts closer than expected, rounded in a way that doesn’t quite match the others. It hovers, turning slightly, its movement controlled but unhurried.

Then, without warning, the body changes.

It expands outward, the outline swelling until the fish no longer resembles something built to move through water at all.

The Northern puffer (Sphoeroides maculatus) does this by rapidly drawing water into a highly elastic stomach, a process that allows the body to expand far beyond its resting shape (Brainerd, 1994). Without rigid skeletal constraints like ribs or pelvic bones, that expansion can happen quickly, transforming the fish into something difficult for a predator to grasp or swallow.

A Northern pufferfish skeleton is made up of spiny modified scales (not bones) that expand like a balloon when threatended. | Photo credit: The Fossil Forum

In these nearshore waters—where predators move quickly and encounters happen at close range—there is little time to outrun what’s coming. Most fish rely on speed to escape. This one changes shape instead.

Speed isn’t part of the solution here.

The fish that locks itself in place: Gray triggerfish

The rule broken: fish don’t anchor themselves

Farther offshore, where the bottom begins to break into scattered hardbottom and reef patches, movement slows in a different way.

Shapes hold just above the structure, adjusting position in small increments, never straying far from the surface below them.

When disturbed, they don’t flee into open water.

They turn downward.

The gray triggerfish (Balistes capriscus) moves into crevices and tight spaces within the structure, where a set of dorsal spines can be raised and locked into place. The first spine lifts, and a smaller second spine holds it there—an arrangement that gives the fish its name and allows it to anchor itself firmly in place (Tyler, 1980; Lobel, 1980).

Its body is built for this kind of movement: deep and laterally compressed, with tough, abrasive skin and strong incisor-like teeth capable of breaking into hard-shelled prey (Tyler, 1980; Lobel, 1980). These are not features meant for speed. They are features meant for contact—pressing into structure, resisting removal, holding position when movement would fail.

In waters often 50–120 feet deep off Onslow County, where reefs and wrecks break the seafloor into pockets and edges, escape doesn’t always mean distance (Bellwood et al., 2004).

Sometimes it means holding ground.

Most fish survive by staying in motion.

This one survives by becoming fixed in place, turning the structure around it into part of its defense.

Light written into skin: Atlantic midshipman

The rule broken: fish don’t carry light in their skin

On warm summer nights near quiet stretches of marsh and inlet edges, the water sometimes carries sound before anything else. A low, continuous hum. It’s easy to miss unless you stop moving.

The Atlantic midshipman (Porichthys plectrodon) produces that sound through specialized sonic muscles vibrating against the swim bladder, creating a sustained hum that can carry through shallow coastal water (Sisneros, 2009; Bass & McKibben, 2003).

If you listen carefully during a quiet evening, the sound of a male midshipman trying to court a female might be heard. | Audio credit: SanctoSound – Integrated Ocean Observing System (IOOS)

Along the sides of the body and across the head are rows of small organs—photophores—set into the skin, giving the fish its name and marking it as something unusual among coastal species found in these waters (Schwartz, 2013). When seen out of the water, those rows catch the light in a very particular way—small, round points that flash gold in direct sunlight, spaced with a regularity that makes them look almost set into the surface, like buttons fixed into the skin.

The Atlantic midshipman has photophores that dazzle when out of the water, and used in seeing in darkened burrows and structures in limited light. | Photo credit: North American Native Fishes Association

Midshipman inhabit shallow coastal environments, often in burrows or beneath structure along muddy or sandy bottoms, typically in depths less than 20 meters.

Light in fish is often associated with deeper water, where darkness is constant and illumination becomes necessary (Haddock et al., 2010). But along the Onslow coast, those conditions can exist in smaller, shifting pockets. Light narrows quickly with depth, suspended sediment moves with the tide, and visibility can collapse even in water shallow enough to stand in.

Not all fish in these waters experience the bottom the same way. A flounder rests exposed on the sand, relying on camouflage and stillness. The midshipman, by contrast, spends much of its time within burrows, beneath structure, or pressed close to the substrate, where light is already limited and often disappears entirely.

In those spaces, the rules of visibility begin to resemble something closer to deeper water, even though the surface is only a few feet above.

The presence of photophores here does not follow the pattern most people expect.

Not all light comes from above.

The deep blade: Long-snouted lancetfish

The rule broken: fish are dense, muscular swimmers

From the beach, the horizon feels like a boundary—beyond the sandbars, beyond the nearshore currents—about two miles out, where the surface lifts just enough to hide what comes after. But beyond that line, the water doesn’t simply continue. It changes.

Depth increases quickly. Layers begin to form. Light fades long before the bottom is reached.

And in those deeper waters off Onslow Bay, some fish are not built to chase anything at all.

The long-nosed lancetfish lives in the middle depths of the ocean where body density is less desirable for a drifting fish. | Photo credit: ML – some rights reserved (CC BY-NC)

The long-snouted lancetfish (Alepisaurus ferox) lives in the midwater column, often hundreds of meters below the surface. Its body is long and thin, almost blade-like, with muscle reduced and tissue that is less dense than most active predators, appearing almost soft in the water (Drazen & Seibel, 2007).

It does not move with the steady, powered swimming most fish rely on. Instead, it drifts, adjusting position and taking prey as it comes within reach. Stomach analyses show a wide range of prey—fish, squid, and even other lancetfish—suggesting opportunism rather than pursuit (Kubota & Uyeno, 1970).

In these deeper layers, energy becomes harder to acquire and more costly to use.

Building and maintaining dense muscle comes at a cost. Chasing prey demands more of it (Sutton, 2013).

Here, that balance shifts.

The lancetfish represents a different solution—one that reduces the cost of movement and relies instead on encounter.

Most fish are built to swim.

This one is built to wait.

The armored survivor: Atlantic sturgeon

The rule broken: fish are supposed to have scales

In cooler months, when water temperatures drop into the 50s and 60s, large shapes move along the bottom of estuaries and nearshore waters.

They do not flash or turn sharply. They move steadily, close to the sediment.

At times, that movement reaches the surface. A back breaks through, arcing briefly before slipping under again, the shape unfamiliar enough that it doesn’t immediately read as a fish.

The Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) retains an older form—rows of bony scutes instead of the flexible scales seen in most fishes (Bemis et al., 1997). Along the underside, a protrusible mouth extends downward, drawing in prey from the bottom through suction rather than pursuit (ASSRT, 2007; Bemis et al., 1997).

An anadromous fish, they move between river systems and coastal waters, passing through estuaries and along the nearshore edge, often in depths ranging from shallow channels to over 100 feet offshore (Dunton et al., 2015; ASSRT, 2007).

This design is not new. It has persisted for tens of millions of years, carried forward through changing coastlines, shifting sea levels, and the rise of entirely different groups of fishes (Bemis et al., 1997).

Atlantic sturgeon have a bony structure that has remained relatively unchanged for millions of years. | Photo credits: mdadswell – some rights reserved (CC BY-NC) (left); Steven McGrath – some rights reserved (CC BY-NC-ND) (right)

It works because the conditions it responds to have never fully disappeared.

Along the bottom, prey remains buried. Sediment still shifts with current and tide. Feeding still depends on contact more than speed. Armor still protects a body that cannot easily maneuver out of danger.

For a long time, these fish seemed to fade from local waters. In Onslow County, encounters became rare enough to feel like absence. But populations have persisted elsewhere, and in nearby systems like the Cape Fear River, they are being observed again with increasing frequency—moving through channels, returning to spawning grounds, reappearing in places where they had not been seen in years (Dunton et al., 2015; ASSRT, 2007).

Their range has shifted before. It may be shifting again.

What remains constant is the need for connection—between river and ocean, between spawning grounds and feeding habitat.

This fish does not depend on a single place. It depends on the continuity between them.

Not all designs are meant to change. Some persist because the system they belong to still exists.

The drifting giant: Ocean sunfish

The rule broken: fish are supposed to be shaped for swimming

Occasionally, especially in warmer months when currents shift, something appears offshore that barely seems to move at all.

A large, flattened body. A fin breaking the surface. Then another, held there longer than expected.

It drifts more than it swims.

At times, it lingers there, tilted at the surface, absorbing the sun before slipping back beneath the water.

The ocean sunfish (Mola mola) is one of the heaviest bony fish, reaching weights over 1,000 kg. Its body is truncated, lacking a true caudal fin, and propulsion is achieved through synchronized movements of dorsal and anal fins (Pope et al., 2010; Watanabe et al., 2009).

After diving into colder, deeper water, sunfish often return to the surface, where this slow, drifting posture allows their body temperature to rise again (Watanabe et al., 2009). Prolonged time at the surface can leave the skin visibly altered—shifting from darker grey to lighter tones, sometimes appearing pale or pinkened under sustained exposure.

Sunfish often inhabit offshore waters but can approach nearshore areas following currents and prey, particularly gelatinous organisms like jellyfish (Cartamil & Lowe, 2004).

By most expectations, this body plan shouldn’t work.

But it does—because efficiency, here, takes a different form. It is about buoyancy, drift, and feeding on abundant, slow-moving prey.

In a system where jellyfish blooms are seasonal and sometimes dense, a fish shaped like this becomes not an anomaly, but a specialist.

Answers to a layered environment

From the shoreline, the water still looks simple.

Small waves rise and fall. Baitfish turn and vanish. The surface holds its shape.

But beneath that surface, the rules have already begun to shift.

Fish move through these waters in ways that don’t match what we expect—crushing shell, stepping across the bottom, changing shape, holding themselves in place, carrying structures that catch light, drifting where others would swim, or moving through forms shaped long before this coastline took its present shape.

What appears, from the beach, to be a single environment is something else entirely. It is layered—sand, structure, depth, temperature, light—each one asking something different of the animals that live within it.

And the fish that seem unusual are not exceptions.

They are answers.

A layered system, at New River Inlet, seen from the surface. | Photo credit: A. Mitchell

References

Atlantic Sturgeon Status Review Team. (1998). Status review of Atlantic sturgeon (Acipenser Oxyrinchus Oxyrinchus). U.S. Fish and Wildlife Service. https://books.google.com/books?id=ee5MhnuurDMC&dq=+Status+review+of+Atlantic+sturgeon+(Acipenser+oxyrinchus+oxyrinchus)

Bardach, J. E., & Case, J. (1965). Sensory capabilities of the modified fins of squirrel hake (Urophycis chuss) and Searobins (Prionotus carolinus and P. evolans). Copeia, 1965(2), 194. https://doi.org/10.2307/1440724

Bellwood, D. R., Hughes, T. P., Folke, C., & Nyström, M. (2004). Confronting the coral reef crisis. Nature, 429(6994), 827-833. https://doi.org/10.1038/nature02691

Bemis, W. E., Findeis, E. K., & Grande, L. (1997). An overview of Acipenseriformes. Developments in Environmental Biology of Fishes, 48, 25-71. https://doi.org/10.1007/0-306-46854-9_4

Blake, R. W. (2004). Fish functional design and swimming performance. Journal of Fish Biology, 65(5), 1193-1222. https://doi.org/10.1111/j.0022-1112.2004.00568.x

Brainerd, E. L. (1994). Pufferfish inflation: Functional morphology of postcranial structures in Diodon holocanthus (Tetraodontiformes). Journal of Morphology, 220(3), 243-261. https://doi.org/10.1002/jmor.1052200304

Cartamil, D., & Lowe, C. (2004). Diel movement patterns of ocean sunfish mola mola off Southern California. Marine Ecology Progress Series, 266, 245-253. https://doi.org/10.3354/meps266245

Deang, J., Persons, A., Oppedal, A., Rhee, H., Moser, R., & Horstemeyer, M. (2018). Structure, property, and function of sheepshead (Archosargus probatocephalus) teeth. Archives of Oral Biology, 89, 1-8. https://doi.org/10.1016/j.archoralbio.2018.01.013

Drazen, J. C., & Seibel, B. A. (2007). Depth‐related trends in metabolism of benthic and benthopelagic deep‐sea fishes. Limnology and Oceanography, 52(5), 2306-2316. https://doi.org/10.4319/lo.2007.52.5.2306

Dunton, K. J., Jordaan, A., Conover, D. O., McKown, K. A., Bonacci, L. A., & Frisk, M. G. (2015). Marine distribution and habitat use of Atlantic sturgeon in New York lead to fisheries interactions and Bycatch. Marine and Coastal Fisheries, 7(1), 18-32. https://doi.org/10.1080/19425120.2014.986348

Fernandez, L. P., & Motta, P. J. (1997). Trophic consequences of differential performance: Ontogeny of oral jaw‐crushing performance in the sheepshead, Archosargus probatocephalus (Teleostei, sparidae). Journal of Zoology, 243(4), 737-756. https://doi.org/10.1111/j.1469-7998.1997.tb01973.x

Grabowski, J. H., & Peterson, C. H. (2007). Restoring oyster reefs to recover ecosystem services. Theoretical Ecology Series, 4, 281-298. https://doi.org/10.1016/s1875-306x(07)80017-7

Haddock, S. H., Moline, M. A., & Case, J. F. (2010). Bioluminescence in the Sea. Annual Review of Marine Science, 2, 443-493. https://doi.org/10.1146/annurev-marine-120308-081028

McIver, E. L., Marchaterre, M. A., Rice, A. N., & Bass, A. H. (2014). Novel underwater soundscape: Acoustic repertoire of plainfin midshipman fish. Journal of Experimental Biology. https://doi.org/10.1242/jeb.102772

Mensinger, A. F., & Case, J. F. (1990). Luminescent properties of deep sea fish. Journal of Experimental Marine Biology and Ecology, 144(1), 1-15. https://doi.org/10.1016/0022-0981(90)90015-5

Petersen, J. C., & Ramsay, J. B. (2020). Walking on chains: The morphology and mechanics behind the fin ray derived limbs of sea-robins. Journal of Experimental Biology. https://doi.org/10.1242/jeb.227140

Peterson, D. L., Bain, M. B., & Haley, N. (2000). Evidence of declining recruitment of Atlantic sturgeon in the Hudson River. North American Journal of Fisheries Management, 20(1), 231-238. https://doi.org/10.1577/1548-8675(2000)020<0231:eodroa>2.0.co;2

Pope, E. C., Hays, G. C., Thys, T. M., Doyle, T. K., Sims, D. W., Queiroz, N., Hobson, V. J., Kubicek, L., & Houghton, J. D. (2010). The biology and ecology of the ocean sunfish mola mola: A review of current knowledge and future research perspectives. Reviews in Fish Biology and Fisheries, 20(4), 471-487. h ttps://doi.org/10.1007/s11160-009-9155-9

Schwartz, F. J. (2013). Atlantic midshipman, Porichthys plectrodon, in North Carolina. Journal of the North Carolina Academy of Science, 129(3), 111-114. https://doi.org/10.7572/2167-5880-129.3.111

Sedberry, G. R. (1987). Feeding habits of Sheepshead, Archosargus probatocephalus, in offshore reef habitats of the southeastern continental shelf. Northeast Gulf Science, 9(1). https://doi.org/10.18785/negs.0901.03

Sisneros, J. A. (2009). Adaptive hearing in the vocal plainfin midshipman fish: Getting in tune for the breeding season and implications for acoustic communication. Integrative Zoology, 4(1), 33-42. https://doi.org/10.1111/j.1749-4877.2008.00133.x

Snelgrove, P. V. (1999). Getting to the bottom of marine biodiversity: Sedimentary habitats. BioScience, 49(2), 129. https://doi.org/10.2307/1313538

Sutton, T. T. (2013). Vertical ecology of the pelagic ocean: Classical patterns and new perspectives. Journal of Fish Biology, 83(6), 1508-1527. https://doi.org/10.1111/jfb.12263

Tyler, J. C. (1980). Osteology, phylogeny, and higher classification of the fishes of the order plectognathi (Tetraodontiformes) (434). U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service. https://10.5962/bhl.title.63022

March 28, 2026
The Shapes the Tide Leaves Behind: Circles, Spirals, and the Mathematics of a Living Coast

Patterns in Nature Along the Coast

Each March 14, mathematicians celebrate π — the constant that links the circumference of a circle to its diameter. But Pi Day in nature appears everywhere along the coast: in boundaries that curve back upon itself, in ripples spreading across still water, in the rounded mouth of a burrow, in the arcs traced by a turning tide. Along the coast, these circles and spirals reveal patterns in nature that emerge so often they begin to feel less like abstract mathematics and more like a language written into sand and water. The shoreline is not calculating anything deliberately, yet the same relationships appear again and again as tides move sediment, organisms grow, and currents redistribute energy. What looks at first like scattered shapes — a curved creek channel, a ring of crab pellets, the fivefold symmetry of a sea star — gradually reveals itself as part of a larger pattern. The coast is full of geometry, briefly visible each time the water recedes.

The Creek Writes in Curves

A tidal creek bends around the marsh edge behind Surf City, where vegetation and sediment redirect the flow of draining water. These shifting boundaries gradually guide channels into widening curves that reappear with each tide. | Photo credit: A. Mitchell

At the creek mouths behind Topsail Island, the marsh edge redraws itself each time the tide drains away. Water retreats through narrow runnels that refuse straight lines, bending around grass hummocks and soft ridges, leaving a fan of nested arcs etched into exposed mud. The channels widen as velocity drops, sediment settling in fractions that record the rate of energy loss, so the surface becomes a temporary map of fluid negotiation.

These curves appear wherever moving water gradually redistributes energy rather than releasing it abruptly. In tidal landscapes, vegetation and sediment interact with flow in feedback loops that reshape channels over time, producing curved drainage networks whose geometry reflects both plant resistance and water momentum (Kirwan & Murray, 2007; Temmerman et al., 2007; Murray & Paola, 1994). Across river basins and tidal creeks alike, these evolving paths often approach widening spiral-like patterns as flow repeatedly adjusts to the boundaries around it (Rodriguez-Iturbe & Rinaldo, 1998).

Foam left behind by the falling tide sometimes dries into thin white filaments that trace these curves for a few quiet minutes before collapsing, a temporary record of motion fixed long enough to be read.

The creek does not preserve a single spiral. Each tide erases and redraws the same proportional tendency. The form emerges not from design but from the repeated redistribution of energy through water and sediment.

Geometry in the Grass

Dense stands of Spartina alterniflora divide space through repeating stem spacing. This structure slows water movement and traps suspended sediment, linking plant growth to the gradual elevation of the marsh surface. | Photo credit: A. Mitchell

Along the marsh margin, stems of Spartina alterniflora divide space through incremental adjustment. Leaves diverge from one another at angles that reduce overlap, distributing light capture through the canopy in repeating offsets that resemble packing patterns seen throughout plant growth.

Experiments in plant development show that when new structures arise under simple inhibitory fields, spiral-like arrangements often emerge as stable growth solutions (Douady & Couder, 1996). These patterns are widely recognized in plant morphology, where spacing between leaves or stems tends to distribute light and nutrients efficiently through the canopy (Niklas, 1997).

In salt marshes, this spacing carries ecological consequences beyond plant structure. Vegetation alters local water flow, slowing currents and promoting the deposition of suspended sediments that gradually elevate the marsh surface (Bouma et al., 2009; Fagherazzi et al., 2013; Leonard & Luther, 1995).

Mud crab burrows often appear in clusters whose spacing echoes the density of surrounding vegetation, each opening maintaining just enough distance to avoid collapse into the next.

Spiral shell growth of the periwinkle snail follows a repeating geometric expansion, allowing the animal to grow while maintaining the same overall shape. | Photo credit: A. Mitchell

Marsh periwinkles climb these stems in staggered lines that mirror the spacing of the leaves, their positions shifting with the tide yet repeatedly settling into the same angular arrangement.

Across the marsh platform, geometry quietly mediates the relationship between plant growth and landscape formation.

Spheres at the Mouth of a Burrow

A mud crab burrow at the edge of marsh vegetation marks the boundary between sand, grass, and moving water where patterns of spacing emerge. | Photo credit: A. Mitchell

Along the upper edge of the beach where grasses begin to anchor the sand, small clusters of rounded pellets often surround the entrances to crab burrows. At first glance they resemble scattered grains or fragments of dry sediment, but kneeling close reveals a more deliberate pattern.

Each pellet forms as damp sand excavated from underground tunnels passes through the crab’s mouthparts before being pushed back to the surface (Lucrezi et al., 2009). As the grains are rolled and compressed together, they settle into rounded shapes before drying in the coastal wind.

Among all possible forms loose material might take, the sphere encloses volume while minimizing surface area — a principle known as the isoperimetric property. When damp sand is compacted from many directions, the grains naturally settle toward this configuration.

The crab does not deliberately engineer spheres; the physics of granular material does the work. Similar rounding appears wherever particles compress together, from bubbles forming in foam to droplets condensing in clouds.

Around the burrow entrance, the pellets accumulate in loose arcs or clustered rings marking the repeated path of excavation. Studies of mud and ghost crab burrowing show that these excavated pellets form characteristic surface patterns around burrow openings as crabs repeatedly transport sediment from their tunnels (Lim & Diong, 2003; Chan et al., 2006).

Within hours the pellets dry and crumble back into ordinary sand. By the next tide the pattern may vanish entirely, erased by waves or shifting grains. Yet while they last, these small spheres record the intersection of animal behavior, sediment physics, and geometry.

Fivefold Bodies in the Wrack

Sand dollars show pentaradial symmetry — a five-part body plan shared by many echinoderms. The familiar white “sand dollar” is the skeleton left behind after the animal dies. Living sand dollars are gray or brown and covered in tiny moving spines that allow them to feed and move through the sand. In North Carolina, collecting live sand dollars is illegal; only empty tests found on the beach may be taken.| Image credit: Suzanne Campbell-O’Rahilly

Along the wrack line, sea stars rest without a preferred direction, their five arms distributing contact evenly across wet sand. Pentaradial symmetry divides the body into five equal sectors, stabilizing locomotion and feeding while allowing regeneration to proceed without disrupting balance (Beadle, 1989).

A broken sea star missing an arm still preserves the angle of the remaining four. The body reorganizes around absence without abandoning its underlying symmetry.

Sand dollars flatten this same geometry into a disk etched with five petal-like openings across the shell surface. These structures guide water across respiratory tissues while reinforcing the skeleton against bending forces generated by waves and sediment movement (Ellers & Telford, 1992; Mooi & David, 1998; Telford, 1981).

In shallow swash zones, freshly uncovered sand dollars often rotate edgewise until resistance equalizes, their circular outlines turning slowly with each pulse of water.

The etched flower is neither ornament nor accident. It records the intersection of circulation and structural strength — a geometry recalculated as abrasion reshapes the shell and burial depth shifts with each surge.

Across many biological systems, similar proportional relationships appear when living structures must distribute forces or transport materials efficiently through tissue networks (Ball, 1999).

Structure Where Sand Breaks

Hard structure embedded in soft sediment creates pockets where currents slow and animals find shelter, turning smooth bottoms into complex habitat. | Photo credit: A. Mitchell

Beneath the surface where oyster shells, coquina fragments, and storm-scattered debris interrupt the sand, the bottom shifts from smooth sediment to broken relief. In these pockets of structure, octopuses occupy cavities narrow enough to seal with the mantle.

Field observations show that octopus dens occur most frequently within crevice-rich substrates where structural complexity provides refuge and leverage for movement and defense (Anderson et al., 2002). Small fish hover near the edges of these openings, maintaining circular perimeters that expand and contract with the reach of a hidden arm. Juvenile sheepshead pick along shell ridges in repeating passes, their feeding paths tracing arcs that mirror the curvature of the structure beneath them.

Within these shelters, the eight arms of an octopus function as semi-independent mechanical units whose forces combine into coordinated motion (Mather & O’Dor, 1991). Much of this control occurs locally within the arms themselves, allowing rapid adjustment as the animal navigates complex surfaces.

As currents pass through these cavities, suspended particles settle into protected depressions, feeding microbial films that alter oxygen exchange and nutrient cycling along the bottom boundary. Structural geometry therefore governs not only animal behavior but also the micro-distribution of material across the seafloor.

Spirals Carried Offshore

As a thin sheet of water drains across the sand, it splits into branching paths that curve and merge before disappearing. These temporary channels briefly record how moving water redistributes energy along the shoreline. | Photo credit: A. Mitchell

Outside the inlet bars, a drifting boat leaves a wake that separates into tightening vortices. Each eddy contracts as it rotates, conserving angular momentum while turbulence redistributes energy through surrounding water.

Similar rotating structures form within rip currents, where narrow jets of water moving seaward generate circulation cells that trap plankton and suspended particles (Feddersen, 2014; MacMahan et al., 2006; Thorpe, 2005).

Fluid motion often organizes into spiraling paths under these conditions, reflecting the conservation of momentum within rotating systems (Longuet-Higgins, 1969; Peregrine, 1976).

Foam left behind by receding breakers sometimes curls into arcs that briefly echo shell fragments scattered across the wash.

Schools of baitfish caught at the margins of these rotations may briefly organize into crescent formations before the structure dissolves.

Incoming waves arrive in layered packets because slightly offset frequencies overlap and reinforce one another. When multiple rhythms travel through the same body of water, their interaction produces envelopes of larger motion surrounding smaller oscillations (Longuet-Higgins, 1969).

From the deck of a small boat these envelopes pass as broad rises containing finer pulses, a hierarchy of motion that continuously reshapes sandbars and sediment pathways along the coast.

Circles the Water Keeps

A fish briefly touching the surface sends expanding rings across the water, one of the simplest expressions of circular motion in nature. | Photo credit: A. Mitchell

At creek mouths and along nearshore bars, circles appear and vanish faster than the eye can catalogue them. These expanding rings are among the simplest patterns in nature, appearing whenever energy spreads outward through still water.

A ripple expands from a falling drop, its edge widening until it meets another wave and dissolves into interference. The distance around that circle always exceeds the span across it by the same proportion — the constant mathematicians call π.

Circular motion governs more than surface ripples. Tidal creeks bend into loops where erosion and sediment deposition redistribute its momentum along the channel edges that gradually produce curved meanders (Phillips, 1977; Temmerman et al., 2007; Seminara, 2006).

Within these bends, suspended sediment slows and settles, forming point bars that redirect flow during the next tidal cycle.

Offshore, rotating eddies may close into temporary rings that trap plankton and organic particles before dissolving again (MacMahan et al., 2006).

The circle becomes a moving boundary that regulates exchange while it lasts.

Proportion in a Moving Margin

Sunlight reflecting across shallow ripples reveals the repeating wave patterns that constantly reshape coastal sand flats. | Photo credit: A. Mitchell

Across marsh edge, wrack line, and nearshore water, similar patterns recur because natural systems governed by energy exchange tend to converge toward stable configurations.

Spiral drainage, fivefold symmetry, clustered leaf spacing, rotating vortices, and circular ripples represent different expressions of the same negotiation between force and structure.

Across biological and physical systems, recurring proportional relationships often emerge because they minimize energetic cost while maintaining stability (Ball, 1999; Cross & Hohenberg, 1993; Rodriguez-Iturbe & Rinaldo, 1998).

As sediment accumulates or erodes and vegetation thickens or thins, these geometric tendencies alter water residence time, root exposure, and nutrient retention within the marsh (Fagherazzi et al., 2013).

Each tide crosses the boundary again.

And each time it does, the coast recalculates its proportions.

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March 13, 2026