Sharks of Onslow County

Category: Marine Ecology

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
When the Water Softens: The First Jellies of Onslow County

Jellyfish of Onslow County

Several species of jellyfish appear along the waters of Onslow County, North Carolina as the coastal ecosystem shifts from winter toward spring. Moon jellies, comb jellies, sea nettles, and cannonball jellyfish all move through these waters at different times of year, responding to temperature, tides, and the seasonal return of plankton (Purcell et al., 2007; Lucas et al., 2012; Cloern & Jassby, 2010).

At the Edge of Winter

Late winter along the estuarine marshes of Onslow County. Marsh grasses remain the color of dried straw while the coastal ecosystem waits for spring. | Photo credit: M. Mitchell

In late February along the Intracoastal Waterway, the coast exists in a kind of suspension. The marsh grasses behind Topsail Island are still the color of dried straw, their green not yet returned. The wind carries more memory than warmth, and the water — though brighter in the lengthening light — remains clear in the way cold water often is, revealing sandy bottom, oyster shell, and shadow without the haze of summer plankton.

Nothing looks abundant. Nothing appears urgent. The shoreline feels patient.

If you lean over a dock and allow your eyes to adjust, the surface begins to resolve into layers. What first appears empty reveals movement — a faint pulse beneath the water, nearly invisible unless sunlight strikes at the right angle. A small translucent bell, no wider than your palm, opens and closes in a steady rhythm while the current carries it sideways through the creek.

The first jellies of the season are easy to miss.

They are small.
They are clear.
And they belong to the quiet phase of the coastal year.

The Water Before Summer

Early spring estuarine water along the coast often appears clear and quiet as plankton populations begin rebuilding after winter. | Photo credit: A. Mitchell

Early spring water along the southern North Carolina coast often carries a glass-like quality. Plankton populations are rebuilding after winter. Suspended sediments have settled during calmer stretches. Against that clarity, the earliest gelatinous drifters seem almost designed to disappear.

Standing along the docks and creeks of Onslow County, most of what we notice are the drifting bells moving slowly through the water.

But the life of a jellyfish does not begin there.

How a Jellyfish Begins

The jellyfish most people recognize — the drifting bell, the trailing tentacles — is only one phase of a much longer life cycle.

Generalized life cycle of a true jellyfish. Many species begin as microscopic larvae that settle into tiny polyps attached to submerged surfaces before releasing young jellyfish into the water column. | Graphic credit: Key West Aquarium

Most true jellyfish begin as fertilized eggs released into the water column. Each egg develops into a tiny, free-swimming larva called a planula. There are many planulae in the water at once, but each one is a single organism, smaller than a grain of sand, carried by currents you would never notice from the surface.

Within a few days — sometimes less than a week, depending on temperature — a planula settles onto a hard surface. It may attach to the underside of a dock piling, the rough edge of an oyster shell, a shaded bridge support, or even a shell resting quietly in the mud. Once attached, it transforms into a polyp (Lucas et al., 2012).

In this stage it does not resemble a jellyfish at all. It is small — often only a few millimeters tall — no larger than a grain of rice. If you could flip that piling into the sunlight in February, you would not see a jellyfish.

You would see something that looked more like a pale freckle against the wood.

And yet, that freckle holds potential.

The polyp may remain in that form for months. Anchored beneath docks and along oyster beds, it feeds on microscopic prey drifting past and survives the colder stretch of winter water (Purcell, 2012).

That freckle — that rice-sized polyp — does not always remain alone.

In some species of true jellyfish, the polyp stage can reproduce asexually, forming small copies of itself along the same piling or oyster shell (Purcell, 2012).

When spring begins to soften the creek and temperatures rise, the polyp changes again. In a process known as strobilation, its body reorganizes into stacked segments (Purcell et al., 2007; Lucas et al., 2012). One by one, those segments separate into the water as tiny juvenile jellyfish called ephyrae (Purcell et al., 2007).

Newly released ephyrae — juvenile jellyfish — pulsing through the water after separating from the polyp stage during strobilation.

As the ephyra develops, its arms fill in and smooth into a rounded bell. It becomes the drifting medusa we recognize along docks, tidal creeks, and open shoreline.

As the ephyra develops, its arms fill in and smooth into a rounded bell. It becomes the drifting medusa we recognize along docks, tidal creeks, and open shoreline.

If you step away from the dock and look toward the darker center of the creek, the pattern shifts without breaking. Not every gelatinous drifter begins life attached to wood or shell. Comb jellies live their entire lives suspended in open water, developing and reproducing where freshwater flowing downriver meets saltwater moving inland on the tide (Purcell et al., 2001).

What can seem like separate coastal experiences — the pale freckle beneath a dock, the first small jellies of spring, the sudden sting beneath a swimsuit — are phases of the same unfolding life cycle.

A Life Without a Brain

Watch a jellyfish long enough drifting beneath a dock or through the calm water of a tidal creek in Onslow County, and the question eventually arises.

What is directing it?

The bell contracts. The animal pulses forward. Tentacles drift outward and close around passing prey. The movement appears deliberate, almost rhythmic, as though some quiet decision were being made.

And yet, jellyfish have no brain.

Instead, their bodies are organized around a diffuse network of nerve cells known as a nerve net. Sensory information travels across this web of neurons distributed throughout the bell and tentacles — more like signals moving along a strand of Christmas lights, where each bulb responds along the line, rather than a single switch controlling everything at once (Mackie & Meech, 1995).

Moon jellyfish pulsing through the water. Jellyfish lack a centralized brain; instead, a diffuse nerve net distributed throughout the bell coordinates their movement and responses to the surrounding water.

Along the margin of the bell, specialized sensory structures known as rhopalia help them sense orientation and balance in the water column. In a way, they function a bit like the balance sensor in a phone that knows when the screen should rotate (Garm et al., 2006; Skogh et al., 2006).

None of these signals pass through a central command center.

Instead, the entire body participates in sensing the surrounding water.

The current shifts.
Light filters through the surface.
Something brushes against the tentacles.

And the jelly responds.

Moon Jellies: The Quiet Pulsers Near Structure

A moon jelly drifting beneath a dock in early spring may be only a few inches across. Its bell is nearly colorless, soft at the edges, its body so transparent that it seems less like an animal and more like a moving lens in the water.

What often gives it away are four faint circles inside the bell — pale rings that resemble small moons suspended within the jelly. Those structures are reproductive organs, and they are the feature that gives the species its common name.

Moon jellyfish (Aurelia aurita) along the shoreline. The four horseshoe-shaped structures visible inside the bell are reproductive organs — the feature that gives the species its “moon jelly” name. | Photo credit: oosty, iNaturalist

Around the margin of the bell hang delicate, hair-fine tentacles. They are far shorter and less conspicuous than the trailing threads of sea nettles that appear later in the summer.

Earlier in its life it exists as a tiny polyp attached beneath docks and oyster shells — the same pale “freckles” that persist quietly through the winter on the shaded structures below the waterline.

As the water slowly warms into the upper 40s and 50s °F (8–13°C), those anchored moon jelly polyps begin releasing young jellyfish into the creek in a process scientists call strobilation (Purcell et al., 2007; Purcell, 2012).

As these young jellies drift through the creek, their bells pulse slowly against the current. The water around them carries clouds of microscopic life — copepods and other plankton rebuilding after winter — and whatever brushes the tentacles becomes food (Lucas et al., 2012; Cloern & Jassby, 2010).

Their tentacles do carry stinging cells, called nematocysts, like microscopic harpoons built to capture animals far smaller than we are. For most people, those harpoons are too small to penetrate the outer layer of human skin.

A swimmer may brush past a moon jelly without feeling anything at all.

Comb Jellies: The Invisible Drifters of Open Water

Comb jellies — ctenophores such as Mnemiopsis leidyi — are even more elusive.

They lack stinging cells and instead capture prey with sticky cells (Purcell et al., 2001). Their bodies are almost entirely transparent. What gives them away are rows of tiny beating cilia that catch the light and flash briefly like moving prisms.

In darkness, some comb jellies can also produce brief flashes of bioluminescent light when disturbed, though along the creeks of Onslow County what we usually notice are the shifting rainbows created as sunlight bends through their beating cilia.

Comb jelly (ctenophore) drifting in the water column. Unlike true jellyfish, comb jellies lack stinging cells and capture prey using sticky cells. | Photo credit: A. Mitchell

Unlike moon jellies that may first appear near docks and pilings, comb jellies are often more noticeable in slightly deeper portions of tidal creeks and open estuary as spring advances (Purcell et al., 2001).

From the dock, they can be invisible.

But scoop a bucket of water in late spring or early summer and the illusion changes. What looked like empty creek water suddenly fills with small gelatinous spheres — clear, bead-like forms tumbling gently against one another, not unlike the soft water beads children play with, often called Orbeez.

In a net, they resemble scattered jelly stones.

They have been there all along.

The difference is scale and perspective.

Sea Lice: The Unseen Larvae of Warm Days

By late spring another gelatinous presence begins to make itself known, though most people never see the organism responsible.

On calm, warm days along the beach, swimmers sometimes step from the water with a faint prickling sensation along their skin. The irritation may begin around the ankles, between the toes, or beneath a swimsuit where fabric presses against the body. Hours later a rash can appear.

Locally this irritation is often called “sea lice,” though the name is misleading. They are not lice at all. The sensation comes from microscopic cnidarians — most commonly the larval stages of the thimble jellyfish (Linuche unguiculata), though larvae of certain sea anemones can produce the same reaction (Segura-Puertas et al., 2001; Wong et al., 1994).

Thimble jellyfish (Linuche unguiculata). The microscopic larval stages of this tiny jellyfish are the most common cause of the irritation known as “sea lice,” or seabather’s eruption. | Photo credit: Foued Kaddachi

At this stage the animals are nearly invisible, drifting in the surface water. Waves and gentle onshore currents can concentrate them along the shoreline, the same shallow areas where swimmers enter the water, children play in the surf, and beachgoers wade while searching for shells.

When these larvae become trapped against the skin — beneath fabric or pressed between toes and folds of skin — the same microscopic harpoons, or nematocysts, used to capture prey can inject a tiny amount of venom when triggered (Wong et al., 1994).

Most people recognize the sudden prickling sensation immediately. In the hours that follow, the irritation can intensify into a fiery rash — a reaction known medically as seabather’s eruption. Relief usually begins by rinsing the skin with fresh water after leaving the ocean and applying cold compresses to calm the irritation (Wong et al., 1994).

Few people ever see the organism responsible.

As the Season Deepens

Spring along the coast rarely arrives all at once. It unfolds in stages — water warming by degrees, plankton building slowly in the creeks and sounds, and the community of gelatinous drifters shifting with those changes.

The nearly invisible jellies of early spring give way to species that are easier to see, easier to avoid, and sometimes easier to feel.

Sea Nettles: The Summer Drifters of Brackish Water

Atlantic sea nettle (Chrysaora quinquecirrha) drifting just beneath the surface of a coastal creek. | Photo credit: A. Mitchell

By late spring and early summer, the Atlantic sea nettle (Chrysaora quinquecirrha) begins appearing more frequently in the creeks and sounds of Onslow County.

Their bells carry warm amber tones, and long tentacles trail behind them like threads drifting through the tide.

Sea nettles favor the brackish mixing zones of the estuary where freshwater flowing down the New River blends with saltwater entering through the inlets. As plankton populations increase with warming water, sea nettles follow the food supply into tidal creeks and quieter sounds (Lucas et al., 2012).

Unlike moon jellies, their nematocysts can penetrate human skin, producing the sharp sting swimmers learn to recognize.

Cannonball Jellies: The Offshore Drifters

Cannonball jellyfish (Stomolophus meleagris) found along the shoreline in Surf City, NC. Many individuals washing ashore are no longer alive once they lose the buoyant support of seawater. | Photo credit: A. Mitchell

Farther offshore another species sometimes appears — the cannonball jellyfish (Stomolophus meleagris).

Their rounded bells give them the appearance of pale drifting mushrooms or underwater buoys.

They often gather in offshore waters where ocean currents concentrate plankton (Graham et al., 2003). Storms and onshore winds can push them toward the beaches of Onslow County, where they sometimes appear along the wrack line.

Many stranded individuals are no longer alive. Their gelatinous bodies collapse quickly once they leave the buoyant support of seawater.

Beyond the breakers, however, they may still be drifting quietly through deeper currents.

An Older Pattern Beneath the Surface

It is easy to think of jellyfish as modern phenomena — summer nuisances or passing curiosities.

Yet their lineage stretches back more than 500 million years, predating vertebrates and surviving multiple mass extinctions (Cartwright et al., 2007).

Fossil impressions of ancient jellyfish alongside modern jellyfish. Soft-bodied animals like jellyfish rarely fossilize, but when preserved they reveal that jellyfish-like organisms have existed in Earth’s oceans for hundreds of millions of years. | Image credit: Fossil photo by B. Lieberman. Cunina photo by K. Raskoff, copyright.

Long before barrier islands formed and migrated, eastern North Carolina lay beneath shallow marine waters.

Soft-bodied drifters pulsed through plankton-rich seas above what would eventually become Onslow County.

The small jelly beneath a dock in March is not something new.

It is continuity.

Returning to the Shoreline

Stand again at the edge of the sound as winter begins to loosen its hold on the coast.

The air is softer now. Ospreys circle overhead. Marsh grass prepares to green.

Beneath the surface, the water is changing too — warming slowly, plankton returning, currents carrying new life through the estuary.

A small bell pulses quietly past the pilings. Nearby, comb jellies flash faint rainbows when the light strikes them just right. Somewhere beyond sight, larvae drift through the tide.

None of it announces itself.

But if you lean over the water long enough in early spring, you can watch the system beginning again.

Early spring in the S. Topsail Island sound. Beneath the surface, plankton, drifting larvae, and young marine life begin to return with the warming water. | Photo credit: M. Mitchell

References

Cartwright, P., Halgedahl, S. L., Hendricks, J. R., Jarrard, R. D., Marques, A. C., Collins, A. G., & Lieberman, B. S. (2007). Exceptionally preserved jellyfishes from the Middle Cambrian. PLoS ONE, 2(10), e1121. https://doi.org/10.1371/journal.pone.0001121

Cloern, J. E., & Jassby, A. D. (2009). Patterns and scales of phytoplankton variability in estuarine–coastal ecosystems. Estuaries and Coasts, 33(2), 230-241. https://doi.org/10.1007/s12237-009-9195-3

Garm, A., Ekström, P., Boudes, M., & Nilsson, D. (2006). Rhopalia are integrated parts of the central nervous system in box jellyfish. Cell and Tissue Research, 325(2), 333-343. https://doi.org/10.1007/s00441-005-0134-8

Graham, W. M. (2001). Size-based prey selectivity and dietary shifts in the jellyfish, Aurelia aurita. Journal of Plankton Research, 23(1), 67-74. https://doi .org/10.1093/plankt/23.1.67

Graham, W. M., Pagès, F., & Hamner, W. M. (2001). A physical context for gelatinous zooplankton aggregations: A review. Jellyfish Blooms: Ecological and Societal Importance, 199-212. https://doi.org/10.1007/978-94-010-0722 -1_16

Lucas, C. H., Graham, W. M., & Widmer, C. (2012). Jellyfish life histories: Role of polyps in forming and maintaining Scyphomedusa populations. Advances in Marine Biology, 133-196. https://doi.org/10.1016/b978-0-12-394282-1.00003-x

Mackie, G. O., & Meech, R. W. (1995). Central circuitry in the jellyfish Aglantha Digitale: I. The relay system. Journal of Experimental Biology, 198(11), 2261-2270. https://doi .org/10.1242/jeb.198.11.2261

Mackie, G. O., & Meech, R. W. (1995). Central circuitry in the jellyfish Aglantha Digitale: II. The ring giant and carrier systems. Journal of Experimental Biology, 198(11), 2271-2278. https://doi.org/10.1242/jeb .198.11.2271

Purcell, J. E. (2012). Jellyfish and ctenophore blooms coincide with human proliferations and environmental perturbations. Annual Review of Marine Science, 4(1), 209-235. https://doi.org/10.1146/annurev-marine-120709-142751

Purcell, J. E., Shiganova, T. A., Decker, M. B., & Houde, E. D. (2001). The ctenophore Mnemiopsis in native and exotic habitats: U.S. estuaries versus the Black Sea basin. Hydrobiologia, 451, 145-176. https://link.springer.com/article/10.1023/A:1011826618539

Purcell, J., Uye, S., & Lo, W. (2007). Anthropogenic causes of jellyfish blooms and their direct consequences for humans: A review. Marine Ecology Progress Series, 350, 153-174. https://doi.org/10.3354/meps07093

Segura-Puertas, L., Ramos, M. E., Aramburo, C., Heimer de la Cotera, E. P., & Burnett, J. W. (2001). One Linuche mystery solved: All 3 stages of the coronate scyphomedusa Linuche unguiculata cause seabather’s eruption. Journal of the American Academy of Dermatology, 44(4), 624-628. https://doi.org/10.1067/mjd.2001.112345

Skogh, C., Garm, A., Nilsson, D., & Ekström, P. (2006). Bilaterally symmetrical rhopalial nervous system of the box jellyfish Tripedalia cystophora. Journal of Morphology, 267(12), 1391-1405. https://doi.org/10.1002/jmor .10472

Wong, D. E., Meinking, T. L., Rosen, L. B., Taplin, D., Hogan, D. J., & Burnett, J. W. (1994). Seabather’s eruption: Clinical, histologic, and immunologic features. Journal of American Academy of Dermatology, 30(3), 399-406. https://www.jaad.org/article/S0190-9622(94)70046-X/abstract

March 6, 2026
When the Coast Was a Shallow Sea: Onslow County 66 Million Years Ago

Onslow County 66 Million Years Ago: Before the Coastline Existed

Today, the shoreline of Onslow County forms part of the Atlantic Coastal Plain — a broad, low landscape stretching from New Jersey to Florida (Riggs et al., 2020). Marshes, barrier islands, and estuaries define the modern coast, shaped by tides, storms, and the slow migration of sand (Riggs et al., 1995; Riggs et al., 2020). But the ground beneath those systems records a far older history. Long before marsh grass rooted the shoreline or barrier islands assembled offshore, this region lay beneath a shallow sea.

Reconstruction of North America during the Late Cretaceous, when high global sea levels flooded large portions of the continent. Shallow epicontinental seas covered much of the interior and extended across the Atlantic Coastal Plain, submerging regions that would later become the southeastern United States. |
Image credit: Illustration of Late Cretaceous North America showing the Western Interior Seaway. Adapted from U.S. Geological Survey educational materials.

Onslow County 66 million years ago looked nothing like it does today. If you could stand where the county sits at the end of the Cretaceous, there would be no ground beneath your feet. No marsh, no barrier islands, no inlet channels breathing with tide. The coastline lay far inland. Eastern North Carolina was submerged beneath a warm, shallow sea that stretched in a broad, quiet shelf from the continent toward an ocean still reorganizing after the breakup of Pangaea.

If a human body could enter that sea, the first sensation would not be clarity but thickness. The water would feel warm and heavy against skin, dense with suspended life. Visibility would shorten to a green haze where light diffused instead of traveling cleanly. Through that haze, movement would register before shape: the passage of large animals built for a shelf no longer occupied by their kind — mosasaurs turning in slow arcs, plesiosaurs rising through layered water, sharks, already ancient, tracing patrol routes beneath them. Each body would displace the plankton-rich column, sending pressure outward. The ocean would feel less like empty space and more like a corridor constantly shared. Each movement would push through plankton-rich water that behaved less like modern surf and more like a living suspension, as if the ocean itself carried weight.

The water would have been green with plankton, heavy with suspended carbonate, the kind of sea that builds geology slowly from drifting skeletons. There were no beaches yet because there was no edge — only a gradual transition from submerged coastal plain into open Atlantic. The sediments beneath modern Onslow County record this as stacked marine layers: sand, clay, marl, and chalky limestones built from microscopic shells settling through millions of seasons (Miller et al., 2005).

This was not an empty sea. It was structured like a city.

Reef communities rose from carbonate platforms. Ammonites spiraled through open water. Early teleost fishes filled midwater niches (Friedman, 2010; Near et al., 2013). Marine reptiles — mosasaurs and plesiosaurs — patrolled the upper food web. And sharks, already ancient by this point, occupied ecological roles recognizable even now: cruisers of the shelf, opportunists of the drop-off, specialists shaped by tooth and speed.

The modern Atlantic Coastal Plain is the memory of that sea compressed into stone.

Teeth as Geological Fossils

Fossil tooth of the giant shark, Otodus megalodon, found in the surf at Surf City, North Carolina. Teeth like this erode from Miocene and Pliocene marine sediments beneath the Atlantic Coastal Plain, remnants of an ocean that covered this region millions of years ago. | Photo credit: Alicia Sanders, 2025

The shark teeth found along Onslow beaches are not simply remnants of animals; they are fragments of sedimentary history washing back to the surface. Rivers, storms, dredging, and shoreline erosion re-expose marine layers that were buried when sea level fell and the continent emerged. Each tooth has traveled twice: first through the animal that grew it, and later through millions of years of burial, erosion, and exposure.

Many of the large triangular teeth people call “megalodon” are younger than the Cretaceous itself. The giant shark Otodus megalodon lived much later, during the Miocene and Pliocene, roughly 23 to 3.6 million years ago — a reminder that the Atlantic shelf has been a marine environment repeatedly across deep time (Pimiento & Balk, 2015). The reason both Cretaceous and Miocene fossils appear in the same coastal region is not contradiction but layering. Eastern North Carolina is a staircase of ancient seas, each episode leaving deposits that modern erosion cross-cuts and reveals.

The shoreline acts like a rotating archive. Storms turn the pages.

The Cretaceous: A Climate Without Ice

Marine reptiles dominated ocean food webs during the Mesozoic Era, when dinosaurs ruled on land. Mosasaurs and other large predators hunted fish, ammonites, and other marine animals in the warm seas that covered much of North America. | Illustration credit: Smithsonian Institution

The Cretaceous sea covering Onslow County existed in a greenhouse world. There were no polar ice caps. Global temperatures were higher. Sea levels stood among the highest in the last 500 million years. Warm currents circulated freely between basins, and the shallow epicontinental seas were engines of biodiversity (Hay, 2011).

In such climates, coastal ecosystems functioned differently. Productivity was driven by ocean circulation and nutrient upwelling rather than the strong seasonal temperature swings that structure many modern coastal systems. Carbonate production accelerated. Marine food webs expanded vertically, filling ecological space with specialists. The shallow shelf that covered North Carolina would have been biologically dense — a continuous gradient from estuarine margins to open marine habitats, without the sharp land–sea boundary we recognize today.

The modern Outer Banks, in this sense, are a recent invention. They are sand arranged by late-Quaternary sea-level oscillation. The deeper story of this coast is marine.

Extinction as a Geological Boundary

At the end of the Cretaceous, about 66 million years ago, the asteroid impact now known as the Chicxulub event closed this chapter abruptly. Marine ecosystems did not vanish overnight; they reorganized under the cascading collapse of planktonic food webs (Schulte et al., 2010). The sedimentary record along the Atlantic margin preserves this boundary as a thin horizon enriched in iridium — a planetary fingerprint marking a moment when global systems reset.

A rock sample showing the Cretaceous–Paleogene boundary, where a thin iridium-rich layer marks the global extinction event triggered by the Chicxulub asteroid impact about 66 million years ago. Specimen from Wyoming, displayed at the San Diego Natural History Museum.| Photo credit: Fossil Crates, 2022

In the hundreds of thousands to millions of years that followed, ocean ecosystems slowly rebuilt (Schulte et al., 2010; Friedman, 2010). Plankton communities recovered first, allowing marine food webs to reassemble from the bottom upward.

The sea that covered Onslow County withdrew gradually over the tens of millions of years following the Cretaceous–Paleogene boundary, not because of the impact alone, but because tectonics and climate redirected Earth’s balance of water and land. Through the Paleogene and into the Neogene, regression exposed portions of the Atlantic Coastal Plain. Rivers carved channels into former seabeds. Marshes colonized low ground. Much later, during the Pleistocene ice-age cycles beginning about 2.6 million years ago, barrier islands assembled from mobile sand as sea level rose and fell repeatedly.

What we walk today is the lifted floor of a vanished ocean.

This interactive reconstruction shows how Earth’s continents shifted through deep time. At 66 million years ago, much of the Atlantic Coastal Plain—including modern eastern North Carolina—lay beneath a warm shallow sea. | Visualization credit: Ian Webster, dinosaurpictures.org

Explore the Interactive Ancient Earth Map

Cretaceous Transition: After the Impact

The end of the Cretaceous did not simply erase species; it reorganized the architecture of marine life. In the first several hundred thousand years after the Chicxulub impact, the collapse of plankton communities removed the base of food webs that had supported ammonites, many marine reptiles, and numerous large predatory fishes. Apex niches did not stay empty for long. During the early Paleogene, roughly 66 to 50 million years ago, sharks, teleost fishes, and early marine mammals diversified rapidly into the ecological space left behind (Schulte et al., 2010; Friedman, 2012).

Reconstruction of marine life near the end of the Cretaceous Period, shortly before the Chicxulub asteroid impact triggered a global mass extinction about 66 million years ago. The event collapsed marine food webs and reshaped ocean ecosystems across the planet. | Illustration: Smithsonian Institution

In the aftermath, the shelf would not look empty at first glance but would feel altered, as large bodies that once displaced water in constant motion were absent, leaving the vertical space above the seafloor open, quieter, and less crowded. A swimmer would sense the difference not through sight alone but through the water’s stillness — fewer passing pressure waves and fewer shadows interrupting the light.

In the shallow seas that once covered eastern North Carolina, this transition marked a shift from reptile-dominated predator guilds to fish- and shark-centered systems. Survivors tended to share traits that remain advantageous in modern estuaries: flexible diets, rapid reproduction, and tolerance for fluctuating conditions. The extinction boundary favored generalists over specialists, and lineages capable of exploiting disrupted ecosystems seeded the foundation of the modern Atlantic marine fauna.

The Cretaceous sea did not end — it evolved under constraint.

The Miocene: A Predator-Rich Shelf

Over the tens of millions of years that followed the Paleogene recovery, marine ecosystems continued diversifying as continents drifted toward their modern positions and ocean circulation strengthened. By the Miocene, roughly 23 to 5 million years ago, the sea covering eastern North Carolina was not the same water body that drowned the Cretaceous coast. Continents had shifted. Currents reorganized. The Atlantic margin was beginning to resemble its modern geometry. What remained constant was the shelf: shallow, warm, nutrient-rich, and biologically crowded.

The Miocene shelf was structured by productivity. Warm global climates intensified circulation patterns that mixed nutrients and supported dense prey fields. Where energy concentrates, ecosystems scale upward. Plankton blooms fueled vast schools of fish and squid that moved through the water column in shifting layers (Hay, 2012; Pimiento et al., 2016).

Reconstruction of a Miocene marine ecosystem (~6 million years ago) featuring dolphins (Eurhinodelphis), a penguin (Spheniscus), the long-necked seal Acrophoca, and the giant shark, Otodus megalodon. During the Miocene, the diversification of marine mammals supported some of the largest predators in ocean history. | Artwork by Julius Csotonyi

This abundance supported a growing diversity of marine vertebrates (Pimiento et al., 2016). Whales diversified explosively: early baleen whales filtered plankton blooms that pulsed across the shelf, while toothed whales pursued schooling fish and squid, their passage shifting the light before their bodies came fully into view. Pinnipeds hauled out on emergent islands. Sea turtles nested along coastlines that advanced and retreated with slow tectonic breathing. Below that movement, sirenian grazers — ancestors of modern manatees — moved slowly through seagrass beds, shaping the shelf from the bottom while predators ruled above (Domning, 2001).

To occupy that Miocene shelf as a small observer would be to feel scale in motion. Migrating whales and large predators would load the surrounding water with momentum before they arrived, a pressure you could feel before you could see its source. The shelf seemed to flex around movement, the water itself shaped by the animals traveling through it. The water carried that weight differently than in the Cretaceous — not the suspension of reptile-dominated seas, but the mass of mammals built for speed and scale.

In ecosystems where prey concentrates and marine mammals flourish, apex predators inevitably emerge. In the Miocene Atlantic, that role belonged to the giant shark whose teeth still surface along North Carolina beaches: Otodus megalodon. Its immense size was not evolutionary extravagance but ecological arithmetic. A predator of that scale can exist only where the energy flowing through the system is great enough to sustain it (Pimiento et al., 2016).

Sediments from Miocene deposits in the Atlantic Coastal Plain preserve a fossil record dominated by marine vertebrates. These fossils accumulate in the same geological staircase as older layers, which is why storms today liberate teeth from multiple epochs simultaneously. The shoreline is a cross-section through predator history.

Megalodon disappears near the Pliocene boundary, likely a casualty of ecological restructuring — shrinking nursery habitat, prey redistribution, and competition from emerging marine mammals (Pimiento & Clements, 2014). The predator city did not vanish; it reorganized.

The Pleistocene: Ice, Sand, and a Moving Coast (~2.6 million – 11,700 years ago)

During glacial low stands, standing on the exposed shelf would produce a disorienting absence. Wind would move across ground that remembered being ocean. The surface would hold the texture of former seabed — compacted, rippled, cut by channels where rivers extended into newly revealed terrain. Air would replace water pressure, but the land would still read as marine, a coastline temporarily paused in withdrawal.

The Pleistocene introduced a rhythm that still governs the modern coastline: glacial cycling. Ice sheets expanded and retreated dozens of times, locking ocean water onto continents and then releasing it. Each cycle shifted sea level by tens of meters. Eastern North Carolina repeatedly alternated between exposed coastal plain and submerged shelf (Lambeck et al., 2014).

When sea levels fell, rivers carved deeply into former seabeds, cutting channels that later became estuaries, while rising seas flooded those valleys again, redistributing sand along migrating shorelines as barrier islands assembled from sediment sorted into long, mobile ridges by waves and currents (Riggs et al., 1995; Riggs et al., 2020).

Reconstruction of a shallow coastal ecosystem similar to those that developed along the Atlantic Coastal Plain as sea levels stabilized after the Ice Age. Seagrass beds, shellfish, fishes, turtles, and marine mammals formed the foundation of the modern estuarine communities that now define the Carolina coast. | Painting by Michael Rothman, Florida Museum of Natural History.

The coast stopped being a static shelf and became a machine in motion, and Pleistocene ecosystems were shaped by that instability as species adapted to shifting salinity, temperature, and shoreline position. Many cold-adapted megafauna disappeared or shifted poleward, while warm-temperate estuarine assemblages consolidated in their place.

The ecological winners were organisms capable of building habitat: marsh grasses trapping sediment, oysters engineering reefs, and filter feeders clarifying water. Those assemblages increasingly resembled the modern Atlantic shelf, with drum, croaker, and mullet occupying estuarine corridors carved by drowned rivers while rays and small coastal sharks patrolled nursery shallows. Oyster reefs rose in dense clusters, and early marsh communities anchored sediment with grasses similar to those that now define the Carolina coastline.

The emerging system favored species tolerant of fluctuation — animals able to move with the shoreline rather than resist it — as cooling climates and destabilized coasts increasingly selected for flexibility over scale, replacing the giants of the Miocene shelf with communities built for movement rather than permanence.

The modern Onslow estuary is therefore a recent equilibrium layered atop instability.

Pleistocene Transition: From Ice Age Coast to Modern Estuary

Shifts in the eastern North American coastline from the Last Glacial Maximum (~20,000 years ago) to the present. During the Ice Age, much of the continental shelf was exposed land. As glaciers melted and sea level rose, coastal rivers flooded and estuaries formed, creating the modern Atlantic Coastal Plain shoreline.| Illustration credit: USGS, Water Science School

The close of the Pleistocene did not feature a single catastrophic boundary but a climatic stabilization. As the last major ice sheets retreated about 11,700 years ago, sea level rose rapidly and then slowed. Coastlines stopped migrating at glacial speed. Estuaries stabilized long enough for persistent marsh systems to develop. Oyster reefs expanded. Seagrass beds colonized shallow bays (Lambeck et al., 2014; Kennett & Shackleton, 1975).

The organisms that dominate modern estuaries are ecosystem engineers. They do not simply inhabit the coast — they build it.

What appears ancient in the marsh is, in geological terms, newly assembled.

Survivors in Motion: Sharks and Teleost Continuity

Standing in modern surf, that continuity is still tactile. The water along the shelf carries suspended sand and organic haze, softening visibility to a few body lengths. Something large can pass nearby without breaking the surface, announced only by a shift in current or a vibration through the feet. The present ocean feels busy in the same quiet way ancient shelves must have felt — full of motion just beyond clear sight. The modern shelf feels lighter, but not empty. The water still carries motion long before form appears, transmitting the passage of sandbar sharks, blacktips, and schooling menhaden through vibration rather than sight. The weight is subtler now — distributed across smaller bodies, faster cycles, suspended sand and organic haze — yet the sensation remains – a medium that remembers being crowded.

The most striking feature of the Atlantic shelf is not how much has changed, but how much has endured. Sharks were already ancient when the Cretaceous sea covered this region, their lineage extending back more than 400 million years (Ebert et al., 2021).

Ancient oceans and modern seas share the same ecological architecture. Slide to compare a Late Cretaceous shark community with a modern marine ecosystem. While species have changed across millions of years, sharks and teleost fishes continue to occupy many of the same roles within ocean food webs. | Left image: Late Cretaceous marine assemblage

Modern coastal sharks reflect this inheritance, with sandbars, blacktips, bonnetheads, and dogfish representing lineages refined through repeated ecological resets (Ebert et al., 2005). Teleost fishes tell a parallel story: after the end-Cretaceous extinction, they diversified explosively, filling feeding niches that define modern marine communities (Friedman, 2010).

Species change across epochs, but functional roles persist, and the system remembers its architecture even when its cast rotates. The sharks offshore now are not echoes of a lost world; they are its direct continuation.

The Coast as a Layered Archive

Shell fragments scattered across the shoreline near Surf City, North Carolina. Each tide exposes pieces of past marine life, reminders that the modern coast sits atop layers of older oceans and ecosystems.| Photo credit: Tom’s Teeth, 2019

When a fossil tooth surfaces in the surf along the Onslow County coast, it is not emerging from a single time but from stacked histories compressed beneath the modern shoreline. Cretaceous seas. Miocene predator guilds. Pleistocene shorelines advancing and retreating with ice age pulses. Each episode writes a layer. Storm energy and human dredging occasionally cut into those layers, returning fragments to circulation.

This is why the coast feels haunted by deep time. The sediment is not just sand; it is a palimpsest of ecosystems.

The sharks that swim offshore now — sandbars, blacktips, bonnetheads — are heirs to lineages that survived the extinction boundary and adapted through cycles of climate and geography. Their teeth will enter the archive in turn. Millions of years from now, another shoreline will release them, and a different species will walk a beach made from our present seafloor.

The coast is not a place fixed in space. It is a moving edge between worlds, carrying memory forward grain by grain.

Explore deep time yourself

References

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Ebert, D. A., Dando, M., & Fowler, S. (2021). Sharks of the world: A complete guide. Princeton University Press.

Friedman, M. (2010). Explosive morphological diversification of spiny-finned teleost fishes in the aftermath of the end-Cretaceous extinction. Proceedings of the Royal Society B: Biological Sciences, 277(1688), 1675-1683. https://doi.org/10.1098/rspb.2009.2177

Hay, W. W. (2012). Experimenting on a small planet: A scholarly entertainment (1st ed.). Springer Science & Business Media.

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Lambeck, K., Rouby, H., Purcell, A., Sun, Y., & Sambridge, M. (2014). Sea level and global ice volumes from the last glacial maximum to the Holocene. Proceedings of the National Academy of Sciences, 111(43), 15296-15303. https://doi.org/10.1073/pnas.1411762111

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Near, T. J., Dornburg, A., Eytan, R. I., Keck, B. P., Smith, W. L., Kuhn, K. L., Moore, J. A., Price, S. A., Burbrink, F. T., Friedman, M., & Wainwright, P. C. (2013). Phylogeny and tempo of diversification in the superradiation of spiny-rayed fishes. Proceedings of the National Academy of Sciences, 110(31), 12738-12743. https://doi.org/10.1073/pnas.1304661110

Pimiento, C., Balk, M., & Celements, C. (2014). Reconstructing the extinction of the giant Megalodon shark (Carcharcoles Megalodon). The Paleontological Society Special Publications, 13, 52-52. https://doi.org/10.1017/s2475262200011102

Pimiento, C., & Balk, M. A. (2015). Body-size trends of the extinct giant shark Carcharocles megalodon : A deep-time perspective on marine APEX predators. Paleobiology, 41(3), 479-490. https://doi.org/10.1017/pab.2015.16

Pimiento, C., & Clements, C. F. (2014). When did Carcharocles megalodon become extinct? A new analysis of the fossil record. PLoS ONE, 9(10), e111086. https://doi.org/10.1371/journal.pone.0111086

Pimiento, C., MacFadden, B. J., Clements, C. F., Varela, S., Jaramillo, C., Velez‐Juarbe, J., &

Silliman, B. R. (2016). Geographical distribution patterns of Carcharocles megalodon over time reveal clues about extinction mechanisms. Journal of Biogeography, 43(8), 1645-1655. https://doi.org/10.1111/jbi.12754

Riggs, S. R., Ames, D. V., Culver, S. J., & Mallinson, D. J. (2020). The battle for North Carolina’s coast: Evolutionary history, present crisis, and vision for the future.

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Schulte, P., Alegret, L., Arenillas, I., Arz, J., Barton, P. J., Brown, P. R., Bralower, T. J., Christeson, G. L., Claeys, P., & Willumsen, P. S. (2010). The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary. Science, 327(5970), 1214-1218. https://www.science.org/doi/10.1126/science.1177265

March 2, 2026
Dolphins of Onslow County Waters: Ecology and Shared Shoreline

Dolphins of Onslow County: A Coastal Population

There is often a moment before you see them.

A breath breaks the air first — a soft exhale that sounds almost human — and then a dorsal fin lifts from the channel like a line drawn through moving water. The tide is falling. Gulls hover over the seam where current tightens. Fishermen pause mid-cast because everyone knows the rhythm: if the dolphins are working the edge, the fish are already gathering.

These encounters feel spontaneous, but they are not accidents. The dolphins that surface beside our piers, marsh creeks, and inlets are not anonymous travelers passing through. Many bottlenose dolphins show long-term site fidelity and structured community patterns in estuarine systems, returning to the same places across years (Urian et al., 2009; Wells, 2014). To live on this shoreline is to share space with minds moving just below the surface — residents of the tidal edge.

Who they are: a coastal population

The dolphins most frequently seen along Onslow County’s waters are common bottlenose dolphins (Tursiops truncatus), a species whose “coastal” lives can look very different from “offshore” lives. Across the western North Atlantic, genetic studies show fine-scale population structure that can separate dolphins using nearshore coastal waters from dolphins using inshore estuarine waters (Rosel et al., 2009). More broadly, integrative work continues to support meaningful coastal vs offshore divergence in the region (Costa et al., 2022).

In estuaries, photo-identification research (matching dorsal-fin markings) repeatedly shows that bottlenose dolphins can form discrete social communities with limited spatial overlap — a pattern consistent with long-term residency and local familiarity (Urian et al., 2009). In practical terms, the dolphin a child watches from a dock in spring may be seen again the following winter, and again the next year: not a rumor, but a biological possibility supported by long-term studies of resident dolphins elsewhere on the coast (Wells, 2014).

Photo-identification doesn’t always rely solely on human matching of fin shapes; new tools such as machine learning are being developed to improve accuracy in identifying individual dolphins and whales in the wild. For example, researchers in Hawaii are using advanced algorithms to distinguish individuals from large photo libraries of dorsal fins. As technology improves, methods like photo-ID only get more reliable — which means studies of habitat overlap and seasonal return become more precise over time.

An inside look at how scientists “read” dorsal fin shapes and markings to track the same dolphins over time.

Reading the geometry of the estuary

Dolphins do not simply occupy estuaries; they interpret them.

Tidal channels function as moving architecture. Falling tides compress fish schools toward narrowing exits. Sandbars redirect flow into faster seams. Marsh edges trap prey against shallow gradients. Dolphins exploit these features with precision, repeatedly targeting conditions that make prey capture more efficient (Barros & Wells, 1998; Torres & Read, 2009).

This is one reason dolphins so often appear where the water “looks alive” — at convergence lines, inlet throats, and channel bends. In Florida Bay, for example, foraging tactics are mapped onto habitat features that define where dolphins have spent their time, thus turning behavior into geography (Torres & Read, 2009). What seems like play from shore can be highly strategic predation.

Bottlenose dolphins breaching off Seaview Pier, N. Topsail Beach, North Carolina. The arc of the body and column spray reflect the mechanics of propulsion – force directed through the tail, momentum carried into the air. | Photo credit: Howard Crumpler Photography, 2026

Reader Question:

Why do dolphins seem more active on rainy or overcast days?

Weather, light, and the illusion of play

You may notice that dolphins seem especially active on overcast or rainy days — surfacing more frequently, breaching, or moving in tight arcs through wind-rippled water. It can look like preference, even mood. But dolphins are responding less to cloud cover than to what cloud cover does to the water.

When the sky darkens, baitfish don’t stay arranged the same way. They may bunch together or rise toward the surface. For a predator already working those upper layers, that shift can make hunting more efficient (Benoit-Bird & Au, 2003). Wind and rain can also stir the surface and cloud the water, changing who sees whom first (De Robertis et al., 2003).

There is also a perceptual component. Overcast skies reduce glare, making dorsal fins and splashes easier for human observers to detect. Wind-textured water highlights movement. What appears to be “more play” may sometimes be improved visibility — a reminder that observer experience and animal behavior are not always the same phenomenon.

In short, dolphins are responding to ecological conditions. The weather alters the water; the water alters the fish.

Two bottlenose dolphins break the surface beneath the gray horizon off Surf City, North Carolina. Overcast light and wind-roughened water can change how fish move – and how easily we notice the dolphins following them. | Photo credit: Johnny Provost, Jr., 2025

Communication and social intelligence

Bottlenose dolphins have been studied for decades not just because they are charismatic, but because their social lives depend on constant communication in a shifting, three-dimensional world. One of the strongest findings to emerge from that research is the existence of signature whistles — individually distinctive call types that function as learned identity signals, something very much like the individual name a dolphin goes by within its community (Janik & Sayigh, 2013).

Social learning runs just as deep. Some dolphin foraging habits spread from one animal to another rather than through genetics — passed along socially, a rare pattern among nonhuman species (Krützen et al., 2005). Mothers and calves stay together for years, giving calves time to learn not just how to hunt, but where — which channels to follow, which bends of water hold fish (Wells, 2014).

In some populations elsewhere in the world, dolphins even use tools — carrying marine sponges on their rostrums while foraging or trapping fish inside empty shells — behaviors that are socially learned and culturally transmitted (Krützen et al., 2005).

That learning shapes how dolphins fit into the estuary. In many tidal systems they sit near the top of the local food web, influencing the fish communities beneath them. Yet beyond those protected waters, they are not beyond risk. Large sharks prey on dolphins, placing them within a broader coastal hierarchy where even predators can become prey (Heithaus, 2001). The role shifts with scale. The ecology remains layered.

Two bottlenose dolphins surfacing together off Seaview Pier, N. Topsail Beach, North Carolina. Close positioning and timing are hallmarks of the complex social bonds that define dolphin societies. | Photo credit: Howard Crumpler Photography, 2026

Dolphins are not guardians

Popular culture has assigned dolphins a role they never chose: protector. People repeat a comforting shoreline myth — “If you’re scared of sharks, find the dolphins; they’ll protect you.” But that story is not grounded in how dolphins behave in the wild.

Bottlenose dolphins are powerful predators. They compete, establish dominance hierarchies, and can deliver forceful blows when defending calves or asserting space. Dolphin–shark interactions occur, but they are not “rescue missions” staged for humans; they are ecological encounters shaped by risk, competition, and opportunity (Heithaus, 2001).

Wild dolphins are also capable of injuring people. Research examining human–dolphin interactions show that close approaches — and especially feeding wild dolphins — increase the likelihood of risky contact and harmful outcomes for both dolphins and people (Cunningham-Smith et al., 2006; Vail, 2016). Over time, those interactions leave visible consequences. Long-term data from Sarasota Bay show that dolphins who have learned to associate people with food are more likely to carry injuries linked to boats and fishing gear (Christiansen et al., 2016).

The danger is not that dolphins are “evil.” The danger is assuming they share human intentions.

Swimming near a pod does not create a protective shield. Dolphins are not lifeguards. They are wild animals navigating their own priorities in a shared environment. Respecting that boundary is what allows coexistence.

A bottlenose dolphin pursuing prey near a recreational vessel in a waterway in Surf City, North Carolina. Foraging behavior can bring dolphins into close proximity with boats – not as companions, but as active predators focused on fish. | Video credit: Cynthia Dirosse, 2024

Winter dolphins

A persistent assumption is that dolphins vanish when the water cools. In reality, seasonal distribution can be more nuanced — changing with prey, temperature, and coastal movement patterns rather than following a simple on/off presence.

Along the mid-Atlantic coast, research shows that bottlenose dolphins shift their movements with the seasons, appearing in different areas at different times of year (Torres et al., 2005). Studies focused on estuarine dolphins in southern North Carolina document similar seasonal patterns closer to home (Silva et al., 2020). From shore, those changes can look like disappearance. But winter quiet does not always mean absence. It may simply mean dolphins are working deeper channels or less visible pathways beyond the easy reach of our eyes.

The estuary in winter is quieter, but not empty.

Dorsal fins in winter light off Surf City, North Carolina. Dolphins may appear less active this time of year, but changes in light, water depth, and travel corridors often influence what we notice from shore. | Photo credit: Surf City Parks, Recreation, and Tourism, 2017

Living beside them

Living near dolphins is a privilege — and it places us within the same waters they navigate. Vessel traffic, fishing gear, and repeated close approaches can shape the lives of animals that live for decades and raise calves slowly (Wells, 2014). Studies of dolphins that have been fed or closely approached by people show that these interactions can shift behavior, making dolphins more likely to approach boats and increasing the risk of injury and conflict (Vail, 2016). Distance, in that sense, preserves the patterns people come to watch.

The presence of dolphins is not guaranteed. It is a sign that the system still functions — prey, water quality, shoreline structure, and the complex social knowledge dolphins carry from year to year. As long-lived predators near the top of the food web, they are indicator species, reflecting the condition of the waters they inhabit — estuary, inlet, and nearshore coast alike.

And so when a dorsal fin rises beyond the channel markers, it means more than a moment of spectacle. It means the currents are still working, the fish are still moving, and the layered relationships that shape this shoreline are still holding.

There is always more to learn about dolphins than fits in a single post. For those who’d like to go further, this episode of the All Creatures Podcast offers a thoughtful exploration of their biology and behavior.

References

Barros, N. B., Wells, R. S., & Barros, N. B. (1998). Prey and feeding patterns of resident bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida. Journal of Mammalogy, 79(3), 1045. https://doi.org/10.2307/1383114

Benoit-Bird, K. J., & Au, W. W. (2003). Prey dynamics affect foraging by a pelagic predator (Stenella longirostris) over a range of spatial and temporal scales. Behavioral Ecology and Sociobiology, 53(6), 364-373. https://doi.org/10.1007/s00265-003-0585-4

Christiansen, F., McHugh, K. A., Bejder, L., Siegal, E. M., Lusseau, D., McCabe, E. B., Lovewell, G., & Wells, R. S. (2016). Food provisioning increases the risk of injury in a long-lived marine top predator. Royal Society Open Science, 3(12), 160560. https://doi.org/10.1098/rsos.160560

Costa, A. P., Mcfee, W., Wilcox, L. A., Archer, F. I., & Rosel, P. E. (2022). The common bottlenose dolphin (Tursiops truncatus) ecotypes of the western North Atlantic revisited: An integrative taxonomic investigation supports the presence of distinct species. Zoological Journal of the Linnean Society, 196(4), 1608-1636. https://doi.org/10.1093/zoolinnean/zlac025

Cunningham-Smith, P., Colbert, D. E., Wells, R. S., & Speakman, T. (2006). Evaluation of human interactions with a provisioned wild bottlenose dolphin (<I>Tursiops truncatus</I>) near Sarasota Bay, Florida, and efforts to curtail the interactions. Aquatic Mammals, 32(3), 346-356. https://doi.org/10.1578/am.32.3.2006.346

De Robertis, A., Ryer, C. H., Veloza, A., & Brodeur, R. D. (2003). Differential effects of turbidity on prey consumption of piscivorous and planktivorous fish. Canadian Journal of Fisheries and Aquatic Sciences, 60(12), 1517-1526. https://doi.org/10.1139/f03-123

Heithaus, M. R. (2001). Shark attacks on bottlenose dolphins (TURSIOPS ADUNCUS) in Shark Bay, Western Australia: Attack rate, bite scar frequencies, and attack seasonality. Marine Mammal Science, 17(3), 526-539. https://doi.org/10.1111/j.1748-7692.2001.tb01002.x

Janik, V. M., & Sayigh, L. S. (2013). Communication in bottlenose dolphins: 50 years of signature whistle research. Journal of Comparative Physiology A, 199(6), 479-489. https://doi.org/10.1007/s00359-013-0817-7

Kalahele, K. (2023, July 21). You’ve heard of facial recognition for humans, but what about dolphins and whales? Hawaii News Now. https://www.hawaiinewsnow.com/2023/07/21/uh-researchers-develop-new-face-id-technology-identify-dolphins-whales-wild/

Krützen, M., Mann, J., Heithaus, M. R., Connor, R. C., Bejder, L., & Sherwin, W. B. (2005). Cultural transmission of tool use in bottlenose dolphins. Proceedings of the National Academy of Sciences, 102(25), 8939-8943. https://doi.org/10.1073/pnas.0500232102

Rosel, P. E., Hansen, L., & Hohn, A. A. (2009). Restricted dispersal in a continuously distributed marine species: Common bottlenose dolphinsTursiops truncatusin coastal waters of the western North Atlantic. Molecular Ecology, 18(24), 5030-5045. https://doi.org/10.1111/j.1365-294x.2009.04413.x

Silva, D. (2020). Abundance and seasonal distribution of the southern North Carolina estuarine system stock (USA) of common bottlenose dolphins (Tursiops truncatus). IWC Journal of Cetacean Research and Management, 21(1), 33-43. https://doi.org/10.47536/jcrm.v21i1.175

Torres, L. G., McLellan, W. A., Meagher, E., & Pabst, D. A. (2023). Seasonal distribution and relative abundance of bottlenose dolphins, Tursiops truncatus, along the US Mid-Atlantic coast. J. Cetacean Res. Manage, 7(2), 153-161. https://doi.org/10.47536/jcrm.v7i2.748

Torres, L. G., & Read, A. J. (2009). Where to catch a fish? The influence of foraging tactics on the ecology of bottlenose dolphins (Tursiops truncatus) in Florida Bay, Florida. Marine Mammal Science, 25(4), 797-815. https://doi.org/10.1111/j.1748-7692.2009.00297.x

Urian, K. W., Hofmann, S., Wells, R. S., & Read, A. J. (2009). Fine‐scale population structure of bottlenose dolphins (Tursiops truncatus) in Tampa Bay, Florida. Marine Mammal Science, 25(3), 619-638. https://doi.org/10.1111/j.1748-7692.2009.00284.x

Vail, C. S. (2016). An overview of increasing incidents of bottlenose dolphin harassment in the Gulf of Mexico and possible solutions. Frontiers in Marine Science, 3. https://doi.org/10.3389/fmars.2016.00110

Wells, R. S. (2013). Social structure and life history of bottlenose dolphins near Sarasota Bay, Florida: Insights from four decades and five generations. Primatology Monographs, 149-172.

February 21, 2026
Winter at the Exposed Marsh

The surface that appears

At low tide in winter the creek mouths behind Topsail Island widen into ground that is usually concealed, and the exposed marsh does not appear emptied so much as translated into another state where water has thinned into channels narrow enough to reveal the structure it normally masks. The flats emerge as a textured plane stitched by the remains of Spartina alterniflora, each stem cluster surrounded by a faint collar of darker mud where drainage lags by seconds, and the surface separates into alternating bands that hold or soften depending on how recently porewater escaped. This firmness reflects sediment consolidation, the gradual compression of mud as water drains between tides, tightening elevated shelves first and leaving adjacent troughs saturated, so the exposed ground becomes a map of load-bearing ridges that anticipates where larger animals will move once the marsh opens (Christiansen et al., 2000; Morris et al., 2002).

Close to the surface, winter resolves into finer evidence that the marsh is neither dormant nor still. Fiddler crab chimneys crumble into damp grains that expose darker sediment beneath a thin crust, while hoofprints from the previous tide hold shallow mirrors rimmed with frost where a faint olive sheen gathers as diatoms trap warmth and moisture (Underwood & Kromkamp, 1999). Beside the prints, spirals of fine sediment rise like coiled handwriting, polychaete casts lifted from below and dried into granular ridges that record upward movement from buried layers. Every centimeter of mud registers exchange between subsurface metabolism and cold air, and the exposed flats behave less like the absence of water than a temporary reorganization of it, one that prepares a surface already structured for the next set of crossings.

Clusters of crab burrow openings mark the marsh surface, each hole a vertical conduit linking oxygen, water, and nutrients to the sediment below. | Photo credit: M. Mitchell, 2026

Where winter concentrates energy

The winter low tide exposes more than terrain, because the withdrawal of water aligns accessibility with abundance in a way that concentrates food at the surface for a brief interval. Spartina rhizomes lie just beneath the crust, their pale ends visible where deer have bitten through the mud, and detached stems gather in wrack lines where microbial films soften fibrous blades into digestible pulp. Small bivalves remain gaping in shallow pools where temperature lingers above the surrounding flats, and worm casts cluster where organic matter has settled densely enough to support continuous feeding below. This alignment functions as a resource pulse, a moment when energy stored in buried plant tissue and invertebrate biomass becomes reachable simultaneously.

Wrack concentrated by winter tides stores organic energy in dense bands, drawing shorebirds to feed where nutrients accumulate along the marsh edge. | Photo credit: American Birding Association

Deer enter the marsh along consolidated ridges that hold their weight, yet the crossings do not run straight through these zones of exposure but instead loop and return around feeding sites where sediment has been churned darker than its surroundings. The mud at these points holds fragments of torn rhizomes pressed into its surface and shredded plant fibers mixed into the crust, while overlapping tracks form shallow basins that later fill with water and preserve the geometry of the feeding circuit. Raccoon prints braid across the same lines, Canada goose droppings mark cropped stems, and dunlin and greater yellowlegs settle repeatedly where the surface softens under pressure, their bills puncturing the crust in arcs that echo the paths carved by hooves. Exposure redistributes energy upward, and movement gathers along the same ridges that consolidation established, tying feeding to structure without separating the two processes.

The skin that reforms

Cross-section of marsh sediment showing deposition, erosion, and consolidation, the shifting layers that form and reform the exposed winter surface. | Graphic credit: G. S. Sylvain, 2011

Between exposures, slack water leaves a thin veneer that dries into a continuous surface film through sediment sealing, a layer fine enough to slow the exchange of gases between air and mud (Christiansen et al., 2000). When intact, the flats dull into a flexible sheet that bends faintly under weight, and breaking it releases a muted sulfur odor that signals redox cycling, the shift between oxygenated and oxygen-poor states driven by microbial respiration in buried sediment (Howarth & Teal, 1979; Mendelssohn et al., 1981). Color reveals the chemistry more reliably than smell. Black veins branch through exposed mud where iron binds sulfide, while pale halos surround Spartina roots where oxygen leaks downward along living tissues.

Each footprint becomes an aperture in this membrane, allowing oxygen to enter and reduced compounds to rise, so the breach brightens temporarily before darkening again as metabolism rebalances. Feeding animals convert chemical gradients into visible patterns, and the flats accumulate a shifting mosaic of sealed and reopened zones that migrate with every tide, ensuring that the next exposure inherits the chemical memory of the previous one.

$Tracks fracture the sealed winter crust, revealing darker sediment where oxygen re-enters and the surface begins to reform. | Photo Credit: M. Gold, 2023$
Tracks fracture the sealed winter crust, revealing darker sediment where oxygen re-enters and the surface begins to reform. | Photo Credit: M. Gold, 2023

The ground below the ground

Beneath the crust, the sediment continues to reorganize through bioturbation, the mixing of mud by infaunal animals whose activity does not cease with falling temperature. Polychaete worms thread galleries through the upper layers, lifting sediment to the surface in tight spirals while their burrows act as ventilation shafts through burrow ventilation, drawing oxygen downward and leaking reduced porewater upward (Kristensen, 2000; Aller, 1982). Small bivalves pump water through siphons that leave paired pinholes scattered across the flats, and amphipods graze biofilms coating the worm casts, linking subsurface feeding to surface texture.

Each round of burrowing lifts buried debris and nutrients toward the surface, making crab tunnels pathways that continually rebuild the marsh from below. | Graphic credit: Wang et al., 2010

Where deer cross and feed, hooves collapse some tunnels while sealing others, producing prints that darken unevenly because subsurface architecture differs from step to step. The feeding circuits therefore overlay hidden engineering that maintains permeability and redistributes nutrients, ensuring that exposure, grazing, and burrowing operate as one continuous process rather than as isolated events separated by layers of mud.

Smell in shallow water

Disturbed sediment releases dissolved compounds that spread through shallow pools as porewater plumes, chemical gradients that extend beyond the visible cloud of suspended mud. Killifish and juvenile mullet navigate these gradients through chemoreception, keeping their snouts close to the surface while pivoting toward intensifying scent (Kneib, 1997; Kristensen, 2000). Their feeding loosens additional sediment and amplifies the plume before particles settle again, creating a moving field of chemical information that overlaps with the physical contours of the flats.

What appears from above as a brief swirl becomes a signal that attracts birds, and dunlin and yellowlegs converge on fresh pits where worms remain exposed. Each crater fills with water and darkens as sulfide seeps upward, and feeding layers stack in sequence so that invertebrate disturbance leads to fish excavation, which leads to avian probing, all anchored to the same exposure that first drew deer into the marsh. Leaning close reveals faint popping as methane and carbon dioxide escape through gas ebullition, ticking upward from saturated sediment while animals feed across the surface. The marsh ventilates audibly, and the sound marks exchange continuing beneath apparent stillness.

As the tide withdraws, exposed mud concentrates scent and invertebrates near the surface, guiding shorebirds to feeding zones written into the sediment. | Photo credit: Ron Watts

Memory in the surface

Winter tides and storms deposit sediment that raises the marsh through vertical accretion, stacking particles in increments small enough to disappear into the surface unless read over time (Morris et al., 2002). Hurricane overwash leaves thin sand sheets that redirect drainage for months, oyster clusters trap suspended grains in their lee (Newell et al., 2005), and worm burrows stabilize some deposits while loosening others (Kirwan & Megonigal, 2013). Feeding compresses ridges and excavation softens troughs, embedding each disturbance into the next layer so that the flats carry a structural memory of their own use.

Returning after weeks reveals crossings shifted, wrack lines buried, and worm casts clustered in new zones, evidence that the marsh does not reset between exposures but accumulates the imprint of repeated winter engineering.

Winters that change

Warmer temperatures extend microbial activity through temperature-driven metabolic acceleration, thinning the interval between sealing and decay and allowing chemical gradients to persist longer at the surface (Bridgham et al., 2006). Rising water levels narrow exposure windows, stronger storms redistribute sediment in thicker pulses, and shifting coastal currents alter nutrient delivery and larval supply, influencing which species occupy the winter flats (Kirwan & Megonigal, 2013). The marsh continues to open, yet the rhythm of exposure recalibrates, and feeding circuits migrate toward higher shelves where consolidation still holds.

Chemical plumes stretch farther in warmer water, grazing concentrates into narrower bands, and the same negotiations between structure and feeding repeat under altered timing, ensuring that winter engineering continues without preserving its previous schedule.

Seasonal temperature outlook showing shifting winter probabilities across the southeastern United States, a regional signal that filters down to marsh-level processes. | NOAA – National Weather Service, 2026

The surface in motion

The creek mouth appears quiet until attention lowers to the scale of sediment. Frost melts along print rims before surrounding crust warms, gas ticks upward through worm tubes, fish pits refill, and diatoms bloom where warmth collects. Each tide writes another layer into a system held in dynamic equilibrium, continuous adjustment that maintains form while never remaining fixed (Morris et al., 2002). Exposure leads to feeding, feeding reshapes structure, and structure governs the next exposure as the marsh opens again.

The same ridges that hold a deer’s weight will soften again when the tide returns, and the feeding circuits traced across them will dissolve into channels that redistribute the next layer of sediment. Worm burrows will reopen where hooves sealed them, chemical plumes will reassemble in newly flooded pools, and the surface will carry forward the imprint of this exposure into the next one. Winter does not suspend the marsh. It recalculates it at a slower tempo, redistributing energy across the same structures that will support spring growth and summer density, so that even in the coldest intervals the creek mouth continues its quiet accounting of exchange, preparing another surface that will open and be read again.

Deer cross the marsh to reach winter feeding exposed by the tide, moving along corridors that appear only when the surface opens. | Photo credit: L. W. Hamilton, 2025

References

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

Bridgham, S. D., Megonigal, J. P., Keller, J. K., Bliss, N. B., & Trettin, C. (2006). The carbon balance of North American wetlands. Wetlands, 26(4), 889-916. https://doi.org/10.1672/0277-5212(2006)26[889:tcbona]2.0.co;2

Christiansen, T., Wiberg, P., & Milligan, T. (2000). Flow and sediment transport on a tidal salt marsh surface. Estuarine, Coastal and Shelf Science, 50(3), 315-331. https://doi.org/10.1006/ecss.2000.0548

Howarth, R. W., & Teal, J. M. (1979). Sulfate reduction in a New England salt marsh1. Limnology and Oceanography, 24(6), 999-1013. https://doi.org/10.4319/lo.1979.24.6.0999

Kirwan, M. L., & Megonigal, J. P. (2013). Tidal wetland stability in the face of human impacts and sea-level rise. Nature, 504(7478), 53-60. https://doi.org/10.1038/nature12856

Kneib, R. T. (1997). The role of tidal marshes in the ecology of estuarine nekton. Oceanography And Marine Biology, 35(35), 159-216. https://doi.org/10.1201/b12590-5

Kristensen, E. (2000). Organic matter diagenesis at the oxic/anoxic interface in coastal marine sediments, with emphasis on the role of burrowing animals. Hydrobiologia, 426(1), 1-24. https://doi.org/10.1023/a:1003980226194

Mendelssohn, I. A., McKee, K. L., & Patrick, W. H. (1981). Oxygen deficiency in Spartina alterniflora roots: Metabolic adaptation to anoxia. Science, 214(4519), 439-441. https://doi.org/10.1126/science.214.4519.439

Morris, J. T., Sundareshwar, P. V., Nietch, C. T., Kjerfve, B., & Cahoon, D. R. (2002). Responses of coastal wetlands to rising sea level. Ecology, 83(10), 2869. https://doi.org/10.2307/3072022

Newell, R. I., Fisher, T. R., Holyoke, R. R., & Cornwell, J. C. (2005). Influence of eastern oysters on nitrogen and phosphorus regeneration in Chesapeake Bay, USA. NATO Science Series IV: Earth and Environmental Series, 282, 93-120. https://doi.org/10.1007/1-4020-3030-4_6

Underwood, G., & Kromkamp, J. (1999). Primary production by phytoplankton and Microphytobenthos in estuaries. Advances in Ecological Research, 29, 93-153. https://doi.org/10.1016/s0065-2504(08)60192-0

February 7, 2026
The Life of a Barnacle
A microscopic epic of drift, decision, and devotion

On a winter walk along a pier in Surf City, the boards are bleached pale by sun and salt. Wind threads through the pilings. Gulls cry over gray water. At your feet, on a beam that has known decades of tides, something clings.

It is no bigger than a fingernail—chalky white, ridged like a tiny volcano. Along this coast, it is often an ivory barnacle—Amphibalanus eburneus—one of the small architects that quietly carpet pilings, docks, and seawalls from Topsail Sound to the Cape Fear. You could scrape it away with the edge of a shell. You probably have, absentmindedly, a hundred times.

But this barnacle is not debris. It is a biography written in calcium.

It began as a drifting dot—an invisible life in a moving sea. It crossed currents. It tasted the chemistry of places. And then, once, it chose.

The choice was final.

Barnacles are among the few animals on Earth that get exactly one chance to decide where they will live. No revisions. No migrations. No second homes. The place where a barnacle settles becomes the place where it will eat, grow, reproduce, and die. Its entire life collapses into a single coordinate on the map of the shore.

To understand a barnacle is to understand what it means to commit.

Ivory barnacles cling to a rock | Photo credit: Ken-ichi Ueda

Drift

A barnacle’s life begins in motion.

After fertilization, barnacle embryos hatch into nauplius larvae—tiny, triangular forms equipped with beating appendages and a simple eye (Anderson, 1994). They rise into the plankton, where they may drift for days to weeks, feeding and growing as tides and currents carry them outward (Chen et al., 2014).

The first larval stage of a barnacle, called a nauplius, is free-swimming and distinguished by a set of “horns.” | Photo credit: Robert Bachand

They are not aimless. Even at this scale, nauplii respond to light, salinity, and gravity. They migrate vertically through the water column, riding layers of current like conveyor belts. Their world is vast and borderless—and lethal.

Most barnacles die here.

Nauplii are eaten by copepods, jellyfish, fish larvae, and filter-feeding invertebrates. Each pulse of water is a gauntlet. Survival depends on number: millions released so that a few may reach shore.

After several molts, the nauplius enters its final larval form: the cyprid.

A late larval barnacle stage, the cyprid, has a bivalved shell of chitin and glands in its first antennae that are used to cement itself permanently to a hard substrate. | Photo credit: Robert Bachand

This is no longer a feeding animal. It is a vessel of stored energy, built for a single task—finding a place to live (Aldred & Clare, 2008).

The cyprid does not eat.

A clock begins.

Much of what we know about this hidden stage comes from decades of work on a close coastal relative, the striped barnacle – Amphibalanus amphitrite—a warm-water barnacle that clings to pilings and boat hulls worldwide, and whose larvae have become a window into how barnacles read the sea.

The striped barnacle (Amphibalanus amphitrite) is a globally distributed, non-native barnacle species that can spread via biofouling. In North Carolina waters it may occur outside its historical native range, but it isn’t widely recognized as a documented invasive species causing major ecological disruption. | Photo Credit: South Australia Marine Lab

The Narrow Window

Now the barnacle is no longer drifting blindly. It swims with intent. The cyprid probes surfaces with specialized antennules, “tasting” the chemistry of rock, wood, shell, and steel. It detects microbial biofilms—thin living skins that signal a surface has been stable long enough to support life (Qian et al., 2007). It senses the presence of other barnacles. It avoids surfaces that feel wrong.

This sensory world evolved in seas that were chemically simpler.

Today, cyprids swim through waters laced with heavy metals, hydrocarbons, microplastics, antifouling compounds, and nutrient-driven microbial shifts. These pollutants alter biofilms, mask settlement cues, and interfere with larval sensory systems. What once read clearly as “home” now arrives as static.

In degraded waters, cyprids often hesitate. They probe and retreat. They circle without committing.

But the clock does not pause.

Depending on species and temperature, a cyprid has only days to a few weeks before its stored energy is exhausted (Aldred & Clare, 2008). Each hour of searching burns fuel. When reserves fall too low, three futures unfold.

Some larvae simply die in the plankton and sink.

Some make a desperate choice—cementing themselves to marginal or unstable surfaces.

Others respond to distorted cues and settle where survival is unlikely.

This is not a failure of instinct. It is a mismatch between ancient sensory logic and a changed sea.

Long before we notice a shoreline growing quieter, its future has already thinned in the plankton.

Adverse intergenerational effects of microplastics might drastically reduce larval recruitment and threaten long-term zooplankton sustainability. | Photo credit: Yu & Chan, 2020.

The Choice

When the answer is yes, the barnacle performs one of the most irreversible acts in the animal kingdom.

It flips upside down.

Using its antennules, the cyprid secretes a permanent biological cement and glues its head to the surface (Kamino, 2016). This adhesive—among the strongest natural glues known—binds underwater to stone, metal, and polymer. Once cured, it cannot be undone.

There is no “testing.” No trial period.

This is the end of motion.

Within hours, the cyprid undergoes a radical metamorphosis. Its eyes degenerate. Its swimming limbs are restructured into feathery feeding appendages called cirri. Its body reorganizes around a new axis—rooted instead of free (Høeg & Møller, 2006).

The barnacle becomes architecture.

Many do not survive even this. Newly settled juveniles are grazed by small fish and invertebrates. Waves scrape them away before cement fully cures. The shoreline is littered with choices that did not last.

Those that remain begin to build something larger than themselves.

A Life Built Around the Tide

Most animals grow by addition. Barnacles grow by reinvention.

Shell plates rise around soft tissue, forming a fortress against wave impact, desiccation, and predation. Inside, muscles and organs reorganize to support a life of rhythmic feeding.

When submerged, the barnacle opens its opercular plates and unfurls its cirri—six pairs of jointed limbs that sweep the water in steady arcs. Each beat captures phytoplankton, detritus, and microcrustaceans (Southward, 2008).

An ivory barnacle (Amphibalanus eburneus) unfurls its cirri that sweep the water to feed. | © Peter J. Bryant

Metabolism slows. Heat and salt concentrate. Time folds inward. Some intertidal barnacles endure body temperatures exceeding 40°C (104°F) and prolonged oxygen deprivation (Harley, 2008). They wait for the sea to return.

Each tide is both a threat and nourishment.

Anatomy of a barnacle. | Photo Credit: AnimalFact.com

Time in Shell

Barnacles record time the way trees do.

Their shells grow in increments, forming visible growth bands that reflect seasonal cycles and environmental stress (Crisp, 1989). Storms leave signatures. Cold winters slow deposition. Productive summers thicken walls.

A barnacle on a piling may live five, ten, even twenty years (Southward, 2008). It will experience thousands of tides, hundreds of storms, and uncountable shifts in salinity and temperature—without ever moving.

Where foraminifera archive ancient seas in sediment, barnacles archive living shorelines in calcium.

They are clocks that cannot leave.

Looking at the head of the barnacle, where it attaches, growth rings can be seen. These concentric rings that represent cyclic growth periods are called ecdysal lines (also known as cuticular slips) and are associated with barnacle molting. | Photo credit: © Michael Ready Photography

Threshold Organisms

Barnacles occupy one of the most punishing habitats on Earth: the intertidal zone.

Here, organisms must withstand:
- Wave forces exceeding hurricane winds
- Repeated drying and rehydration
- Rapid temperature swings
- Salinity changes from rain and evaporation
- Intense ultraviolet exposure
Few animals can survive here. Barnacles not only survive—they structure the place.

Every barnacle on this shore is the consequence of a single larval decision made weeks earlier in open water.

They stabilize surfaces. They retain moisture. They create crevices for algae, worms, snails, and juvenile crustaceans. They shape temperature gradients and water flow. They turn bare rock into habitat.

When settlement falters—when larvae cannot read the shore or run out of time—the architecture of the coast changes.

Bare rock expands. Algal communities shift. Grazers lose shelter. Predators lose prey. The intertidal simplifies.

A piling with fewer barnacles is not merely cleaner. It is quieter. Biologically poorer and less layered.

The Lesson in Shell

Return now to that single barnacle on the pier.

It has no eyes. It has never seen the ocean. It will never know the gull overhead or the human who pauses above it. And yet it has shaped its entire existence around this exact sliver of coast.

It did not choose perfectly.

Some barnacles settle too high and starve. Some attach where sand scours them away. Some cement themselves beside competitors that outgrow and smother them.

There is no guarantee.

Only the act of choosing.

In a world that prizes movement, flexibility, and endless revision, the barnacle offers a quieter philosophy:

At some point, life must become a place.

To belong is not to drift forever. It is to accept exposure. To endure storms. To open when the tide allows. To grow, layer by layer, into the shape of your ground.

Every barnacle on this coast is a monument to a single irreversible decision.

And the sea is full of them.

Bay barnacle, Amphibalanus improvisus, on a rock in the New River | Photo credit: Alina Michele, iNaturalist, 2022

References

Aldred, N., & Clare, A. S. (2008). The adhesive strategies of cyprids and development of barnacle-resistant marine coatings. Biofouling, 24(5), 351-363. https://doi.org/10.1080/08927010802256117

Anderson, D. T. (1994). Barnacles: Structure, function, development and evolution (1st ed.). Springer Dordrecht.

Chen, Z., Zhang, H., Wang, H., Matsumura, K., Wong, Y. H., Ravasi, T., & Qian, P. (2014). Quantitative Proteomics study of larval settlement in the barnacle balanus Amphitrite. PLoS ONE, 9(2), e88744. https://doi.org/10.1371/journal.pone.0088744

Crisp, D. J. (1989). Tidally deposited bands in shells of barnacles and molluscs. Origin, Evolution, and Modern Aspects of Biomineralization in Plants and Animals, 103-124. https://doi.org/10.1007/978-1-4757-6114-6_8

Harley, C. D. (2008). Tidal dynamics, topographic orientation, and temperature-mediated mass mortalities on rocky shores. Marine Ecology Progress Series, 371, 37-46. https://doi.org/10.3354/meps07711

Høeg, J. T., & Møller, O. S. (2006). When similar beginnings lead to different ends: Constraints and diversity in cirripede larval development. Invertebrate Reproduction & Development, 49(3), 125-142. https://doi.org/10.1080/07924259.2006.9652204

Kamino, K. (2016). Barnacle underwater attachment. Biological Adhesives, 153-176. https://doi.org/10.1007/978-3-319-46082-6_7

Qian, P., Lau, S. C., Dahms, H., Dobretsov, S., & Harder, T. (2007). Marine Biofilms as mediators of colonization by marine Macroorganisms: Implications for antifouling and aquaculture. Marine Biotechnology, 9(4), 399-410. https://doi.org/10.1007/s10126-007-9001-9

Southward, A. J. (2008). Barnacles: Keys and notes for the identification of British species. Field Studies Council. Yu, S., & Chan, B. K. (2020). Intergenerational microplastics impact the intertidal barnacle Amphibalanus Amphitrite during the planktonic larval and benthic adult stages. Environmental Pollution, 267, 115560. https://doi.org/10.1016/j.envpol.2020.115560
January 17, 2026
The Hidden City in the Grass

How seagrasses and marsh grasses—and the animals within them—build the marshes of Onslow County

In Onslow County’s estuarine marshes, the best time to understand how the landscape works is when the water pulls back. As tides drain from creeks and shallow flats, patterns begin to emerge—where water lingers, where it moves easily, and where it hesitates. These patterns are not random. They reflect the combined influence of plants, animals, and sediments continually reshaping the boundary between land and sea.

Like the microscopic shells of foraminifera preserved in sediment, marsh and seagrass communities record environmental conditions. But unlike the past locked in mud, these systems are alive, constantly negotiated by plants, grazers, predators, and microbes.

From permanently submerged seagrass beds to the highest marsh edge, each elevation zone in Onslow County is maintained not just by vegetation, but by species that actively regulate growth, chemistry, and water flow.

Subtidal shallows: seagrass beds maintained by grazers

In the shallow, light-penetrated waters of the New River Estuary and protected soundside areas, seagrass beds form underwater meadows that stabilize sediments and provide nursery habitat for fish and invertebrates. Species present or expected in Onslow County waters include eelgrass (Zostera marina), shoalgrass (Halodule wrightii), and widgeongrass (Ruppia maritima) (Mallin, 2000; Orth, 1984).

Seagrass blades rapidly accumulate epiphytic algae and microbial films. Without constant grazing, this layer can block light and suppress photosynthesis. Amphipods, isopods, and small gastropods act as continuous maintenance crews, grazing epiphytes and preventing them from overwhelming the plants themselves (Orth & van Montfrans, 1984; Valentine & Duffy, 2006).

Experimental studies show that when these grazers are removed, seagrass condition declines even under favorable light conditions, demonstrating that plant survival depends as much on animal activity as on physical environment (Duffy et al., 2015). Beneath the canopy, burrowing worms and bivalves recycle nutrients and oxygenate sediments, preventing organic matter from accumulating around roots (Orth, 1984).

In this zone, seagrass persists because grazers keep blades clean and sediments breathable—a cooperative system built on constant biological upkeep.

Gammarus mucronatus, a common amphipod grazer on eelgrass | Photo credit: E. A. Lazo-Wasem, Yale Peabody Museum, 2013.

The low marsh edge: cordgrass shaped by snails and crabs

At the daily-flooded edge of the marsh, smooth cordgrass (Spartina alterniflora) dominates. This narrow fringe marks the boundary between open water and marsh interior, where erosion pressure is highest and stability matters most.

Left: Healthy smooth cordgrass (Spartina alterniflora) line the estuary edge in Surf City, NC. | Photo credit: A. Mitchell, 2022. Right: Salt marsh die-off from grazing stress by marsh periwinkle snails and reduced predation by crabs, such as blue crabs, can create bare mudflats. | Photo credit: By Esuglia at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=65794096

Cordgrass growth here is tightly regulated by the marsh periwinkle snail (Littoraria irrorata). These snails climb grass stems to avoid inundation and graze directly on living tissue, often intensifying damage by facilitating fungal infection. At high densities, periwinkle grazing can dramatically reduce cordgrass height and biomass, effectively mowing the marsh edge (Silliman & Zieman, 2001).

Marsh periwinkle snails (Littoraria irrorata) are a common sight on cordgrass (Spartina alterniflora) in North Carolina | Photo credit: North Carolina Aquarium at Roanoke Island, 2018.

Unchecked grazing can destabilize the marsh platform—but periwinkles themselves are regulated by crabs, including blue crabs (Callinectes sapidus), fiddler crabs (Genus Uca), purple marsh crabs (Sesarma reticulatum), hermit crabs and other burrowing species. Crabs prey on snails, limiting grazing pressure and indirectly protecting cordgrass (Silliman et al., 2005).

Crabs also function as ecosystem engineers. Their burrows aerate sediments, relieve sulfide stress around plant roots, and improve tidal water movement through compacted soils (Bertness, 1985; Thomas & Blum, 2010). Where crabs are abundant, cordgrass grows taller and denser; where they are lost, marsh die-off can occur rapidly.

This zone persists through a trophic cascade: grass builds land, snails limit grass, and crabs keep the system in balance.

Mid-marsh: mussels and detritus processors reinforce the platform

Just upslope, where flooding becomes less frequent, plant communities shift toward mixtures that often include saltmeadow cordgrass (Spartina patens). Here, the ribbed mussel (Geukensia demissa) emerges as a key stabilizing force.

Saltmeadow cordgrass (Spartina patens) is an important marsh stabilizer that has higher productivity when it grows near ribbed mussel aggregations | Photo credit: Kristie Gianopulos

Ribbed mussels form dense clusters at the base of marsh vegetation, binding sediments with byssal threads and physically reinforcing marsh soils against erosion (Bertness, 1984). As filter-feeders, they concentrate nutrients by removing organic matter from tidal waters and depositing nitrogen-rich biodeposits directly into marsh sediments (Jordan & Valiela, 1982).

Ribbed mussels (Geukensia demissa) at the base of marsh vegetation | Photo credit: R. Bachand

Grasses growing near mussel aggregations exhibit higher productivity than those without mussels, demonstrating a strong facilitative relationship between animals and plants (Bertness, 1984). As vegetation senesces, detritivorous worms, insects, and microbial decomposers break down dead plant material, converting standing biomass into detritus that fuels food webs throughout the estuary (Mann, 1988).

The mid-marsh functions as a processing zone, reinforcing marsh structure while converting plant matter into usable energy.

High marsh: microbes that manage chemical stress

In the high marsh, dominated by black needlerush (Juncus roemerianus) and saltmeadow cordgrass (Spartina patens), flooding is limited to spring tides and storms. Prolonged exposure to air creates harsh soil conditions, including elevated salinity and sulfide accumulation.

Black needlerush grass (Juncus roemerianus) dominates the high marsh | Photo credit: ©Andy Newman

Here, microbial communities play a central role. Sulfate-reducing and sulfur-oxidizing bacteria regulate sulfide concentrations that would otherwise become toxic to plant roots, while microbial decomposition controls nutrient availability under fluctuating oxygen conditions (Howarth & Giblin, 1983).

Beneath the marsh surface, soil microbes regulate decomposition, carbon exchange, and chemical stress. Changes in salinity and flooding reshape microbial communities, influencing how marsh soils process organic matter and support vegetation across tidal elevations. | Image credit: Zhang et al., 2023.

Small soil invertebrates maintain pore spaces that allow brief pulses of oxygenated water to penetrate during flooding. Unlike the visibly engineered low marsh, the high marsh is stabilized largely through biogeochemical regulation rather than grazing or predation.

This zone endures because microbes quietly buffer plants against chemical extremes.

From microbes in the soil to grasses at the surface, biological interactions drive marsh formation. Microbial processes govern decomposition and organic matter buildup, helping determine whether marsh platforms gain elevation, remain stable, or collapse | Image credit: Abbot, Quirk & Fultz, 2022.

The marsh–upland transition: keeping the boundary intact

At the uppermost margin of the marsh, tidal influence becomes intermittent and environmental stress shifts from salinity to erosion and freshwater input. Burrowing invertebrates increase soil permeability, allowing stormwater and tidal surges to infiltrate rather than scour the surface (Thomas & Blum, 2010).

A profile illustration . depicting the recommended transition of plant types from the edge of the salt marsh to the upland buffer. | Image credit: Massachusetts Office of Coastal Zone Management

Vegetation root networks stabilize soils exposed to drying and wave action, while animal burrows act as pressure-release pathways during extreme events. When these biological processes are disrupted—by shoreline hardening or vegetation removal—the marsh edge often collapses abruptly rather than adjusting gradually.

This boundary holds only as long as water can move through it.

Black, organic-rich peat exposed after storms marks the remains of an ancient salt marsh once buried beneath barrier sands. Its reappearance along North Topsail Beach records long-term shoreline change and marsh migration. Photo credit: Bill Tresnan, 2024.

A marsh built by interactions

Across all elevations in Onslow County marshes, the pattern is consistent:

Plants define the zones—but animals and microbes determine whether those zones endure.

Conceptual diagram of revised juvenile blue crab ontogenetic habitat shifts. Arrows depict transitions between habitats with increases in size. Arrow widths denote abundance contributions of individuals between habitats. | Image credit: Hyman et al., 2023

From grazers that keep seagrass blades clean, to crabs that hold the marsh edge together, to microbes that manage invisible chemical stress, the marsh is sustained by small organisms with outsized influence. Together, these interactions determine not just what lives in the marsh, but whether the marsh itself endures.

Purple marsh crabs (Sesarma reticulatum) moving together along the marsh edge on South Topsail Island, North Carolina. Their collective movement and feeding activity illustrate how small organisms play outsized roles in maintaining marsh structure. Photo credit: A. Mitchell, 2025.

References

Abbott, K. M., Quirk, T., & Fultz, L. M. (2022). Soil microbial community development across a 32-year coastal wetland restoration time series and the relative importance of environmental factors. Science of The Total Environment, 821, 153359. https://doi.org/10.1016/j.scitotenv.2022.153359

Bertness, M. D. (1984). Ribbed mussels and Spartina Alterniflora production in a New England salt marsh. Ecology, 65(6), 1794-1807. https://doi.org/10.2307/1937776

Bertness, M. D. (1985). Fiddler crab regulation of Spartina alterniflora production on a New England salt marsh. Ecology, 66(3), 1042-1055. https://doi.org/10.2307/1940564

Duffy, J. E., Reynolds, P. L., Boström, C., Coyer, J. A., Cusson, M., Donadi, S., Douglass, J. G., Eklöf, J. S., Engelen, A. H., Eriksson, B. K., Fredriksen, S., Gamfeldt, L., Gustafsson, C., Hoarau, G., Hori, M., Hovel, K., Iken, K., Lefcheck, J. S., Moksnes, P., … Stachowicz, J. J. (2015). Biodiversity mediates top–down control in eelgrass ecosystems: A global comparative‐experimental approach. Ecology Letters, 18(7), 696-705. https://doi.org/10.1111/ele.12448

Howarth, R. W., & Giblin, A. (1983). Sulfate reduction in the salt marshes at Sapelo island, Georgia. Limnology and Oceanography, 28(1), 70-82. https://doi.org/10.4319/lo.1983.28.1.0070

Hyman, A. C., Chiu, G. S., Seebo, M. S., Smith, A., Saluta, G. G., Knick, K. E., & Lipcius, R. N. (2023). Model-based evaluation of critical nursery habitats for juvenile blue crabs through ontogeny: Abundance and survival in seagrass, salt marsh, and unstructured bottom. https://doi.org/10.1101/2023.07.20.549877

Jordan, T. E., & Valiela, I. (1982). A nitrogen budget of the ribbed mussel, Geukensia demissa, and its significance in nitrogen flow in a New England salt marsh. Limnology and Oceanography, 27(1), 75-90. https://doi.org/10.4319/lo.1982.27.1.0075

Mallin, M. A., Burkholder, J. M., Cahoon, L. B., & Posey, M. H. (2000). North and South Carolina coasts. Marine Pollution Bulletin, 41(1-6), 56-75. https://doi.org/10.1016/s0025-326x(00)00102-8

Mann, K. H. (1988). Production and use of detritus in various freshwater, estuarine, and coastal marine ecosystems. Limnology and Oceanography, 33(4part2), 910-930. https://doi.org/10.4319/lo.1988.33.4part2.0910

Orth, R. J., Heck, K. L., & Van Montfrans, J. (1984). Faunal communities in seagrass beds: A review of the influence of plant structure and prey characteristics on predator: Prey relationships. Estuaries, 7(4), 339. https://doi.org/10.2307/1351618

Orth, R. J., & Van Montfrans, J. (1984). Epiphyte-seagrass relationships with an emphasis on the role of micrograzing: A review. Aquatic Botany, 18(1-2), 43-69. https://doi.org/10.1016/0304-3770(84)90080-9

Silliman, B. R., Van de Koppel, J., Bertness, M. D., Stanton, L. E., & Mendelssohn, I. A. (2005). Drought, snails, and large-scale die-off of southern U.S. salt marshes. Science, 310(5755), 1803-1806. https://doi.org/10.1126/science.1118229

Silliman, B. R., & Zieman, J. C. (2001). Top-down control of Spartina alterniflora production by periwinkle grazing in a Virginia salt marsh. Ecology, 82(10), 2830. https://doi.org/10.2307/2679964

Thomas, C., & Blum, L. (2010). Importance of the fiddler crab Uca pugnax to salt marsh soil organic matter accumulation. Marine Ecology Progress Series, 414, 167-177. https://doi.org/10.3354/meps08708

Valentine, J. F., & Duffy, J. E. (n.d.). The central role of grazing in seagrass ecology. Seagrasses: Biology, Ecology and Conservation, 463-501. https://doi.org/10.1007/1-4020-2983-7_20

Zhang, G., Bai, J., Jia, J., Wang, W., Wang, D., Zhao, Q., Wang, C., & Chen, G. (2023). Soil microbial communities regulate the threshold effect of salinity stress on SOM decomposition in coastal salt marshes. Fundamental Research, 3(6), 868-879. https://doi.org/10.1016/j.fmre.2023.02.024

January 10, 2026
Foraminifera: The Marsh’s Memory Keepers

What microscopic shells along Topsail and Surf City tell us about ancient seas, living marshes, and the future coastline

On a winter walk along the marsh edge in Topsail or Surf City, the landscape feels quiet. Cordgrass has faded to straw, tidal creeks run clear, and storm tides have pulled back layers of sediment that were hidden just months ago. Winter slows the marsh, but it also reveals it. Along exposed creek banks and tidal flats, the smallest residents of these ecosystems leave behind subtle traces — grains, spirals, and pin-sized shells that most people would mistake for sand.

These are the remains of foraminifera, key marsh indicators, and they carry a record far older than the marsh itself (Murray, 2006; Scott et al., 2001).

What Are Foraminifera?

Foraminifera, often called forams, are single-celled marine organisms — not animals, but protists — that live in oceans, estuaries, and salt marshes around the world (Murray, 2006). Despite their microscopic size, most foraminifera build protective shells, known as tests, made either from calcium carbonate or from tiny grains of sediment cemented together (Scott et al., 2001; Debenay & Guillou, 2002).

Different species occupy very specific zones within a marsh. Some live high in the intertidal, others closer to open water. Their distribution reflects precise environmental conditions such as salinity, tidal elevation, oxygen availability, and sediment type (Edwards et al., 2004; Culver & Horton, 2005). Because of this tight ecological coupling, foraminifera respond quickly when conditions change (Debenay & Guillou, 2002).

Peneropolis proteus is the one of three most dominant species of fossil foraminifera in the Onslow Bay area, occurring in about 15% of samples (Schnitker, 1971).

Why Winter Reveals the Record

In summer, marsh surfaces are busy and obscured. Dense vegetation, algae, burrowing organisms, and constant sediment mixing make it difficult to see what lies beneath. In winter, vegetation thins, biological activity slows, and storm tides rework creek edges and tidal flats. Fine sediments are redistributed, exposing layers that formed years, decades, or even centuries earlier (Scott et al., 2001; Gehrels, 1994).

Winter does not create this record — it simply makes it visible (Murray, 2006).

Size, Stability, and Ancient Seas

Some fossil foraminifera grew to the size of coins, while most living forms today are no larger than grains of sand (Murray, 2006). This contrast reflects the environments they evolved within. In ancient shallow seas, conditions were often warm, stable, and chemically consistent for long periods of time. Temperature, salinity, and carbonate availability changed slowly, allowing foraminifera to grow over many years, build thick and complex shells, and, in some cases, form partnerships with symbiotic algae — similar to the relationship between corals and the algae that live within their tissues — which provided an additional energy source through photosynthesis (Hallock, 1981; Murray, 2006). These systems favored persistence and size.

Over time, coastlines shifted and sea levels changed, giving rise to the highly dynamic estuaries and marshes we see today. In these modern environments, conditions can fluctuate over hours or seasons. Salinity rises and falls, oxygen levels vary, sediments are rearranged, and water chemistry responds quickly to storms and freshwater input (Debenay & Guillou, 2002; Culver & Horton, 2005). Under such variability, smaller foraminifera that grow rapidly and tolerate change are more likely to survive. Because foraminifera respond directly to these environmental conditions, even subtle shifts can reorganize their communities, altering shell size, composition, and diversity in ways that can persist in sediments long after the initial change has occurred (Edwards et al., 2004; Kemp et al., 2013).

Tiny Shells, Deep Time: How Marshes Remember

Foraminifera are among the most powerful tools scientists use to reconstruct ancient coastal ecosystems because the conditions they live in are permanently recorded in their shells. Individual species occupy narrow ecological ranges defined by salinity, tidal elevation, oxygen availability, temperature, and sediment type. Because of this specificity, the particular mix of foraminifera preserved in a layer of marsh sediment reflects the environmental conditions present when that layer formed.

When scientists extract sediment cores from marshes, they are not looking for isolated snapshots in time, but for transitions. As layers accumulate, changes in species composition, shifts between calcium-based shells and sediment-built shells, and variations in diversity reveal how marsh conditions evolved. These biological signals can indicate changes in flooding frequency, sediment stability, freshwater influence, and tidal reach — often aligning with known shifts in sea level or shoreline position.

What makes foraminifera especially valuable is that they record change continuously. Each generation reflects the conditions it experienced, leaving behind a layered biological archive that links past marshes to present ones — comparable to how sedimentary layers exposed in the Grand Canyon record changing environments over deep time.This continuity allows scientists to distinguish gradual environmental adjustment from more abrupt change and to assess whether modern conditions resemble states marshes have previously endured — or represent departures from historical patterns.

Quinqueloculina seminula (left) and Plancopsilina confusa (right) are the top three most dominant species of fossil foraminifera in the Onslow Bay area, each occurring in about 20% of samples (Schnitker, 1971).

What Lives in a Handful of Marsh Sand

If you scoop a small handful of sand or mud from a North Carolina marsh and let it dry, it looks ordinary—grains, bits of plant matter, flecks of shell. Where sediment cores reveal depth at the scale of decades and centuries, living marsh surfaces show that same pattern compressed into just a few centimeters. But research from the Outer Banks suggests that even this unremarkable material holds a surprisingly rich living community.

Foraminifera under biological microscope with sand.

In a detailed study of marsh sediments along the North Carolina coast, scientists examined not just which foraminifera were present, but which ones were alive at the time of sampling. What they found was not a thin layer of life resting at the surface, but a vertically structured community extending down into the sediment itself (Culver, 2005).

Some foraminifera lived right at the surface, where tides regularly wash over the marsh. Others occupied sediments a centimeter or more below, in darker, less oxygenated layers. In total, more than twenty species were documented living within marsh sediments, their distributions shaped by subtle differences in tidal flooding, salinity, and marsh elevation (Culver, 2005).

Not all species were equally widespread. A few, including Jadammina macrescens and Tiphotrocha comprimata, appeared across multiple sites and depths, suggesting a tolerance for changing marsh conditions. Many others were more selective, occurring only in certain zones or at particular depths. This means that even small changes in where you stand—closer to a tidal creek or higher on the marsh platform—can correspond to a different microscopic community beneath your feet (Culver, 2005).

Upper image: Jadammina macrescens under microscope.| Image credit: Parker, G. G., Phleger, et al. 1953. Cushman Found.Foram.Research Spec.Pub. (n.2): 15, pl.3,f.8.
Lower image: Tiphotrocha comprimata under microscope | Image credit: Hesemann, M., The Foraminifera.eu Database (2026). Accessed at http://www.foraminifera.eu.
https://doi.org/10.13140/RG.2.2.22727.11680/1.

As these organisms die, their shells remain. Layer by layer, those shells become part of the sediment, preserving a record of where tides reached, how often flooding occurred, and how stable the marsh surface was at that moment in time (Scott et al., 2001). What begins as a living community quietly becomes part of the marsh’s long-term record.

Although the Outer Banks are not identical to the marshes behind Topsail and Surf City, the pattern holds across North Carolina’s coast: foraminifera respond to local conditions at very small scales. Their presence, abundance, and depth within the sediment shift from place to place, reflecting the marsh’s relationship with water, salt, and time (Edwards et al., 2004; Culver & Horton, 2005).

Cibicidoides bradyi (horizontal scale bar = 200μm, vertical scale bar = 400μm) occur in less than 20 m at about 1% of samples in the Onslow County area (Schnitker, 1971).

For someone walking the marsh in winter, this means that the sand exposed along a creek bank carries more than the imprint of the last storm. It carries traces of countless tides before it—each one leaving behind shells small enough to escape notice, yet durable enough to remember.

What Changes in Foraminifera Mean for the Ecosystem

An example of how shifts in reef communities reflect shifts in foraminiferal communities below (Prazeres, Martínez-Colón & Hallock, 2020).

Foraminifera do not exist in isolation. They are part of the marsh food web, contributing to the transfer of energy and nutrients from microscopic primary producers to larger organisms (Murray, 2006). Many small invertebrates consume foraminifera directly, while others rely on the microbial communities and organic matter associated with their shells (Debenay & Guillou, 2002). In turn, these invertebrates support fish, crabs, and birds that depend on marsh productivity (Scott et al., 2001).

When foraminiferal communities shift, the effects can ripple outward. A decline in diversity or a move toward stress-tolerant species often reflects changes in sediment stability, oxygen availability, or salinity — conditions that also influence marsh plants, benthic invertebrates, and juvenile fish habitat (Culver & Horton, 2005; Edwards et al., 2004). In this way, changes in foraminifera can foreshadow broader ecological adjustments, even when the marsh surface still appears healthy (Debenay & Guillou, 2002).

Because foraminifera respond quickly to environmental change, they often register these shifts before larger organisms do. Their shells capture early signals of altered flooding patterns, reduced sediment input, or changing water chemistry (Gehrels, 1994; Kemp et al., 2013). What follows may be changes in plant community structure, altered nutrient cycling, or shifts in the species that use marshes as nursery grounds. Foraminifera do not cause these changes, but they reveal when the system’s internal balance begins to shift (Scott et al., 2001).

Reading Change in Living Marshes

Salt marshes are dynamic systems by nature. They grow, erode, migrate, and rebuild as sediment moves and sea level changes (Kemp et al., 2013). The challenge for scientists is distinguishing normal variability from directional change — shifts that push marshes beyond the conditions they have historically been able to tolerate. Foraminifera are especially useful in making that distinction because they respond quickly and directly to their surroundings (Debenay & Guillou, 2002).

When marsh conditions move outside typical ranges — whether through altered hydrology, changes in sediment supply, or shifts in salinity — foraminiferal communities reorganize. Species diversity may decline, stress-tolerant forms can become dominant, and assemblages tied to specific tidal elevations may disappear (Culver & Horton, 2005). These changes often occur before larger, more visible signs of stress appear, such as widespread plant die-off or shoreline erosion (Edwards et al., 2004). In this sense, foraminifera act as early responders, recording change while the marsh still appears intact at the surface (Scott et al., 2001).

Along the marshes behind Topsail and Surf City, this sensitivity gives foraminifera particular importance. They help establish local baselines for what healthy marsh conditions look like, provide context for interpreting present-day shifts, and preserve a record of the conditions that supported marsh stability in the past (Culver & Horton, 2005; Kemp et al., 2013). By linking modern observations to sedimentary records, foraminifera allow scientists to ask not only what is changing, but how quickly change is occurring and whether it remains within the range marshes have previously endured. Understanding marsh resilience in this way is not abstract or theoretical — it is grounded in the specific history and behavior of this coastline.

Salt marsh in Surf City, NC. | Photo credit: Mitchell (2026)

Closing

Standing at the marsh edge in winter, it is easy to miss the smallest details. Yet beneath the quiet surface, microscopic shells record centuries of change — how water moved, how shorelines shifted, and how marshes adapted (Murray, 2006). Foraminifera remind us that long before satellites or tide gauges, coastlines were already keeping their own records. All we have to do is learn how to read them.

References

Culver, S. J. (2005). Infaunal marsh foraminifera from the Outer Banks, North Carolina, U.S.A. The Journal of Foraminiferal Research, 35(2), 148-170. https://doi.org/10.2113/35.2.148

Debenay, J., & Guillou, J. (2002). Ecological transitions indicated by foraminiferal assemblages in paralic environments. Estuaries, 25(6), 1107-1120. https://doi.org/10.1007/bf02692208

Edwards, R., Wright, A., & Van de Plassche, O. (2004). Surface distributions of salt-marsh foraminifera from Connecticut, USA: Modern analogues for high-resolution sea level studies. Marine Micropaleontology, 51(1-2), 1-21. https://doi.org/10.1016/j.marmicro.2003.08.002

Gehrels, W. R., & Kemp, A. C. (2021). Salt marsh sediments as recorders of Holocene relative sea-level change. Salt Marshes, 225-256. https://doi.org/10.1017/9781316888933.011

Hallock, P. (1981). Algal symbiosis: A mathematical analysis. Marine Biology, 62(4), 249-255. https://doi.org/10.1007/bf00397691

Kemp, A. C., Horton, B. P., Vane, C. H., Berhhardt, C. E., Corbett, D. R., Engelhart, S. E., Anisfeld, S. C., Parnell, A. C., & Cahill, N. (2013). Sea-level change during the last 2500 years in New Jersey, USA. Quaternary Science Reviews, 81(2013), 90-104. https://www.whoi.edu/cms/files/Kemp2013QSR_170144.pdf

Murray, J. W. (2006). Ecology and applications of benthic foraminifera. Cambridge University Press.

Schnitker, D. (1971). Distribution of Foraminifera on the North Carolina Continental Shelf. Tulane Studies in Geology and Paleontology, 8(4), 169-215. https://journals.tulane.edu/tsgp/article/view/560

Scott, D. B., Medioli, F. S., & Schafer, C. T. (2001). Monitoring in coastal environments using foraminifera and Thecamoebian indicators. Cambridge University Press.

January 3, 2026
Threshold Species at the Year’s Turn

Winter birds and hidden skates in a changing coastal system

Late December along the coast does not announce itself loudly. The holidays have passed, the shoreline empties, and the light—almost imperceptibly—begins to return. The winter solstice marks the shortest day of the year, but its ecological counterpart is quieter. The water does not reset. It settles.

This is the moment when the coastal ecosystem stops negotiating with the season and begins to accept it. That acceptance is visible, if you know where to look—above the waterline in the form of a small diving duck, and below the surface in the stillness of a benthic predator that does not announce its presence at all.

In our region, ecologists recognize certain animals as threshold species: species whose presence, or subtle change in behavior, signals that the system has crossed a seasonal threshold in energy, behavior, and stability — moving from late year into what comes next.

Above the Water: When Winter Is No Longer a Question

Male (left) and female (right) Bufflehead ducks enjoying a winter swim | Photo credit: Judy Gallagher, iNaturalist

By late December, one species begins to appear with quiet regularity across protected sounds and estuaries: the Bufflehead (Bucephala albeola).

Buffleheads are not early winter arrivals. They do not surge in during the first cold fronts of autumn, nor do they linger indecisively during seasonal transition. Instead, their presence reflects commitment. By the time buffleheads settle into coastal waters, water temperatures have stabilized at winter lows, turbulence has eased in protected areas, and benthic prey communities—particularly small crustaceans and mollusks—have shifted into predictable winter distributions (Eadie et al., 2000; Goudie et al., 1994).

Ecologically, buffleheads are specialists. They forage by diving, relying on clear water and reliable prey patches. Their winter distribution is shaped not by calendar dates but by energy economics: cold water increases metabolic demands, and winter habitats must reliably repay that cost (Eadie & Kehoe, 2022). Where buffleheads remain, the system has crossed a threshold from fluctuation to stability.

In this way, they function less as migrants and more as indicators. Their presence signals that the coastal year has finished rearranging itself. Winter has arrived—not dramatically, but decisively.

Below the Water: When Stillness Makes Life Visible

Clearnose skate in winter waters | Photo credit: NOAA Fisheries

Below the surface, the signal is subtler.

Skates do not arrive in winter with the clarity of birds overhead. Species such as the Clearnose skate (Rostroraja eglanteria) are present along the southeastern U.S. coast throughout much of the year. What changes in late December is not their location, but their visibility.

As water temperatures drop, skates reduce activity, conserving energy through decreased movement and prolonged periods of resting on the seafloor (Di Santo & Bennett, 2011). This metabolic slowdown coincides with seasonal increases in water clarity driven by reduced biological productivity, lower sediment resuspension, and diminished boat traffic (Cloern et al., 2014). The result is a paradox: winter reveals what summer conceals.

In these conditions, skates become easier to observe—not because they have increased in number, but because the system itself has slowed enough to make persistence visible. Their flattened bodies blend seamlessly into sandy or muddy substrates, a strategy optimized for ambush predation and energy conservation rather than movement (Carrier et al., 2012).

If buffleheads announce that winter has settled, skates confirm it. They represent endurance over motion, patience over migration.

The Ecological Hinge Between Years

Neither of these species marks a beginning. Neither signals renewal or arrival in the way spring migrants do. Instead, they occupy the hinge between years—the moment when the ecosystem accepts the constraints of winter and reorganizes around them.

Late December is not biologically empty. It is a period of recalibration. Energy budgets tighten. Movements become deliberate. Survival depends less on abundance than on efficiency.

Above the water, buffleheads gather where the math works. Below it, skates persist by minimizing expenditure altogether. One is easily seen, the other almost never. Together, they reveal the same truth: the system has crossed a line.

After the Turn

January will bring its own changes. Cold will deepen, or ease. Migratory patterns will sharpen. New signals will emerge. But the moment just after the solstice—just after the holidays—is different. It is when the coast pauses, holds, and commits.

The year does not turn loudly here.
It settles, and then it holds.

References

Carrier, J. C., Musick, J. A., & Heithaus, M. R. (2012). Biology of sharks and their relatives (2nd ed.). CRC Press. https://doi.org/10.1201/b11867

Cloern, J. E., Foster, S. Q., & Kleckner, A. E. (2014). Phytoplankton primary production in the world’s estuarine–coastal ecosystems. Biogeosciences, 11(9), 2477–2501. https://doi.org/10.5194/bg-11-2477-2014

Di Santo, V., & Bennett, W. A. (2011). Is post-feeding thermotaxis advantageous in elasmobranch fishes? Journal of Fish Biology, 78(7), 1950–1965. https://doi.org/10.1111/j.1095-8649.2011.02976.x

Eadie, J. M., & Kehoe, F. P. (2022). Energetics and foraging ecology of diving ducks. In P. G. Rodewald (Ed.), The birds of North America. Cornell Lab of Ornithology.
https://doi.org/10.2173/bna

Eadie, J. M., Savard, J. P. L., & Mallory, M. L. (2000). Barrow’s Goldeneye (Bucephala islandica) and Bufflehead (Bucephala albeola). In A. Poole & F. Gill (Eds.), The birds of North America. Cornell Lab of Ornithology. https://doi.org/10.2173/bna.548

Goudie, R. I., Brault, S., Conant, B., Kondratyev, A. V., Petersen, M. R., & Vermeer, K. (1994). The status of sea ducks in the North Pacific Rim: Toward their conservation. Transactions of the North American Wildlife and Natural Resources Conference, 59, 27–49. https://pubs.usgs.gov/publication/70187692

December 27, 2025
5 Marine Myths Under the Mistletoe: Folklore and Real Creatures in North Carolina’s Waters
Winter Stories Along the Water’s Edge

Winter settles softly over Onslow County. The marshes turn the color of worn rope, the New River flows like cold steel between its banks, and the wind carries the sharp scent of salt and pine. December is the quiet season — the estuary’s heartbeat slows, nights stretch longer than tides, and the imagination grows louder than the surf.

This is also when stories rise like mist from the water. Coastal families have passed down tales of mysterious shapes in winter surf, glowing wakes following skiffs, and ghostly sounds echoing across moonlit water. These legends don’t appear in ship logs or lighthouse reports — they survive instead in memories, dockside conversations, and the long tradition of storytelling that has shaped coastal community identity for generations (Cecelski, 2001; Carmichael, 2018).

Yet behind every winter myth lies a real creature — moving, feeding, navigating the season’s challenges. The line between wonder and wildlife is thin along North Carolina’s coast. These are the marine myths under the mistletoe — stories rooted in an enchanted and scientifically alive winter sea.

Mermaids of the Winter Shoals

The shimmering ghosts of the inlet

The Legend

Stories collected from coastal residents sometimes describe pale forms just beyond the surf — long shapes rising from green water, a head here, an arm-like movement there, then gone. In fog or dusk, when horizon and water dissolve into the same dull light, figures appear closer to humans than animals.

The Science — Manatees and Mirage Tricks

Although uncommon, West Indian manatees (Trichechus manatus) occasionally visit North Carolina waters during warmer periods or anomalous Gulf Stream intrusions (Deutsche et al., 2003). Through Fata Morgana, a mirage formed when warm water meets cold air, large mammals in the water can look elongated or upright — a trick that has sparked mermaid sightings worldwide (Pinney, 2018).

Reduced daylight, fatigue at sea, and the human brain’s pattern-seeking instincts complete the illusion.

A legend, yes — but one that begins with a real, gentle giant in cold coastal waters.

A pair of manatees resemble mermaids swimming in the water

The Kraken of Cape Lookout

Monsters in the storm-worn deep

The Legend

When Atlantic gales hammered the coast, some fishermen believed immense tentacled beasts rose from deeper waters and brushed their vessels — massive, silent shapes that existed more in feeling than sight. Winter storms made the ocean seem alive with things too large to name.

The Science — Giant Squid and Deep-Sea Drifters

Off Cape Lookout, the continental shelf plunges sharply into canyon habitats that host large cephalopods. Giant squid (Architeuthis dux), while rarely seen alive, have been recorded washing ashore along the U.S. East Coast and retrieved from research and commercial nets in the broader Northwest Atlantic (Guerra et al., 2011; Roper et al., 2015; Roper & Boss, 1982).

Winter nor’easters can dislodge deep-sea life, delivering strange shapes to shoals or leaving long white arms tangled in wrack.

What was once interpreted as a monster was instead a rarely seen animal from the dark beneath winter waves.

A deceased giant squid (Architeuthis dux) on Golden Mile Beach in Britannia Bay, South Africa | Image credit: Adéle Grosse

The Ghost Lights of Bogue Banks

Blue sparks swirling under December stars

The Legend

Local night fishermen describe glowing water that erupts into blue light when a net drops or a school passes below — a phenomenon that feels supernatural under a new moon in the stillness.

The Science — Bioluminescent Dinoflagellates

The glow comes from dinoflagellates, such as Noctiluca scintillans, which emit bright light when disturbed. Warmer months, calmer seas and reduced sediment can make these flashes stand out like underwater meteors (Haddock, Moline & Case., 2010; Johnson & Allen, 2005).

A natural process — but dazzling enough to inspire talk of spirits beneath the tide.

U.S. Navy photo of bioluminescence | Image Credit: Specialist 3rd Class Devin M. Langer

The Siren of the Shoals

Voices carried by cold seas

The Legend

Some boaters recall hearing a sound — a long moan or rising wail — seeming unmistakably like a human voice drifting over calm winter water. One sound can feel like a warning. Another, like grief.

The Science — Migrating Whales and Phantom Songs

Every winter, North Atlantic right whales (Eubalaena glacialis) migrate through waters off North Carolina, including Onslow Bay (Keller et al., 2012). Their massive bodies, seen at dusk, can resemble the curves of a human torso rising unexpectedly from the deep.

But the haunting songs that travel tens of kilometers belong to humpback whales (Megaptera novaeangliae) farther offshore (Dunlop, Cato & Noad, 2008; Handel, Todd & Zoidis, 2012). Sound refracts through cold, dense winter water — bending, echoing, transforming — until a distant whale becomes a mysterious voice in the marsh.

A ghost in the story.
A whale in the science.
A song carried home by the sea.

A breaching humpback whale

The Marsh Giant

A slow breath in frozen reeds

The Legend

In winter stillness, some describe hearing something large moving in marsh grass — heavy, careful steps that push aside reeds, a dark back slipping between creek holes. Too cold for gators, they say — so what else could it be?

The Science — North Carolina’s Cold-Tolerant Alligators

The American alligator (Alligator mississippiensis) reaches its northernmost range in coastal North Carolina. Even in winter, they can surface and move during brief warm spells — and they maintain openings in ice by pushing upward with their snouts (Brisban, Standora & Vargo, 1982).

Slow movement in a hushed marsh can feel enormous.
The “giant” is real — scaled and silent in the cold.

Alligator in Onslow County, NC | Photo credit: G. Newman

Where Myth and Marsh Converge

Winter strips the coast to its bones. Sound travels farther. Shapes blur quicker. The familiar becomes unfamiliar beneath cold air and low light.

And so legends rise.

Behind them:
- a manatee distorted by mirage
- a giant squid arm pushed ashore by storms
- living lanterns beneath December water
- whale voices refracted through the sea
- an alligator surfacing to breathe through ice
Folklore and biology share the same tides — wonder and curiosity driving us to explain what the winter coast reveals only in glimpses.

Even in the quietest months, the estuary is alive with mystery that create marine myths under the mistletoe.

Learn more about winter estuary ecology here.

References

Brisbin, I. L., Standora, E. A., & Vargo, M. J. (1982). Body temperatures and behavior of American alligators during cold winter weather. American Midland Naturalist, 107(2), 209. https://doi.org/10.2307/2425371

Carmichael, S. (2018). Mysterious tales of coastal North Carolina. Arcadia Publishing.

Cecelski, D. S. (2001). The waterman’s song: Slavery and freedom in maritime North Carolina.

Deutsch, C. J., Reid, J. P., Bonde, R. K., Easton, D. E., Kochman, H. I., & O’Shea, T. J. (2003). Seasonal Movements, Migratory Behavior, and Site Fidelity of West Indian Manatees along the Atlantic Coast of the United States. Journal of Wildlife Management, 67(1), 1-77. https://www.jstor.org/stable/3830830

Dunlop, R. A., Cato, D. H., & Noad, M. J. (2008). Non‐song acoustic communication in migrating humpback whales (Megaptera novaeangliae). Marine Mammal Science, 24(3), 613-629. https://doi.org/10.1111/j.1748-7692.2008.00208.x

Guerra, Á., González, Á. F., Pascual, S., & Dawe, E. G. (2011). The giant squid Architeuthis: An emblematic invertebrate that can represent concern for the conservation of marine biodiversity. Biological Conservation, 144(7), 1989-1997. https://doi.org/10.1016/j.biocon.2011.04.021

Haddock, S. H., Moline, M. A., & Case, J. F. (2010). Bioluminescence in the Sea. Annual Review of Marine Science, 2(2010), 443-493. https://www.annualreviews.org/content/journals/10.1146/annurev-marine-120308-081028

Handel, S., Todd, S. K., & Zoidis, A. M. (2012). Hierarchical and rhythmic organization in the songs of humpback whales (Megaptera novaeangliae). Bioacoustics, 21(2), 141-156. https://www.tandfonline.com/doi/abs/10.1080/09524622.2012.668324

Johnson, W. S., & Allen, D. M. (2005). Zooplankton of the Atlantic and Gulf coasts: A guide to their identification and ecology. JHU Press.

Keller, C., Garrison, L., Baumstark, R., Ward-Geiger, L., & Hines, E. (2012). Application of a habitat model to define calving habitat of the North Atlantic right whale in the southeastern United States. Endangered Species Research, 18(1), 73-87. https://doi.org/10.3354/esr00413

Pinney, C. (2018). The waterless sea: A curious history of mirages. Reaktion Books.

Roper, C. F., & Boss, K. J. (1982, April). The Giant Squid. Scientific American, a division of Nature America, Inc, 246(4), 96-105. https://www.jstor.org/stable/24966572

Roper, C. F., Judkins, H., Voss, N. A., Shea, E., Dawe, E., Ingrao, D., Rothman, P. L., & Roper, I. H. (2015). A compilation of recent records of the giant Squid, Architeuthis dux (Steenstrup, 1857) (Cephalopoda) from the western North Atlantic Ocean, Newfoundland to the Gulf of Mexico. American Malacological Bulletin, 33(1), 78-88. https://doi.org/10.4003/006.033.0116
December 19, 2025