Sharks of Onslow County

Category: Marine Ecology

Beyond the Horizon: The Pelagic Sharks Off Onslow County

Most people standing on the beach watch the Atlantic as though the ocean ends where detail disappears.

Nearshore water is easy to read. Pelicans diving offshore reveal where baitfish have gathered near the surface. The first sea turtle crawls of the season begin appearing along the upper beach. Sandbars reveal themselves through shifting wave patterns and changes in water color. Even when the water is murky, the coastline still feels structured because the movement happening near shore leaves visible clues.

Farther offshore, those visible clues become harder to read.

Beyond the breakers, past the shrimp boats and distant military vessels that sometimes mark the horizon, the Atlantic off Onslow County drops across the continental shelf into deeper pelagic water. From shore, that open water can appear empty simply because most of its structure is hidden beneath distance, depth, and moving currents. But the offshore ocean is highly organized. Temperature layers separate water masses. Squid and fish rise toward the surface at night and descend again before daylight. Currents gather plankton and compress bait schools into dense patches of life that may stretch for miles before dissolving again.

And moving through those shifting layers are sharks most beachgoers never see.

Species like the bigeye thresher shark, scalloped hammerhead, Carolina hammerhead, smooth hammerhead, great hammerhead, and tiger shark all occupy different parts of the same Atlantic system connected to North Carolina’s coast. They are not interchangeable predators simply sharing the same water. Each species is specialized for a different way of hunting, sensing, and moving through the pelagic environment.

Even though most people never see these sharks directly, their influence does not remain offshore.

They work their way back toward the coast through changes in prey behavior, bait distribution, migration timing, and the balance of the food web itself.

The Shark Built for Dim Water

The bigeye thresher shark (Alopias superciliosus) does not resemble most sharks people imagine from coastal documentaries or fishing piers. Its eyes are unusually large, and nearly half of its body length is tail.

A bigeye thresher shark (Alopias superciliosus) moves through dim offshore Atlantic water beyond the Carolina coast. Its enlarged eyes help it hunt in low light, while its elongated tail can be used to stun schooling prey before feeding. | Image credit: NC Sea Grant

Both features are tied directly to life in deeper offshore water.

Bigeye threshers spend much of their time moving vertically through the water column, often descending into dim water during daylight hours and returning closer to the surface at night as squid and mesopelagic fish migrate upward under darkness (Weng & Block, 2004). Offshore pelagic systems are layered environments. Light fades rapidly with depth, and many prey species spend daylight hours far below the surface where visibility is limited.

The shark’s large eyes help gather more available light in those darker layers.

For someone standing on the beach at sunset, the horizon still appears bright. Offshore, hundreds of feet below the surface, the bigeye thresher is already hunting in water where daylight barely penetrates.

Its tail is equally specialized. Schooling fish survive by moving together in synchronized motion, creating confusion for predators trying to isolate individual prey. The elongated upper lobe of the thresher’s tail evolved as a way to disrupt that coordination. Researchers have documented threshers using powerful overhead tail strikes to stun schooling fish before circling back to feed (Oliver et al., 2013).

That hunting strategy matters ecologically because the species targeted by threshers are often highly connected to broader Atlantic food webs. Squid, mackerel, and schooling pelagic fish move energy between offshore and coastal systems. Large predators help regulate those populations and alter how tightly schools gather, where they move, and how heavily they feed on smaller forage species beneath them in the food web (Heithaus et al., 2008).

Without predators thinning and disrupting those mid-level prey schools, feeding pressure shifts downward. Larger populations of squid and predatory fish consume more small forage species, including baitfish that later support seabirds, larger fish, and predators closer to shore. The result is not an empty ocean, but a gradual reorganization of how energy moves through the coastal ecosystem.

What beachgoers may eventually notice are changes in feeding activity: fewer concentrated bird flocks offshore, shifting bait movements, or less predictable surface eruptions beyond the breakers.

The Sharks That Hunt Electricity

Hammerheads occupy a different sensory world than most coastal predators.

The broad hammer-shaped head shared by species like the scalloped hammerhead, great hammerhead, smooth hammerhead, and Carolina hammerhead is called a cephalofoil. Spread across that wide structure are sensory pores known as ampullae of Lorenzini, specialized organs capable of detecting weak electrical fields produced by other animals (Kajiura, 2001).

Every muscle contraction and heartbeat generated by prey produces tiny electrical signals in the water.

A stingray buried beneath sand may be invisible to a human observer, but to a hammerhead it is still broadcasting electrical information.

The widened head helps the shark compare those signals across a broader sensory field, improving directional accuracy while hunting. Scientists have compared shark electroreception to detecting the output of a small household battery from extraordinary distances under ideal conditions, though in the ocean the system functions at close range to help sharks pinpoint hidden prey.

While beachgoers scan the water looking for dorsal fins, hammerheads are effectively scanning the seafloor for living electrical currents.

That sensory adaptation helps explain why multiple hammerhead species can occupy overlapping Atlantic waters without performing identical ecological roles.

The Offshore Traveler

The scalloped hammerhead (Sphyrna lewini) is one of the more oceanic hammerhead species associated with continental shelf edges, offshore structures, and migratory routes through deeper Atlantic water (Klimley, 1993).

A scalloped hammerhead shark (Sphyrna lewini) moves through offshore Atlantic water beyond the Carolina coast. The broad cephalofoil spreading from its head contains electroreceptors capable of detecting faint electrical signals produced by prey hidden beneath sand and low-visibility water. | Image credit: A. Murch

Scalloped hammerheads often move in schools, particularly when younger, and feed heavily on fish, squid, and smaller sharks. Their body shape and behavior are well suited for highly mobile pelagic hunting where prey concentrations shift constantly with temperature and current boundaries.

They are not simply “using deeper water.” They are adapted to a system where the structure itself is always moving.

Warm and cool water masses sliding against one another can compress bait into narrow feeding corridors. Squid rise toward the surface after dark. Pelagic fish move vertically and horizontally depending on light levels and prey availability. The scalloped hammerhead’s movement patterns mirror that instability.

Because they occupy such mobile offshore environments, scalloped hammerheads help regulate prey populations across broad sections of the continental shelf rather than within a single localized habitat.

The Hidden Hammerhead

For decades, scientists believed many hammerheads moving through the western Atlantic belonged to the same species.

But the Carolina hammerhead (Sphyrna gilberti) had likely been there the entire time unnoticed.

Researchers eventually discovered that some sharks identified as scalloped hammerheads were genetically distinct and consistently possessed fewer vertebrae, revealing that two separate species had been moving through the same waters unnoticed (Quattro et al., 2013).

Radiographs of the Carolina hammerhead (Sphyrna gilberti) (left) helped reveal that a second hammerhead species had been moving through western Atlantic waters largely unnoticed. Although visually similar to the scalloped hammerhead (right), skeletal differences and genetic analysis confirmed the Carolina hammerhead as a distinct species in 2013. | Image credit: J. Quattro et al., 2013 (left); S. Raredon, Smithsonian Institution, National Museum of Natural History (right)

The discovery revealed that even sharks moving through the same Atlantic waters were more specialized than they first appeared.

From the beach, the offshore Atlantic often appears open and uniform because distance hides most of its detail. But even scientists were still uncovering hidden structures within those waters. Sharks that looked nearly identical from the surface were occupying the same coastline as separate species with potentially different ecological roles.

The Carolina hammerhead still overlaps geographically with other hammerheads along the southeastern United States, and researchers are continuing to study how those species divide habitat, prey, and movement through the Atlantic.

For beachgoers, the discovery is a reminder that the Atlantic beyond the breakers is more ecologically layered than it first appears, with multiple shark species occupying waters that can look uniform from shore.

The Ray Hunter

The great hammerhead (Sphyrna mokarran) occupies a different ecological role than its smaller relatives.

A great hammerhead shark (Sphyrna mokarran) moves through offshore water. The species is highly specialized for hunting rays, using its broad cephalofoil to improve maneuverability and detect prey hidden along the seafloor. | Image credit: Oregon State University

Great hammerheads are more solitary and strongly associated with rays, including stingrays and cownose rays. Their cephalofoil is not simply a sensory structure. It also improves maneuverability and may help pin rays against the seafloor during feeding attempts (Strong et al., 1990).

That specialization matters because rays themselves strongly influence coastal ecosystems.

Rays such as cownose rays and Atlantic stingrays disturb sediment, expose buried organisms, and alter benthic communities while feeding across shallow coastal bottoms. Great hammerheads help regulate those ray populations and influence where rays spend time feeding.

Great hammerheads influence more than the number of rays moving through coastal habitats. The presence of large predators changes prey behavior as well. Rays may avoid lingering in exposed feeding areas when hammerheads are nearby, redistributing feeding pressure across habitats.

For beachgoers, those ecological effects may eventually appear through changes in ray abundance, feeding activity, or shifting patterns of disturbed sediment along shallow coastal waters.

The Cooler-Water Hunter

The smooth hammerhead (Sphyrna zygaena) can look, at first glance, like another variation of the same hammerhead design.

But its head gives away part of its story.

Unlike the scalloped hammerhead, the smooth hammerhead lacks the central notch along the front edge of the cephalofoil. That difference may seem small to a casual observer, but it reflects a separate species adapted to a somewhat different part of the Atlantic system. Smooth hammerheads are often associated with cooler temperate waters and feed heavily on schooling fish and cephalopods moving through offshore shelf waters (Compagno, 2001).

A smooth hammerhead shark (Sphyrna zygaena) moves through open offshore water. Unlike the scalloped hammerhead, the smooth hammerhead lacks the central notch along the front edge of the cephalofoil and is more commonly associated with cooler temperate waters and schooling prey along the continental shelf. | Image credit: S. Judd

That specialization matters because schooling fish and squid help move energy through the open Atlantic.

These prey species do not stay fixed in one place. They shift with temperature, currents, light, and season, gathering in patches that may appear briefly before dispersing again. Smooth hammerheads are part of the predator community that follows and regulates that movement through cooler portions of the continental shelf.

The relationship is not simply a shark chasing fish through open water. By feeding within those moving schools, smooth hammerheads help shape how prey gathers, how long those schools remain concentrated, and how much pressure they place on smaller forage species below them in the food web.

For beachgoers, those ecological effects may eventually appear through seasonal changes in bait movement, bird activity, or the mix of predators feeding along the shelf as offshore waters warm and cool through the year.

The Shark That Connects Habitats

Few sharks move between offshore and coastal systems as fluidly as the tiger shark.

Tiger sharks (Galeocerdo cuvier) are often reduced in public imagination to sensational headlines or descriptions as “garbage eaters,” largely because of their opportunistic feeding behavior and willingness to consume a wide range of prey.

But ecological flexibility is precisely what makes them important.

A tiger shark (Galeocerdo cuvier) moves through tropical offshore water. Tiger sharks travel between offshore habitats, shoals, and coastal systems following seasonal prey movements, linking distant parts of the Atlantic food web through their wide-ranging movements and opportunistic feeding behavior. | Image credit: Fishes of Sarasota County, FL

Tiger sharks move between offshore waters, shoals, nearshore habitats, and sometimes estuarine environments following seasonal prey movements and temperature shifts (Heithaus, 2001). Sea turtles, rays, fish, carrion, and other prey species all become part of that broader movement pattern.

Their presence changes how other animals use the same habitats.

Sea turtles may avoid grazing too heavily in exposed areas when tiger sharks are nearby. Rays redistribute feeding activity. Schools of fish alter where they gather. The presence of a large predator changes how long prey species remain in one place and how intensely they feed before moving on. Areas that might otherwise experience constant grazing or disturbance begin receiving periods of recovery as animals move more cautiously through the habitat (Heithaus et al., 2008).

That movement connects habitats that people often think of as separate parts of the ocean.

A tiger shark feeding offshore may later move closer to shoals, estuaries, or coastal waters as prey shifts with season and temperature. The same predator influencing sea turtle grazing patterns offshore may eventually pass along the edges of bait schools closer to shore weeks later.

For beachgoers, those connections may appear through changing patterns of sea turtle activity, shifting schools of fish near the breakers, or the seasonal movement of predators along the Carolina coast.

The Sharks People Talk About Most

Not all sharks connected to Onslow County remain far offshore.

Species like the great white shark and bull shark tend to dominate public attention because they are more familiar through media coverage and coastal sightings. Tagged great whites moving along the Atlantic coast frequently make headlines, while sharks seen near inlets or murky water are often assumed to be bull sharks whether identification is confirmed or not.

But those assumptions can flatten the complexity of the coastal ecosystem.

Bull sharks (Carcharhinus leucas) are well known for their ability to tolerate freshwater, but they are not the only sharks capable of handling changing salinity. Along the Carolina coast, species such as bonnetheads and juvenile hammerheads also use estuarine environments where tides, rainfall, and river flow constantly shift the balance between salt and fresh water. Coastal systems are not divided into simple categories of “ocean” and “freshwater.” They are gradients, and many sharks are adapted to move through those changing conditions.

A bull shark (Carcharhinus leucas) moves through offshore water accompanied by remoras. Although bull sharks are known for their ability to tolerate lower salinity and move into estuaries and rivers, they are also highly mobile coastal and offshore predators that regularly travel through marine waters along the Atlantic coast. | Image credit: B. Skinstad

Great whites (Carcharodon carcharias), meanwhile, are often discussed as solitary coastal hunters, but along the western Atlantic they are also highly migratory predators tied to seasonal prey movements, temperature ranges, and offshore habitats (Block et al., 2011).

A great white shark (Carcharodon carcharias) moves through open offshore water. Great whites are highly migratory predators capable of traveling vast distances between offshore habitats and productive coastal feeding grounds, linking distant regions of the Atlantic and Pacific through seasonal movement. | Image credit: E. Levy

Both species are part of the broader Atlantic system connected to North Carolina’s coast, but the sharks occupying pelagic waters beyond the visible horizon often receive far less attention despite shaping offshore food webs just as strongly.

Why Recovery Takes So Long

Many fish species along the Carolina coast mature quickly and reproduce in enormous numbers. Menhaden, mullet, and other forage fish may begin reproducing within only a few years while releasing hundreds of thousands—or even millions—of eggs.

Large sharks follow a very different strategy.

Species like great hammerheads, tiger sharks, and threshers often require more than a decade to reach reproductive maturity, and they produce far fewer offspring than most bony fish (Cortés, 2000). Some large female sharks may spend well over a decade surviving storms, fishing pressure, predators, disease, and changing ocean conditions before producing pups for the first time.

That slower reproductive strategy evolved partly because large sharks occupy upper levels of the food web where adults face relatively few natural predators. Evolution favored longer lifespans, slower growth, and fewer offspring with higher survival chances.

But the same strategy creates vulnerability.

A fish population capable of reproducing within two or three years can rebound relatively quickly after declines. A shark population that requires fifteen years or more to produce breeding adults cannot.

The offshore Atlantic built these predators slowly.

And when populations decline, recovery happens slowly as well.

Why More Sightings Do Not Always Mean More Sharks

For many people along the Carolina coast, sharks can feel more visible now than they did decades ago.

Drone footage from the North Carolina coast reveals how modern technology now captures shark movement near beaches that would have gone largely unseen from shore only a few decades ago. Increased visibility does not necessarily mean sharks are suddenly overwhelming coastal waters, but it does change how people perceive the Atlantic around them. | Image credit: L. Abed

Anglers report more sharks taking hooked fish before they can be reeled in, a behavior known as depredation. Drone footage captures feeding activity that would have gone unseen from shore years ago. Social media spreads sightings quickly, sometimes creating the impression that sharks are suddenly overwhelming coastal waters.

Some shark populations have shown signs of recovery following decades of decline and changing fishing regulations. Long-time fishers noticing more shark encounters in certain areas may not be imagining it. In some cases, there likely are more sharks present than there were during periods of heavier population decline in the late twentieth century.

But recovery is not the same as overabundance.

Forty years ago, far fewer people were fishing offshore, kayaking through estuaries, filming the surf with drones, or posting shark encounters online in real time. Coastal waters are now observed more continuously than at any point in history, while recreational fishing activity itself creates more opportunities for sharks and people to interact.

Even with signs of recovery, many large shark species along the Atlantic coast still exist at a fraction of the population levels seen before major declines in the late twentieth century (Baum et al., 2003; Worm et al., 2013).

A true overabundance of large predators would likely look very different along the Carolina coast. Bait schools would become harder to find, feeding activity along the surface would begin thinning out, and predators would increasingly compete over limited prey. Instead, much of what people are witnessing today is the overlap between recovering shark populations, concentrated recreational fishing activity, and a coastline watched more closely than ever before (Heithaus et al., 2008).

For beachgoers, that change can make sharks feel suddenly more common, even as many offshore ecosystems are still rebuilding from declines that unfolded over generations.

What Changes Along the Coast When They Decline

By the time most people arrive at the beach in summer, the offshore system is already in motion.

Pelicans are not simply following random schools of fish. The bait moving through the breakers may have spent weeks feeding along temperature boundaries farther offshore. Rays passing through the shallows are connected to predators that hunt them beyond the visible edge of the continental shelf. Squid rising toward the surface at night become part of a food web that stretches from deep Atlantic water back toward the surf zone.

Most of those connections remain invisible from shore.

A person standing on the beach cannot see a bigeye thresher moving through dim offshore water hundreds of feet below the surface, or a hammerhead sweeping across the bottom searching for the electrical signals of buried prey. They cannot see tiger sharks shifting between offshore and coastal habitats as water temperatures change through the season.

But those predators still influence what eventually reaches the coastline.

The schools of fish birds gather over, the movement of rays through shallow water, the distribution of predators and prey along the continental shelf, and even the timing of seasonal feeding activity are tied to an offshore ecosystem organized partly by sharks most people never encounter directly.

From the beach, the Atlantic often appears flat and open beyond the horizon.

In reality, it is layered with movement, specialization, and predators adapted to parts of the ocean most people never realize are there.

What the Horizon Conceals

From the beach, the Atlantic often appears flat and empty beyond the breakers. Most people will never see a bigeye thresher rising from dim offshore water or a hammerhead sweeping across the continental shelf searching for prey hidden beneath the sand. The larger structure of the pelagic Atlantic remains mostly invisible from shore.

But the absence of visibility is not the same as absence of life.

Far beyond the swimming beaches and nearshore bars, sharks continue moving through layered offshore habitats shaped by depth, temperature, migration, and prey. Some travel between offshore waters and shoals. Others patrol deeper pelagic systems where sunlight fades and the surface reveals little of what exists below.

Those movements eventually connect back to the coast itself.

The same Atlantic that carries sea turtle hatchlings past the breakers, pushes baitfish toward the shoreline, and gathers pelicans over feeding fish also extends outward into a far larger offshore ecosystem organized by predators most people never see directly.

The horizon does not separate the beach from another ocean.

It only marks the point where the visible Atlantic gives way to the hidden one.

Even from the shoreline, the Atlantic extends into a far larger offshore ecosystem shaped by predators, migration, depth, and movement beyond what can easily be seen from shore. The horizon does not mark the end of the ocean’s structure, only the limit of what we can observe from the beach. | Image credit: A. Mitchell

References

Baum, J. K., Myers, R. A., Kehler, D. G., Worm, B., Harley, S. J., & Doherty, P. A. (2003). Collapse and conservation of shark populations in the Northwest Atlantic. Science, 299(5605), 389-392. https://doi.org/10.1126/science.1079777

Block, B. A., Jonsen, I. D., Jorgensen, S. J., Winship, A. J., Shaffer, S. A., Bograd, S. J., Hazen, E. L., Foley, D. G., Breed, G. A., Harrison, A., Ganong, J. E., Swithenbank, A., Castleton, M., Dewar, H., Mate, B. R., Shillinger, G. L., Schaefer, K. M., Benson, S. R., Weise, M. J., … Costa, D. P. (2011). Tracking APEX marine predator movements in a dynamic ocean. Nature, 475(7354), 86-90. https://doi.org/10.1038/nature10082

Compagno, L. J. (2001). Sharks of the world: An annotated and illustrated catalogue of shark species known to date (2nd ed.). Food and Agriculture Organization of the United Nations.

Cortés, E. (2000). Life history patterns and correlations in Sharks. Reviews in Fisheries Science, 8(4), 299-344. https://doi.org/10.1080/10408340308951115

Heithaus, M. R. (2001). The biology of tiger sharks, Galeocerdo Cuvier, in Shark Bay, Western Australia: Sex ratio, size distribution, diet, and seasonal changes in catch rates. Environmental Biology of Fishes, 61(1), 25-36. https://doi.org/10.1023/a:1011021210685

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

Kajiura, S. M. (2001). Head morphology and Electrosensory pore distribution of Carcharhinid and Sphyrnid sharks. Environmental Biology of Fishes, 61(2), 125-133. https://doi.org/10.1023/a:1011028312787

Klimley, A. P. (1993). The Behavior and Ecology of the Scalloped Hammerhead Shark. Stanford University Press.

Musick, J. A., Burgess, G., Cailliet, G., Camhi, M., & Fordham, S. (2000). Management of sharks and their relatives (Elasmobranchii). Fisheries, 25(3), 9-13. https://doi.org/10.1577/1548-8446(2000)025<0009:mosatr>2.0.co;2

Oliver, S. P., Turner, J. R., Gann, K., Silvosa, M., & D’Urban Jackson, T. (2013). Thresher sharks use tail-slaps as a hunting strategy. PLoS ONE, 8(7), e67380. https://doi.org/10.1371/journal.pone.0067380

Quattro, J. M., Driggers, W. B., Grady, J. M., Ulrich, G. F., & Roberts, M. A. (2013). Sphyrna gilberti, a new hammerhead shark (Carcharhiniformes, Sphyrnidae) from the western Atlantic Ocean. Zootaxa, 3702(2), 159. https://doi.org/10.11646/zootaxa.3702.2.5

Sims, D. W. (2006). Differences in habitat selection and reproductive strategies of male and female sharks. Sexual Segregation in Vertebrates, 127-147. https://doi.org/10.1017/cbo9780511525629.009

Strong, W. R., Snelson, F. F., & Gruber, S. H. (1990). Hammerhead shark predation on Stingrays: An observation of prey handling by Sphyrna mokarran. Copeia, 1990(3), 836. https://doi.org/10.2307/1446449

Weng, K. C., & Block, B. A. (2004). Diel vertical migration of the bigeye thresher shark (Alopias superciliosus), a species possessing orbital retia mirabilia (102:221–229). NMFS Scientific Publications Offic. https://spo.nmfs.noaa.gov/sites/default/files/pdf-content/2004/1021/weng.pdf

Worm, B., Davis, B., Kettemer, L., Ward-Paige, C. A., Chapman, D., Heithaus, M. R., Kessel, S. T., & Gruber, S. H. (2013). Global catches, exploitation rates, and rebuilding options for sharks.

May 22, 2026
When the Water Turns Gelatinous: The Hidden Filter Feeders of Onslow County

Sometimes the estuary changes before people notice why.

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

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

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

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

The drifting forms

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

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

To most people, they look like debris.

Ecologically, they are processing the estuary in real time.

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

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

That shift affects everything around them.

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

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

The bloom itself becomes food.

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

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

But like many ecological events, balance matters.

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

Most blooms are temporary.

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

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

The attached forms

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

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

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

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

Tunicates are part of that layer.

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

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

To most people, these surfaces register as slime.

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

Sea squirts

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

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

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

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

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

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

That filtration matters.

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

Their presence also signals something about the surrounding water.

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

Sea pork

Some tunicates take a different form entirely.

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

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

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

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

The colony functions collectively (Van Name, 1945).

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

That structure changes the surface around it.

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

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

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

Nudibranchs

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

These are nudibranchs.

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

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

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

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

Built for sensing, not speed

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

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

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

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

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

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

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

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

Nudibranchs move through that texture selectively.

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

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

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

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

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

Borrowed defenses, redistributed energy

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

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

This changes how energy moves through the system.

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

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

Where they sit in the trophic cascade

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

They feed on organisms that build habitat.

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

Remove the visible predators, and people notice quickly.

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

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

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

Why they stay hidden

There’s a reason most beachgoers never encounter them.

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

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

What changes if they’re gone

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

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

That loss doesn’t stay at the bottom.

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

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

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

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

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

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

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

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

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

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

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

The ones moving across the surface

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

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

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

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

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

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

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

Beneath the surface layer

Most of the time, these organisms go unnoticed.

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

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

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

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

Together, they reshape the estuary constantly.

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

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

References

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

At the Line Where Air Meets Water

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

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

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

What Birds Are Following Beneath the Surface

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

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

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

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

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

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

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

When Surface Activity Signals Pressure Below

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

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

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

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

Indicator Species at the Water’s Edge

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

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

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

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

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

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

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

Where the System Tightens

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

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

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

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

Standing Within It

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

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

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

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

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

References

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

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

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

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

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

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

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

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

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

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

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

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

Where the Ground Doesn’t Hold

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

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

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

It holds just long enough to believe that.

Then it gives way.

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

Sometimes the mud keeps what you brought with you.

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

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

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

Where It Forms: Water That Slows Down

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

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

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

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

Much of that material begins only a few feet away.

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

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

Where the water lingers, that material accumulates.

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

The Surface: What Almost Holds

From above, it can look continuous.

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

That thin layer is not just sediment.

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

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

It is just enough structure to mislead you.

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

Why It Gives Way: Structure Without Support

Once that surface breaks, the difference becomes immediate.

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

Instead of holding its shape, the ground shifts.

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

This does not (Folk, 1980).

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

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

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

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

Below the Surface: Where the Air Runs Out

The smell arrives as soon as the surface opens.

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

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

But the process doesn’t stop.

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

Each step releases it.

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

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

What Stays Behind

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

Here, much of it does not.

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

It does not stop changing.

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

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

What smells like decay is also storage.

The Surface Is Breathing

Even without oxygen below, the surface is not sealed.

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

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

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

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

It is uneven. Temporary. Constantly shifting.

At the surface, gases move both ways.

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

The boundary is thin.

But it is active.

Movement You Don’t See

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

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

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

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

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

Crabs hold the edges.

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

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

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

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

The surface does not tell you everything that is there.

When the Water Returns

Then the water comes back.

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

Fish arrive with the water.

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

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

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

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

Other species follow.

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

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

What looked still becomes active.

Not because it changed.

But because the conditions around it did.

What Comes From the Marsh

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

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

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

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

But they also export material.

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

What settles here is not separate from the marsh.

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

What Changes, and What Doesn’t

The ground beneath you is not fixed.

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

A storm can undo that quickly.

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

Other changes move more slowly.

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

The system continues.

But the way it moves through the landscape can change.

Standing at the Edge of It

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

But nothing about it failed.

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

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

It does not hold because it is not meant to.

It holds because it is already in motion.

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

References

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

What People Are Seeing

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

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

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

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

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

There is awe in it.

And sometimes hesitation.

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

The question follows quickly:

Are there more of them this year?

Maybe.

But that question lingers longer than the answer.

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

What Brings Them Here

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

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

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

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

But movement alone does not explain what people are seeing.

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

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

And beneath all of it is food.

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

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

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

Where prey is accessible, rays follow.

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

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

They are not simply “here more.”

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

What Happens When They Feed

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

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

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

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

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

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

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

And neither does the system.

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

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

Not removed entirely—but changed.

And that change does not stay in one place.

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

Layers of the Food Web

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

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

What they do in that space matters.

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

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

That pressure shapes the bottom itself.

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

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

At the same time, they carry that energy upward.

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

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

This is what it means to sit in the middle.

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

If that middle shifts, the balance does not disappear.

It changes direction.

Why It Feels Sudden

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

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

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

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

Sometimes you don’t.

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

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

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

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

It is a convergence.

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

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

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

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

For a brief window, all of it overlaps.

Not more.
But more visible.

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

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

References

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The Surface That Holds

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

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

This is when people begin to notice them again.

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

An alligator does not arrive in that moment.

It becomes visible.

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

Seasonal Absence Is Not Absence

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

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

But the system does not empty.

It compresses.

The System Wakes in Layers

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

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

The alligator moves within that shift.

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

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

Reading What It Is Responding To

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

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

It is the arrangement of prey.

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

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

The alligator positions itself within those patterns.

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

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

And the predator tracks that.

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

The alligator does not respond to the individual movement.

It responds to the pattern that produces it.

Where Freshwater Meets Salt

These are not just places where water mixes.

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

There are places along this coastline where those changes concentrate.

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

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

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

But that limitation does not exclude them.

It defines how they move through them.

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

Within that field, movement compresses.

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

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

It needs to hold where movement is forced.

And so it does.

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

At the Edge of the Open Water

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

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

It has not.

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

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

But the cost is higher.

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

And so it does not.

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

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

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

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

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

What Its Presence Changes

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

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

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

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

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

What holds the system in place is not removal alone.

It is pressure.

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

More Than Predation

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

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

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

These processes do not occur in isolation.

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

Seeing the Surface, Reading the System

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

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

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

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

The alligator is not an interruption to that system.

It is an expression of it.

What Becomes Visible

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

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

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

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

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

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

When That Pressure Is Reduced

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

It shifts.

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

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

The change is subtle.

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

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

A System Written Into Temperature

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

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

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

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

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

When conditions become more consistent, that variation narrows.

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

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

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

Where the Next Generation Is Set

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

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

That band is not fixed.

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

Human alteration compresses this space further.

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

The number of suitable sites decreases.

More importantly, the variability between them narrows.

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

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

What Its Presence Means

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

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

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

It is supported by them.

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

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

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

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

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

Epilogue: Chicken Nugget

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

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

He was directly below us.

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

A juvenile alligator, watching.

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

Waiting.

I came back later and stayed longer.

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

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

Energy, without effort.

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

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

It is behavior.

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

And expectation changes how an animal uses space.

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

It is the continuation of the same pattern.

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

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

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

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

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

It carries outward.

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

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

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

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

Let it remember the water as it is.

And you, only as something that passed through it.

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

References

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Where Expectations Begin to Slip

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

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

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

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

But that impression doesn’t hold for long.

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

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

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

Teeth built for stone: Sheepshead

The rule broken: fish are supposed to have simple teeth

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

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

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

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

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

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

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

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

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

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

The fish that walks: Bluespotted and Northern searobin

The rule broken: fish move by swimming

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

Then something moves without swimming.

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

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

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

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

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

But the seafloor is a different environment entirely.

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

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

The fish that swells: Northern puffer

The rule broken: fish don’t change shape

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

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

Then, without warning, the body changes.

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

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

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

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

Speed isn’t part of the solution here.

The fish that locks itself in place: Gray triggerfish

The rule broken: fish don’t anchor themselves

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

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

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

They turn downward.

The gray triggerfish (Balistes capriscus) moves into crevices and tight spaces within the structure, where a set of dorsal spines can be raised and locked into place. The first spine lifts, and a smaller second spine holds it there—an arrangement that gives the fish its name and allows it to anchor itself firmly in place (Tyler, 1980; Lobel, 1980).

Its body is built for this kind of movement: deep and laterally compressed, with tough, abrasive skin and strong incisor-like teeth capable of breaking into hard-shelled prey (Tyler, 1980; Lobel, 1980). These are not features meant for speed. They are features meant for contact—pressing into structure, resisting removal, holding position when movement would fail.

In waters often 50–120 feet deep off Onslow County, where reefs and wrecks break the seafloor into pockets and edges, escape doesn’t always mean distance (Bellwood et al., 2004).

Sometimes it means holding ground.

Most fish survive by staying in motion.

This one survives by becoming fixed in place, turning the structure around it into part of its defense.

Light written into skin: Atlantic midshipman

The rule broken: fish don’t carry light in their skin

On warm summer nights near quiet stretches of marsh and inlet edges, the water sometimes carries sound before anything else. A low, continuous hum. It’s easy to miss unless you stop moving.

The Atlantic midshipman (Porichthys plectrodon) produces that sound through specialized sonic muscles vibrating against the swim bladder, creating a sustained hum that can carry through shallow coastal water (Sisneros, 2009; Bass & McKibben, 2003).

If you listen carefully during a quiet evening, the sound of a male midshipman trying to court a female might be heard. | Audio credit: SanctoSound – Integrated Ocean Observing System (IOOS)

Along the sides of the body and across the head are rows of small organs—photophores—set into the skin, giving the fish its name and marking it as something unusual among coastal species found in these waters (Schwartz, 2013). When seen out of the water, those rows catch the light in a very particular way—small, round points that flash gold in direct sunlight, spaced with a regularity that makes them look almost set into the surface, like buttons fixed into the skin.

The Atlantic midshipman has photophores that dazzle when out of the water, and used in seeing in darkened burrows and structures in limited light. | Photo credit: North American Native Fishes Association

Midshipman inhabit shallow coastal environments, often in burrows or beneath structure along muddy or sandy bottoms, typically in depths less than 20 meters.

Light in fish is often associated with deeper water, where darkness is constant and illumination becomes necessary (Haddock et al., 2010). But along the Onslow coast, those conditions can exist in smaller, shifting pockets. Light narrows quickly with depth, suspended sediment moves with the tide, and visibility can collapse even in water shallow enough to stand in.

Not all fish in these waters experience the bottom the same way. A flounder rests exposed on the sand, relying on camouflage and stillness. The midshipman, by contrast, spends much of its time within burrows, beneath structure, or pressed close to the substrate, where light is already limited and often disappears entirely.

In those spaces, the rules of visibility begin to resemble something closer to deeper water, even though the surface is only a few feet above.

The presence of photophores here does not follow the pattern most people expect.

Not all light comes from above.

The deep blade: Long-snouted lancetfish

The rule broken: fish are dense, muscular swimmers

From the beach, the horizon feels like a boundary—beyond the sandbars, beyond the nearshore currents—about two miles out, where the surface lifts just enough to hide what comes after. But beyond that line, the water doesn’t simply continue. It changes.

Depth increases quickly. Layers begin to form. Light fades long before the bottom is reached.

And in those deeper waters off Onslow Bay, some fish are not built to chase anything at all.

The long-nosed lancetfish lives in the middle depths of the ocean where body density is less desirable for a drifting fish. | Photo credit: ML – some rights reserved (CC BY-NC)

The long-snouted lancetfish (Alepisaurus ferox) lives in the midwater column, often hundreds of meters below the surface. Its body is long and thin, almost blade-like, with muscle reduced and tissue that is less dense than most active predators, appearing almost soft in the water (Drazen & Seibel, 2007).

It does not move with the steady, powered swimming most fish rely on. Instead, it drifts, adjusting position and taking prey as it comes within reach. Stomach analyses show a wide range of prey—fish, squid, and even other lancetfish—suggesting opportunism rather than pursuit (Kubota & Uyeno, 1970).

In these deeper layers, energy becomes harder to acquire and more costly to use.

Building and maintaining dense muscle comes at a cost. Chasing prey demands more of it (Sutton, 2013).

Here, that balance shifts.

The lancetfish represents a different solution—one that reduces the cost of movement and relies instead on encounter.

Most fish are built to swim.

This one is built to wait.

The armored survivor: Atlantic sturgeon

The rule broken: fish are supposed to have scales

In cooler months, when water temperatures drop into the 50s and 60s, large shapes move along the bottom of estuaries and nearshore waters.

They do not flash or turn sharply. They move steadily, close to the sediment.

At times, that movement reaches the surface. A back breaks through, arcing briefly before slipping under again, the shape unfamiliar enough that it doesn’t immediately read as a fish.

The Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) retains an older form—rows of bony scutes instead of the flexible scales seen in most fishes (Bemis et al., 1997). Along the underside, a protrusible mouth extends downward, drawing in prey from the bottom through suction rather than pursuit (ASSRT, 2007; Bemis et al., 1997).

An anadromous fish, they move between river systems and coastal waters, passing through estuaries and along the nearshore edge, often in depths ranging from shallow channels to over 100 feet offshore (Dunton et al., 2015; ASSRT, 2007).

This design is not new. It has persisted for tens of millions of years, carried forward through changing coastlines, shifting sea levels, and the rise of entirely different groups of fishes (Bemis et al., 1997).

Atlantic sturgeon have a bony structure that has remained relatively unchanged for millions of years. | Photo credits: mdadswell – some rights reserved (CC BY-NC) (left); Steven McGrath – some rights reserved (CC BY-NC-ND) (right)

It works because the conditions it responds to have never fully disappeared.

Along the bottom, prey remains buried. Sediment still shifts with current and tide. Feeding still depends on contact more than speed. Armor still protects a body that cannot easily maneuver out of danger.

For a long time, these fish seemed to fade from local waters. In Onslow County, encounters became rare enough to feel like absence. But populations have persisted elsewhere, and in nearby systems like the Cape Fear River, they are being observed again with increasing frequency—moving through channels, returning to spawning grounds, reappearing in places where they had not been seen in years (Dunton et al., 2015; ASSRT, 2007).

Their range has shifted before. It may be shifting again.

What remains constant is the need for connection—between river and ocean, between spawning grounds and feeding habitat.

This fish does not depend on a single place. It depends on the continuity between them.

Not all designs are meant to change. Some persist because the system they belong to still exists.

The drifting giant: Ocean sunfish

The rule broken: fish are supposed to be shaped for swimming

Occasionally, especially in warmer months when currents shift, something appears offshore that barely seems to move at all.

A large, flattened body. A fin breaking the surface. Then another, held there longer than expected.

It drifts more than it swims.

At times, it lingers there, tilted at the surface, absorbing the sun before slipping back beneath the water.

The ocean sunfish (Mola mola) is one of the heaviest bony fish, reaching weights over 1,000 kg. Its body is truncated, lacking a true caudal fin, and propulsion is achieved through synchronized movements of dorsal and anal fins (Pope et al., 2010; Watanabe et al., 2009).

After diving into colder, deeper water, sunfish often return to the surface, where this slow, drifting posture allows their body temperature to rise again (Watanabe et al., 2009). Prolonged time at the surface can leave the skin visibly altered—shifting from darker grey to lighter tones, sometimes appearing pale or pinkened under sustained exposure.

Sunfish often inhabit offshore waters but can approach nearshore areas following currents and prey, particularly gelatinous organisms like jellyfish (Cartamil & Lowe, 2004).

By most expectations, this body plan shouldn’t work.

But it does—because efficiency, here, takes a different form. It is about buoyancy, drift, and feeding on abundant, slow-moving prey.

In a system where jellyfish blooms are seasonal and sometimes dense, a fish shaped like this becomes not an anomaly, but a specialist.

Answers to a layered environment

From the shoreline, the water still looks simple.

Small waves rise and fall. Baitfish turn and vanish. The surface holds its shape.

But beneath that surface, the rules have already begun to shift.

Fish move through these waters in ways that don’t match what we expect—crushing shell, stepping across the bottom, changing shape, holding themselves in place, carrying structures that catch light, drifting where others would swim, or moving through forms shaped long before this coastline took its present shape.

What appears, from the beach, to be a single environment is something else entirely. It is layered—sand, structure, depth, temperature, light—each one asking something different of the animals that live within it.

And the fish that seem unusual are not exceptions.

They are answers.

A layered system, at New River Inlet, seen from the surface. | Photo credit: A. Mitchell

References

Atlantic Sturgeon Status Review Team. (1998). Status review of Atlantic sturgeon (Acipenser Oxyrinchus Oxyrinchus). U.S. Fish and Wildlife Service. https://books.google.com/books?id=ee5MhnuurDMC&dq=+Status+review+of+Atlantic+sturgeon+(Acipenser+oxyrinchus+oxyrinchus)

Bardach, J. E., & Case, J. (1965). Sensory capabilities of the modified fins of squirrel hake (Urophycis chuss) and Searobins (Prionotus carolinus and P. evolans). Copeia, 1965(2), 194. https://doi.org/10.2307/1440724

Bellwood, D. R., Hughes, T. P., Folke, C., & Nyström, M. (2004). Confronting the coral reef crisis. Nature, 429(6994), 827-833. https://doi.org/10.1038/nature02691

Bemis, W. E., Findeis, E. K., & Grande, L. (1997). An overview of Acipenseriformes. Developments in Environmental Biology of Fishes, 48, 25-71. https://doi.org/10.1007/0-306-46854-9_4

Blake, R. W. (2004). Fish functional design and swimming performance. Journal of Fish Biology, 65(5), 1193-1222. https://doi.org/10.1111/j.0022-1112.2004.00568.x

Brainerd, E. L. (1994). Pufferfish inflation: Functional morphology of postcranial structures in Diodon holocanthus (Tetraodontiformes). Journal of Morphology, 220(3), 243-261. https://doi.org/10.1002/jmor.1052200304

Cartamil, D., & Lowe, C. (2004). Diel movement patterns of ocean sunfish mola mola off Southern California. Marine Ecology Progress Series, 266, 245-253. https://doi.org/10.3354/meps266245

Deang, J., Persons, A., Oppedal, A., Rhee, H., Moser, R., & Horstemeyer, M. (2018). Structure, property, and function of sheepshead (Archosargus probatocephalus) teeth. Archives of Oral Biology, 89, 1-8. https://doi.org/10.1016/j.archoralbio.2018.01.013

Drazen, J. C., & Seibel, B. A. (2007). Depth‐related trends in metabolism of benthic and benthopelagic deep‐sea fishes. Limnology and Oceanography, 52(5), 2306-2316. https://doi.org/10.4319/lo.2007.52.5.2306

Dunton, K. J., Jordaan, A., Conover, D. O., McKown, K. A., Bonacci, L. A., & Frisk, M. G. (2015). Marine distribution and habitat use of Atlantic sturgeon in New York lead to fisheries interactions and Bycatch. Marine and Coastal Fisheries, 7(1), 18-32. https://doi.org/10.1080/19425120.2014.986348

Fernandez, L. P., & Motta, P. J. (1997). Trophic consequences of differential performance: Ontogeny of oral jaw‐crushing performance in the sheepshead, Archosargus probatocephalus (Teleostei, sparidae). Journal of Zoology, 243(4), 737-756. https://doi.org/10.1111/j.1469-7998.1997.tb01973.x

Grabowski, J. H., & Peterson, C. H. (2007). Restoring oyster reefs to recover ecosystem services. Theoretical Ecology Series, 4, 281-298. https://doi.org/10.1016/s1875-306x(07)80017-7

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

McIver, E. L., Marchaterre, M. A., Rice, A. N., & Bass, A. H. (2014). Novel underwater soundscape: Acoustic repertoire of plainfin midshipman fish. Journal of Experimental Biology. https://doi.org/10.1242/jeb.102772

Mensinger, A. F., & Case, J. F. (1990). Luminescent properties of deep sea fish. Journal of Experimental Marine Biology and Ecology, 144(1), 1-15. https://doi.org/10.1016/0022-0981(90)90015-5

Petersen, J. C., & Ramsay, J. B. (2020). Walking on chains: The morphology and mechanics behind the fin ray derived limbs of sea-robins. Journal of Experimental Biology. https://doi.org/10.1242/jeb.227140

Peterson, D. L., Bain, M. B., & Haley, N. (2000). Evidence of declining recruitment of Atlantic sturgeon in the Hudson River. North American Journal of Fisheries Management, 20(1), 231-238. https://doi.org/10.1577/1548-8675(2000)020<0231:eodroa>2.0.co;2

Pope, E. C., Hays, G. C., Thys, T. M., Doyle, T. K., Sims, D. W., Queiroz, N., Hobson, V. J., Kubicek, L., & Houghton, J. D. (2010). The biology and ecology of the ocean sunfish mola mola: A review of current knowledge and future research perspectives. Reviews in Fish Biology and Fisheries, 20(4), 471-487. h ttps://doi.org/10.1007/s11160-009-9155-9

Schwartz, F. J. (2013). Atlantic midshipman, Porichthys plectrodon, in North Carolina. Journal of the North Carolina Academy of Science, 129(3), 111-114. https://doi.org/10.7572/2167-5880-129.3.111

Sedberry, G. R. (1987). Feeding habits of Sheepshead, Archosargus probatocephalus, in offshore reef habitats of the southeastern continental shelf. Northeast Gulf Science, 9(1). https://doi.org/10.18785/negs.0901.03

Sisneros, J. A. (2009). Adaptive hearing in the vocal plainfin midshipman fish: Getting in tune for the breeding season and implications for acoustic communication. Integrative Zoology, 4(1), 33-42. https://doi.org/10.1111/j.1749-4877.2008.00133.x

Snelgrove, P. V. (1999). Getting to the bottom of marine biodiversity: Sedimentary habitats. BioScience, 49(2), 129. https://doi.org/10.2307/1313538

Sutton, T. T. (2013). Vertical ecology of the pelagic ocean: Classical patterns and new perspectives. Journal of Fish Biology, 83(6), 1508-1527. https://doi.org/10.1111/jfb.12263

Tyler, J. C. (1980). Osteology, phylogeny, and higher classification of the fishes of the order plectognathi (Tetraodontiformes) (434). U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service. https://10.5962/bhl.title.63022

March 28, 2026
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

Domning, D. P. (2001). The earliest known fully quadrupedal sirenian. Nature, 413(6856), 625-627. https://doi.org/10.1038/35098072

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.

Kennett, J. P., & Shackleton, N. J. (1975). Laurentide ice sheet Meltwater recorded in Gulf of Mexico deep-sea cores. Science, 188(4184), 147-150. https://doi.org/10.1126/science.188.4184.147

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

Miller, K. G., Kominz, M. A., Browning, J. V., Wright, J. D., Mountain, G. S., Katz, M. E., Sugarman, P. J., Cramer, B. S., Christie-Blick, N., & Pekar, S. F. (2005). The Phanerozoic record of global sea-level change. Science, 310(5752), 1293-1298. https://doi.org/10.1126/science.1116412

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.

Riggs, S. R., Cleary, W. J., & Snyder, S. W. (1995). Influence of inherited geologic framework on barrier shoreface morphology and dynamics. Marine Geology, 126(1-4), 213-234. https://doi.org/10.1016/0025-3227(95)00079-e

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