Sharks of Onslow County

Category: Marine Ecology

The Hidden City in the Grass

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

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

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

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

Subtidal shallows: seagrass beds maintained by grazers

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

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

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

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

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

The low marsh edge: cordgrass shaped by snails and crabs

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

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

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

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

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

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

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

Mid-marsh: mussels and detritus processors reinforce the platform

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

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

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

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

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

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

High marsh: microbes that manage chemical stress

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

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

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

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

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

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

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

The marsh–upland transition: keeping the boundary intact

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

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

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

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

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

A marsh built by interactions

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

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

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

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

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

References

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

What Are Foraminifera?

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

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

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

Why Winter Reveals the Record

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

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

Size, Stability, and Ancient Seas

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

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

Tiny Shells, Deep Time: How Marshes Remember

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

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

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

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

What Lives in a Handful of Marsh Sand

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

Foraminifera under biological microscope with sand.

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

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

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

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

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

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

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

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

What Changes in Foraminifera Mean for the Ecosystem

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

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

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

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

Reading Change in Living Marshes

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

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

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

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

Closing

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

References

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

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

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

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

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

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

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

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

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

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

Winter birds and hidden skates in a changing coastal system

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

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

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

Above the Water: When Winter Is No Longer a Question

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

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

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

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

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

Below the Water: When Stillness Makes Life Visible

Clearnose skate in winter waters | Photo credit: NOAA Fisheries

Below the surface, the signal is subtler.

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

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

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

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

The Ecological Hinge Between Years

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

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

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

After the Turn

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

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

References

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

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

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

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

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

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

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

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

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

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

Mermaids of the Winter Shoals

The shimmering ghosts of the inlet

The Legend

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

The Science — Manatees and Mirage Tricks

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

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

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

A pair of manatees resemble mermaids swimming in the water

The Kraken of Cape Lookout

Monsters in the storm-worn deep

The Legend

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

The Science — Giant Squid and Deep-Sea Drifters

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

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

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

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

The Ghost Lights of Bogue Banks

Blue sparks swirling under December stars

The Legend

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

The Science — Bioluminescent Dinoflagellates

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

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

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

The Siren of the Shoals

Voices carried by cold seas

The Legend

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

The Science — Migrating Whales and Phantom Songs

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

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

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

A breaching humpback whale

The Marsh Giant

A slow breath in frozen reeds

The Legend

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

The Science — North Carolina’s Cold-Tolerant Alligators

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

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

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

Where Myth and Marsh Converge

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

And so legends rise.

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

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

Learn more about winter estuary ecology here.

References

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

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

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

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

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

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

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

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

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

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

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

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

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

December hushes the coastline of Onslow County. The marshgrass stiffens in the cold, the surf stills between storms, and the New River Inlet carries the metallic stillness of early winter. Yet beneath that calm, the water hums with motion — tiny pulses, ripples, and vibrations that weave a hidden holiday soundtrack, a kind of underwater sleigh bells rung in pressure waves.

Sharks, lingering along the nearshore troughs or cruising the outer edge of the estuary, sense these disturbances with remarkable clarity. Every mullet tail-beat, crab scuttle, and sediment shift radiates through the water as a low-frequency pressure wave. In the quiet of December, these signals travel farther and cleaner, strengthened by winter’s denser water, slower prey, and reduced turbidity (Mickle & Higgs, 2021; Mogdans, 2019).

To sharks, these vibrations form a map, a three-dimensional winter soundscape that reveals direction, distance, and urgency (Montgomery, Baker & Carton, 2000; Montgomery et al., 2000). And layered beneath these hydrodynamic cues, the faint electric fields produced by the heartbeat and muscle activity of nearby prey glow through the water, detectable at nanovolt precision (Anderson et al., 2017; England et al., 2021).

This “music” is not metaphor — it is the sensory world sharks inhabit, sharpened by the very conditions winter imposes.

The Winter Sea as a Soundscape

Sharks detect a wide range of underwater vibrations—from the rolling displacement waves of schooling fish to the intermittent pulses of crabs and the subtle fin flicks of solitary prey—using their highly sensitive mechanosensory systems.

Cold water shifts the physics of survival. As temperatures fall, prey metabolism slows, creating weaker and more irregular movement patterns — the exact low-frequency signatures sharks detect most easily (Sisneros & Rogers, 2016). Reduced plankton and sediment yield a clearer path for particle motion, allowing hydrodynamic cues to propagate farther through the winter water column (Mogdans, 2019).

This turns the estuary into a rich field of vibrations. Fish schooling tightly create rolling displacement waves. Crabs shifting beneath the sand produce intermittent pulses. Even subtle fin flicks produce particle motion detectable by sharks’ sensory systems (Maruska, 2001).

Winter looks barren to us.
To sharks, it resonates.

Hydrodynamic “Bells”: The Lateral Line

Sharks use their lateral line to “feel” tiny vibrations in the water. Winter makes these signals even easier to detect, helping sharks follow the movement of fish, crabs, and other prey in low-light conditions.

The shark’s lateral line is a mechanosensory canal system tuned to detect water displacement in the exact frequency range produced by struggling fish and crustaceans (Montgomery, Baker & Carton, 2000). Neuromasts within the canal encode both direction and amplitude, transforming low-frequency motion into a spatial map of nearby activity (Mogdans, 2019).

In December, this system excels:
- cold water enhances transmission of pressure waves,
- prey move more predictably and more weakly,
- low-light conditions reduce visual noise,
- and inlet geometry funnels vibrations along natural corridors.
Even acoustic cues — particle motion at frequencies under ~300 Hz — become part of this integration. Sharks are most sensitive to these low-frequency bands, enabling discrimination of movement types in murky or dark winter water (Poppelier et al., 2022).

To a shark, each pulse is information.
Each ripple is direction.
Each vibration is a bell rung underwater.

Watch how sharks use their lateral line system to sense ripples and vibrations long before they see their prey. | Video courtesy of National Aquarium – “Sharks Lateral Line”

Closer Than Sight: The Ampullae of Lorenzini

When a shark closes the final distance, tracking transitions from vibration to electricity. The Ampullae of Lorenzini detect microvolt-scale electric fields emitted by the body of every living animal. Sensitivity thresholds fall into the tens of nanovolts per centimeter — among the most refined biological detection limits known (Anderson et al., 2017; Newton, Gill & Kajiura, 2019; England et al., 2021).

Electroreception enables sharks to:
- locate prey buried beneath sand,
- perceive fish hidden in silt clouds,
- detect immobile or slow-moving animals,
- and navigate complex, low-light environments.
Classic electroreception work demonstrated these capacities decades ago, and modern experimental studies in hammerheads confirm high-resolution electro-sensitivity during close-range hunting (Kajiura & Holland, 2002; Kalmijn, 2000).

In winter, when storms churn the sediment and twilight comes early, this sense becomes even more essential.

Sharks do not need light — they follow electricity.

Video courtesy of PBS Deep Look, illustrating how sharks use electroreception to locate prey invisible to sight or sound.

A December Hunt at the New River Mouth

A juvenile Atlantic sharpnose shark follows the faint hydrodynamic pulse of a cold-slowed mullet, then locks onto its electric field—an underwater hunt guided by vibration and microvolts.

Picture a December evening at the New River Inlet. The ebb tide pulls cold water from the sound toward the ocean. A juvenile Atlantic sharpnose shark glides along a shallow bar, guided not by sight, but by the underwater vibrations pulsing through its lateral line.

A faint, uneven pressure wave reaches the shark — the hydrodynamic signature of a mullet slowed by the cold (Montgomery et al., 2000). The shark turns. Another pulse follows, the rhythm revealing both direction and weakness.

Within a few body lengths, electric cues rise above the hydrodynamic noise. The Ampullae of Lorenzini detect microvolt-scale oscillations from the mullet’s buried body (Newton, Gill & Kajiura, 2019; England et al., 2021). One quick strike completes the hunt.

This is winter’s choreography:
vibrations at a distance,
electricity up close,
all woven seamlessly through still December water.

The Importance of Winter Hunting

Even as the season quiets the coast, sharks thrive—reading vibrations, following winter corridors, finding weakened prey, and navigating the dim water with senses far beyond our own.

Although prey slow in winter, sharks must continue to feed. Their dual sensory systems allow efficient predation in the season that challenges most marine animals. These abilities help sharks:
- build winter energy reserves,
- exploit predictable movement corridors,
- maintain population stability by removing weakened individuals (Tricas & McCosker, 1984),
- and navigate cold, low-visibility environments effectively (Mickle & Higgs, 2021).
Even as water temperatures drop, species like Atlantic sharpnose sharks, bonnetheads, and offshore Atlantic spiny dogfish remain active, relying heavily on the interplay of hydrodynamic and electroreceptive cues (Maruska, 2001).

Winter is not lifeless.
It is a sensory masterclass.

Bells That Never Stop Ringing

While we celebrate the holidays with sleigh bells, carols, and glowing lights, the Atlantic hums with its own winter rhythms. Sharks navigate December through vibrations, particle motion, and faint electrical fields — signals older than any tradition and tuned to the pulse of life beneath the cold.

Their bells are not made of metal.
They are made of motion.
Of electricity.
Of the quiet echoes of survival beneath the tide. These are the Shark Sleigh Bells, ringing softly beneath Onslow County’s winter waters.

References

Anderson, J. M., Clegg, T. M., Véras, L. V., & Holland, K. N. (2017). Insight into shark magnetic field perception from empirical observations. Scientific Reports, 7(1). https://doi.org/10.1038/s41598-017-11459-8

England, S. J., & Robert, D. (2021). The ecology of electricity and electroreception. Biological Reviews, 97(1), 383-413. https://doi.org/10.1111/brv.12804

Kajiura, S. M., & Holland, K. N. (2002). Electroreception in juvenile scalloped hammerhead and sandbar sharks. Journal of Experimental Biology, 205(23), 3609-3621. https://doi.org/10.1242/jeb.205.23.3609

Kalmijn, A. J. (2000). Detection and processing of electromagnetic and near–field acoustic signals in elasmobranch fishes. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 355(1401), 1135-1141. https://doi.org/10.1098/rstb.2000.0654

Maruska, K. P. (2001). Morphology of the Mechanosensory lateral line system in elasmobranch fishes: Ecological and behavioral considerations. Environmental Biology of Fishes, 60(1-3), 47-75. https://doi.org/10.1023/a:1007647924559

Mickle, M. F., & Higgs, D. M. (2021). Towards a new understanding of elasmobranch hearing. Marine Biology, 169(1). https://doi.org/10.1007/s00227-021-03996-8

Mogdans, J. (2019). Sensory ecology of The Fish lateral‐line system: Morphological and physiological adaptations for the perception of hydrodynamic stimuli. Journal of Fish Biology, 95(1), 53-72. https://doi.org/10.1111/jfb.13966

Montgomery, J., Carton, G., Voigt, R., Baker, C., & Diebel, C. (2000). Sensory processing of water currents by fishes. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 355(1401), 1325-1327. https://doi.org/10.1098/rstb.2000.0693

Montgomery, J. C., Baker, C. F., & Carton, A. G. (1997). The lateral line can mediate rheotaxis in fish. Nature, 389(6654), 960-963. https://doi.org/10.1038/40135

Newton, K. C., Gill, A. B., & Kajiura, S. M. (2019). Electroreception in marine fishes: Chondrichthyans. Journal of Fish Biology, 95(1), 135-154. https://doi.org/10.1111/jfb.14068

Poppelier, T., Bonsberger, J., Berkhout, B. W., Pollmanns, R., & Schluessel, V. (2022). Acoustic discrimination in the grey bamboo shark Chiloscyllium griseum. Scientific Reports, 12(1). https://doi.org/10.1038/s41598-022-10257-1

Tricas, T. C., & McCosker, J. E. (1984). Predatory behavior of the white shark (Carcharodon carcharias) and other large sharks. Proceedings of the California Academy of Sciences, 43(14), 221-238. https://ia801302.us.archive.org/16/items/biostor-78396/biostor-78396.pdf
December 7, 2025
The Leftovers: What Happens to Summer’s Prey When the Big Fish Leave?

The Quiet Season Begins

When the red drum, flounder, and summer sharks follow the cooling tides offshore, Onslow County’s estuaries fall quiet. The flashy chases fade, and the splashes that once rippled through the creeks give way to stillness. But the story doesn’t end. Beneath November’s calm water, the estuary begins to rewrite itself.

The absence of its top hunters leaves behind both energy and opportunity — a banquet for the small and the overlooked. The currents no longer echo with the heavy pulse of pursuit. Instead, what remains is a more deliberate rhythm — a slow exchange between detritus, crabs, and the smaller fish that endure the cold months ahead.

Winter in the New River Estuary: The Vacancy in the Food Web

Every migration leaves an ecological vacancy. When red drum and southern flounder depart, they take with them both predatory pressure and nutrient export. The estuary briefly relaxes its guard. Prey fish, shrimp, and crabs experience a momentary release from predation from top predator populations that cause a cascade that momentarily alters predation pressure on lower-level prey (Clark et al., 2003).

In this lull, energy that once fueled apex biomass lingers in the system, stored in crustaceans and schooling fish that escaped the hunt (Baird et al., 1998). The estuary, ever adaptive, redistributes that energy downward. Blue crabs (Callinectes sapidus) and juvenile spot (Leiostomus xanthurus) surge in number, exploiting the leftovers of summer’s feast (Allen et al., 2024). The marsh becomes a recycling ground — energy looping through smaller players instead of flowing outward to the sea.

Late-fall estuarine food web diagram showing energy flow from detritus to shrimp, fish, and mesopredators.

The Winter Guardians

But not all predators have gone. When the warm-water hunters leave, colder visitors arrive. Along the inlets and nearshore waters of Onslow Bay, Atlantic spiny dogfish (Squalus acanthias) drift in with the falling temperatures. They are the quiet inheritors of the season — small sharks with silver eyes and slate-gray backs, moving in disciplined schools just offshore.

Atlantic spiny dogfish (Squalus acanthius) — the “winter guardians” — patrol coastal waters when larger predators have departed, sustaining the rhythm of predation. | Photo credit: Andy Murch

Where the big sharks of summer — sandbars, blacktips, and bulls — have vanished southward or deeper, the dogfish remain. Their bodies are built for cold water, thriving where others slow (Carlson et al., 2014). And while their size may not inspire awe, their purpose is no less vital: they fill the empty seats at the top of the table.

Dogfish are mesopredators, but in winter they act as temporary apex hunters, patrolling the inlet and inner shelf where menhaden, herring, and squid still linger (Carlson et al., 2014). Their presence keeps the ecosystem in motion. They thin out the schools that might otherwise explode in number, preventing imbalance and decay. Like patient custodians, they maintain the continuity of predation, ensuring that energy continues to flow up and down the food web even in the cold months (Prugh et al., 2009).

In their absence, the estuary might collapse inward — prey would overgraze, detritus would pile, and oxygen would vanish from the mud. But the dogfish, efficient and tireless, keep the waters breathing.

Crabs and Killifish Take the Stage

Blue crabs roam the winter marsh, feeding on detritus and benthic invertebrates. Their slow foraging helps recycle nutrients and sustain the estuary’s energy balance through the cold season.

Within the estuary itself, the smaller actors continue their work. By December, the New River’s mudflats and marsh creeks host a quieter cast — mummichogs (Fundulus heteroclitus), sheepshead minnows (Cyprinodon variegatus), and grass shrimp (Palaemonetes pugio). These resident species, often unnoticed, now carry the estuary’s metabolism on their backs.

They thrive on detritus and microbial mats, converting decay into new life (Kneib, 2015). Blue crabs roam like slow-moving janitors, shifting through sediment to feed on worms and organic matter (Kennedy & Cronin, 2007). Each movement releases trapped nutrients, fueling microbial blooms that will later nourish the first plankton of spring.

While the spiny dogfish patrol the edges of the continental shelf, these smaller species sustain the inner heart of the estuary. Their labor keeps the water alive long after the glamour of migration fades.

Nutrient Loops and Winter Stability

Without large predators, the estuary depends on microbial and detrital loops to keep its energy cycling. Up to 70% of carbon transfer between November and February occurs through benthic detritivory and microbial remineralization rather than direct predation (Friedrichs & Perry, 2001).

This invisible economy sustains the overwintering fish and crustaceans — the leftovers that, in time, will become the first meal of spring’s returning predators. It’s the estuary’s savings account: energy stored as biomass and sediment, ready to be withdrawn when the tides warm again.

When winter quiets the hunt, the estuary turns inward. Instead of predators driving the cycle, nutrients move through the mud itself — microbes and detritivores recycling what’s left behind. This unseen flow keeps the New River alive until spring’s return (adapted from Erler et al., 2020).

A Resilient Feast

By January, the estuary seems dormant to the casual eye, but beneath its glassy surface, life reorganizes with quiet precision. Crabs clean the table. Dogfish patrol the edge. Minnows and shrimp sift through the silt for remnants of summer.

The New River continues to breathe — slower, deeper, deliberate.
When the big fish return with the first warm tides, the table is set once more, and the energy once left behind has been transformed — recycled through countless small mouths and patient currents into the promise of another season’s chase.

References

Allen, D. M., Govoni, J. J., Able, K. W., Buckel, J. A., Hale, E. A., Hilton, E. J., Kellison, G. T., Targett, T. E., Taylor, J. C., & Walsh, H. J. (2024). Long-term dynamics of larval and early juvenile spot (Leiostomus xanthurus) off the U.S. East Coast: Relating ocean origins, estuarine Ingress, and changing environmental conditions. Fishery Bulletin, 122(4), 162-185. https://doi.org/10.7755/fb.122.4.3

Baird, D., Luczkovich, J., & Christian, R. (1998). Assessment of spatial and temporal variability in ecosystem attributes of the St marks national wildlife refuge, Apalachee Bay, Florida. Estuarine, Coastal and Shelf Science, 47(3), 329-349. https://doi.org/10.1006/ecss.1998.0360

Carlson, A. E., Hoffmayer, E. R., Tribuzio, C. A., & Sulikowski, J. A. (2014). The use of satellite tags to redefine movement patterns of spiny dogfish (Squalus acanthias) along the U.S. East Coast: Implications for fisheries management. PLoS ONE, 9(7), e103384. https://doi.org/10.1371/journal.pone.0103384

Clark, K. L., Ruiz, G. M., & Hines, A. H. (2003). Diel variation in predator abundance, predation risk and prey distribution in shallow-water estuarine habitats. Journal of Experimental Marine Biology and Ecology, 287(1), 37-55. https://doi.org/10.1016/s0022-0981(02)00439-2

Foster, S. Q., & Fulweiler, R. W. (2014). Spatial and historic variability of benthic nitrogen cycling in an anthropogenically impacted Estuary. Frontiers in Marine Science, 1. https://doi.org/10.3389/fmars.2014.00056

Friedrichs, C. T., & Perry, J. E. (2001). Tidal Salt Marsh Morphodynamics: A Synthesis. Journal of Coastal Research, (27), 7-37. https://www.jstor.org/stable/25736162

Kennedy, V. S., & Cronin, L. E. (2007). The blue crab: Callinectes Sapidus. Maryland Sea Grant College University of Maryland.

Kneib, R. T. (1986). The role of Fundulus heteroclitus in salt marsh trophic dynamics. American Zoologist, 26(1), 259-269. https://doi.org/10.1093/icb/26.1.259

Prugh, L. R., Stoner, C. J., Epps, C. W., Bean, W. T., Ripple, W. J., Laliberte, A. S., & Brashares, J. S. (2009). The rise of the Mesopredator. BioScience, 59(9), 779-791. https://doi.org/10.1525/bio.2009.59.9.9

November 29, 2025
The Estuary Feast: November Predators of the New River Estuary, NC
Each November, as the hardwoods fade to rust and the air over Onslow County turns crisp, the New River estuary begins its quiet transformation. Beneath the calm surface, baitfish, shrimp, and crabs gather in the creeks and channels like guests arriving early to dinner. Cooling waters, shifting salinity, and autumn tides all cue a feeding frenzy among the river’s top hunters – red drum (Sciaenops ocellatus), southern flounder (Paralichthys lethostigma), and spotted seatrout (Cynoscion nebulosus).

To the casual observer, it’s just another turn of the season. But for these predators, November is the defining moment of survival – the “estuary feast” that powers them through the winter ahead.

The Science Behind the Feast

As water temperatures drop, oxygen and prey shift. Shrimp slow, mullet school tightly, and predators move into perfect feeding conditions. In November, the estuary’s food web compresses – a short, fierce burst of activity before winter quiets the water.

Autumn brings an ecological reshuffling. As air temperatures drop, water density increases, pushing oxygen-rich layers deeper into the estuary. Cooler water slows the metabolism of small prey, but keeps predators in their metabolic sweet spot – a narrow temperature window where they can feed efficiently (Facendola & Scharf, 2012).

In the New River, this dynamic compresses the food web: prey such as mullet, menhaden, and shrimp concentrate in fewer, warmer microhabitats, and predators follow. Southern flounder and red drum migrate from the upper estuary toward the inlet, using the last strong tides of the season to feed before moving offshore to spawn (Midway et al., 2024).

At the same time, spotted seatrout remain nearshore longer than most species, prowling deep bends and channel edges for sluggish crustaceans and cold-stunned baitfish (Bortone, 2003; TinHan et al., 2018; Whaley et al., 2023). This makes November one of the few months when all three predators share overlapping hunting grounds – a temporary “banquet hall” of intersecting habits and appetites.

Predators at the Table

Red Drum

Known locally as “channel bass”, red drum rely heavily on macro-crustaceans and juvenile fishes during the late fall surge (Facendola & Scharf, 2012). In the New River estuary, they patrol marsh edges and oyster-reef margins where baitfish funnel out with the ebbing tide. These habitats not only provide prey but also structure – a three-dimensional refuge network that concentrates food in predictable corridors.

Red drum are particularly sensitive to dissolved oxygen and salinity changes; they exploit the higher oxygen zones along shell hash and sandy bottoms where shrimp and crabs are most active.

Southern Flounder

Flat, camouflage, and opportunistic, southern flounder are the ambush specialists of November. As they stage for ocean migration, they feed voraciously along the lower estuary and inlet shoals, striking from beneath the sand when shrimp or menhaden schools pass overhead.

Telemetry data show that most adult flounder exit the estuary between mid-October and mid-November (Midway et al., 2024), making this their final feeding push before winter. The energy stored in liver and muscle tissue during this period directly fuels their offshore spawning.

Spotted Seatrout

The spotted seatrout, or “speckled trout”, represents a different strategy: persistence.Unlike flounder or drum, they remain within the estuary for much of the winter. Their adaptive physiology lets them remain active in cooler water, hunting shrimp and small schooling fish even below 15℃, or 59℉ (Bortone, 2003; TinHan et al., 2018; Whaley et al., 2023).

This endurance gives them a late-season advantage – fewer competitors and concentrated prey. In Onslow County’s deeper channels, dock lights and tidal flows create perfect feeding grounds long after other predators have departed.

Prey and Energy Flow

From marsh to mouth: The energy of the estuary: Energy flows up the ladder – detritus -> shrimp -> baitfish -> predator. This seasonal burst fuels migrations and maintains balance in Onslow County’s estuary ecosystem. But when prey species are overfished, that balance falters.

Every feast depends on abundance. In the New River system, fall prey peaks come from several sources:
- Penaeid shrimp (brown, pink and white shrimp) and blue crabs provide high-calorie meals critical to red drum and flounder growth (Facendola & Scharf, 2012).
- Striped mullet (Mugil cephalus) migrate seaward in vast schools during November, offering short bursts of energy-rich prey (NCDMF, 2022).
- Juvenile fishes – menhaden, spot, croaker – linger in the brackish middle reaches, serving as transitional prey before exiting the estuary.
As predators consume these resources, energy moves up the trophic ladder. That transfer of biomass – from detritus to shrimp to fish to apex predator – defines the estuary’s productivity and resilience (Bortone, 2003; TinHan et al., 2018; Whaley et al., 2023).

Beyond the Feast: Ecological Balance

The estuary’s “Thanksgiving” is not just a seasonal event. It’s a reset of the entire system. By removing weaker or late-season prey, predators help balance populations and redistribute nutrients through excretion and predation scars. Their feeding activity also stirs sediments and oxygenates bottom layers, improving microbial decomposition that recycles organic matter for the next year’s growth.

But this rhythm is vulnerable. Habitat loss, water-quality decline, and overfishing can all truncate the feast. Striped mullet, a keystone prey species, remains overfished statewide (NCDMF, 2022), while southern flounder face chronic recruitment declines. (Recruitment is the process of small, young fish transitioning into their older, larger lifestage.) Each missing link reduces the estuary’s resilience – and the energy pulse that sustains these predators through winter.

Climate Notes: A Shifting Season

Recent NOAA data suggests that fall water temperatures in coastal North Carolina are trending 1°-2℃, or 1.8°-3.6℉, warmer than historical averages. Warmer autumns can delay predator migrations, alter prey timing, and extend disease risks for estuarine fish (Bortone, 2003; TinHan et al., 2018; Whaley et al., 2023; Llansó et al., 1998). For Onslow County, this means the “feast” could increasingly occur later, or not at all, in some years. Tracking these shifts can help monitor how climate variability reshapes local predator cycles.

Conclusion

In the quiet weeks before winter, the New River estuary hosts its grandest ritual: a final surge of life and energy. Flounder lie in wait beneath the sand; red drum sweep through oyster channels; speckled trout strike in the moonlit current. Together they embody the estuary’s cyclical resilience – a natural Thanksgiving built on balance, adaptation, and timing.

For those who walk the riverbanks or wade the flats in November, the story unfolding beneath the surface is as rich and meaningful as any holiday tradition: a reminder that even in cooling waters, the rhythm of life continues, fierce and beautiful.

References

Bortone, S. A. (2002). Biology of the spotted Seatrout. CRC Press.

Facendola, J. J., & Scharf, F. S. (2012). Seasonal and ontogenetic variation in the diet and daily ration of estuarine red drum as derived from field-based estimates of gastric evacuation and consumption. Marine and Coastal Fisheries, 4(1), 546-559. https://doi.org/10.1080/19425120.2012.699018

Llansó, R. J., Bell, S. S., Vose, F. E., & Llanso, R. J. (1998). Food habits of red drum and spotted Seatrout in a restored mangrove impoundment. Estuaries, 21(2), 294. https://doi.org/10.2307/1352476

Midway, S. R., Scharf, F. S., Dance, M. A., Brown-Peterson, N. J., Ballenger, J. C., Beeken, N. S., Borski, R. J., Darden, T. L., Erickson, K. A., Farmer, T. M., Fincannon, A., Godwin, J., Graham, P. M., Green, J. L., Hershey, H., Kiene, D., Lee, L. M., Loeffler, M. S., Markwith, A., & McGarigal, C. (2024). Southern Flounder: Major Milestones and Remaining Knowledge Gaps in Their Biology, Ecology, and Fishery Management. Reviews in Fisheries Science & Aquaculture, 32(3), 450-478. https://www.stevemidway.com/publication/midway2024rfsa/midway2024RFSA.pdf

North Carolina Division of Marine Fisheries (NCDMF). (2022, August). Fishery Management Plan Update Striped Mullet. NC Dept. of Environmental Quality (NCDEQ). https://www.deq.nc.gov/marine-fisheries/fisheries-management/annual-fmp-review/2023/2023-striped-mullet-fmp-review/open

TinHan, T. C., Mohan, J. A., Dumesnil, M., DeAngelis, B. M., & Wells, R. J. (2018). Linking habitat use and trophic ecology of spotted Seatrout (Cynoscion nebulosus) on a restored oyster reef in a subtropical Estuary. Estuaries and Coasts, 41(6), 1793-1805. https://doi.org/10.1007/s12237-018-0391-x

Whaley, S. D., Shea, C. P., Santi, E. C., & Gandy, D. A. (2023). The influence of freshwater inflow and seascape context on occurrence of juvenile spotted seatrout Cynoscion nebulosus across a temperate Estuary. PLOS ONE, 18(11), e0294178.
November 10, 2025