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Chapter Three

Habitats of theEstuarine Reserve

78

Ocean Beaches

The ocean beach that sunbathers love is only onepart of the ocean beach habitats found at the Reservesites. The beach in a sense begins underwater,extending in some places for miles offshore to theedge of the continental shelf. The water currents andpatterns of sediment deposition along the shelfinfluence what a beach looks like – how it erodes, itssize. Along the shore itself are three contrastingenvironments – the subtidal, intertidal and supratidalzones – which are populated by organisms speciallyadapted to the harsh characteristics of each area.

Subtidal zone

The shallow waters, breaking waves, and swirlingsand of the subtidal zone are home to plankton,algae, jellyfish, starfish, mollusks, crustaceans andfish. The only plants that survive here are one-celledalgae. The constant movement of water and sandprevents organisms that need to be attached to ahard surface (such as barnacles) from taking hold.As the water rakes shell fragments and coarse sandacross the bottom, each wave can injure or buryorganisms.

Starfish

Cannonball jellyfish

Mole crab

Coquina clam

Ocean Beaches

Great Southern White

79

Intertidal zone

Animals living in the sandy environment of theintertidal zone are exposed to alternating periods ofwave action and salt- laden drying breezes. Althoughit may appear that the only creatures here are birds,millions of tiny worms, shrimp and other organismslive among the sand grains. Coquina clams, Donaxspp., and mole crabs, Emerita talpoida, survive byburrowing into the sand and filtering plankton(microscopic plants and animals) from the wavesthat wash over them.

Quiick escape into the sand is essential to avoid beingeaten by the groups of sandpipers, Caladris spp.,andother shorebirds patrolling the beach. Scavengerbirds like the herring gull, larus argentatus, are com-mon and feed on dead fish, mollusks and crustaceans.

Supratidal zone

The supratidal beach zone – above the high tide mark– is a desert-like environment except during stormtides. Plants that occasionally grow in this zone at theReserve sites are the sea rocket, Cakile spp., and seaoats, Uniola paniculata. They may be found alongthe drift line where bits of organic matter and debrisin the soil make it possible for the plants to grow.

Herring gull

Sea rocket

Sand shrimp

Brown pelican

Ocean Beaches

80

The scavenging ghost crab, Ocypode albicans,makes deep tunnels with front and back entrances toavoid predators and the high temperatures of theupper beach, but must daily wet its gills in the ocean.The beach flea, Talorchestia spp., survives the harshconditions by hiding in burrows or debris and feedson dead plant and animal material.

At night during the summer, female loggerhead seaturtles, Caretta caretta, a federally protectedthreatened species, come from the ocean and nest inthe upper beach on Masonboro Island, Zeke’s sandspit and occasionally at Currituck Beach. In latesummer and fall, the emerging baby turtles must digout of their nests and make a short yet perilousjourney to the sea, avoiding predators such as ghostcrabs, birds and raccoons. The female turtles thatsurvive will eventually return to the same area fornesting.

Sand Dunes

Sand dunes are a critical part of the coastal ecosystem. They protect the individual barrierislands from the wind, waves and storms, much asthe islands protect the mainland. On islands whereextensive dune systems are able to establish,complex communities like the shrub thicket andmaritime forest can grow sheltered from salty winds.Salt marshes can develop along the protectedshoreline.

Raccoon

Prickley pear

Ghost crab

Laughing gull

Sand Dunes

81

Dunes also protect buildings and beach cottages, animportant fact for people who enjoy vacationing orliving at the beach. Natural dunes occur on the oceanside of Zeke’s Island, Masonboro Island and theCurrituck Banks sites. The Rachel Carson sitecontains small dunes on Bird Shoal.

Sea oats, Uniola paniculata, and American beachgrass, Ammophila breviligulata, are primarilyresponsible for creating the dunes. Sea oats occurthroughout the mid-Atlantic area. American beachgrass is native to the coast north of Cape Hatteras,although it does grow in some areas of the southerncoast. Both plants are uniquely adapted to the harshenvironment of salt-laden winds, shifting sands, poorsoil and glaring sun. The grasses’ roots and under-ground stems – which can extend as much as 30 feetbelow the surface of the dune to reach water – form anetwork that holds mounds of sand together. Asmore grasses stabilize the sand, a dune line is established.

These plants have flexible leaves that can withstandbeing whipped about by the wind. A waxy coating oneach leaf conserves water, which is essential forsurvival on this desert-like environment. The rootshave to absorb moisture efficiently because theporous sands hold virtually no water. Salt spray, theplants’ primary source of nutrients, is absorbed eitherfrom the soil or the plant surface.

Loggerhead turtle

Atlantic bottle-nose dolphin

American beach grass

Ring-billed gull

Sand Dunes

82

Other dune plants include sea elder, Iva imbricata,sea rocket, Calike spp., croton, Croton punctatus,sand primrose, Oenothera humifusa, panic grass,Panicum amarum, and sea spurge, Euphorbiapolygonifolia. Although these species are not thecolonizers that sea oats and American beach grassare, they have adapted to the dune environment withflexible, waxy leaves and stems, like those of the seaelder and sea rocket, or by growing flat on theground, like the sea spurge and trailing sandprimrose.

There are few animals in the frontal dunes, all ofwhich also forage in the upper beach. Many of theseorganisms are insects – digger wasp, Bembex sp.,velvet ant, Dasymutilla sp., earwig, Anislabis sp.,and mole cricket, Gryllotalpa hexadactyla – whichare adept at digging or hiding under debris forprotection. The digger wasp cools itself during itsexcavating efforts by periodically flying up frombaking sediments.

Ghost crabs and beach fleas are upper beachresidents that also forage in the dunes.Storm-overwash areas – where the dunes have beenbreached and fresh deposits of sand blanket thevegetation – are prime habitats for ground nestingbirds such as the black skimmer, Rhynchops niger,Wilson’s plover, Charadrius wilsonia, common tern,Sterna hirundo, and least tern, Strerna alsifrons.

Black skimmer

Beach flea

Panic grass

Croton

Sand Dunes

83

Grasslands

Behind the dunes, protected from the salty windsand waves of the ocean, are grasslands. A greaterdiversity of species can survive in this milderenvironment.

Sea oats, Uniola paniculata, or American beachgrass,Ammophila breviligulata, which dominate the frontaldunes, share this habitat with salt meadow cordgrass,Spartina patens, broom sedge, Andropogon virginicus,panic grass, panicum spp., and sandspur, Cenchrusspp. Other plants found here include seaside goldenrod,Solidago sempervirens, gaillardia, Gaillardia pulchella,yucca, Yucca filamentosa, sand primrose, Oenetherahumifusa, Drummond’s prickly pear cactus, Opuntiadrummondii, camphorweed, Heteratheca axillaris,pennywort, Hydrocotyle bonariensis, and beach morn-ing glory, Ipomea spp.

Vines, shrubs and small trees grow in the back duneswhere direct salt spray is reduced, often marking agradual transition to the shrub thicket community. Cat-brier, Smilax spp., Spanish bayonet, Yucca spp.,yaupon, Ilex vomitoria, Hercules’ club, Zanthoxylumclava-herculis, live oak, Quercus virginiana, and redcedar, Juniperus virginiana, are examples of shrubthicket species occasionally found in grassland areas.

Broom sedge

Seaside goldenrod

Hercule’s club

Grasslands

84

Grassland animals that move between the dunes andshrub thicket/maritime forest include the housemouse, Mus musculus, meadow mouse, Microtuspennsylvanicus, cottontail rabbit, Syvilagusfloridanus, eastern glass lizard, Ophisaurusventralis, corn snake, Elaphe guttata, and six-linedracerunner, Enemidophorus sexlineatus. At theRachel Carson and Currituck sites, feral horses,Equus caballus, graze on upland and marsh grasses.These are domestic horses that have turned wild.

Various birds such as the red-winged blackbird,Agelaius phoeniceus, mockingbird, Mimuspolyglottos, and boat–tailed grackle, Quiscalusmajor, forage in the grasslands for insects and seeds.Mourning doves, Zenaida macroura, ground doves,Colunbina passerina, and nighthawks, Chordeilesminor, nest and feed there as well.

Shrub Thickets

As distance from the ocean increases, the effects ofsalt spray and temperature variations from tidalchanges are reduced, making it possible in someparts of the Reserve for shrub thicket to grow. Thishabitat typically consists of a dense mixture of vines,shrubs, and small trees. Depending on the level ofexposure to sea breezes, the seaward edge of thethicket may be dramatically angled.

Meadow mouse

Boat-tail grackle

Six-lined racerunner

Virginia creeper

Shrub Thickets

85

When salt spray kills the terminal, or exposed, budson the shrubs and small trees, they branch out to thesides. This creates a closely woven canopy thatprotects the interior plants from salt spray. Earlysettlers of the barrier islands discovered that thethickets and the maritime forests were the safestplaces to build their homes because of the shelter theyprovided from the sun, wind and storms. Shrubthicket is found at the Currituck Banks site and partsof the Rachel Carson and Zeke’s Island sites. Isolatednooks of shrub thicket paralleling the dunes are alsofound on Masonboro Island.

Plants that often dominate the thicket include live oak,Quercus virginiana, yaupon, Ilex vomitoria,wax myrtle, Myrica cerifera, silverling, Baccharishalimifolia, red cedar, Juniperus virginiana,persimmon, Diospyros virginiana, and at CurrituckBanks, bayberry, Myrica pennsylvanica.

Growing over and through the shrubs and small treesare vines such as the Catbrier, Smilax spp., Virginiacreeper, Parthenocissus quinquefolia, muscadinegrape, Vitis rotundifolia, pepper vine, Ampelopsisarborea, and poison ivy, Rhus radicans. Where lightcan penetrate the canopy, there are patches of herbscontaining partridge berry, Mitchella repens, panicgrass, Panicum spp., elephant’s foot, Elephantopusnudatus, pepper grass, Lepidium virginicum, andbeggars ticks, Bidens spp..

Yaupon

Poison ivy

Yellow-rumped warbler

Wax myrtle

Shrub Thickets

86

The vegetation in this community provides manyniches for animal habitation. White-tailed deer,Odocoileus virginianus, are found at CurrituckBanks, while raccoon, Procyon loto, opossum,Didelphus virginicus, cottontail rabbit, Sylvilagusfloridanus, gray fox, Urocyon coneroargenteus, cottonmouse, Peromyseas gossypinus, least shrew, Cryptotisparva, and meadow mouse, Microtus pennsylvanica,are typical inhabitants of all Reserve sites.

Birds nesting on the dense vegetation include thepainted bunting, Passerina ciris, catbird, Dumetellacarolinensis, mockingbird, Mimus polyglottos,cardinal, Richmondena cardinalis, and Carolinawren, Thryothorus ludovicianus. There are alsonumerous warblers, Dendroica spp., and sparrows,Melospiza spp., and Spizella pusilla. Typicalwoodland reptiles of the Reserve are the six-linedracerunner, Enemidophorus sexlineatus, rough greensnake, Opheadrys aestivus, corn snake, Elapheguttata, and yellow rat snake, Elaphe obsoleta.

Maritime Forests

One of the most impressive barrier island plantcommunities is the maritime forest. The forests haveadapted to seaside conditions to become the moststable, least changing habitat on the islands.

Opossum

Cotton mouse

Painted bunting

Red-bellied woodpecker

Maritime Forests

87

These characteristics make maritime forests importantfor preventing soil erosion, protecting against stormdamage, preserving groundwater and providinghabitat for plants, wildlife and humans alike.

Although each maritime forest developed differently,in many places it is believed that forests followed apattern called “succession.” This is a lengthy processthat occurs where simple plant communities, likegrasslands, develop into more complex communities.Shrub thicket areas may gradually develop into forestif salt spray, flooding, fire or storm damage do notalter the gradual overtopping of shrubs by trees.

This trend may be observed on North Island of theZeke’s Island site, on the east end of Carrot Island,throughout the Kitty Hawk, Buxton and Bald HeadWoods Coastal Reserve sites and throughout themore extensive forested areas of Currituck Banks.

Paradoxically, the characteristics that make amaritime forest a “climax” – or highly stable – plantcommunity also make it vulnerable to damage fromstorms, fires, and development. This is becauseforests take a long time to develop, and oncedamaged, do not recover easily.

Live Oak

Bayberry

Corn snake

Deer

PalPalam

Pala

Maritime Forests

Palamedes Swallowtail

88

Whereas grasses might reseed an area fairly quicklyfollowing a disturbance, the trees of a maritime forestrequire hundreds of years to establish. If the canopyis broken, allowing salt spray to reach vulnerableinterior trees, a forest can be seriously damaged ordestroyed. The forest on Shackleford Banks, part ofthe Cape Lookout National Seashore, is an exampleof this.

The primary distinction between shrub thicket andmaritime forest is that in the forest the dominanttrees, generally more than ten feet high, grow tallerthan shrubs and smaller trees like silverling, waxmyrtle and yaupon. Also, there is less diversity(fewer woody plants) in this community.

Except for the effect of salt shear on the edges of thecanopies, the dominant maritime trees may grow astall as those of mainland forests, particularly onCarrot Island and Currituck Banks. The primary treefound in the forests is the live oak, Quercusvirginiana. Other common trees include the loblollypine, Pinus taeda, and the red cedar, Juniperusvirginiana. Some hardwood species – red maple,Acer rubrum, sweetgum, Liguidambar straciflua,Carolina laurel cherry, Prunus caroliniana, andhackberry, Celtis laevigata – may also be found inthe forest. The shrubs, herbs, mammals, birds, andreptiles found in the forest are essentially the same asthose of the shrub thicket.

Eastern red cedar

Sweetgum

Black gum

Loblolly Pine

Maritime Forests

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Coastal Marshes

Some of the most productive and valuable wetlandsare coastal marshes. These marshes are regularly andirregularly flooded lands where specific plants growdepending on the tides, salinity levels and elevation.Four types of marshes are found within the Reservesites: low salt, high salt, brackish and freshwater.

Salt marshes are found along the estuarine shorelinesof the Zeke’s Island, Masonboro Island and RachelCarson sites. The wind-fluctuated, low salinity soundwaters of the Currituck Banks site border brackishmarshes. Freshwater marshes occur in depressionswithin the grassland, shrub thicket or maritime forestof all four sites.

Low Salt Marsh

The intertidal, or low, salt marsh is the foundation ofthe estuarine food web, and therefore is relied upon,directly or indirectly, by most organisms in theestuarine system. Fringing thousands of miles ofestuarine shoreline in the state, this community is oneof the most productive and self-sustaining habitats onearth.

The marshes are created as fine particles of silt andclay are deposited from slow-moving waters. Thesediments are stabilized, much as sand dunes are,by a plant that is specially adapted to this harshenvironment.

White ibis

Glasswort

Mud snail

Saltmeadow hay

Coastal Marshes

90

This key plant species is salt marsh cordgrass, Spartinaalternaflora. This coarse grass can be from one to fourfeet tall, depending upon the elevation, and establishesan extensive network of roots and underground stemsthat bind the soft, sandy or muddy soil. Such an exten-sive “foundation” is necessary to maintain the grasscolonies because there is no hard surface, or substrate,that the plants could attach to and avoid being washedaway by the tides and wind-generated waves. Well-developed cordgrass stands actually protect the main-land from the effects of tides and waves by slowing theincoming waves and reducing soil erosion.

Salt marsh cordgrass has adapted to the dramaticallychanging salinities, fluctuating surface temperatures andchanges in water levels by regulating salt and waterconcentrations in its cells and releasing excess water orsalt through pores on grass blades.

Salt marsh cordgrass is one of the important producersin the estuarine food web. Each fall, the plant dies backand is washed into the estuary. There, bacteria breakdown the plant tissues into detritus, a primary foodsource for numerous aquatic animals, many of which areconsumed in turn by other species. The detritus-richestuarine waters also contain highly productive phy-toplankton (microscopic plants) which further supple-ment the estuarine “soup” for the various consumers..

Marsh periwinkle

Black needlerush

Speckled crab

Saltmarsh cordgrass

Low Salt Marsh

91

The intertidal marsh does contain other plant species,although cordgrass clearly is dominant. The upperintertidal zone typically has colonies of cordgrass of asmaller size with patches or zones of sea ox-eye,Borrichia frutescens, salt grass,Distichlis spicata, sealavender, Limonium carolinianum, black needlerush,Juncus roemerianus, salt marsh cordgrass, Spartinapatens, and in depressions(called pannes) where saltlevels tend to be highest,glasswort, Salicornia spp.

Animals of the intertidal marsh are either permanentresidents or species from nearby habitats that forage inthe marsh at different times of the day, depending on thewater level. Marsh periwinkles, Littorina irrorata, aresnails that graze on the microscopic algae growing oncord grass stalks. The snails climb up the stalks as thetide rises to avoid predators. Ribbed mussels, Moliolusdemissus, attach to plant bases while oysters,Crassostrea virginiana, form colonies on any solidobject. Both of these organisms are filter feeders, whichmeans that they strain plankton, bacteria and detritusfrom the water for food.

Found in large numbers on muddy sediments, the mudsnails, Ilyanassa obsoleta, are generallyscavengers for food on the marsh surface.

Sea lavender

Ribbed mussel

Sea ox-eye

Blue crab

Low Salt Marsh

92

Marsh fiddler crabs, Uca pugnax, burrow during low tideby scraping organic matter from the surface. Male crabsare distinguished by having one large claw and one smallone while females have two small claws.

The diamondback terrapin, Malaclemys terrapin, is aturtle that lives in stands of cord grass and eats dead fish,live crabs and small mollusks.

Birds that nest in the upper intertidal marsh include theclapper rail, Rallus longirostris, marsh wren, Cistothoruspalustris, and least bittern, Ixobrychus exilis. Myriads ofgnats, flies and mosquitoes are also part of the marsh foodweb.

Numerous birds and mammals forage in the salt marshduring low tide. The American egret, Casmerodius albus,great blue heron, Ardea herodias, tricolored heron,Hydranassa tricolor, black-crowned night heron,Nycticorax nycticorax, willet, Catoptrophorussemipalmatus, boat-tailed grackle, Quiscalus major,black skimmer, Rhynchops niger, American oystercatcher,Haematopus palliatus, and osprey, Pandion haliaetus,are only some of the birds dependent upon the bountifulmarsh food production.

Clapper rail

Great blue heron

Sand fiddler crab

Low Salt Marsh

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Typical mammals regularly visiting the intertidal marshinclude the raccoon, Procyon lotor, river otter, Lutracanadensis, meadow mouse, Microtus pennsylvanicus,red bat, Lasiurus borealis, Seminole bat, Lasiurusseminolus, and marsh rice bat, Oryzomys palustris.

High Salt Marsh

Supratidal, or high, salt marsh is only flooded by stormtides or extremely high spring tides. The daily flooding ofthe intertidal marsh gradually increases the soil elevationby deposition of fine sediments. As the land level in-creases, intertidal flooding shifts toward the sound andthe supratidal zone follows. As a result of this process,supratidal species will move into former intertidal lands.

The upland edge of the supratidal zone will, in turn,gradually be invaded by shrubs. This general trend,however, is influenced by variations in inlet formation,storm erosion and deposition of overwash sedimentsalong the coast.

River otter

Dune spurge

Sea beach amaranth

Marsh mallow

High Salt Marsh

Saltmarsh Skipper

94

Above the daily tidal limits there is a gradual changein plant dominance from salt marsh cordgrass to amosaic of salt meadow cordgrass, salt grass, seaox-eye, black needle rush and glasswort, with feweroccurrences of sea lavender, salt marsh aster, Astertenuifolius, and sabatia, Sabatia stellaris.

Considerably fewer animals use the supratidal thanuse the intertidal marsh zone. Insect-seeking birdssuch as the red-winged blackbird, Agelaiusphoneceus, meadowlark, Sturnella magna, andseaside sparrow, Ammospiza maritima, regularlyforage and nest in the high marsh. Other commonanimals include the meadow mouse, marsh crab,Sesarma reticulata, sand fiddler crab, Uca pugilator,and various insects such as the dragonfly,Erythrodiplax berenice.

Brackish Marsh

At the Currituck Banks site brackish marshes fringethe edge of the sound 45 miles from the nearestsource of salt water – Oregon Inlet in Dare County.Currituck Sound receives freshwater from a numberof creeks draining the mainland, plus irregularamounts of salt water from the inlet. The resultingsound water is classified as brackish, rarely exceedingtwo parts of salt per thousand parts of water,compared with 35 parts per thousand in ocean water.

Red bay

Sedge wren

Salt meadow hay

Cardinal

Brackish Marsh

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These waters are not influenced by regular lunar tides butby wind. This creates considerably different influences thanthose described under the tidal and supratidal marshes.

Dense colonies of giant cord grass, Spartinacynosuroides, spike rush, Eleocharis obtusa, blackneedle rush and cattail, Typha spp., dominate theCurrituck marshes. Other associates include duck potato,Sagittaria falcate, sabatia, Sabitia dodecandra, bul-rushes, Scirpus spp., and marsh mallows, Hybiscusmoscheutos and Kosteletskya virginica. Transition toupland vegetation is characterized by a shrub marshcomposed primarily of marsh elder and wax myrtle.Hempweed, Mikania scadnes, is a vine in the aster family,which occurs sporadically throughout the marsh.

These marshes serve as important nesting andforaging grounds for numerous species. Typical birdsinclude the great blue heron, American egret, eastern greenheron, Butorides straitus, snowy egret, Egretta thula,red-winged blackbird and numerous ocean seabirds suchas gulls and sandpipers. Mammals regularly feeding in thearea include the raccoon, marsh rabbit, Sylvilaguspalustris, and white-tailed deer, Odocoileus virginianus.

Marsh rabbit

Duck potato

Giant cordgrass

Cattail

Brackish Marsh

Giant Swallowtail

96

Depressions within the grassland, shrub thicket ormaritime forest communities may contain permanentto seasonally flooded ponds vegetated to varyingdegrees by marsh plants. The depressions within theReserve are interdunal swales originally created bywind and water working and reworking depositedsediments. Where low spots intersect with the watertable, a pond is formed. Low spots just above thewater table hold rainwater and runoff until theyevaporate. The best-developed freshwater marshes ofthe Reserve are found at the Currituck Banks site,while the other three sites contain isolated seasonallywet areas.

At Currituck Banks typical plants in the pondsinclude cattail, Typha angustifolia and T. latifolia,bulrushes, duck potato and pickerel weed,Pontederia cordata, mixed with patches of waterpennywort, hydrocotyle umbella, bacopa, bacopamonnieri, marsh fleabane, Pluchea purpurascens,lippia, Lippia lanceolata, and diodia, Diodiavirginiana.

Seasonal marshes at the other Reserve sites containmany of these species, often mixed with invadingshrubs such as wax myrtle, silverling, marsh elder andwillow, Salix spp. These marshes also serve asreservoirs for plants not typically found within theneighboring habitats.

Reed

Marsh elder

Pickerel weed

Bulrush

Freshwater Marsh

97

Freshwater marshes within the Reserve sites are vitalwater sources for the upland animals. Mammals,birds and reptiles from nearby habitats regularly visitthese “watering holes.” The feral horses of theRachel Carson site dig down to fresh water when theponds are dry. Amphibians, such as toads, Bufo spp.,and various insects – flies and mosquitoes – requirethese freshwater areas as well.

Tidal FlatsLow salt marshes are often bordered by mud and sandflats, which, although seemingly barren, are neverthelessan important part of the estuarine system. The flats areeasily seen at low tide when, in some places, they stretchfor several hundred yards. Tidal flats are found at theZeke’s Island, Masonboro Island and, especially, theRachel Carson site of the Reserve. Many organisms feedon the flats, for this is where the broken down marshgrasses are carried.

The flats are formed by the deposition of various typesof sediments – sand, silt or clay, depending upon localcurrents. The finer textured sediments settle with lowerwater velocities, while heavier sands are found wherecurrents are stronger. Ebb and flow tides, however,typically mix the sediments to varying degrees andprevent the flats from drying out.

Southern toad

Eastern box turtle

Feral horse

Diamondback terrapin

Tidal Flats

98

The estuarine water associated with the flats varies inits chemical and physical properties during each tidalcycle and throughout the year. Water temperatureschange with the tides; in summer the sun heats theexposed sediments during low tide, while the risingtide brings cooler water. This process is just theopposite in winter when the air is cooler and thewater warmer. Salinities in isolated pools willincrease with evaporation, but heavy rains or riverinflow will decrease these concentrations.

Regular tidal flows of ocean water further modify thewater chemistry. Dissolved oxygen, which is vital tomost aquatic organisms, is often plentiful in the tidalwater, although sustained high temperatures inshallow water deplete the oxygen concentration.Muddy sediments usually have very low oxygenconcentrations as indicated by the smell of “rotteneggs” (hydrogen sulfide gas).

Organisms permanently living in this habitat must beadapted to the many environmental fluctuationsmentioned above. Burrowing worms, such as theblood worm, Glycera spp., lugworm, Arenicola spp.,and clam worm, Nereis spp., find protection in thesediments, while many polychaete worms formpermanent burrows or tubes, including the plumedworm, Diopatra sp., and parchment tube worm,Chaetopterus sp.

The quahog clam, Mercenaria mercenaria, andmarsh razor clam, Tagelus spp., burrow with “feet”

Lugworm

Bloodworm

Atlantic jacknife clam

Northern quahog clam

Tidal Flats

99

and extend siphons into the water above the flat to drawin water, detritus and plankton. Most of theorganisms move either into the sediments or out tosub tidal waters during the low tide. Two that do notare the filter-feeding oyster, Crassostrea virginica,and scavenging mud snail, Ilyanassa obsoleta.Young, mobile oysters attach to any hard surface,often other oyster shells, to form extensive colonies.The muddy sediments also team with anaerobicbacteria that are essential to the process ofdecomposing dead organic matter so that it canbecome part of the food web.

Transient organisms from the sub tidal zone areabundant when rising and high tides cover the flats.The primary plants are algae, ranging from unicellularmud algae and phytoplankton, to green, brown andred seaweeds such as sea lettuce, Ulva lactuca,dicyota, Dictyota spp., and sewing thread seaweed,Gracilaria spp., which float in the shallow waters andoften become stranded on the substrate at low tide.Numerous small fishes and crustaceans, which seekthe protection of the shallow waters, are killifish,Fundulus spp., silversides, Menidia menidia, pipe-fish, Sygnathus spp., filefish, Monocanthus hispidus,flounder, Paralichthys spp., pinfish, Lagodonrhomboides, shrimp, Penaeus spp., spider crab,Libinia spp., and blue crab, Callinectes sapidus.Jellyfish occasionally drift into the flats, includingmoon jelly, Aurelia aurita, and cabbagehead,Stomolophus meleagris.

Atlantic silverside

Summer flounder

Sea lettuce

Peacock’s tail

Tidal Flats

100

Terrestrial mammals and birds that forage extensivelyin the tidal flats, primarily during low tide, are theraccoon, Procyon lotor, great blue heron, Ardeaherodias, willet, Catoptrophorous semipalmatus,clapper rail, Rallus longirostris, and Americanoystercatcher, Haematopus palliates. The blackskimmer, Rhynchops niger, flies just above the surfaceof the water, capturing fish and crustaceans in its lowerbill.

Subtidal Soft Bottoms

The bottoms of the sounds provide a habitat similarto that of the tidal flats, but one which is more stablebecause it is constantly underwater. Thus, thephysical and chemical fluctuations of these areas arenot as severe as they are in the flats. All four Reservesites contain extensive sub tidal areas. Although mostof this habitat is made up of mud and sand flats withoccasional algae cover, in some areas floweringplants grow that are specially adapted to beingunderwater. These submerged aquatic beds areimportant to estuarine productivity. Beds of eelgrass,Zostera marina, are found at Rachel Carson site andMasonboro Island. Currituck Banks containsextensive submerged aquatic beds composed ofspecies typical of low salinity sounds.

The open sub tidal bottoms of the Zeke’s Island,Masonboro, and Rachel Carson sites are home to awealth of fishes, mollusks, crustaceans, worms,jellyfish and other organisms. Many of the species

Dowitcher

Little blue heron

Willet

Dunlin

Subtidal Soft Bottoms

101

mentioned in the Intertidal Flats section are found belowthe low tide mark. Pinfish, Lagodon rhomboides,lookdown, Selene vomer, Atlantic silversides, Menidiamenidia, mullet, Mugil spp., flounder, Paralichthysspp., pipefish, Syngnathus spp., spot, Leiostomusxanthurus and killifish,Fundulus spp., are some of thefishes common atthe sites. Deeper portions of the subtidal areas are foraged by oceanic species such as theAtlantic bottlenose dolphin, Tursiops truncatus, amarine mammal found particularly around the RachelCarson site, and large fishes including dogfish shark,Mustelus canis, stingray, Dasyatis sp., bluefish,Ponatomus saltatrix, and spotted seatrout, Cynoscionnebulosus.

Aside from the vertebrates listed above, there areother organisms in this community which scientistsclassify as Chordates – animals with at least aprimitive type of spinal cord at some stage ofdevelopment. Sea squirt, Styela spp., sea grape,Molgula spp., and sea pork, Amaroucium spp., are“glob-like” colonial organisms as adults and filterplankton from the water for food. Invertebrates,animals without backbones, are plentiful throughoutthe subtidal flats. Representative examples fromvarious groups are listed below:

• Crustaceans (segmented organisms with hard outerskeletons that usually breathe through gills) – bluecrab, Callinectes sapidus, and shrimp, Penaeus spp.

Striped killifish

White mullet

Clearnose skate

Sea squirt

Subtidal Soft Bottoms

• Mollusks (unsegmented, soft-bodied animals withshells and feet) – whelk or conch, Busycon spp.,quahog clam, Mercenaria mercenaria, and squid,Lolliguncula brevis.

• Annelids (worms and related organisms) –parchment tube worm, Chaetopterus sp.,and lugworm, Arenicola sp.

• Coelenterates (soft animals with a central digestivecavity, the opening of which is ringed by stingingtentacles) – moon jelly, Aurelia aurita, cabbage head,Stomolophus meleagris, and sea whip, Leptogorgiavirgulata.

• Echinoderms (spiny animals with tube feet) –sea cucumber, Leptosynapta sp., and sand dollar,Mellita sp.

• Ctenophores (gelatinous animals with rows ofcomb like plates) – comb jelly, Mnemiopsis sp.

• Zooplankton (microscopic animals) – unicellularorganisms and larval stages of the groups mentionedabove.

Algae can form dense colonies in sandy sub tidalareas, particularly where shells or other hard surfacesare available for attachment. Sporadic patches ofgreen, red and brown algae occur at all the sitesexcept Currituck Banks. Typical species include sealettuce, Ulva lactuca, dead man’s fingers, Codium

Channeled whelk Egg case

Parchment tube worm

Moon jelly

Dicyota

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sp., dicyota, Dictyota spp., hypnea, Hypnea spp., andsewing thread seaweed, Gracilaria spp.Phytoplankton and bacteria are abundant throughoutthe water and on the surface of the bottom.

Submerged aquatic plant beds, often called “grassbeds,” occur within various salinity patterns at theRachel Carson, Masonboro Island and CurrituckBanks sites. Beds of eelgrass, Zostera marina, arescattered along Carrot Island and within Middlemarshes of the Rachel Carson site, while isolatedpatches are found on the sound side of MasonboroIsland. An economically important associate of thiscommunity is the bay scallop, Aequipecten irradians,a bivalve prized for its sweet-tasting meat. Numerousalgae and microscopic animals live on the eelgrassleaves.

Extensive colonies of underwater plants cover theshallow mud and sand bottom of Currituck Sound.Dominant species include Eurasian water-milfoil,Myriophyllum spicatum, redhead grass, Potamogetonperfoliatus, pondweeds, Najas spp., wild celery,Vallisneria americana, widgeon grass, Ruppiamaritima, and horned pondweed, Zanichelliapalustris. Eurasian water-milfoil was introducedinto Currituck Sound in 1965 and rapidly becamedominant. Phytoplankton, in the form of diatoms,dinoflagellates and micro algae, are also abundant inthe sound, particularly in winter when nitrogen levelsare high.

Hypenea

Eelgrass

Atlantic bay scallop

Eurasian water-milfoil

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104

Animals associated with Currituck Sound’sunderwater plant beds and sediments are primarilybottom dwelling organisms and fishes. Organismsliving in the sediments include amphipods, isopods,annelid worms, midge fly larvae and marsh clams,Rangia cuneata.

The low salinity levels are reflected by the presenceof both freshwater and brackish species of fishes:largemouth bass, Micropterus salmoides,pumpkinseed, Lepomis gibbosus, bluegill, Lepomismacrochirus, white perch, Morone americana,catfish and bullhead, Ictalurus spp., and striped bass,Morine saxatilis.

Currituck Sound is famous as a migratory waterfowlstopover along the Atlantic Flyway. Ducks and geesethat seasonally visit the estuary and feed on theaquatic plants include redheads, Aytha americana,pintails, Anas acuta, ruddy ducks, Oxyurajamaicensis, American wigeon, Amas americana,canvasbacks, Athya valisineria, buffleheads,Bucephala abeola, black ducks, Anas rubripes,ring-necked ducks, Aytha collaris, and Canada geese,Branta canadensis.

Dredge Spoil Areas

Both the Masonboro Island and the Rachel Carsonsites contain areas that, over the past few decades,

Largemouth bass

Bluegill

Canada goose

Hooded merganser

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105

have been used by the U.S. Army Corps of Engineersto dispose of spoil material from maintenance dredging of shipping channels. The Corps has perma-nent easements for deposition at the Reserve sites –at Masonboro Island along the Atlantic IntracoastalWaterway and at Rachel Carson along Taylor’sCreek.

The deposition procedure typically involves the useof a cutter head dredge and long pipes, known asdredge lines, through which the dredged sedimentsand water are pumped into a diked basin on the site.Initially, the brackish slurry of sand and mud forms aturbid “lake.” As evaporation and drainage cause thesediments to settle out and be exposed, a mound ofspoil is left. Regulations prohibit placing spoil onwetlands, therefore dredge material is only depositedon existing spoil mounds.

The newly created upland surface can then becolonized by plants and animals. Initial speciesinvading the sediments are pennywort, Hydrocotylebonariensis, reed, Phragmites communis, diodia,Diodia teres, broomsedge, Andropogon scoparius,panic grass, Panicum spp., beach pea, Strophostyleshelvola, and morning glory, Ipomoea spp.

Ground nesting bird species typically found in duneareas also use the open ground. Mourning doves,Zenaida macroura, night hawks, Chordeiles minor,black skimmer, Rhynchops niger, and terns, Sternaspp., are among the species occasionally found there.

Beach morning-glory

Sandwich tern

Least tern

American beach grass

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106

In time, other herbs and small shrubs graduallyinvade the spoil areas. Large forbs such asgoldenrods, Solidage spp., asters, Aster spp.,blackberry, Rubus spp., pokeberry, Phytolaccaamericana, asparagus, Asparagus officinalis,mustard, Brassica sp., and ground cherry, Physalisviscosa spp. maritime, grow sporadically on theedges of the spoil areas and where soil and water issufficient. Red cedar, Juniperus virginiana, silverling,Baccharis halimifolia, wax myrtle, Myrica cerifera,Spanish bayonet, yucca spp., yaupon, Ilex vomitoria,and willow, Salix spp., then invade, eventually creating ashrub thicket habitat with animal species essentially thesame as those discussed under the shrub thicket section.Some areas even acquire forest-like stature with loblollypine, Pinus taeda, live oak, Quercus virginiana, andother trees becoming established. However, not all spoilareas succeed to shrub thicket or forest. Portions ofinterior areas and dikes remain covered with pennywortor reed, even after more than 10 years.

Hard Surfaces

The geology of North Carolina beaches and estuariesprimarily involves sediments, such as sand or silt, in

Loblolly pine

Groundsel tree

Fire wheel

Eastern red cedar

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contrast to rocky shorelines found in other regions,like New England. There are a few outcroppings ofmarine limestone on ocean beaches and in the nearshore waters of New Hanover and Carteret counties,but these are exceptions. However, numerousman-made hard surfaces, or substrates, exist alongthe coast in the forms of rock jetties and wood orcement pilings of docks, bridges, and seawalls.

These types of structures are found within theReserve at Zeke’s Island, Masonboro Island andRachel Carson sites. Zeke’s Island includes a portionof a rock jetty (locally known as “the Rocks”) thatextends several miles from Fort Fisher to SmithIsland. The northern tip of Masonboro Island serves asthe anchor point for one of the large twin jetties thatstabilizes Masonboro Inlet. The remains of a small rockbreakwater are found along the Taylor’s Creek side ofTown Marsh within the Rachel Carson site.

All of these hard surfaces are places where organismsoften not found in the ocean or estuarine communi-ties previously mentioned can become attached andgrow. Attaching, or sessile, plants and animals livingin this environment must be able to tolerate the watervelocities and abrasion of sand-bearing waves,periods without covering water, flooding andtemperature extremes. The reserve’s rock jetties haveimpervious surfaces, which are subject to direct

Eastern oyster

Rock barnacle

Sea anemone

Keyhole limpet

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108 HABITATS

environmental contact with the sun, wind and water, incontrast to the soft sediments available forburrowing organisms.

Organisms organize in vertical zones, depending ontheir adaptations to fluctuations in water level. Thissubtidal, intertidal and supratidal zonation creates amore pronounced difference in living conditionsduring a given tidal cycle than the gently slopingintertidal and subtidal flats.

Jetty organisms living in the subtidal area exhibitfurther zonation. Brown algae, sea anemones,Aiptasia spp., red beard sponge, Microciona sp., seasquirts, Styela spp., and bryozoans, Amathia spp.,grow just below the tide line and are exposed onlyduring unusually low tides. Deeper surfaces of therocks are covered with such organisms as white seaurchins, Lytechinus variegates, and red algae. Thesesubtidal animals either graze the algae-coatedsubstrate or strain plankton from the water.

Intertidal species are subject to the greatest changesin daily environmental conditions. Green algae suchas sea hair, Enteromorpha spp., sea lettuce, Ulvaspp., and dead man’s fingers, Codium spp., formpatches in suitable habitats mixed with filamentouslayers of blue-green algae, Calothrix spp. andLyngbya spp. Sessile intertidal animals include thescorched mussel, Brachidontes exustus, oyster,Crassostrea virginica, and rock barnacle, Balanusspp.

Sea hair

Chenille-weed seaweed

Sea Whip

Sargassum

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The keyhole limpet, Diodora cayenensis, and theAtlantic chiton, Cheotopleura apiculata, are mobilespecies in this zone which can hold very tightly to thesubstrate and graze on algae. The Atlantic starfish,Asterias forbesi, uses its tube feet to move and preyupon the shells of oysters, scallops, mussels and clams.Another molluscan predator is the banded tulip shell,Fasciolaria hunteria, a large snail with a radula (atooth-like structure) for boring into the victim’s shell.

Waves striking the intertidal zone of the Masonboroisland and Zeke’s island jetties send spray into thesupratidal area. This “splash zone” is often delineatedby the high tide barnacle, Chthamalus fragilis, afragile, flattened barnacle which survives by filteringphytoplankton from the spray water. The nonporousplates of its shell prevent it from drying out duringlow tides. The debris and detritus-feeding seacockroach is actually an isopod, Lygida sp., whichcrawls over the rocks and hides in crevices forprotection. It occasionally gets wet, but will drownif it is under water for a long period of time.

Banded tulip

Brittle starfish

Red-beard sponge

Baby’s ear

Hard Surfaces