SCORE

South Carolina Oyster Restoration and Enhancement
South Carolina Department of Natural Resources

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Oyster Biology & Ecology

Photo of an oyster reef.Scientific Name: Crassostrea virginica

Common Names: Eastern oyster, American oyster

Classification:

Kingdom Animalia
 Phylum Mollusca
Class Pelecypoda or Bivalvia
Order Lamellibranchia
Family Filibranchia
Genus Crassostrea
species virginica

Range and Habitat

The American or eastern oyster is found along the Atlantic and Gulf of Mexico coasts of North America. Oysters form reefs, which are a dominant feature of many coastal estuaries. Oysters are often considered a "keystone species," providing valuable shelter and habitat for many other estuarine organisms, improving water quality, and reducing bank erosion.

Oysters are typically found in estuaries, sounds, bays, and tidal creeks from brackish water (5 parts per thousand [ppt] salinity) to full strength seawater (35 ppt salinity). Oysters are tolerant organisms, able to withstand wide variations in temperature, salinity, and concentrations of suspended sediments and dissolved oxygen. Throughout much of its range, the oyster occurs mostly in subtidal areas. But in South Carolina, almost all oysters live in the intertidal zone. Intertidal oysters typically have elongated, irregularly shaped shells. When submerged by the tide, oysters feed by filtering phytoplankton (microscopic plants) from the water column.

Explore the image below to identify and learn about organisms commonly found in South Carolina estuaries, a typical environment for oysters.

Drawing of salt marsh
 

dotacorn barnacle
dotAmerican oystercatcher
dotAtlantic croaker
dotAtlantic marsh fiddler
dotAtlantic sharpnose shark
dotblack sea bass
dotblue crab
dotbottlenosed dolphin
doteastern brown pelican
doteastern oyster

dotFlorida stone crab
dotgreat blue heron
dothard clam
dotknobbed whelk
dotlongwrist hermit crab
dotmarsh grass shrimp
dotribbed-mussel
dotred drum
dotred-winged blackbird

dotsheepshead
dotshort-billed marsh wren
dotsmooth cordgrass
dotsnowy egret
dotsouthern flounder
dotsouthern stingray
dotspotted seatrout
dotstriped mullet
dottarpon

smooth cordgrass American oystercatcher eastern oysters red-winged blackbird marsh grass shrimp Atlantic croaker hard clam red drum sheepshead southern stingray Florida stone crab acorn barnacles black sea bass southern flounder blue crab spotted seatrout Atlantic marsh fiddler snowy egret great blue heron smooth cordgrass tarpon striped mullet longwrist hermit crab short-billed marsh wren knobbed whelk Atlantic sharpnose shark ribbed-mussel eastern brown pelican bottlenosed dolphin humans

Life Cycle

Adult oysters begin reproduction when water temperatures become greater than 68�F (~20�C). In South Carolina this generally occurs from May through October. Oysters are broadcast spawners, meaning they release eggs and sperm into the water column. A fertilized egg develops into a planktonic (free-swimming) trochophore larva in about 6 hours. A fully shelled veliger larva is formed within 12 to 24 hours. The larva remains planktonic for about three weeks. Towards the end of this period it develops a foot (hence, pediveliger) and settles to the bottom of the water column where it seeks a hard substrate. When a suitable surface (ideally adult oyster shell) is located, the larva cements itself and metamorphoses to the adult form. This newly attached oyster is known as a "spat."

Figure of the oyster life cycle, from egg to veliger larva to pediveliger stage to attached juvenile (spat) to adult, and back to egg.

Reef Ecology

Oysters are the building blocks of one of the most important benthic communities in South Carolina estuaries, the oyster reef. Formed as a result of years of oyster production and settlement in concentrated areas, reefs have become home to a complex assemblage of animals and plants. Benefits of oyster reefs to the coastal environment include the following:

  • Providing solid structure within the water column for sessile (permanently attached or fixed) organisms (for example, barnacles and sea anemones)
  • Creating homes and hiding places for organisms seeking refuge from predation (for example, polychaete worms and soft-shell blue crabs)
  • Providing spawning substrate for fishes (for example, gobies, blennies, and skilletfish)
  • Stabilizing bottom sediments for benthic organisms (for example, hard clams) and aquatic plants
  • Concentrating prey (food) species for larger predator fishes (for example, striped bass)
  • Serving as breakwaters to protect adjacent shorelines from erosion
  • Filtration and clarification of water

Some of the information in this section is modified from Oysters in the Environment found at www.mdsg.umd.edu.

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