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Oyster Reef Habitats


Oyster reefs, often referred to as oyster bars, are common submerged habitats in the southern United States. Oyster reefs in Florida are found in nearshore areas and estuaries of both coasts, but grow especially vigorously near estuarine river mouths where waters are brackish and less than 10 meters deep. For example, the Apalachicola River in northern Florida is a particularly productive area for oysters, and supplies over 90% of the state's annual oyster catch. Within the Indian River Lagoon, oyster reefs may be found in the vicinity of spoil islands and impounded areas. In addition to being commercially valuable, oyster reefs serve a number of important ecological roles in coastal systems: providing important habitat for a large number of species; improving water quality; stabilizing bottom areas, and influencing water circulation patterns within estuaries.

Oyster reefs are built primarily by the eastern oyster, Crassostrea virginica, through successive reproduction and settlement of larvae onto existing reef structure. Oysters in Florida spawn from late spring through the fall. The planktonic larvae that develop require a hard substratum to settle upon in order to complete development to the juvenile stage, and prefer to settle on the shells of other oysters. Thus, over time, continued settlement and subsequent growth of generations of oysters may form massive reef structures consisting of staggering numbers of individuals. Luntz (1960), estimated that 5,895 oysters, the equivalent of 45 bushels, occurred within a single square yard of oyster reef.

As successive generations of oysters settle and grow, reefs become highly complex, with many structural irregularities and infoldings that provide a wealth of microhabitats for many different species of animals. Wells (1961) listed 303 different species utilizing oyster reef as habitat in North Carolina. Common Indian River Lagoon species associated with oyster reefs include bivalves such as the hard clam (Mercenaria mercenaria) and bay scallop (Argopecten irradians concentricus); space competitors such as the scorched mussel (Brachidontes exustus), ribbed mussel (Geukensia demissa), the jingle shell (Anomia simplex), and barnacles of the Balanus genus; gastropod mollusks such as the conchs (Melongena spp. and Strombas spp.) and rocksnails (Thais spp.); numerous sponge species; flatworms; polychaete worms; amphipods; isopods; shrimp; and fishes such as blennies, gobies, spadefish, snappers, drum, and seatrout, among others.

Beyond providing smaller organisms with habitat, oyster reefs also provide food to a wide variety of secondary consumers. Many species of fish prey upon oyster reef associates; while others such as the black drum (Pogonias cromis) and cow-nosed ray (Rhinoptera bonasus) prey upon oysters themselves. Other species that utilize oyster reefs for foraging and feeding include the xanthid crabs, also known as mud crabs; swimming crabs of the genus Callinectes; mollusks such as the thick lipped oyster drill (Eupleura caudata), the sharp-rib drill (E. sulcidentata), the Atlantic oyster drill (Urosalpinx cinerea), the Tampa drill (U. tampaensis), the knobbed whelk (Busycon carica), the lighthire whelk (B. contrarium), and the pear whelk (B. spiratum pyruloides); flatworms such as oyster leeches (Stylochus spp.); boring sponges (Cliona spp.); and annelid worms (Polydora spp.).

Oyster reefs also contribute to improved water quality in areas where they occur. Oysters are filter feeders which strain microalgae, suspended particulate organic matter, and possibly dissolved organic matter from the water column over their gills in order to feed. Under optimal temperature and salinity conditions, a single oyster may filter as much as 15 liters of water per hour, up to 1500 times its body volume. Spread over an entire reef, for an entire day, the potential for oysters to improve water clarity is immense. Additionally, since oysters are sessile, and bioaccumulate some potential toxins and pollutants found in the water column, they have been used to assess the environmental health of some areas.

Over-harvesting, as well as persistent diseases such as MSX and Dermo have taken a devastating toll on many oyster populations along the east and Gulf coasts. In recent years, oyster reef restoration has been a concern for resource managers all along the East Coast of the United States, but especially in areas where oyster harvesting has historically been commercially important. In the late 1800s, for example, annual oyster harvests in the southeastern United States routinely topped 10 million pounds per year, and peaked in 1908 when the harvest was nearly 20 million pounds. However, annual harvests since that time have declined steadily. Today, annual harvests for oysters in the southeast averages approximately 3 million pounds per year. In many areas, efforts are underway to revitalize depleted oyster reefs and encourage growth of new reefs. For example, the Florida Department of Agriculture has stockpiled calico scallop shells from processors and placed these on depleted oyster reefs from the spring through the fall spawning periods, when larvae are most abundant in the water column. Oyster larvae, having a preference for settling on shell material, then attach themselves onto the newly placed shells and metamorphose to the juvenile stage. These young oysters, under optimal conditions, will grow to marketable size in as little as 18 - 24 months.

A more detailed look at some emerging human-induced threats facing the oyster reefs of the IRL is available here

Click a highlighted link to read more about individual species:

Species Name Common name Comments

Invertebrates:

Amygdalum papyriumAtlantic Paper Mussel
Anadara transversaTransverse Ark
Anomia simplexCommon Jingle
Argopecten irradians concentricusBay Scallop
Astyris lunataLunar Dovesnail
Balanus spp.Barnacles
Bittiolum variumGrass Cerith
Boonea impressaImpressed Odostome
Boonea seminudaHalf-smooth Odostome
Brachidontes exustusScorched Mussel
Busycon spp.Whelks
Busycon caricaKnobbed Whelk
Busycon contrariumLightning Whelk
Busycon spiratum pyruloides
Caecum pulchellumBeautiful Caecum
Callinectes ornatusOrnate Blue Crab
Callinectes sapidusBlue Crab
Callinectes similisLesser Blue Crab
Cerithiopsis greenii
Choristodon robustumAtlantic Petricolid
Cliona spp.Boring Sponges, Shell-burrowing Sponges
Costoanachis avaraGreedy Dovesnail
Crassostrea virginicaAmerican Oyster, Atlantic Oyster, Common Oyster, Eastern
Oyster, Virginia Oyster
Crepidula aculeataSpiny Slipper Snail, Spiny Slippersnail
Crepidula convexaConvex Slipper Snail
Crepidula planaEastern White Slipper Shell, Eastern White Slipper Snail
Diodora cayenensisCayenne Keyhole Limpet
Dyspanopeus spp.Mud crabs
Dyspanopeus sayiSay's Mud Crab
Epitomapta roseola
Eupleura caudataThick-lip Drill
Eupleura sulcidentataSharp-rib Drill
Eurypanopeus spp.Mud crabs
Eurypanopeus depressusDepressed Mud Crab, Flatback Mud Crab
Geukensia demissaRibbed Horsemussel, Ribbed Mussel
Hemipholis elongataBanded Brittle Star
Hexapanopeus spp.Mud crabs
Hexapanopeus angustifronsNarrow mud crab
Ischadium recurvumHooked Mussel
Isognomon alatusFlat Tree Oyster, Flat Tree-oyster
Lithophaga bisulcataMahogany Date Mussel
Luidia clathrataGray Sea Star, Grey Sea Star
Luidia senegalensisNine-arm Sea Star, Nine-armed Sea Star
Melongena coronaCrown Conch
Melongena sprucecreekensis
Menippe mercenariaFlorida Stone Crab, Stone Crab
Mercenaria mercenariaCherrystone, Hard Clam, Littleneck, Northern Quahog
Mulinia lateralisCoot Clam, Dwarf Surf Clam, Dwarf Surfclam
Musculus lateralisLateral Mussel
Mytilopsis leucophaeataDark falsemussel
Nereis spp.Clamworms
Ophiactis savignyiSavigny's Brittlestar
Ophiothrix angulataAngular Brittle Star, Angular Brittlestar
Oreaster reticulatusCushion Star, Cushioned Star
Ostreola equestrisCrested Oyster
Panopeus spp.Mud crabs
Panopeus herbstiiAtlantic Mud Crab
Panopeus lacustrisKnotfingered Mud Crab
Parastarte triquetraBrown gemclam
Pinnotheres maculatus
Pinnotheres ostreumOyster Crab
Polydora spp.Blisterworms
Polydora ligniPolydora Mudworm
Pyrgocythara plicosaPlicate Mangelia
Seila adamsi
Siphonaria pectinataStriped False Limpet
Sphenia antillensisAntillean Sphenia
Spurilla neapolitanaNeopolitan Spurilla
Strombus gigas
Stylochus spp.Oyster Leech
Thais spp.Rocksnails
Triphora nigrocinctaBlack-line Triphora
Truncatella pulchellaBeautiful Truncatella
Urosalpinx cinereaAmerican Tingle, American Whelk Tingle, Atlantic Oyster
Drill
Urosalpinx tampaensisTampa Drill
Vitrinella floridanaFlorida Vitrinella

Vertebrates:

Abudefduf saxatilisAsan, Badret, Castagnole, Castanheta, Chauffet Soleil, Pesce
Damigella, Petaca Rayada, Pintano, Sargento, Sergeant Major
Chaetodipterus faberAtlantic Spadefish
Cynoscion nebulosusSpotted Seatrout
Cynoscion nothusSilver Seatrout
Eucinostomus argenteusSilver Mojarra, Spotfin Mojarra
Eucinostomus gulaSilver Jenny
Eucinostomus havanaBigeye Mojarra
Eucinostomus jonesiiSlender Mojarra
Eucinostomus lefroyiMottled Mojarra
Eucinostomus melanopterusFlagfin Mojarra
Lutjanus analisKing Snapper, Mutton Fish, Mutton Snapper
Lutjanus apodusSchoolmaster, Schoolmaster Snapper
Lutjanus cyanopterusCubera Snapper
Lutjanus griseusBlack Snapper, Gray Snapper, Lowyer, Mango Snapper, Mangrove
Snapper
Lutjanus jocuDog Snapper
Lutjanus mahoganiMahogany Snapper
Lutjanus synagrisCandy Striper, Lane Snapper, Rainbow Snapper
Mugil cephalusBlack Mullet, Flathead Mullet, Gray Mullet, Sea Mullet,
Striped Mullet
Mugil curemaSilver Mullet, White Mullet
Mugil curvidensMullet
Mugil gaimardianusRedeye Mullet
Mugil gyransFantail Mullet
Mugil lizaLiza
Opsanus taoOyster Toadfish
Pogonias cromisBlack Drum, Corvina Negra, Tambor Negro
Rhinoptera bonasusCara De Vaca, Cowfish, Cownose Ray, Skeete

Further Reading

Bahr, L.M. and W.P. Lanier. 1981. The Ecology of Intertidal Oyster Reefs of the South Atlantic Coast: a
   Community Profile. U.S. Fish and Wildlife Service, Blot. Program, Washington D.C. FWS/OBS 81/15. 105 pp.

Burrell, V.G. 1986. Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and
   Invertebrates (South Atlantic): American Oyster. U.S. Fish and Wildlife Service. Biological Report 82(11.57).
   U.S. Army Corps of Engineers. TR EL-82-4. 17 pp.

Kumari, Siva, and C. Solis. 1995. The State of the Bay: a Characterization of the Galveston Bay Ecosystem. Rice university, Houston, TX. Accessed on-line at: www.rice.edu/armadillo/Galveston/Chap3/oyster.html.

Livingston, Robert J. 1990. Inshore Marine Habitats. In: Ecosystems of Florida, Ronald L. Myers and John J.
   Ewel, Eds. University of Central Florida Press, Orlando, FL. Pp. 549-573.

Lunz, G.R., Jr. 1960. Intertidal Oysters. Wards Natl. Sci. Bull. 34(1): 3-7

Wells, H.W. 1961. The Fauna of Oyster Beds with Special Reference to the Salinity Factor. Ecological
   Monographs 31(3): 239-266.