Smithsonian Marine Station at Fort Pierce

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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


Amygdalum papyrium Atlantic papermussel  
Anadara transversa transverse ark  
Anomia simplex jingle shell  
Argopecten irradians concentricus bay scallop  
Astyris lunata lunar dovesnail  
Balanus spp. barnacles  
Bittiolum varium grass cerith  
Boonea impressa impressed odostome  
Boonea seminuda half-smooth odostome  
Brachidontes exustus scorched mussel  
Busycon carica knobbed whelk  
Busycon contrarium lightning whelk  
Busycon spiratum pyruloides none  
Busycon spp. whelks  
Caecum pulchellum beautiful caecum  
Callinectes ornatus ornate blue crab  
Callinectes sapidus blue crab  
Callinectes similis lesser blue crab  
Cerithiopsis greenii none  
Cliona spp. boring sponges  
Costoanachis avara greedy dovesnail  
Crassostrea virginica eastern oyster  
Crepidula aculeata spiny slippersnail  
Crepidula convexa convex slippersnail  
Crepidula plana eastern white slippersnail  
Diodora cayenensis cayenne keyhole limpet  
Dyspanopeus_sayii Say’s mud crab  
Dyspanopeus spp. mud crabs  
Epitomapta roseola none  
Eupleura caudata thick lipped oyster drill  
Eupleura sulcidentata sharp-rib drill  
Eurypanopeus depressus depressed mud crab  
Eurypanopeus spp. mud crabs  
Geukensia demissa ribbed mussel  
Hemipholis elongata none  
Hexapanopeus angustifrons narrow mud crab  
Hexapanopeus spp. mud crabs  
Ischadium recurvum hooked mussel  
Isognomon alatus flat tree oyster  
Lithophaga bisulcata mahogany datemussel  
Luidia clathrata gray sea star  
Luidia senegalenis nine-armed sea star  
Melongena corona crown conch  
Melongena sprucecreekensis none  
Menippe mercenaria stone crab  
Mercenaria mercenaria hard clam  
Mulinia lateralis dwarf surfclam  
Musculus lateralis lateral mussel  
Mytilopsis leucophaeata dark falsemussel  
Nereis spp. clamworms  
Ophiactis savignyi savigny’s brittlestar  
Ophiothrix angulata angular brittlestar  
Oreaster reticulatus cushion star  
Ostreola equestris crested oyster  
Panopeus herbstii common mud crab  
Panopeus lacustris knotfingered mud crab  
Panopeus spp. mud crabs  
Parastarte triquetra brown gemclam  
Pinnotheres maculatus mussel peacrab  
Pinnotheres ostreum oyster peacrab  
Polydora ligni Polydora mudworm  
Polydora spp. blisterworms  
Pyrgocythara plicosa plicate mangelia  
Rupellaria typica Atlantic rupellar  
Seila adamsi none  
Siphonaria pectinata striped false limpet  
Sphenia antillensis Antillean sphenia  
Spurilla neapolitana neopolitan spurilla  
Strombas gigas queen conch  
Stylochus spp. oyster leech  
Thais spp. rocksnails  
Triphora nigrocincta black-line triphora  
Truncatella pulchella beautiful trucatella  
Urosalpinx cinerea Atlantic oyster drill  
Urosalpinx tampaensis Tampa drill  
Vitrinella floridana Florida vitrinella  


Abudefduf saxatilis sergeant major  
Chaetodipterus faber spadefish  
Cynoscion nebulosus spotted seatrout  
Cynoscion nothus silver seatrout  
Eucinostomus argentus spotfin mojarra  
Eucinostomus gula silver jenny  
Eucinostomus havana bigeye mojarra  
Eucinostomus jonesii slender mojarra  
Eucinostomus lefroyi mottled mojarra  
Eucinostomus melanopterus flagfin mojarra  
Lutjanus analis mutton snapper  
Lutjanus apodus schoolmaster  
Lutjanus cyanopterus cubera snapper  
Lutjanus griseus gray (mangrove) snapper  
Lutjanus jocu dog snapper  
Lutjanus mahogani mahogany snapper  
Lutjanus synagris lane snapper  
Mugil cephalus striped mullet  
Mugil curema white mullet  
Mugil curvidens none  
Mugil gaimardianus redeye mullet  
Mugil gyrans fantail mullet  
Mugil liza liza  
Opsanus tao oyster toadfish  
Pogonias cromis black drum  
Rhinoptera bonasus cownosed ray  

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:

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.

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