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:




Amygdalum papyrium

Atlantic papermussel


Anadara transversa

transverse ark


Anomia simplex

jingle shell


Argopecten irradians concentricus

bay scallop


Astyris lunata

lunar dovesnail


Balanus spp.



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



Busycon spp.



Caecum pulchellum

beautiful caecum


Callinectes ornatus

ornate blue crab


Callinectes sapidus

blue crab


Callinectes similis

lesser blue crab


Cerithiopsis greenii



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



Say’s mud crab


Dyspanopeus spp.

mud crabs


Epitomapta roseola


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



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



Menippe mercenaria

stone crab


Mercenaria mercenaria

hard clam


Mulinia lateralis

dwarf surfclam


Musculus lateralis

lateral mussel


Mytilopsis leucophaeata

dark falsemussel


Nereis spp.



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.



Pyrgocythara plicosa

plicate mangelia


Rupellaria typica

Atlantic rupellar


Seila adamsi



Siphonaria pectinata

striped false limpet


Sphenia antillensis

Antillean sphenia


Spurilla neapolitana

neopolitan spurilla


Strombas gigas

queen conch


Stylochus spp.

oyster leech


Thais spp.



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



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



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



Mugil gaimardianus

redeye mullet


Mugil gyrans

fantail mullet


Mugil 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.


Report by:  K. Hill, Smithsonian Marine Station
Submit additional information, photos or comments to:
Page last updated: June 23,  2002