American oyster, continued 



effects of bioaccumulation of toxic substances from 

 dredge materials (Parrish et al. 1989). Rates of accu- 

 mulation and depuration of mercury from the environ- 

 ment by this species have also been studied (Palmer et 

 al. 1993). 



Ecological : This species is important in providing reef 

 habitats that serve as areas of concentration for many 

 other organisms (Wells 1 961 , Bahr and Lanier 1 981 ), 

 as well as a food source for a variety of estuarine fish 

 and invertebrates (Burrell 1986). Oysters form an 

 important link between pelagic and benthic food webs 

 by making available a portion of the organic material 

 they filter as dense, mucus-bound biodeposits that can 

 provide a food resource for benthic organisms (Newell 

 1 988). Oysters and other molluscan suspension feed- 

 ers may also act as a natural control against the 

 adverse effects of eutrophication in estuaries by filter- 

 ing out both inorganic and organic particles and limit- 

 ing turbidity and phytoplankton blooms. This could 

 enable greater light penetration through the water 

 column, and benefit submerged aquatic vegetation. 

 Thus, oysters can affect many aspects of an estuarine 

 ecosystem (Kennedy 1991). 



Range 



Overall : The American oyster occurs from the Gulf of 

 St. Lawrence to the Yucatan Peninsula of Mexico and 

 to Venezuela. It is abundant in the estuaries along the 

 coast of the Gulf of Mexico. Along the Atlantic coast, it 

 is historically abundant in Chesapeake Bay and Long 

 Island Sound (Burrell 1 986, Stanley and Sellers 1 986). 

 Results of biochemical analyses suggest that four 

 distinct races occur: Canadian, U.S. Atlantic, U.S. Gulf 

 of Mexico, and Bay of Campeche (King and Gray 

 1989). 



Within Study Area : Along the U.S. Gulf coast, this 

 species occurs from Texas to Florida (Table 5.02). 

 The estuaries of Louisiana and Texas east of Corpus 

 Christi generally have the highest abundances. Re- 

 cent evidence indicates two races occupying the Texas 

 coast, with the upper Laguna Madre being the location 

 of the transition zone (King and Gray 1 989). It is not yet 

 known if this is a race unique to the Texas coast, or the 

 northernmost population of the Bay of Campeche race. 



Life Mode 



Eggs are planktonic. Larvae are meroplanktonic to 

 benthic. Larvae are gregarious, enabling oysters to 

 form extensive reefs over long periods of time. Juve- 

 niles (spat) and adults are sessile and benthic (Burrell 

 1986, Stanley and Sellers 1986). 



Habitat 



Ty pe: All oyster life stages are estuarine, and can occur 

 in coastal sounds, bays, and estuaries of the coastal 



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