its food. This fact may also account for the drastic elimination of the 

 important sensitive benthic crustacean, Pontoporeia spp . , from station 

 20, and its failure to reoccupy the station as of August 1978 (see 

 section 6.3.2). 



The apparent contrasting behavior of Mytilus and Macoma vis-a-vis 

 ingested oil may reflect more the duration of exposure and source trans- 

 port route of the petroleum than any intrinsic differences in the two 

 bivalve species. Depuration of acutely acquired hydrocarbons by Mytilus 

 is apparently accomplished through flushing of water through the animal's 

 gills. Other studies have shown that depuration of acutely acquired 

 petroleum is fairly rapid though perhaps not complete (Fossato and 

 Conzonier, 1976; Anderson, 1975; Kanter, 1974; Stegeman and Teal, 1973; 

 Lee et al., 1972; among others). However, Boehm and Quinn (1978) and 

 DiSalvo et al. (1975) have shown that chronically accumulated hydro- 

 carbons are slow to be eliminated from bivalve tissues, thus suggesting 

 that the duration of exposure is critical to the post-spill chemical 

 recovery of a particular bivalve community. The transport and reintro- 

 duction to and long resistance time of petroleum in the benthic environ- 

 ment in the regions of the Tsesis spill may result in the much slower 

 recovery of Macoma and the entire soft-bottom community from the effects 

 of this spill, and in general points to the environmental complications 

 caused by transport of petroleum to the benthos. 



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