Shaw et al. (1976) have suggested that Ma coma balthica represents 

 an ideal organism to monitor exposure of the benthos to pollutant input 

 due to its deposit feeding behavior, while others have suggested that 

 filter feeders (e.g., mussels, Mytilus species) are good indicators of 

 oil in the aqueous environment due to their manner of processing large 

 volumes of water. 



Due to their widespread distribution in coastal waters, mussels 

 (Mytilus sp.) have been closely studied in laboratory and field experi- 

 ments for their responses to hydrocarbon pollutant exposures. Studies 

 on the hydrocarbon chemical content of species of mussels have been 

 performed relating to (1) background or chronic input levels in Mytilus 

 galloprovincialis (Fossato and Siviero, 1974), M. edulis (Ehrhardt and 

 Heinemann, 1975; Rudling, 1976), M. californianus and M. edulis (DiSalvo 

 et al., 1975); (2) laboratory hydrocarbon uptake and depuration studies 

 (Lee et al., 1972; Fossato and Canzonier, 1976; Kanter, 1974; Clark and 

 Finley, 1975); (3) field transplantation (uptake and depuration) studies 

 (DiSalvo et al., 1975; Fossato, 1975; (4) oil spills in the field (Grahl- 

 Nielsen et al. , 1978; Clark et al., 1978, among others). Mytilus sp . is 

 a suspension feeder which processes large volumes of water to obtain 

 food and in doing so is exposed to hydrocarbon and other pollutant 

 compounds dispersed in the water or adsorbed to particulates. Mytilus 

 itself is a food source for many animals, but in the Baltic it is not 

 utilized by man. Furthermore its sedentary nature within the littoral 

 community makes Mytilus populations both excellent markers of pollutant 

 exposure within this zone as well as indicators of temporal recovery of 

 the littoral zone. 



This chapter concentrates on the extent of Tsesis oil exposure of 

 the Mytilus edulis population and the long-term (1 year) tissue hydro- 

 carbon burden of populations around the region affected by the Tsesis 

 oil spills. For details on the spill, see section 1.2. Of particular 

 interest were the changes in both the quantitative and qualitative 

 nature of the aliphatic and aromatic hydrocarbon assemblages in the 

 tissues. Ma coma balthica , a prominent resident of the soft-bottom 

 community, was used as an indicator of pollutant input to the benthos. 



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