Higher molecular weight aromatics, flupranthene through perylene, 

 although present in small amounts in crude oil, are more characteristic 

 of pyrogenic hydrocarbon assemblages (Neff, 1979). Concentrations of 

 these aromatics were similar in reference and Aber oysters and there 

 was no consistent pattern of temporal change. These hydrocarbons 

 probably have a similar origin in all three populations, namely from 

 particulate organic matter derived from smoke of wood and fossil fuel 

 combustion. Several of these aromatics, including benz[a]anthracene, 

 benzofluoranthenes, and benzopyrenes, are known carcinogens. Their 

 presence in tissues of oysters at relatively high concentration could 

 be cause for concern. 



Whole fish and muscle samples of plaice Pleuvoneates platessa 

 contained low concentrations of aliphatic and aromatic hydrocarbons 

 (Table 12). Most of the muscle samples contained aliphatic hydrocarbon 

 distributions characteristic of oil (Tables 13-15). Nearly tenfold 

 higher concentrations of aliphatics were found in liver samples than 

 in muscle samples of reference plaice and plaice from the oil-polluted 

 Abers. In the August 1979 samples, some of this was identified as 

 petroleum. In later samples, no petroleum-derived hydrocarbons were 

 detected in liver samples. The aromatic fraction showed a distribution 

 pattern similar to that of the aliphatic fraction. Liver aromatic 

 fractions were dominated by biogenic squalene. Liver samples also 

 contained high concentrations of what appeared to be naphthenic 

 (cyclic alkanes) hydrocarbons. 



Aliphatic fractions from all liver samples were dominated by hydro- 

 carbons in the C21 - C30 molecular weight range. In the three liver 

 samples from Aber Benoit, two of the three samples from Aber Wrac'h, and 

 one reference sample, dominant aliphatics were C27 and C2g. In the 

 remaining two samples, dominant aliphatics were C^r and C2g. With few 

 exceptions light aliphatics, C^q - C20» were present at low or non- 

 detectable concentrations in the plaice livers. 



Plaice muscle contained 1-10% of the concentration of aliphatics 

 that liver did. Alkane distribution patterns in muscles varied consid- 

 erably. In most cases alkanes above C24 were dominant. Concentrations 

 of aliphatic hydrocarbons in muscle and liver were higher in summer 

 (August 1979 and June 1980) than in winter (February 1980) , suggesting 

 a seaonal cycle of tissue hydrocarbon concentration. This seasonal 

 pattern was not correlated with seasonal changes in total lipid content 

 of plaice tissues (Table 18). As in the oysters, there was no consistent 

 difference between reference plaice and plaice from oil-contaminated Aber 

 Benoit and Aber Wrac'h with respect to pristane/phytane ratio, alkane/ 

 isoprenoid ratio, or carbon preference index (Table 16). 



298 



