The aromatic hydrocarbon GC ami GC/MS runs fail to indicate a 

 chemical relation between either the spilled oil or the sediment trap 

 material to the surface sediment. The GC trace of a typical surface 

 sediment aromatic fraction is presented in Fig. 11.10 and shows mainly a 

 series of large, unidentified biogenic peaks and some indication of a 

 weathered petroleum input, as evidenced by small quantities of members 

 of the phenanthrene homologous series (phenanthrene = 0.03 Mg/g> methyl 

 phenanthrenes = 0.07 Hg/g, dimethylphenanthrenes = 0.03 Mg/g> triethyl- 

 phenanthrenes = 0.02 (Jg/g) . 



11.3.4 Macoma balthica 



Macoma balthica samples were obtained from the soft bottom at 8 

 Stations indicated in Fig. 11.1 and at a control station 15 located 

 south of Asko Island. In contrast to the Mytilus edulis hydrocarbon 

 contents, which show dramatic increases and rapid and near complete 

 depuration over the course of a year, concentrations in this benthic 

 deposit feeder show a rapid but modest concentration increase to the 500 

 to 900 pg/g level in the aliphatic fraction and 500 to 1,700 Mg/g level 

 in the aromatic fraction. The initial uptake appears to be location- 

 specific in contrast to the initial Mytilus behavior which is similar 

 over the entire study area (see Table 11.1). The concentration infor- 

 mation in Tables 11.8 and 11.9 indicates that while depletion of tissue 

 hydrocarbon burdens may be occurring at stations D and 20 between November 

 and December, for the most part Macoma continues to take up petroleum 

 hydrocarbons with aliphatic hydrocarbon tissue levels clearly on the 

 increase at stations 20 and 7 (.Table 11.8) and aromatic levels increasing 

 at stations D and 20 after a winter decrease (.Table 11.9). Whether the 

 depuration and re-uptake phenomenon is a function of reintroduction of 

 petroleum-bearing particulates to these stations or can be attributed to 

 aspects of the animals feeding rate and metabolic state is not apparent 

 from the Macoma data or from sediment trap data which characterize 

 sedimented material only through mid-December. 



The hydrocarbon levels in Tables 11.8 and 11.9 should be viewed in 

 relation to the control (.station 15) levels. Furthermore, the August 



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