1978 Ma coma sampling afforded the opportunity to determine the variation 

 of gross parameter hydrocarbon levels within the population through 

 triplicate analyses. In the aromatic fraction the resolved components 

 exhibit a coefficient of variation of ± 51.6 percent (x = 321.8 |.ig/g ± 

 165.9) but the total concentrations varied by ±11.5 percent (x = 1,738.4 

 |jg/g ± 200.3). The corresponding aliphatic hydrocarbon data yield 

 values of ±17.7 percent (x = 165.6 fjg/g ±27.1) and ±16.4 percent 

 (x = 1,618.8 |.ig/g ± 287.0) for the resolved and total gross parameters. 

 The apparent reintroduction of petroleum hydrocarbons to the ben- 

 thic environment is dramatically seen in the station 20 Macoma values. 

 Initially, the Macoma population at this station received a petroleum 

 input. This is shown in the high pristane and phytane levels in the 

 tissue (Table 11.8) as well as the high levels of naphthalene and 

 phenanthrene compounds (Tables 11.9 and 11.10) in the tissues. However, 

 by the time of the first sampling (November 20 to November 30) what 

 remains in the tissue has taken on the degraded oil composition, 

 featuring relatively enhanced levels of the isoprenoids (Table 11.8, 

 ALK/IS0 ratio; Fig. 11.11) and the branched alkanes. Indeed this 

 alkane-depleted GC pattern, common both to the second Mytilus sampling 

 (December 14) and to some extent even the November Mytilus group (see 

 Fig. 11.1b), as well as the sediment trap material (Fig. 11.6b), is also 

 common to the Macoma populations in the entire impacted region. Samples 

 from the control station 15 do not exhibit this profile but instead 

 reveal indications of weathered petroleum in a higher boiling UCM over- 

 ridden by small resolved components. It is not known whether an earlier 

 Macoma sampling (e.g., early November) would have yielded a fresher, 

 less degraded petroleum input. However, judging from the sediment trap 

 chromatrograhic profiles, which indicate that sedimented material col- 

 lected in early November already showed that the aliphatic hydrocarbon 

 composition had been drastically altered, it can be hypothesized that 

 little or no unweathered petroleum reached the benthos. By contrast, 

 relatively unweathered petroleum impacted the littoral zone, but ex- 

 posure to fresh oil even in this zone was short-lived. 



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