Hydrocarbon levels in Ha coma first increase relative to control 

 values, then decrease, and in June through August begin to increase 

 again. Throughout the entire study period the aliphatic hydrocarbon 

 compositions, as revealed by GC profiles, remain more or less the same 

 with the branched alkane, isoprenoid compounds and unresolved complex 

 dominating. This is true through August. That fact, coupled with the 

 increase in absolute concentrations, indicates that weathered petroleum 

 remains in the benthic system and is apparently resistant to further 

 rapid degradation. Thus the chromatograms in Fig. 11.11 reflect this 

 constancy in aliphatic hydrocarbon composition. 



Data on the aromatic hydrocarbon levels at Station 20 (Table 11.10) 

 also reveal a winter decrease followed by a summer reintroduction. 

 Chromatographic profiles (Fig. 11.12 and 11.13) illustrate that the 

 lower boiling compounds naphthalenes, biphenyl, and fluorene are de- 

 pleted initially in tissue relative to the spilled oil, but in winter 

 the relative aromatic composition is most like the sediment trap samples 

 (Fig. 11.13) with the lighter end being more weathered. Although lower 

 in absolute concentrations by August, the aromatic composition in the 

 tissues remains generally constant throughout the study period (Fig. 

 11.12). 



As was the case in the Mytilus samples the presence of the tri- 

 methyl benzene (TMB) series plays a prominent minor role in the aromatic 

 hydrocarbon chemistry of Macoma throughout the study (Fig. 11.12). 

 Buried in the overall Tsesis oil chromatograms, the TMB series emerges 

 as other resolved components weather, indicating an interesting resis- 

 tance to degradation both within the animals and in particulate or 

 sedimented material comprising their food. As was the case for Mytilus , 

 the TMB series is not present in the pre-spill or control environments. 



11.4 Discussion 



From the previous presentation of the analytical results of this 

 year-long study one can piece together the chemical fate and effects of 

 the Tsesis oil spill on the marine environment in the region. 



264 



