3.6 Oysters and Fish (Michel, ISTPM) 



An analytical chemical program in support of the early post-spill 

 (March 1978 - March 1979) programs of the Institute Scientifique et 

 Technique des Peches Maritimes (ISTPM) was undertaken (Tables 20 to 22 

 and Fig. 3.79). Samples of freeze-dried oysters and fish (various 

 species) were analyzed by GC and several samples by GC/MS. The results 

 of the analyses are tabulated in Tables 23 to 25. Based on the nature 

 of the GC traces, sources of observed hydrocarbon distributions are 

 derived: fresh AMOCO CADIZ oil, weathered oil, and biogenic hydrocar- 

 bons. Often combined sources are apparent (e.g. weathered oil/biogenic 

 hydrocarbons) . 



Two oyster time series, summarized in Table 26, indicate that 

 initial heavy oil impacts on the tissues are reduced over time but 

 certainly not eliminated. GC traces illustrating the change in aroma- 

 tic hydrocarbon composition with time (Fig. 3.80) show that again the 

 alkylated phenanthrene (P) and dibenzothiophenes (DBT) dominate the 

 assemblage through February of 1979. 



Fish tissues do not reveal significant oil impacts. For the most 

 part the hydrocarbons consist mainly of biogenic compounds (e.g. 

 olefins) with an occasional UCM and again the presence of DBT and P 

 compounds probably, though not definitely, related to AMOCO CADIZ oil 

 (see Table 24) . 



An attempt at decontamination via oyster transplantation yielded 

 lower levels of hydrocarbons (Table 23; sample 143) indicating that 

 once removed from a polluted substrate the oysters can depurate their 

 oil burden significantly. 



Thus the oysters exhibit similar area-wide uptake of AMOCO oil, 

 initially at the 3000 ppm level, rapidly reduced to the 300-700 ppm 

 level and to the 50-200 ppm level a year after the spill. However, 

 identifiable oil residues remain. Fish samples show only sporadic 

 uptake of any oil indicating that the oil has not significantly impac- 

 ted coastal fish, or that once impacted the fish rapidly depurate 



and/or metabolize petroleum 



FIGURE 3.79. Oysters and fish sampling locactions. 



89 



