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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 hydrocarbons.
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 aromatic
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 impacted
coastal fish, or that once impacted the fish rapidly depurate
and/or metabolize petroleum
FIGURE 3.79. Oysters and fish sampling locactions.
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