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A most interesting observation from our investigations is that
oysters, which were heavily contamianted by the oil spill and remained
so for the duration of the investigation, showed little evidence of
histopathological or biochemical damage, whereas plaice from the Abers,
although not heavily contaminated with oil, showed evidence of serious
and progressive histopathological and biochemical damage. This may
be due to differences in the sensitivity of molluscs and fish to petrolurn.
However, an alternative hypothesis is that the metabolites of
petroleum hydrocarbons, particularly of the polycyclic aromatic hydrocarbons,
are much more toxic than the unmetabolized parent compounds
and cause much of the damage in a chronic pollution situation. It is
well-established that the phenolic, epoxide and diol metabolites of
polycyclic aromatic hydrocarbons are much more elctrophilic and biologically
reactive than the unoxygenated parent compounds (Neff, 1979).
Since oysters have little or no capability to oxygenate polycyclic aromatic
hydrocarbons to reactive metabolites, they are quite tolerant to
oil. Fish on the other hand have a highly active mixed-function oxygenase
system and so rapidly convert polycyclic aromatics to reactive
metabolites which cause tissue damage. This hypothesis warrents further
investigation.
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