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There was also some indication, based on observations of gonadal
condition, that oysters from the Abers had an altered reproductive cycle
compared to reference oysters, possibly including near complete reproductive
suppression for one year after the spill. Sample sizes and frequencies
were not great enough to demonstrate this convincingly.
II. Petroleum Contamination and Biochemical
Indices of Stress in Oysters and Plaice
The most obvious immediate biological effect of the Amoco Cadiz
spill was a very large kill of benthic estuarine and coastal marine
organisms (Cross et al. , 1978). The rate of recovery of these benthic
communities would depend on the rate and success of reproduction by the
surviving animals in the affected area and on the success of recruitment
from adjacent unpolluted areas. The resident benthic fauna in the oilimpacted
area which survived the spill were undoubtedly severely stressed.
Because of the heavy contamination of the estuarine sediments with oil
it is highly probable that the surviving resident benthic fauna would
continue for some time to be stressed and potential immigrants to the
estuaries would be subjected to stress as they settled there.
Considerable research has been conducted in recent years on sublethal
physiological stress responses of marine animals to oil and other
types of pollution (Neff et al. , 1976a; Anderson, 1977; Johnson, 1977;
Patten, 1977; Neff, 1979; Thomas et al., 1980; Neff and Anderson, 1981).
A variety of sublethal physiological and biochemical responses to
pollutant stress have been described. In an ecological perspective,
the net effect of chronic pollutant stress on marine organisms is to
shunt limited energy resources away from growth and reproductive
processes to maintenance and homeostatic functions. The result is
decreased growth, fecundity and reproductive success in the stressed
population. A variety of biochemical parameters are altered in stressed
animals and reflect the stress-induced changes in energy balance and
partitioning. These biochemical parameters can be used as an index
of pollutant stress in marine animals.
Biochemical indices of pollutant stress chosen for use in this
investigation include hemolymph glucose concentration and adductor
muscle-free amino acids in oysters; and blood glucose and cholesterol,
liver glycogen and ascorbic acid, and muscle-free amino acids in plaice.
We have discussed elsewhere the rationale for using these parameters as
indices of pollutant stress (Thomas et al. , 1980, 1981 a,b).
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