conspired to create a "worst case" scenario for marine oil pollution. 

 Therefore, the Amoco Cadiz spill offered a unique opportunity to study 

 in detail the long-term impact and timecourse of biological recovery 

 from a catastrophic pollution incident. 



While we already know that the immediate biological effects of the 

 spill were very serious in some areas (Cross et al. , 1978; Chasse, 1978; 

 Chasse and Morvan, 1978), there was very little information upon which 

 to base estimates of the rate at which the impacted area would be returned 

 to pre-spill biological productivity. We have used several biochemical 

 parameters and histopathological examination in an ongoing biological 

 survey to assess the health and rate of recovery of marine animals from 

 the two heavily polluted estuaries. 



The primary objective of this research program was to assess the 

 degree of chronic sublethal pollutant stress experienced by representa- 

 tive species of benthic fauna from Aber Benoit and Aber Wrac'h. Two 

 indices of stress were used. These are histopathology and biochemical 

 composition. We expected the fauna of these severely impacted estuaries 

 to exhibit an elevated incidence of various histopathological lesions 

 directly or indirectly related to oil pollution stress. As the estuaries 

 recovered from the spill the incidence of these lesions was expected to 

 diminish. Similarly, the concentrations of certain diagnostic biochemical 

 components of the severely stressed fauna were expected to deviate sig- 

 nificantly from normal. These diagnostic biochemical indices were 

 expected to return to normal as the estuaries recovered and the resident 

 fauna became less severely stressed. The results of this investigation 

 provide valuable information for assessing the biological recovery of 

 these severely polluted estuaries. They also provide a means of diagnos- 

 ing, pollutant stress in other polluted environments. 



I. Histopathology of Oysters Crassostrea gigas 



Marine animals readily accumulate petroleum hydrocarbons in their 

 tissues from dispersion or solution in sea water and to a lesser extent 

 from petroleum-contaminated sediments and food (see recent reviews by 

 Neff et al., 1976 a,b; Lee, 1977; Varanasi and Malins, 1977; Neff, 1979; 

 Neff and Anderson, 1981). The accumulated hydrocarbons and in particular 

 the more toxic aromatic hydrocarbons interact with cellular membranes 

 and interfere with membrane-mediated biological processes (Roubal and 

 Collier, 1975). Two types of histopathological lesions may result from 

 chronic contamination of marine animals with oil. 



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