Immediate impact of Amoco Cadiz environmental oiling : oil behavior and burial, and biological aspects

Weathering states of oil ranging from sheen oil to mousse have signifi­cant effects during oil stranding on oil-water and oil-sediment interaction. Observations of oiled sandy beaches suggest two mechanisms of beach contamination - general penetration and contamination of beach substrate by sheen oil,and burial of discrete layers resulting from entrapment of mousse slicks. Depending on timing of oiling with respect to beach dynamics, large amounts of stranded oil can be accommodated in beach sediments. These are then available for later release. Acute lethal toxicity of stranded Amoco Cadiz oil is intermediate to Bunker C and of Kuwait crude. Simulated weathering studies suggest, however, that acute toxicity increases directly with weathering. Mortalities in the intertidal zone were highly variable, some species experiencing near total mortality while others, notably burrowing annelids and nemerteans, appeared highly resistant to oiling. Hydrocarbon concentrations and aryl hydrocarbon hydroxylase activity of oiled birds and oiled fish were found to be markedly higher than those in non-oiled species. The implications of weathering on toxicity of stranded and buried oil, and possible ecological and physiological defense mechanisms are discussed.