Effects of an Organic Pollutant (Tributyltin) on Genetic Structure in the Pacific Oyster Crassostrea gigas

Within the overall context of coastal ecosystem monitoring, the effects of an organic pollutant (i.e. tributyltin) on the genetic structure of the Pacific oyster Crassostrea gigas along Brittany (France) coasts were studied in order to identify specific genetic indicators. Contamination experiments were conducted using two concentrations of tributyltin (TBT). Electrophoretic analyses focused on six enzyme loci and the results were analysed to discern allozyme differences between samples. The survival curves obtained clearly reveal the high toxicity of TBT on adult oysters. Electrophoretic data also highlighted the existence of allozymes which can be used as putative genetic indicators of TBT contamination. It would appear that the following enzyme systems, aspartate-amino-transferase (Aat-2), adenylate kinase (Ak) and phosphoglucomutase (Pgm) are involved in the main physiological processes affected by tributyltin; allozymes of these loci are characterized by frequencies which vary significantly between TBT-resistant and more TBT-sensitive adults. These data reflect the adaptive nature of certain allozymes and show that relatively simple methods associated with an appropriate biological material may be a powerful tool to assess the effects of pollutants on marine invertebrates.