Biochemical response of the mussel Mytilus galloprovincialis from Bizerta (Tunisia) to chemical pollutant exposure

Three biomarkers (glutathione S-transferase [GST] activity, catalase [CAT] activity, and malonedialdehyde [MDA] levels) were measured in specimens of the mussel Mytilus galloprovincialis collected from two different stations (BC and MJ) in the lagoon of Bizerta (Tunisia). Animals were allowed to acc limate in the laboratory for some days. They were then exposed for 48 h to two concentrations of pp'DDE and two doses of mercury chloride. The acclima tion period increased CAT activities and MDA levels in control mussels from both sites. GST activities were not modified during the acclimation period , whereas the sampling site of mussels appeared to exert a significant infl uence (higher values in control mussels from MJ than in those from BC). The treatment with both contaminants also increased GST activities of mussels from BC and not from MJ. It is hypothesized that animals from this last loc ation are more exposed to the urban waste waster disposal, their biochemica l response (GST activity) to pollutant exposure will be less marked. The tr eatment with pp'DDE or mercury did not show significant trend in CAT activi ties or MDA levels due to the variation of controls, and comparison of site s for mussels exposed to either pollutant therefore seems difficult. The ac climation period in the laboratory and the origin of mussels must be taken into consideration when studying the biochemical responses of mussels exper imentally exposed to chemical pollutants.