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 acclimate 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 acclimation 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 influence (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 location are more exposed to the urban waste waster disposal, their biochemical response (GST activity) to pollutant exposure will be less marked. The treatment with pp'DDE or mercury did not show significant trend in CAT activities or MDA levels due to the variation of controls, and comparison of sites for mussels exposed to either pollutant therefore seems difficult. The acclimation period in the laboratory and the origin of mussels must be taken into consideration when studying the biochemical responses of mussels experimentally exposed to chemical pollutants.