Potential use of multixenobiotic defense mechanism (mxdm) in dreissena polymorpha as a biomarker for the monitoring of freshwater pollution

Multixenobiotic defense mechanism (MXDM) has been recently described in marine mussels as potential biomarker for the monitoring of water pollution by organic compounds. In this paper, the measurement of MXDM activity was achieved in a freshwater bivalve, Dreissena polymorpha. Two methods were tested and compared. The first one (MXDM associated ATPase activity) is an indirect method based on the evaluation of the inorganic phosphate production during MXDM activity. The second one (MXDM efflux activity) consists in the measurement of a dye (Rhodamine B) efflux from gill cells in living organisms. Both methods were optimized and evaluated for in situ studies. The results showed a significant induction (4.5 fold) of the MXDM efflux activity after the implantation of organisms for 21 days in a high polluted site. This preliminary study suggests a potential use of the MXDM efflux activity in Dreissena polymorpha as a biomarker for the monitoring of freshwater pollution by organic compounds.