Changes in intracellular free amino acids in tissues of the caged mussel,Elliptio complanata,exposed to contaminated environments

Intracellular tissue concentrations of free amino acids (FAA) were monitored in caged mussels (Elliptio complanata) exposedin situ for 27–29 days and 77–79 days in the Yamaska River watershed (Quebec, Canada). Total concentrations of FAA (nmol/mg wet weight) increased in both mantle and adductor muscle tissue at several sites impacted by agricultural runoff and urban effluent from municipal sewage and light industries when compared to levels in mussels located at a site with little anthropogenic impact. Consistent changes in the per cent composition of individual FAA to the total FAA pool included decreases in serine, threonine, glycine and valine as well as increases in glutamic acid and glutamine at 27–29 days but results were not consistent with longer exposure and varied amongst sites. Few changes in total or individual FAA were observed in gill tissue. The results suggest that increases and/or decreases in total FAA in some tissues of freshwater bivalves may be indicative of generalized stress induced by a variety of environmental factors and may be useful as anin situ biochemical index of toxicity.