EFFECTS OF TEMPERATURE AND EXPOSURE DURATION ON TRANSFER OF CADMIUM BETWEEN NATURALLY CONTAMINATED SEDIMENTS AND BURROWING MAYFLY NYMPHS (HEXAGENIA-RIGIDA)

Burrowing mayfly nymphs (Hexagenia rigida) were exposed to naturally c ontaminated sediments collected from two stations along a metallic pol lution gradient on the Lot River (France) using indoor microcosms. Bio accumulation kinetics (0, 20, 40, and 60 days) of cadmium (Cd) and the combined effects of temperature (12, 18, and 24 degrees C) were evalu ated by a complete experimental design, jointly with the analysis of g rowth rate of the nymphs, bioturbation, and total and dissolved Cd con centrations in the water column. Cadmium was transferred from the sedi ment to the organisms with uptake influenced by contamination levels o f the sediments, exposure duration, and temperature. The two complemen tary criteria-Cd concentration and burden in the nymphs-clearly demons trate the importance of the growth dilution on the quantification of C d bioaccumulation at the whole organism level.