Changes in oxygen consumption and biochemical composition of the marine fouling dreissinid bivalve Mytilopsis sallei (Recluz) exposed to mercury.

The effect mercury (Hg) on tolerance, oxygen consumption, and body biochemical composition of a marine dreissinid bivalve Mytilopsis sallei was investigated. The 96-hr LC50 of Hg for M. sallei was found to be 0.2571 mg/liter and the safe concentration was 2.6 micrograms/liter. Exposure of M. sallei to Hg resulted in a significant decrease in oxygen consumption with increasing concentration of the metal. The effect of exposure time and concentration of Hg on body biochemical composition was also studied in M. sallei. In time-dependent experiments, carbohydrates were utilized, whereas both proteins and carbohydrates were consumed in concentration-dependent exposure. A decrease in the ratios of glycogen/protein and glycogen/lipid was observed in time-dependent experiments. In concentration-dependent experiments, there was also a decrease in glycogen/lipid ratio but the glycogen/protein ratio was almost constant at all exposure concentrations. The caloric concentration was also presented for both time and concentration-dependent exposure of Hg. However, the results of the present investigation indicate that this bivalve exhibited a differential preference in their utilization of biochemical constituents during time- and concentration-dependent stress of Hg. The decrease in oxygen consumption together with the utilization of glycogen and carbohydrates during Hg exposure suggests that these bivalves might shift to anaerobic metabolism in order to encounter the heavy metal stress in the environment.