Cellulolytic responses to heavy metal accumulation in Corbicula fluminea and Mudalia dilatata
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Cellulolytic responses of the Asiatic clam, Corbicula fluminea and a snail, Mudalia dilatata, to selected constituents of power plant effluents (i.e., zinc, cadmium, acidic and alkaline pH, individually and paired) were investigated in 30-day exposures. Exposures were conducted in both laboratory and field-oriented artificial streams and then validated in the river receiving system of a power plant. Cellulolytic activi ty was reduced by laboratory and field exposures to cadmium and zinc at all levels tested from 0.012 to 0.10 mg cadmium/L and generally at 0.025 to 1.0 mg zinc/L. Clams detected acute lethal levels of metal and used valve closure as an avoidance mechanism for 14 days. Snails, however, did not effectively avoid exposures and were more sensitive to acute stress during all exposures. These behavioral responses were corroborated by both cellulolytic activity and metal accumulation.
Measurements of cellulolytic activity for both test species in laboratory exposures differed from those in field artificial streams. Reduced enzyme activity in controls by day 30 was attributed to artificially induced stress associated with the laboratory environment. This factor precluded any analysis of laboratory responses for periods of exposure longer than 20 days as well as recovery analysi s. Field oriented artificial streams provided a sufficient environment to adequately assess long-term stress and recovery as measured by cellulolytic activity and metal accumulation in both clams and snails. Enzyme activity responded to metal exposure with respect to both degree and duration of exposure.
- Doctoral Dissertations