The influence of substrate, pH, diet and temperature upon cadmium accumulation in the asiatic clam (Corbicula fluminea) in laboratory artificial streams

The influence of substrate, pH, diet and temperature upon the accumulation of cadmium (0.05 mg l⁻¹ dose < 0.001 mg l⁻¹ control) in the visceral mass of the Asiatic clam Corbicula fluminea was studied in laboratory artificial stream systems at intervals of 0, 3, 5, 7, 10 and 14-day exposures. Four substrate conditions, sand; sand, silt and clay (SSC); sand, clay and organic matter (SCO); and no substrate (NoS), were considered. The greatest tissue accumulation of cadmium in C. fluminea occurred at 0.05 mg l⁻¹ Cd in NoS and the lowest in clams occupying SCO. Complexation of available metals, lower clam filtering rates and physical protection by the substrate were attributed to the depressed cadmium accumulation of clams exposed in the SCO substrate. Lower pH exposures (5.0 vs 7.8) significantly (P 0.05 level) reduced cadmium uptake at 21°C but had little effect at 9°C. Uptake was higher in clams fed with cadmium-exposed Chlamydomonas reinhardt at 21°C but not at 9°C. In temperature exposures alone at 0.05 mg l⁻¹ Cd, accumulation was significantly higher in C. fluminea exposed at 21°C than at 9°C. The results are discussed relative to the importance of standardized laboratory protocol and the use of C. fluminea as a bioindicator of heavy metal stress.