Evaluation of bivalve clearance rate (CR) as a physiological indicator of heavy metal toxicity in freshwater mussel, Anodonta cygnea (Linea, 1876)

This study was performed to evaluate suitability of clearance rate (CR) as a physiological indicator of zinc (essential element) and chromium (non-essential element) toxicity in Anodonta cygnea (Linaea, 1876). CR of bivalves was measured before and after 9 and 18 days exposure to 100 µg l-1 Zn and Cr during 120 min with 15 min intervals. 5, 25 and 125 µg l-1 concentrations of each metal were used for CR measurement. Irregular fluctuations were observed in pre-exposed CR of bivalves in all three concentrations of both metals during 2 hour period. There was significant difference (?=0/05; P < 0/025) between CR of Zn and Cr in lowest (5 µg l-1) and highest (125 µg l-1) exposure concentrations. Maximum CR for both metals was obtained in lower concentration. Also, calculated post-exposed CR for both metals in days 9 and 18 after exposure were significantly (?=0/05; P < 0/01) lower than control bivalves. Based on the results, clearance rate is a useful measure of heavy metal toxicity in A. cygnea as a model of freshwater bivalves.