Acute toxicities of selected heavy metals to the softshell clam, Mya arenaria

Static acute toxicity bioassays with adult softshell clams and salts of copper, cadmium, zinc, lead, manganese, and nickel were conducted at 30 0/00 salinity and 22 degrees C. Concentrations fatal to 50% in 168 hours, in mg/l (ppm) metal added at start, were 0.035 for Cu, 0.150 for Cd, 1.55 for Zn, 8.80 for Pb, 300.0 for Mn, and less than 50.0 for Ni. Additional tests were conducted with Zn2+ and Cu2+ at 30 0/00 during fall (17.5 degrees C) and winter (4 degrees C); clams displayed increasing survival with decreasing temperature. For Cu, LC-50 (336 hr) values at 17 degrees C and 4 degrees C were 0.086 and greater than 3.00 mg/l, respectively; for Zn these were 2.65 and greater than 25.0, respectively.