Effect of cupric ion activity on calcium accumulation in juvenile flounder ( Paralichthys spp.)

Abstract

To test the effects of cupric ion activity on calcium accumulation, juvenile flounder ( Paralichthys spp.) were exposed to five different activities of ionic copper for 14 days. The negative log of the cupric ion activity (pCu) of the seawater-based exposure media were controlled with a nitrilotriacetic acid (NTA) trace metal buffer system. The pCu ranged from 13·0 (analogous to background cupric ion activities measured in Beaufort seawater) to 9·0 (which could exist in grossly contaminated environments). The rates of 45Ca accumulation by flounder were significantly reduced with increasing cupric ion activities. The rates at pCu 10·0, 9·5, and 9·0 were lower than those at pCu 13·0 and 11·0. Additionally, it was shown that after the fish were exposed to the different activities for 14 days and then placed in seawater without added copper or NTA, there was increased 45Ca accumulation at the two highest pCu of 9·5 and 9·0. This increased accumulation suggests that the fishes were trying to overcome a calcium deficit that was induced by the copper exposure. The demonstrated non-lethal effects of copper/cupric ion activity on flounder occurred at cupric ion concentrations that were two to three orders of magnitude lower than the lethal concentrations.