Sensitivity of Natural Bacterial Communities to Additions of Copper and to Cupric Ion Activity: A Bioassy of Copper Complexation in Seawater

Abstract

Cupric ion bioassays with natural bacterial communities were conducted in seawater samples at five stations in the Gulf of Mexico, ranging from low-productivity oceanic to high-productivity coastal. In these bioassays, we measured the incorporation of 3H-labeled amino acids by marine microbial communities following serial additions of ionic copper (CuSO4) and cupric ion buffers (combinations of CuSO4 and nitrilotriacetic acid, a synthetic chelator). The bioassays were designed to yield relations between (1) amino acid incorporation and total copper concentration, (2) incorporation and cupric ion activity, and (3) cupric ion activity and total copper concentration.