Bioenergetic effects of aqueous copper and cadmium on the grass shrimp, Palaemonetes pugio

Adult grass shrimp (Palaemonetes pugio) were exposed to either aqueous copper (ranging from 7.54 to 41.29 microg Cu(2+)/L) or cadmium (2.48- 6.55 microg Cd(2+)/L) for 14 days in laboratory experiments to quantify effects on survival and bioenergetic processes, including respiration, somatic growth, energy (lipid) storage, and food consumption. The lowest observed effect concentrations for mortality were 41.29 microg Cu(2+)/L or 6.55 microg Cd(2+)/L, expressed as free metal ion concentrations. Both copper and cadmium caused a decrease in respiration rate at concentrations of 7.54 to 41.29 microg Cu(2+)/L or 6.55 microg Cd(2+)/L. Exposure to copper (>or=27.03 microg Cu(2+)/L) resulted in negative somatic growth (i.e., weight loss). Cadmium exposure (6.17 microg Cd(2+)/L) caused a decrease in growth rate, relative to the control, but growth remained positive. Nonpolar lipid content and food consumption were not significantly affected by exposure to either copper or cadmium. Our results suggest that both copper and cadmium result in overall metabolic depression, decreasing energy allocation to both maintenance and production.