Effects of cadmium on survival, osmoregulatory ability and bioenergetics of juvenile blue crabs Callinectes sapidus at different salinities

Abstract

Juvenile blue crabs, Callinectes sapidus, from the Barataria estuary (Louisiana, USA) were exposed to a range of dissolved cadmium concentrations at 2.5 and 25%. to determine their response to cadmium. 21-Day LC 50s were an order of magnitude lower at 2.5%. (19μg liter −1) than at 25%. (186μg liter −1). Crabs were exposed to Cd levels of 0, 50 and 100μg liter −1 for measurements of feeding, respiration and excretion rates. Respiration was the primary component (x̄ = 86.2%) of the energy expenditure budget in all cases, relative to excretion. Rates of energy expenditure did not vary with cadmium concentration at either salinity, and were much lower than those of energy consumption and absorption. Scope for growth paralleled energy consumption and absorption. Scope for growth did not vary as a function of cadmium concentration at 25%.; scope for growth at 2.5%. was significantly lower in crabs exposed to 50 and 100μg liter −1 Cd relative to control crabs. Cadmium levels of up to 100μg liter −1 do not stress juvenile blue crabs at 25%.; but at 2.5%., these same levels of Cd result in mortality and sub-lethal stress. This finding is important since nursery grounds for juveniles of this species often lie in low salinity, estuarine waters, and high dissolved cadmium levels have been reported in Louisiana estuaries.