The Effect of Salinity on Cadmium Uptake by the Tissues of the Shore Crab Carcinus Maenas

Cadmium accumulation by the haemolymph, gills and carapace of the shore crab Carcinus maenas (L.) was significantly higher in dilute sea water. This was reflected in the whole-body cadmium concentrations. There was no salinity effect with the hepatopancreas or muscle cadmium concentration. Over a 68-day period, cadmium was steadily accumulated by the carapace, with the salinity effect becoming increasingly apparent. In 50 % sea water the gill cadmium concentration apparently reached a maximum level after about 2 weeks of uptake. This was eventually overtaken by the tissue cadmium concentration in the gills of 100 % s.w. animals. After about 48 days the salinity effect had disappeared and the gill cadmium concentration of both 50% and 100% s.w. animals (in 20/i-mol Cd I" = 2*3 mg I-) remained at approximately 0-3 /i-mol Cd g" ( = 33-7 mg kg-) wet weight of tissue. The hepatopancreas cadmium also levelled off at about this concentration although no salinity effect was apparent. When animals loaded with cadmium for a 37-day period were returned to clean sea water, their whole body cadmium concentration fell by about 50 % after 11 days. Losses from carapace and gills were important components of this reduction in cadmium concentration.