Control of cadmium levels inHolopedium gibberum(crustacea, cladocera) in canadian shield lakes

Abstract

Cadmium concentrations (Cd-h) of Holopedium gibberum (Crustacea, Cladocera) collected from 26 Canadian Shield lakes with positive alkalinity ranged from 0.9 to 31 μg/g. Levels were positively correlated with aqueous Cd concentrations (Cd-aq) and negatively correlated with clutch size. Animals collected from acidified lakes did not have elevated Cd-h concentrations despite elevated Cd-aq levels. In three intensive study lakes, the presence of eggs lowered Cd-h concentrations and Cd-h levels frequently increased with increases in body size. In two of these lakes, many H. gibberum occupied waters rich in particulate iron just above the anoxic interface. Cd-h levels fell when animals were experimentally confined to this layer, presumably because much of the Cd-aq was adsorbed by the particulate iron and was unavailable for uptake. We suggest that the behavior of animals, specifically their movement to light-scattering layers just above the anoxic interface, influences the accumulation of Cd by H. gibberum in Canadian Shield lakes.