Use of whole-body and subcellular Cu residues of Lumbriculus variegatus to predict waterborne Cu toxicity to both L. variegatus and Chironomus riparius in fresh water.

We tested the use of whole-body and subcellular Cu residues (biologically-active (BAM) and inactive compartments (BIM)), of the oligochaete Lumbriculus variegatus to predict Cu toxicity in fresh water. The critical whole-body residue associated with 50% mortality (CBR(50)) was constant (38.2-55.6 µg g(-1) fresh wt.) across water hardness (38-117 mg L(-1) as CaCO(3)) and exposure times during the chronic exposure. The critical subcellular residue (CSR(50)) in metal-rich granules (part of BIM) associated with 50% mortality was approximately 5 µg g(-1) fresh wt., indicating that Cu bioavailability is correlated with toxicity:subcellular residue is a better predictor of Cu toxicity than whole-body residue. There was a strong correlation between the whole-body residue of L. variegatus (biomonitor) and survival of Chironomus riparius (relatively sensitive species) in a hard water Cu co-exposure. The CBR(50) in L. variegatus for predicting mortality of C. riparius was 29.1-45.7 µg g(-1) fresh wt., which was consistent within the experimental period; therefore use of Cu residue in an accumulator species to predict bioavailability of Cu to a sensitive species is a promising approach.

Mechanisms of waterborne Cu toxicity to the pond snail Lymnaea stagnalis: physiology and Cu bioavailability.

We examined the mechanisms of toxicity of waterborne Cu to the freshwater pond snail Lymnaea stagnalis. The snail is one of the most sensitive species to acute Cu exposure (96 h LC(50), LC(20): 24.9, 18.0 µgl(-1)); they are not protected by the water quality criteria of the US EPA. Tissue Na and Ca were also reduced by Cu in the acute exposure. In contrast, during 28 d chronic exposures to Cu in the presence of food, which resulted in higher DOC concentrations, there was no significant mortality but an inhibition of growth, which may reflect a re-allocation of resources to detoxification. Cu detoxification was evidenced in chronic exposure by increases in metallothionein-like protein concentrations and Cu binding to metal-rich granules, decreases in thiobarbituric acid-reactive substances, and changes in the subcellular distribution in the soft tissues. Our results demonstrated that apart from external Cu bioavailability, compartmentalization of metals within the cells can alter toxicity of Cu to the snails.