Validation of a chronic dietary cadmium bioaccumulation and toxicity model for Hyalella azteca exposed to field-contaminated periphyton and lake water.

A model previously developed in the laboratory to predict chronic bioaccumulation and toxicity of cadmium to Hyalella azteca from a diet of periphyton was validated by comparing predictions with measurements of Cd in two exposure scenarios: laboratory-cultured H. azteca exposed for 28 d to field-contaminated water and periphyton, and Cd measured in field-collected H. azteca. In both exposure scenarios, model predictions of bioaccumulation were shown to be robust; however, effects on Cd bioaccumulation from complexation with dissolved organic carbon (DOC) and inhibition of Cd bioaccumulation by Ca²⁺ must be incorporated into the model to permit its wider application. The model predicted that 80 to 84% of Cd in H. azteca came from periphyton when H. azteca were chronically exposed to dissolved Cd in lake water at 2.63 to 3.01 nmol/L and periphyton at 1,880 to 2,630 nmol/g ash-free dry mass. Dietary Cd contributed markedly to the model-predicted decrease in 28-d survival to 74% at environmental Cd concentrations in food and water. In reality, survival decreased to 10%. The lower than predicted survival likely was due to the higher nutritional quality of periphyton used to develop the model in the laboratory compared with the field-collected periphyton. Overall, this research demonstrated that Cd in a periphyton diet at environmental concentrations can contribute to chronic toxicity in H. azteca.