Uptake and tissue distributions of cadmium, selenium and zinc in striped marsh frog tadpoles exposed during early post-embryonic development

Metals and metalloids released through anthropogenic activities can accumulate in aquatic organisms, resulting in adverse effects in sensitive species. We investigated the influence of feeding regime and exposure complexity (i.e., mixture) on bioaccumulation kinetics and body distribution of common metal(loid) pollutants in Limnodynastes peronii during early post-embryonic development. Tadpoles were exposed to radiolabelled 109Cd, 75Se and 65Zn alone and in a mixture for 4 days, followed by 3 days depuration in clean water. One group was fed directly in exposure aquaria, whereas a second group was transferred to clean water for feeding, to investigate the potential influence of sorption to food on uptake. Bioconcentration factor and retention was observed to be greatest for Se. Results demonstrate that tadpoles accumulated and retained half the amount of Cd when exposed in mixture, suggesting that Se and/or Zn may have antagonistic effects against Cd uptake. Additionally, tadpoles fed directly in exposure water accumulated 2-3-times more Cd and Zn compared to tadpoles fed in clean water, indicating that the presence of food particles is an important factor that may influence uptake. Interestingly, this had a negligible impact on Se uptake. The study reveals how exposure conditions can influence the bioaccumulation of metal(loid)s, highlighting experimental factors as important considerations for both controlled toxicity experiments and for understanding exposure risks for amphibian populations.