Tributyltin uptake and depuration in Hyalella azteca: implications for experimental design.

The purpose of this study was to address four aspects of the kinetics of tributyltin (TBT) in the freshwater amphipod Hyalella azteca: time to steady state, route of uptake, depuration rates, and effect of gut clearance. The amphipods accumulated TBT rapidly, reaching steady state within 14 d. Body concentrations were similar between caged and sediment-exposed animals, indicating that the primary route of uptake is via dissolved TBT. However, the rate of uptake was significantly higher in sediment-exposed amphipods. During depuration, body concentrations of TBT exhibited a biphasic decline, with a stronger decrease over the first 24 h that is attributed primarily to gut clearance, followed by a more gradual decrease most likely due to excretion from the body. Gut contents contributed significantly to body concentrations of TBT, accounting for 30% of the initial total body burden in sediment-exposed amphipods. Half-lives of TBT in gut-cleared H. azteca were 8 d and 14 d for amphipods exposed to spiked water and spiked sediment, respectively. The results of this study have significant implications in the experimental design and interpretation of studies involving the effects of TBT in H. azteca.

Accumulation of tributyltin in Hyalella azteca as an indicator of chronic toxicity: survival, growth, and reproduction.

The chronic toxicity of tributyltin (TBT) was examined by exposing two successive generations of the freshwater amphipod, Hyalella azteca, to sediments spiked with TBT. Survival was the most sensitive measure of effect, with lethal concentration resulting in 50% mortality (LC50) values on a water and body concentration basis ranging from 76 to 145 ng Sn/L and 2,790 to 4,300 ng Sn/g, respectively. Individual growth of amphipods was not negatively affected by TBT, and although reproduction might be more sensitive than survival, the data were too variable to use on a routine basis. There were no detectable TBT-induced differences in the response between first- and second-generation animals. The relationship between toxicity and bioaccumulation of TBT in H. azteca was determined and can be used as a tool to predict the toxicity of TBT in environmental samples. Body concentrations exceeding 2,000 ng Sn/g in H. azteca exposed to field-collected samples would indicate that chronic toxicity due to TBT is likely occurring in amphipod populations at those sites.