Chronic toxicity of tributyltin to the marine polychaete worm, Neanthes arenaceodentata

Abstract

Life cycle toxicity tests provide ecologically relevant indices for estimating long-term ‘safe’ concentrations of environmental contaminants. Tissue concentrations observed in animals from these tests can also be used to estimate the risk associated with contaminant residues in field collected animals. Such residue-effects information was generated for the marine polychaete worm, Neanthes arenaceodentata, exposed to the organometal, tributyltin (TBT). Juvenile Neanthes were exposed in the laboratory to five concentrations (500, 100, 50, 10, 0 ng l ) of TBT. After ten weeks, effects on survival, growth and reproduction were evaluated. Significant mortality (79%) was observed only in the highest TBT exposure concentration. Growth (dry weights of individual worms) was significantly reduced in the two highest TBT treatments. Reproduction (mean number of eggs and emergent juvenile (EJ) worms) was significantly reduced in the 100 ng l treatment. Reproduction was not evaluated in worms from the 500 ng l treatment due to low survival and an inability to distinguish sexes. No adverse effect on survival, growth or reproduction was observed in worms exposed to 50 or 10 ng l TBT. TBT had no observed effect on egg size, estimated individual EJ dry weight or timing of reproductive events. Neanthes arenaceodentata accumulated significant amounts of TBT which mirrored the exposure gradient; i.e. 16.81, 6.27, 2.99, 1.47 and 0.21 μg g dry weight. Chronic effects were observed in worms with tissue concentrations 6.3 μg TBT g dry weight. No significant effects were observed at tissue concentrations < 3.0 μg g . Detectable amounts of TBT metabolites (di- and monobutyltin) were found in all tissue samples with a greater proportion found in worms with lower TBT residues. These TBT residue data are discussed in relation to comparative laboratory and field information.