Bioassaying the toxicity of tributyltin-(TBT)-oolluted sediment to spat of the bivalve Scrobicularia plana

A solid-phase sediment toxicity bioassay with small spat (2 to 3 mm in length) of the estuarine bivalve Scrobiculana plana (da Costa) was run for 36 d in 1992: lethal and sublethal effects were investigated. While 2 negatlve control sediments allowed juvenile weight gain in excess of 140% of initial weight, a control sediment contaminated with non-tributyltin (TBT) compounds resulted in mortalities > 8 0 % in 12 d. A TBT-polluted sediment (0.27 1-19 Sn g-' dry wt) did not produce any mortality or avoidance response, but both growth and burying activity of clams at the end of the trial were significantly reduced with respect to those of spat in control treatments. Although frozen storage of sediment samples renders this experiment somewhat inconclusive, results confirm suspicion of field TBT-sediment deleterious effects at -0.3 pg Sn g" dry wt. The environmental implications of findings are discussed in relation to the disappearance of S. plana populations throughout Atlantic Europe concurrent with TBT bulld-up in deposits; in addition, arguments are presented to emphasize the ecological relevance of sublethal stress affecting parameters such as the differential capabhty of benthic bivalves to avoid predation. Finally, the suitabhty of S. plana spat for widespread sediment toxicity bioassays is assessed.