Growth and survival of Mytilus edulis larvae exposed to low levels of dibutyltin and tributylin

Two studies were conducted to observe effects of dibutyltin (DBT) and tributyltin (TBT) on larvae of Mytilus edulis for an exposure period of 25 d. Endpoints for evaluation were shell growth and mortality measured at 33 d. Larvae were cultured in a new laboratory assay chamber in a recirculating static test. The control, 2, 20, and 200 mu g/l DBT-treated populations had mean shell lengths of 527, 523, 417, and 180 mu m, respectively. Survival was 1% for the 200 mu g/l DBT-treated population, but ranged from 73 to 83% for controls, 2, and 20 mu g/l treatments. The no-observed-effect concentration (NOEC) was 2 mu g/l for DBT, while the lowest-observed-effect concentration (LOEC) was 20 mu g/l. The chronic toxicity value was 6.3 mu g/l. In the TBT bioassay, mean shell lengths for the control, 0.006, 0.050, and 0.130 mu g/l-treated populations were 565, 437, 385, and 292 mu m, respectively. Control survival was 74%, whereas TBT-treated populations survival ranged from 52 to 58%. The NOEC for TBT was 0.006 mu g/l TBT and the LOEC was 0.050. A chronic toxicity value of 0.017 mu g/l was calculated.