PARENT SESSION

(043) Acute Amphipod Toxicity to Sediment with Total DDT Concentrations Less than 100 ppb.

Gardiner, W¹, Word, J¹, Moore, D¹, ¹ MEC Analytical Systems, Inc, Sequim, WA, USA

ABSTRACT- Many ports and harbors are located at the terminus of large agricultural watersheds. In these waterways, the persistent pesticide DDT and its degradation products are present at moderate concentrations (50 to 100 ppb dry weight) and may be the principal contaminant of concern in sediment. Recent evaluations of sediment in several California waterways have indicated significantly increased mortality with the estuarine amphipod Eohaustorius estuarius. In each case, toxicity was observed in sediment with DDT (p,p′-DDT, DDD and DDE) concentrations exceeding 50 to 80 ppb dry weight. Toxicity was generally not observed for other species that were tested concurrently. Sediment with DDT concentrations below approximately 50 ppb dry weight did not show acute amphipod toxicity. These results compare favorably with DDT-spiked-sediment tests conducted with Rhepoxynius abronius and sediment screening values (Effects-Range Median and Probable Effects Level) for DDT. The results of the current field investigations with E. estuarius suggest a lowest observable effects level for DDT of 50 to 60 ppb dry weight. Clean up levels that were based on bioaccumulation tests in sediment from Richmond Harbor and the Palos Verdes Shelf have exceeded this effects level and would likely not be protective of amphipods based on acute toxicity and presumably chronic toxicity.