USING A SPIKED SEDIMENT BIOASSAY TO ESTABLISH A NO-EFFECT CONCENTRATION FOR DIOXIN EXPOSURE TO THE AMPHIPOD AMPELISCA-ABDITA

A recent study conducted by the National Oceanic and Atmospheric Admin istration (NOAA) reported a highly significant correlation between 2,3 ,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) concentrations and amp hipod (Ampelisca abdita) mortality in sediment samples collected from the lower Passaic River and Newark Bay. However, there is a paucity of data regarding the potential effects of 2,3,7,8-TCDD on benthic inver tebrates under controlled laboratory exposures. In this study, 10-d wh ole-sediment bioassays using the marine amphipod A. abdita were conduc ted on spiked sediment samples representing a range of 2,3,7,8-TCDD co ncentrations (0-25 mu g/kg dry weight). No effects on survival or grow th relative to controls were observed at any test concentration. The h ighest 2,3,7,8-TCDD concentration reported from the NOAA study was 0.6 2 mu g/kg. Therefore, the lack of 2,3,7,8-TCDD toxicity in this study indicates that the mortality observed in the NOAA study was probably d ue to factors or chemicals other than 2,3,7,8-TCDD. This study demonst rates the utility of spiked sediment bioassays in evaluating cause and effect relationships between sediment contamination and benthic inver tebrate mortality.