SEDIMENT TOXICITY TESTING WITH THE AMPHIPOD AMPELISCA-ABDITA IN CALCASIEU ESTUARY, LOUISIANA

Discharges from chemical and petrochemical manufacturing facilities ha ve contaminated portions of Louisiana's Calcasieu River estuary with a variety of organic and inorganic contaminants. As part of a special s tudy, sediment toxicity testing was conducted to assess potential impa ct to the benthic community. Ten-day flow-through sediment toxicity te sts with the amphipod Ampelisca abdita revealed significant toxicity a t 68% (26 of 38) of the stations tested. A. abdita mortality was highe st in the effluent-dominated bayous, which are tributaries to the Calc asieu River. Mortality was correlated with total heavy metal and total organic compound concentrations in the sediments. Ancillary experimen ts showed that sediment interstitial water salinity as low as 2.5 o/oo did not significantly affect A. abdita's response in the flow-through system; sediment storage for 7 weeks at 4 degrees C did not significa ntly affect toxicity. Sediment toxicity to A. abdita was more prevalen t than receiving water toxicity using three short-term chronic bioassa ys. Results suggest that toxicity testing using this amphipod is a val uable tool when assessing sediments containing complex contaminant mix tures and for assessing effects of pollutant loading over time. In con junction with chemical analyses, the testing indicated that the efflue nt-dominated, brackish bayous (Bayou d'Inde and Bayou Verdine) were th e portions of the estuary most impacted by toxicity.