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(P677) Use of a Correction Factor for Interpreting Historical Amphipod Bioassays at Navy Offshore Facilities in San Francisco Bay, California.
Ward, Jeffrey*,1, Michael, D2, Holder, J3, Leather, J5, Pound, M4, 1 Battelle Marine Sciences Laboratory, Sequim, WA, USA2 Neptune and Company, Los Alamos, NM, USA3 ENTRIX, Inc, Ventura, CA, USA5 SPAWAR Systems Center San Diego, San Diego, CA, USA4 Southwest Division Naval Facilities Engineering Command, San Diego, CA, USA
ABSTRACT- The objective of this study was to determine the confounding factors influencing the usability of the historical bioassay data involving E. estuarius for risk assessment, which led to the development of a correction factor for assessing environmental risk at Navy offshore sites in San Francisco Bay. In 1999, the Sediment Working Group (SWG) reviewed bioassay data collected from Hunters Point Shipyard (HPS) and Treasure Island (TI), and found that observed toxicity in the amphipod did not appear to correlate with known contaminant concentrations. Further, within-replicate variability, expressed as the coefficient of variation (CV) from 5 replicate observations, was often high for this type of biological test, exceeding 40% in some cases. Further evaluation of the data suggested that incorrect acclimation of test organisms was one possible reason for poor survival and high variation. To test this hypothesis, the SWG conducted a Pretest Study to determine whether short acclimation could influence test organism survival. The study was important in that it resulted in a better understanding of the influence of test organism acclimation on bioassay results, and provided guidance concerning how future amphipod bioassays should be conducted. The Pretest Study also enabled the development of a preliminary amphipod correction factor that would allow use of historical bioassay data at other Navy sites where inappropriate acclimation influenced the test results. The presentation will focus on the evaluation of historical information from candidate sites in San Francisco Bay, the use of Pretest Study data to develop an initial correction factor estimate, and the confirmation of the estimate using comparisons of historical data with recent information from appropriately conducted bioassays tests in support of the Navy HPS Validation Study.
Key words: amphipod, sediment assessment, risk assessment
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