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(PM136) Comparison of amended and diluted sediment copper toxicity using the amphipod, Hyalella azteca (Saussure).

Jones, Ryan1, Rodgers, Jr., John1, 1 Clemson University, Clemson, SC, USA

ABSTRACT- Laboratory sediment toxicity tests are frequently used as a portion of the evidence to discern toxicity in field collected sediments. If toxicity is elicited, dilutions are required to measure the degree of toxicity or potency of those field collected sediments. Sediment amendments can be used to study concentration–response relationships and to evaluate the relative sensitivity of test organisms to concentrations of known toxic contaminants such as copper. Contrasting results from amended sediments with sediment dilutions could be informative. The objective of this study was to compare concentration-response relationships of Hyalella azteca (Saussure) in copper–amended sediments with sediment dilutions of the same concentrations (mg Cu/kg sediment dry weight). Nontoxic, field–collected sediments were amended with copper sulfate to concentrations of 100, 250, 500, 750, and 1000 mg Cu/kg (dry weight) above background. Using unamended (control) sediment, dilutions of the highest amended sediment concentration were made to obtain the same respective nominal concentrations. Responses of H. azteca were measured in 10–d static non–renewal toxicity experiments. Atomic absorption spectroscopy was used to measure total sediment copper concentrations. Amended and diluted sediment LC50s were estimated at 181.98 and 854.77 mg Cu/kgsediment, respectively. Growth of surviving amphipods was not significantly affected in either experiment. Amended sediment can provide a (positive) control for sediment toxicity tests. Recently amended sediment appeared to be more toxic than sediments in contact with copper for two months. Therefore, the relationship between amending and diluting sediment is apparently influenced by the duration of contact between copper and the sediment. Testing of recently amended or contaminated sediments can provide an instantaneous estimate of binding sites for elements such as copper. For a less conservative measure of binding potential, longer contact duration is required.

Key words: Hyalella azteca, toxicity, sediment, copper

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