PW13 Metals in the Environment: Regulatory and Risk Concerns
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(PW222) Validation study of acute Biotic Ligand Model for silver.

Bielmyer, G1, 2, Grosell, M.1, Brix, K2, 1 RSMAS, University of Miami, Miami, Fl, USA2 ECOTOX, Key Biscayne, Fl., USA

ABSTRACT- Over the past 10 years, an extensive research program has been undertaken to develop an acute biotic ligand model (BLM) for silver (Ag). An important final step of this research program is to conduct a validation study to assess the predictive capabilities of the BLMs developed for fish and invertebrates. To accomplish this, ten natural waters with varying water quality characteristics were collected from across the United States. Each water was or is being rigorously characterized with respect to ionic composition (including sulfide), pH, and dissolved organic carbon. Acute toxicity tests using the cladoceran Ceriodaphnia dubia (48 h static) and fish Pimephales promelas (96 h static renewal) were then conducted to determine the toxicity (LC50) of Ag in each of these waters. The toxicity of Ag in a standard laboratory water was also determined to allow for calculation of a water effect ratio (WER) for each of the natural waters. The current WER methodology does not include acclimation of test organisms to the site waters prior to determining the WER. In contrast, the BLM has been developed using a mix of studies where test organisms were or were not acclimated to test waters. To evaluate the effects of acclimation to water quality conditions on WERs and BLM predictions, a subset of the natural waters were also tested with P. promelas using fish that had been acclimated to the natural water for 7 days prior to testing. Results from non-acclimated and acclimated tests were then compared to predicted LC50s and WERs using the BLM.

Key words: ligand , biotic, model, silver

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