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TP2 Metals in the Environment: Regulatory and Risk Concerns
(ARN-1117-824716) Potential effects of commonly used synthetic sea salts on copper toxicity tests using Mytilus.
Arnold, W1, Cotsifas, Jeffrey2, Playle, Richard3, 1 Copper Development Association Inc., New York, NY, USA2 Pacific EcoRisk Inc., Martinez, CA, USA3 Department of Biology, Wilfrid Laurier University, Waterloo, ON, Canada
ABSTRACT- The salinity of effluents, ambient, and laboratory water samples often requires adjustment to meet guidelines for testing of marine species. Sample salinity is often increased via addition of synthetic sea salts. The US Environmental Protection Agency in its saltwater test guidelines specifically mentions that commercial sea salts, such as Forty Fathoms® (now Crystal Sea Marinemix®, Bioassay Grade), HW Marinemix® or equivalent salts can be used for salinity adjustment. This study focused on the use of synthetic sea salts and their potential effects on toxicity tests of samples where copper is of concern. Thirty-two commercial toxicity testing laboratories in Canada and the USA were surveyed, 27 of which use artificial sea salts. The proportion using Crystal Sea Marinemi® (Bioassay Grade), HW Marinemix®, Instant Ocean® and Tropical Marin® were 56%, 22%, 11%, and 11%, respectively. Saline solutions (30 g/L) were made by adding each sea salt to reverse osmosis deionized water. In addition modified GP2, Kent Marine®, and Red Sea Salt® were similarly prepared. All solutions were analyzed for dissolved organic carbon (DOC) and copper concentrations. Crystal Sea Marinemix® had elevated DOC concentrations (5.4 to 6.4 mg C/L) while other brands generally contained <1 mg/L DOC. Some salt solutions at 30 g/L contained >2.0 g dissolved Cu/L. Dissolved copper EC50s for Mytilus sp. (probably M. galloprovincialis) were determined in saline solutions made from Crystal Sea Marinemix® (9.7 g Cu/L), HW Marinemix® (8.6 g Cu/L) and GP2 (7.5 g Cu/L). Based on a model developed by Arnold (2005), natural DOC at levels found in Crystal Sea Marinemix® should have increased the dissolved copper EC50 to approximately 30 g Cu/L. Excitation-emission spectral analysis and toxicity testing indicate that the DOC in Crystal Sea Marinemix® differs considerably from natural DOC, which could explain the low level of influence of the DOC on copper toxicity.
Key words: synthetic sea salts, copper, acute toxicity,
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