Acute toxicity of copper to the threespine stickleback, Gasterosteus aculeatus

This study focuses on characterizing the acute toxicity of copper in freshwater to the threespine stickleback, Gasterosteus aculeatus, a small and widely distributed euryhaline fish. The threespine stickleback is used as an effluent monitoring species in both Canada and the United States, yet in some locations natural populations are listed as threatened or endangered. Four 96-h static renewal acute toxicity tests were performed in moderately hard water using U.S. EPA methods with adult fish (mean wet weight = 0.41 g/fish). The geometric mean of the 24-, 48-, 72- and 96-h LC(50)s based on measured concentrations of total copper (estimated dissolved copper in parentheses) in the test solutions were 382.2 (366.9), 278.7 (267.6), 256.6 (246.3), and 227.2 (218.1) microg Cu/L, respectively. Conservative estimates of acute toxicity thresholds, made using LC1 values, for adult threespine sticklebacks over 24-, 48-, 72- or 96-h exposure periods in moderately hard water are approximately 114.3 (109.7), 78.3 (75.2), 67.0 (64.3), and 52.4 (50.3) microg Cu/L, respectively. Test results were normalized to a range of water hardness from very soft to very hard using two U.S. EPA methods, the water hardness and the Biotic Ligand Model normalization procedures. Subsequently, interspecies sensitivity comparisons were made with aquatic animal species used in both the current and proposed U.S. EPA copper water quality criteria documents. Information reported in this study may be useful in effluent toxicity identification evaluations, ecological risk assessments and criteria development where copper is a concern.