Assessing the Differential Toxicity of Dissolved, Complexed and Ionic Copper in Natural Waters on the Lateraline System in Juvenile Fish
Research Idea Scope
Copper toxicity to salmonids is currently referenced to a series of Laboratory tests that were conducted using well water and copper that was deliberately kept ionic, uncomplexed. Toxicity in these tests showed temporary effects to the fish olfactory nerves at levels around 3-5 ppb copper. Copper in natural waters is not usually found as an ionic species but is most often bound to organic and inorganic molecules that render it biologically un-available. I propose a study that will expose juvenile fish to a series of concentrations of ionic copper in well water (similar to the protocol and concentration used by researchers at NOAA) in parrallel to a series of copper concentrations complexed with a standard Humic substance again in well water, and with a series of copper concentrations mixed natural stream water. A series would also be included to assess the reaction time required for copper to be absorbed by the ligands. UV spectroscopy would be used to characterize the fraction of organic compounds absorbing the most copper. A series of tests conducted on natural stream water, using filtration (0.45um) compared with ultracentrifugation would also be conducted to distinguish the operationally defined “dissolved copper” from truly dissolved copper in field samples.
Urgency and Payoff
Research would help resolve the differences seen in Laboratory tests conducted with ionic copper in well water with the lack of toxicity seen in field samples with much higher “dissolved” copper concentrations, and help establish a better field copper toxicity criteria.
William Van Peeters, Resource Center FHWA San Francisco California, Telephone: 415 744 0116