Copper Toxicity to Non-Targeted Organisms
Animal Considerations
Some species of fish are highly sensitive to copper and will die even at concentrations below therapeutic levels (i.e., less than 0.15 mg/L free copper). Other considerations that will affect survival include acclimation period (exposing fish to slowly increasing concentrations of free copper over the course of several days until the treatment target concentration is reached), as well as age or life stage of the fish. In one study, larvae acclimated to copper exposure more quickly than juvenile and adult fish and had better survival (Sellin et al. 2005). In some fish species, younger fish are more resistant to copper toxicity than older fish; in others, the reverse is true (Howarth and Sprague 1978; Pickering and Lazorchak 1995; Furata et al. 2008). Copper will damage a number of organs and systems, including the gills, liver, kidney, immune system, and nervous system (Cardeilhac and Whitaker 1988). Gills appear to be the most affected organ during acute toxicity, and will become blunt and thickened and lose ability to regulate body fluid ion concentrations. Copper also suppresses immune system function, and can affect the lateral line of fish. Prolonged copper exposure also may result in reduced growth (Wong et al. 1999). During toxicity, in addition to general signs of distress (e.g., increased respiration), fish may display darkening and behavioral abnormalities: lethargy, incoordination, problems with posture and balance, and, eventually, death (Cardeilhac and Whitaker 1988).
Most invertebrates are highly sensitive to copper and will not survive a copper treatment. If systems with invertebrates are to be treated, the invertebrates should be moved and not returned until Cu2+ concentrations are 0.01 mg/L or less, but ideally zero (Cardeilhac and Whitaker 1988). Copper levels should be monitored for some time after treatment, because copper bound to substrate (e.g., coral, shells, decorations) may be released if pH drops or other changes in water quality parameters occur (see Environmental Factors below).
