Copper is biocidal and the oxide form is incorporated into treatments such as paints for aquaculture netting.
Most finfish antifouling net coatings currently incorporate Copper Oxide (Cu2O) as the active ingredient. Nearly all commercial net coatings are water-borne (no organic solvents) and have Cu2O as the prime biocide in concentrations up to 20%, often in combination with one or more organic booster biocides such as SeaNine, Zinc pyrithione (=Zinc Omadine) and Dichlofluanid.
Key Factors Positive
- Efficacy at lowering the rate of fouling is good.
Key Factors Negative
- Environmental effects.
For netting the current cost (2007) is approximately 4 Euro per litre paint/kg netting. Cost of treatment varies with location and is likely to increase with the increasing demand for copper as a raw material. Results from CRAB suggest that cleaning costs can in some cases be roughly halved for netting with a copper treatment. Periodic cleaning and re-treatment is required which is costly.
Due to its complex nature and the uncertainty over its level of interaction with other substances, it is difficult to establish the precise effect of elevated levels of copper in the marine environment. It is therefore difficult to generalise about the toxicity of copper to marine organisms. There is evidence that certain species of fish are sensitive to quite low levels of copper even though other species are tolerant of much higher levels. Benthic marine organisms are thought to be slightly more sensitive to copper than fish, although some species demonstrate a capacity to adapt to elevated levels. Legislative pressure on biocidal antifoulings is increasing but there are no clear indications that copper based products will be prohibited in the near future for aquaculture.
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