Pollution-Induced Community Tolerance (PICT) in coastal phytoplankton communities exposure to copper

The toxic effect of copper to coastal phytoplankton communities was studied in 6 m(3) enclosures during 15 days using the PICT (Pollution-Induced Community Tolerance) methodology. PICT, primary production, algal biomass, species composition and diversity in phytoplankton communities were measured in control enclosures and enclosures with 1, 3, 6 and 15 mu g Cu l(-1) added. Increased copper tolerances were induced in the enclosures with added copper and, related to the pooled mean value of the controls, the mean values for copper tolerance were significantly higher in enclosures with 1, 6 and 15 mu g Cu l(-1). In enclosures with 6 and 15 mu g Cu l(-1), photosynthetic activity was significantly depressed. Fundamental changes in taxonomic diversity and species composition occurred in enclosures with 15 mu g Cu l(-1). Algal biomass was not affected by the addition of copper. The distribution and concentration of copper in the enclosures showed that copper exposure was almost constant over time in the enclosures and was proportional to the amount of copper added to them. Our studies indicate that the PICT methodology is sensitive enough to detect even minor effects of copper on phytoplankton communities. The PICT measurements indicate effects from concentrations as low as 1 mu g Cu l(-1) in highly eutrophic coastal areas, where the bioavailability of copper is assumed to be low. Copper concentration in the fjord and control enclosures was high, about 0.5 mu g Cu l(-1), only a factor two below the effect concentration measured by PICT. These results are significant in view of the increased release of copper to the coastal marine environment as results of the substitution of copper-based ship paints for tri-n-butyltin (TBT) antifouling paints.