The Effects of Cu and Cu+Zn on Biomass and Taxonomic Composition in Algal Periphyton Communities

In order to evaluate the long-term (24-day) influence of copper alone (Cu) and with combination of Cu+Zn on biomass and taxonomic composition in algal periphyton communities, indoor artificial streams were used with copper (50 μg.l-1) and copper and zinc (50 μg Cu l-1 and 1 mg Zn l-1). The effects of copper and zinc on community productivity were assessed by measuring biomass, ash-free dry mass (AFDM), chlorophyll-a, taxonomic composition, relative abundance and biovolume. In artificial streams with Cu and Cu + Zn, there was a significant (p < 0.05) reduction of chlorophyll-a, dry mass and AFDM. Species diversity and relative abundance of periphyton species changed drastically under the influence of copper and zinc. In an artificial streams containing copper and zinc (50 μg Cu l-1 and 1 mg Zn l-1), the taxonomic composition of the population shifted from a cyanophyceaen dominated community to a community mainly consisting of chlorophyceae, while changes among species within the bacillariophyceae did not show a marked difference under the influence of copper and zinc. In artificial streams with copper alone Oocystis gigas and Stigeoclonium tennue became dominant species while in artificial streams containing copper and zinc Oocystis crassa and Scenedesmus sp. dominated the periphyton community. This study showed that copper alone or with combination of zinc not only influences community productivity but also causes changes in species composition.