Cadmium and lead toxicity on tropical freshwater periphyton communities under laboratory-based mesocosm experiments |
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Authors: | Taurai Bere José Galizia Tundisi |
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Institution: | 1.Instituto Internacional de Ecologia,S?o Carlos,Brazil;2.Univeridade Federal De S?o Carlos, Programa de Pós-Gradua??o em Ecologia e Recursos Naturais,S?o Carlos,Brazil |
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Abstract: | Periphyton constitutes an important community that is useful for assessment of ecological conditions in lotic systems. The
objective of this study was to assess the effects of different mixtures of Cd and Pb on periphyton growth as well as Cd and
Pb mixtures toxicity to diatom assemblages in laboratory mesocosm experiments. A natural periphyton community sampled from
the Monjolinho River (South of Brazil) was inoculated into five experimental systems containing clean glass substrates for
periphyton colonization. The communities were exposed to mixtures of dissolved Cd and Pb concentrations of 0.01 and 0.1 mg l−1 Cd and 0.033 and 0.1 mg l−1 Pb. Periphyton ash-free dry weight, growth rate, diatom cell density and diatom community composition were analyzed on samples
collected after 1, 2 and 3 weeks of colonization. High Cd concentration (0.1 mg l−1) has negative effects on periphyton growth while high concentration of Pb (0.1 mg l−1) decreased the toxic effects of Cd on periphyton growth. Shifts in species composition (development of more resistant species
like Achnanthidium minutissimum and reduction of sensitive ones like Cymbopleura naviculiformis, Fragilaria capucina, Navicula cryptocephala, Encyonema silesiacum, Eunotia bilunaris, and Gomphonema parvulum), decreases in species diversity of diatom communities with increasing Cd and Pb concentrations and exposure duration have
been demonstrated in this study making diatom communities appropriate monitors of metal mixtures in aquatic systems. |
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