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2F - Site Specific Testing (MOP/105) Toxic effects of acid mine drainage on diatoms and the duckweed Lemna gibba. Gerhardt, A.1, 2, Janssens de Bisthoven, L.1, 2, Reboleira, A.S.P.S.1, Pereira, M.J.1, Soares, A.M.V.M.1, 1 University of Aveiro, Aveiro, Portugal2 LimCo International, Ibbenbueren, Germany ABSTRACT- São Domingos Mine (SE Portugal) is an abandoned cupriferous pyrite mine with highly varying pH and metal concentrations. The effects of Acid mine drainage (AMD) on diatoms and the macrophyte Lemna gibba were studied in the laboratory and in situ in a natural pH and metal gradient. At four sampling sites in the AMD gradient and at additionally two control sites, periphytic algae were scraped from the substrate for diversity and abundance evaluation. Moreover, clay tiles were exposed in 3 replicates at the sites during 4 weeks to study colonization. Short-term toxicity tests with water from the AMD (pH 6.4, 5.5, 5.0, 4.4 and 3.3) as well as from two control sites were performed with Lemna gibba according to standard protocols in the laboratory and in situ, with the number of leaves on each plant and the color being recorded daily. Metal concentrations (As, Cd, Co, Cr, Cu, Fe, Mn, Pb and Zn) were analysed in the water and plants after 7 d of exposure. The composition of diatom species (Epithemia sorex, Eunotia exigua, Mastogloia smithii, Pinnularia acoricola, Rhopalodia gibba) distinguished well between control sites (alkalophilic and mesothrophic species) and the AMD gradient (acidobiontic, acidophilic species) due to indicators of trophy and acidity. Diatoms cells microanalysed by X-ray energy dipersive spectrometry in scanning electron microscopy also have revealed differences in elemental content, regading Fe, Cu, Zn, and S accumulated. Lemna gibba proved to be tolerant to AMD, 50 % chlorosis was not reached in any exposure and mortality was low. Mortality was higher in the in situ experiments compared to laboratory experiments. Key words: phytotoxicity, phytoassessment, Lemna gibba, algae |
