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(70-20) Effects of AMD on Choroterpes picteti (Insecta: Ephemeroptera) and Chironimus gr. thummi (Insecta: Diptera). Janssens de Bisthoven, L.*,1,2, Gerhardt, A.1,2, Guhr, K.1,2, Soares, A.2, 1 LimCo International, Ibbenbueren, Germany2 University of Aveiro, Aveiro, Portugal ABSTRACT- The abandoned S. Domingos mine (Portugal) offers a natural pH and metal gradient of the drainage water, an ideal model for toxicity studies in situ. Short-term toxicity bioassays were performed in artificial flow-through systems with water from the AMD (ph 6.4, 5.5, 5.0, 4.4 and 3.3) and 2 local control sites and the site of origin of the respective test species in the laboratory and in situ. Survival of 10-20 organisms per system was monitored daily as well as pH, temp. and oxygen. Moreover behavioural stress responses and time to death were continuously monitored in 12-16 organisms per pH condition with the Multispecies Freshwater Biomonitor (MFB) in real time. Condition parameters (sizes, DW) and metal burdens in the organisms were measured at the end of the experiments. Simultaneously the following elements were measured in the water: metals: As, Cd, Co, Cr, Cu, Fe, Mn, Pb and Zn, other elements: Ca, K, Mg, Na, Cl and S. Choroterpes picteti (local test species) contained 10 times more Cd than Chironomus sp with no clear pH-effect. The insects contained ca. 100 times more Fe than Crustacea and 10 times more than fish. Mortality of Choroterpes picteti and Chironomus gr. thummi started increasing at pH <= 4.4 to max 30-40% at pH 3.3. Stress behaviour of Choroterpes picteti consisted of two phases (1:decreased locomotion, 2h (pH 3.3), 16h (pH 4.4), 2: increased ventilation (18h, pH 4.4), thus following the Stepwise Stress Model. In situ, Choroterpes picteti decreased locomotion at pH 5 compared to pH 6. Key words: Multispecies Freshwater Biomonitor, toxicity, stress behaviour, metal pollution |
