Limnetica 39

Rivers are prone to contamination from agricultural activities, industrial waste and mining, with effects on the biota ranging from the scale of biochemical processes to that of ecosystems. Ongoing climate change requires the replacement of carbon energy sources with alternative energies, and nuclear power is an option. Uranium mining may result in run-off and the contamination of water courses. We investigated the effects of uranium on enzyme activities (cholinesterases (ChEs), Na⁺K⁺-ATPase, glutathione S-transferase (GST) and catalase (CAT)) in a freshwater caddisfly shredder Schizopelex festiva exposed to six U concentrations up to 100 μg/l. Enzyme activities and U accumulation were determined at 24 h and 32 d of exposure. We also measured growth rates (32 d) and calculated bioconcentration factors, as the ratio of U in the whole body of the invertebrates to U concentration in the test water. Enzyme activity from 24 h to 32 d was reduced for ChEs (~52 %), GST (~44 %) and CAT (78 %). No change was observed for Na⁺K⁺ATPase activities. Enzyme activities for Na⁺K⁺ATPase decreased after 32 d only at the highest U concentration. For GST activities, there were significant differences among concentrations for each time, but the treatments did not differ from the control groups. The growth rates of S. festiva under laboratory conditions averaged 6.23 ±0.66 μg g^-1animal d^-1, with no significant differences between treatments and control groups. The ratio of U in the invertebrate body to U concentrations in the water ranged from 211 to 1663, increasing with time and decreasing with the concentration of U in the water. The exposure of S. festiva to U resulted in its accumulation and triggered changes in the activities of some enzymes, but the species was in general tolerant to realistic values observed in the field. If our findings can be extrapolated to other consumers, then larger amounts of U would be needed to cause measurable biological changes.