Spring gammarids in difficulties? : gammarus fossarum exposed to copper and rising temperatures

Global Change including climate change, environmental pollution and habitat destruction are taking place all over the world. Temperature rises are occurring and changing the ecosystems. Glaciers are melting and as a result the sea level is rising, just to give one example of the impact Global Change is having. Taking these changes into consideration and the fact that little is known about the exact consequences of these changes on freshwater species, the aim of this thesis was to find out how a model organism reacts to rising water temperatures and copper exposure. In order to test this, experiments were conducted with G. fossarum in flow channels in a laboratory and one set of experiments was conducted in the field directly in a spring.
In the first set of experiments the temperature tolerance of G. fossarum was determined in laboratory flow channel experiments. Three different temperature scenarios were tested and the end points chosen in these and all further experiments were the feeding and respiratory electron transport system (ETS) activity. These endpoints are complementary in determining different aspects of the metabolic activity of the tested organisms. The feeding activity increased with temperature increase; no significant temperature effect on the ETS activity was observed. This is discussed and the implications of our results portrayed for more sensitive spring species.
In the second set of experiments an additional stressor in the form of copper sulphate was added to the set-up, in order to assess what impact elevated water temperatures in combination with a sub-lethal copper exposure would have on G. fossarum. Although it is known that temperature can raise the toxicity of substances and is a determining factor for growth, relatively few experiments have been conducted in the field of ecotoxicology considering temperature. Therefore we conducted a set of LC50-tests at different water temperatures prior to these experiments. We were able to confirm that elevated water temperature raises copper toxicity to gammarids. The second set of experiments demonstrated no significant effect of copper on the feeding activity; it was however slightly raised at the higher water temperatures. The ETS activity of G. fossarum was significantly lowered when exposed to copper, but increased with increasing water temperature. In this set of experiments we demonstrated the importance of using different endpoints to find answers to a question. The approach of using two methods which enable assertions on the same biological responses is desirable. A higher risk of adverse effects with increase in water temperature and exposure to copper can be reasonably inferred from our results.
The value of field experiments is not disputed and yet experiments of such nature are seldom, especially in the field of ecotoxicology. Flow channel experiments are a good option for conducting experiments with freshwater species under controlled conditions. In this project we went a step further and conducted the stird set of experiments in the natural habitat of G. fossarum. We designed the experimental set-up to be suitable for experiments both in flow channels in the laboratory and in a natural spring. Since we did not want to pollute the entire spring we opted for contaminated leaf litter, which was placed in the spring in test chambers. The water temperature was not changed in this set of experiments. The feeding activity was not significantly affected by the copper; the ETS activity was significantly lowered. Generally the metabolic activity of the gammarids was higher in the laboratory than in the spring. In this last set of experiments we took a crucial step towards a more realistic approach when examining environmental pollutants on organisms.