RTG R3- Responses to biotic and abiotic changes, Resilience and Resposibilty of lake ecosystems
Freshwater ecosystems are under severe pressure by a multitude of anthropogenic stressors. A central assumption of the European environmental legislation is that degraded ecosystems return to their “natural state” after relief from anthropogenic pressures. Unfortunately, we still lack sufficient understanding of the responses of ecosystems to changing conditions to predict, e.g. whether lake restoration measures indeed result in the reversal of past changes in lake ecosystems. The research training group (RTG R3), situated at the Limnological Institute in Konstanz, aims to improve such understanding using Lake Constance, one of the best-studied lakes in the world, as a model system. Lake Constance is perfectly suited for studying response patterns, including reversibility, as the lake has been affected by a multitude of environmental stressors (e.g. eutrophication, climate change, neobiota), and because eutrophication, the stressor of main concern during the 1960s to 1980s, has been removed successfully. The effects of these changes on the lake ecosystem have been documented in unique long-term data sets.
Changes in trophic state can impose major challenges on aquatic organisms and thus are expected to drive micro-evolutionary processes. Cyanobacterial mass developments, frequently observed during eutrophication, represent one important challenge aquatic consumers have to cope with. Cyanobacteria are of poor food quality for aquatic consumers due to morphological properties that hamper ingestion, the production of harmful secondary metabolites, and/or a deficiency in essential lipids, i.e. polyunsaturated fatty acids (PUFA) and especially sterols. Many zooplankton populations experienced long-term changes in food quantity and quality during the last decades due to eutrophication and re-oligotrophication. I am interested in exploring micro-evolutionary changes in the adaptation to cyanobacteria food within Daphnia populations in Lake Constance. By hatching resting eggs from sediments deposited during different time periods, I recovered different genotypes from past populations. The isolated Daphnia clones are used to conduct comparative life history experiments in which genotype-specific changes in the ability to cope with cyanobacteria food are investigated. The focus in these experiments is on differences in essential lipid requirements among clones.
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