Aquatic Ecology

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Current Research Projects:

Flexibility matters: Interplay between trait diversity and ecological dynamics using aquatic communities as model systems (DynaTrait)

Funded by German Science Foundation (DFG), M. Stockenreiter; H. Stibor; P. Fink (University Köln); PhD Student: S. Hammerstein

In this project we focus on the effects of diversity loss and trait dynamics in natural plankton communities (DYNATLOSS). Considering traits as mechanistic links between biodiversity loss and ecosystem services we focus on questions (1) how a loss of traits is affecting phytoplankton production, zooplankton composition and food web transfer efficiency?; (2) and do such trait dynamics result in feedback effects on the phytoplankton community? These questions will be addressed with diversity manipulated natural phytoplankton communities in lab and large scale field experiments.

Impacts and dynamics of nitrogen supply in lake ecosystems

Funded by German Science Foundation (DFG), G. Trommer, PhD Student: M. Poxleitner

Anthropogenically enhanced nitrogen supply in lakes often implies changes in the lakes ecosystems and due to the worlds' increasing food demand and the related nitrogen rich fertilizers, nitrogen supply will further increase in the future. This study investigates the influence of enhanced nitrogen load on plankton communities in lakes in Upper Bavaria (Lakes Brunnsee, Klostersee and Thalersee near the Limnological Research Station in Seeon) and determines changes of the nitrogen load in the past. For the evaluation of the recent nitrogen flux from the atmosphere to lake sediments, nitrogen concentrations are measured in precipitation, lake pelagial and lake sediments. Analyses of total nitrogen content and nitrogen stable isotopes in lake sediment cores allow to detect changes in the nitrogen load of the past ~150 years. In mecocosm-experiments on the lakes, the influence of enhanced nitrogen supply on biomass stoichiometry and biodiversity of natural phytoplankton communities and the interaction with zooplankton will be investigated.

Genetic and ecological characterization of the invasive freshwater jellyfish Craspedcausta sowerbii

Funded by German Science Foundation (DFG), H. Stibor; S.Gießler; PhD Student: K. Schachtl

The increasing introduction of non-native species into new ecosystems is a consequence of growing mobility. The freshwater jellyfish Craspedacusta sowerbii is one example of a recently globally distributed species, which originated from China. Since 1905 it is known to be present in German lakes. Although mass occurrences of medusae were recorded and effects on aquatic food web dynamics are expected, the consequences of the jellyfish's introduction to aquatic systems has not been analyzed yet. To figure out the trophic position of medusae, mesocosm experiments will be conducted. In laboratory experiments, competitiveness of medusa and polyp with other organism will be determined. To check for long-time establishment and evolutionary dynamics, genetic and sexual diversity will be quantified using molecular markers. These results will give evidence if multiple introductions are likely and if both sexes and different genotypes are present. Combined analyses of genetic diversity and ecological function of this species, will allow a better understanding of cause and effect relationships within aquatic food webs exposed to invasion.