Algal dynamics in Floodplains (ALGFLO)

According to ecological theory, the frequency of disturbance strongly affects the diversity of biological communities. Whether such a disturbance results in an increase or decrease in the diversity of a community also depends on the productivity and the resource supply rate. Thus, in environments with low nutrient supply, the same disturbance may have opposing effects on communities as compared to environments with high nutrient supply. This important interaction is, however, seldom considered in investigations of disturbance effects on plankton and benthic communities. To elucidate this interaction between disturbance, productivity and diversity, floodplain water bodies are the particularly suited ones. A strong relationship between disturbance and the development and structure of algal communities can be found there. The particular features in these water bodies also enable us to address the interactions between benthic and planktonic communities with regard to the above described interplay. Hydrological retention in floodplain water bodies is associated with lower flows, increased transparency of the water column, and lower nutrient inputs from the main channel. Disturbance and gradients of productivity and resource supply are given in an appropriate range to test the relationships between diversity, productivity and physical disturbance. Thus, the impact of environmental disturbances on productivity - diversity relationships are research questions which can be addressed excellently in these types of ecosystems. Our research program will deal with productivity-diversity relationships, effects of physical disturbances on phytoplankton and phytobenthos communities, and with phytoplankton-phytobenthos interactions at variable environmental conditions. To investigate our research questions we will perform a field survey to test if a relation between productivity and species (functional) richness of natural communities exists. We will evaluate species diversity along a major environmental gradient, incorporating variations in productivity and disturbance. By focusing on phytoplankton, phytobenthos, and their interaction we will cover important primary producers in these dynamic aquatic systems. In a second step we will perform two large field experiments with natural aquatic communities under defined conditions. We will investigate the responses of phytoplankton, phytobenthos, ciliate, and zooplankton biomass and diversity parameters in a combined mesocosm approach. We will investigate the key factors affecting diversity, biomass stoichiometry, and interaction of natural phytoplankton and phytobenthos communities after a flood event: light (turbidity) and nutrients (primarily phosphorus). Additionally, we will perform laboratory experiments to test the concurrence-interactions between phytoplankton and phytobenthos under different environmental parameters in detail. The project will advance existing knowledge on the response of natural plankton communities in highly dynamic ecosystems. It will help to develop a more detailed understanding about the coupling between diversity and productivity in floodplain ecosystems and how physical disturbances shape algal communities and their interaction in aquatic ecosystems.

According to ecological theory, the frequency of disturbance strongly affects the diversity of biological communities. Whether such a disturbance results in an increase or decrease in the diversity of a community also depends on the productivity and the resource supply rate. Thus, in environments with low nutrient supply, the same disturbance may have opposing effects on communities as compared to environments with high nutrient supply. To investigate this interaction between disturbance regimes, productivity and diversity, floodplain water bodies are the particularly suited ones. A strong relationship between disturbance and the development and structure of aquatic communities can be found there. Hydrological retention in floodplain water bodies is associated with lower flows, increased transparency of the water column (and thus higher light intensities available), and lower nutrient inputs from the main channel. Disturbance and gradients of productivity and resource supply are given in an appropriate range to test the relationships between diversity, productivity and physical disturbance. Thus, the impact of environmental disturbances on productivity diversity relationships are research questions which can be addressed excellently in these types of ecosystems. Our research program dealt with productivity-diversity relationships, effects of physical disturbances on phytoplankton communities, and with phytoplankton-zooplankton interactions at variable environmental conditions. To investigate our research questions we performed a field survey testing the relationship between productivity and species (functional) richness along an environmental gradient. In a second step we performed four large mesocosm experiments with natural aquatic communities under defined conditions. We investigated the responses of phytoplankton, ciliate, and zooplankton biomass and diversity parameters in different combined mesocosm approaches. We investigated key factors affecting diversity, biomass stoichiometry, and interaction of natural phytoplankton and zooplankton communities after a flood event: light (turbidity) and nutrients (primarily phosphorus). Additionally, we perform laboratory experiments to test the effect of temperature changes (including fluctuations) on phytoplankton communities of different diversity and disturbance history.