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 Wasser Cluster Lunz
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Algal productivity in riverine wetlands - living along the edge and affecting key ecosystem functions
PI: T Hein
2007-2008
financed by KIOES/OEAW
Rivers and their adjacent aqatic areas such as riverine wetlands, riparian and in-stream zones are hot spots for biogeochemical processes and represent functional retention areas, which are important for the control and maintenance of river water quality. They provide an intense turnover of organic matter, therefore controlling transport, alteration and degradation of organic matter. 
Fig. 1 Reconnected side channel in the Danube
Floodplain National Park | Planktonic and benthic algae are major players in the physical, chemical and biochemical processes occurring in shallow waters within wetland areas and riparian zones. Because of their high turnover rate and rapid colonization along the aquatic-terrestrial boundary, algal communities are significant primary producers in wetlands. Additionally, due to their high biomass production, algae support benthic and pelagic food webs thusly supporting entire riparian communities. The developped structure of planctonic and benthic algae has also an effect on chemical an physical exchange condition. |
These communities transform nutrients, acting as a nutrient sinks as well as impacting the invironmental conditions, such as oxygen saturation gradients in the adjacent sediment layers. By providing a source of dissolved organic matter for heterotrophic bacteria, these algal communities control riverine wetland nutrient cycles.
The central question of the proposal is how and to what extent hydrogeomorphic conditions, especially surface water connectivity, control the productivity and composition of phytobenthos communities.
The phytobenthos communities represent a large diverse community within the Danube River Basin. Their effect on bacterial communities is an example of how ecosystems do not follow traditional disciplinary boundaries. This project relies upon the interdisciplinary expertise offered by the WasserCluster Lunz and the links between micobial ecology, limnology and hydrology of the research partners involved (University of Vienna, University of Natural Resources and Applied Life Sciences, CNRS - CEFE, BWF). | 
Fig. 2 Developed phytobenthos growth on artificial
substrate after an exposure time of 25 days
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The taxonomic information of the specific performance of different algal communities gained from this research contributes to answer the question how species composition and productivity is linked under changing environmental conditions. The research will be performed in a floodplain reach of the Danube River (fig. 1) and will also contribute to the understanding of long term human impacts (river regulation) on these short term processes including the impacts on ecosystem functions and services. The project uses innovative methods for algal community development and productivity in order to determine how small-scale processes affect the nutrient retention capacity at the wetland scale and how changing exchange conditions (e.g. restoration measures) could shape these microscale processes and how these microscale processes impact the overall ecosystem performance.
To understand the effect of connectivity on the development an in-situ experimental design will be used. The incubation of racks with artificial substrata (fig. 2) will be performed and measurements follow differnt hydrological conditions (e.g. flood and flow pulses). Frequent measurements of the electron transport rate (ETR) and the fv/fm ratio (maximum quantum yield of photochemistry) will be conducted in the field. The physiological performace parameters (ETR and fv/fm ratio) allow a better resolution to detect enviromental effects and the response of the phytobenthos communities. Additional primary production measurements in the laboratory of phytobenthos and phytoplankton with an oxygen microsensor will be performed.
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