B1: Impact of nutrient emissions from land on the species composition and productivity of communities of macrophytes in shallow waters
supervised by Schubert, Voss
Macrophytobenthos composition, seasonality and productivity of ground-water influenced plots will be compared with neighboring uninfluenced areas. The main focus ist to unravel the impact of sub-surface freshwater inflow on species composition and productivity in the „critical salinity range“.
State of the art
Macrophytes are important structural components of shallow waters and important habitats for a large variety of marine animals. They provide shelter and food for a large number of organisms, however, are threatened by several factors like eutrophication and reduced light intensities. Off the “Hütelmoor” a partly degraded bog east of Rostock, macrophyte stands are important known features but their occurrence and species composition not well understood. Macrophytes are capable to take up nutrients through their leaves and rhizoids however which pathway is most relevant is not well understood. The plants are also able to acclimate to different conditions so that the species composition depends upon the environmental settings like the nutrient input from land. At our study site the nutrient emissions through permeable sediment layers delivering water and nutrients from the bog may be especially relevant for the occurrence and species composition in the coastal macrophyte stands.
In the first phase field investigations of species composition, coverage and recruitement potential (incl. diaspores) will be performed. Seasonality of the respective species will be investigated by repetitive samplings. Nutrient uptake kinetics of species where literature data are missing will be performed in the lab as well as measurements of the salinity dependence of growth and photosynthesis. To investigate the influence of submarine groundwater discharge (SGD) on macrophytobenthos we will compare sites with SGD to those without SGD.