The impact of biological invasions on the food web of the Wadden Sea (INFOWEB)
09 / 2011 - unknown
To demonstrate the impact of invasive species on the food web of the Wadden Sea three characteristic areas with a different degree of invasive impact will be analysed with respect to the food web, the status of the system and its interaction with human activities. In contrast to the bulk of monitoring data and long term series for the different parts of the Wadden Sea, there hardly exists a synthesized and integrated view of the food web of the area that could indicate the influence of the changing environment on the complex interactions within the biota of the Wadden Sea. In recent years the data on biotic and abiotic components have been synthesized for the Sylt-Rømø Bight, Northern Wadden Sea, resulting in a food web model based on network analysis for the total bay as well as for the dominant intertidal communities (Baird, Asmus, Asmus 2004, 2007, 2008, 2011). This food web describes carbon flow as well as nitrogen and phosphorus cycling within a larger geographic unit based on the data material of the mid nineties representing a snapshot of this tidal basin before the major alterations occurred due to the invasion of neophytic and neozoic species. We therefore plan an update of the model including new communities such as Pacific oyster beds, Sargassum muticum- forests, and American razor clam beds. We also have to include new species such as Mnemiopsis leydii and Caprella mutica and investigate their probable place in the food web and their role as predators and prey. For the established communities we have to consider alterations in species composition and in energy flow rates due to altered seasonal temperatures. Using the already existing model as a background we plan to establish the food web of the Sylt-Rømø Bight as a reference food web for the Northern German and Danish part of the Wadden Sea. We would like to initiate an adaptation of this idea to the Trilateral strategy of the Wadden Sea, by installing two additional areas for research, as in the Central Wadden Sea the Jade Bay that is more directly influenced by the large estuaries of the rivers Elbe, Weser and Ems and the Balgzand area in the Southern Wadden Sea in order to cover the whole area. These reference food webs will be compared and will deliver scenarios of the changing environment of the Wadden Sea, especially due to biotic invasions and temperature. They will be helpful tools for the management of the area and will be especially helpful in detecting indirect effects between components and trophic cascades of the area. The multiple factors that are changing in the Wadden Sea require their integration at the ecosystem level. Finally, this ecosystem approach can be used as a start of an ecosystem based management. Especially the future trends in the development of populations of invertebrates, fishes, birds and mammals could be proven from a trophic perspective and the influence of mussel, shrimp as well as flatfish fishery could be evaluated by an ecosystem based management concept.