Abstract

In the framework of the Dutch National Research Programme on Global Air Pollution and Climate Change, ecological responses of the Wadden Sea ecosystem to changing climate conditions have been studied. A number of characteristic processes, organisms and steering factors have been chosen as themes. From morphological studies it followed that a future increase in storm surge level and frequency will seriously affect salt marsh development; Friesian salt marshes will develop less fast; salt marshes at the Groninger main land will erode. Loss of foraging possibilities for migrating birds is the main cause of a decline in bird numbers as a result of sea level rise. Higher environmental temperatures may cause a lower larvae growth development for the Baltic Tellin Macoma balthica. From a comparison of southern and northern populations it followed that southern populations are possibly better adapted to higher temperatures, and they might have a chance to move northwards when situations change. From the mesocosm studies it followed that for bivalves, the two major climate change aspects had opposite effects: sea level rise stimulated biomass and production, whereas temperature rise depressed bivalve production. A developed expert system (EcoFuzz) covers time scales that exceed the ones feasible for laboratory research or experiments in model systems or the field. It provides a suitable means for the incorporation of ambiguities and lack of quantitative data into a classification scheme. The description for benthic filter feeders in the integrating ecosystem model EcoWasp was capable to reproduce and laboratory filtration and respiration measurements, individual mussels growth rates in the field and mussel bed grazing intensities upon algae and particulate matter. Primary production remained underestimated by the model. Scenario studies showed that the Wadden Sea system is especially sensitive to sea level changes, and temperature changes, especially to whole year temperature changes.