English 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.