The mutual relationship between the monitoring and modelling of estuarine ecosystems

A general simulation model developed for the Ems estuary (a part of the Wadden Sea), to describe the main carbon flow through the foodweb, was applied for monitoring purposes. In this model, the estuary is divided into five compartments, in each of which a pelagic, an epibenthic and a benthic submodel operates. A transport model regulates the distribution of dissolved and particulate substances over the area. Two parameters that partly regulate the carbon flow are the concentrations of phosphate and of the particles (turbidity) in the water. From the sensitivity analyses for phosphate and turbidity it can be concluded that the relative effects of changes in turbidity and changes in the influx of phosphate from the rivers are large in the upper reaches and small in the lowest reaches of the estuary. This is due to the increasing influence of the coastal waters in the lower reaches. These results indicate that the reaches, which represent the beginning and the end of a gradient in the estuary, are also very suitable for monitoring the quality status of this estuary in terms of production and standing stock of groups of organisms. The need to use monitored data from the boundaries (sea and rivers) of those ecosystems as input in simulation models is discussed. Moreover, the possibilities of using simulation models to generate new ideas on the functioning of estuarine ecosystems under changing environmental conditions and to help administrators to decide on specific future management strategies are also discussed. Presented at the VI International Wadden Sea Symposium (Biologische Anstalt Helgoland, Wattenmeerstation Sylt, D-2282 List, FRG, 1–4 November 1988).