| The lagoons and estuaries of West Pomerania form a characteristic zone between landside discharges and the open sea. For the southern Baltic Sea the Oder estuary acts as a filter and buffer for nutrients, pollutants, fine sediments and organic substances. The high pollution of the influxes to the Oder estuary contributes to the eutrophication and alteres the natural biochemical cycle. he analysis of the waters-internal conversion rates in the context of the project GOAP showed that a fixation and storage of the nutrients are predominatly made on the short way by the phytoplankton. The transformation of nutrients into particles takes place mainly in the inner estuary. The excess production of the phytoplankton is concentrated in the sediment or delivered into the Baltic Sea. The long-term accumulation rate of nutrient input is 2-5 %. The accumulation of trace metals is predominatly bound on suspended and particulated substances and averages 10-15 % of the total input. The filter efficiency is particularly for nutrients very low and the assumption of a high retention in the Oder estuary is not justifiable. Due to the lack of data about former pollutions it could not be said whether this retention function was fundamentally higher in former times. Another focal point of the project was the development of models for simulation of water exchange and conversion rates of substances in the Oder estuary. At the modelling of water exchange and the associated balance of dissolved and particle bound nutrients there was a great match between the measured values and the predicted values of the model. The low availability of data and the propagation of errors by calculations with great space and time scales were problematic for the physical models. The high variability of the boundary conditions made the modelling of the conversion rates difficult. Thus, predictions of future trends derived from an ecological model are not possible. |
