THE INFLUENCE OF CURRENTS AND WAVES ON ECOLOGICAL CONDITIONS OF THE VÄINAMERI

Abstract

Based on field measurements (1993-99) and hydrodynamic modelling the influence of currents on the ecological situation of the Väinameri is analysed and an introductory study on the resuspension is reported. 2D flow charts are presented. The Väinameri is a highly dynamic water body, where the situation is mostly determined by the water exchange processes forced by two major nearby basins (i.e., the Baltic Proper and the Gulf of Riga) and resuspension events during storms. The hydrophysical and hydrochemical front fluctuates in N-S direction and the local conditions are frequently overrun by these excursions. Resuspension events due to currents (in the straits) and surface waves (in the shallow parts of the Väinameri) affect the study area with high turbidity and cause an about 2-3-fold increase in phosphorus concentrations. On the basis of hydrodynamic behaviour two sub-basins could be defined in the Väinameri. The eastern part has about 85% of the water exchange, lower salinity, and higher nutrient concentrations. In the western section hydrological conditions are more marine and less variable.