PREDICTION OF BOTTOM DYNAMIC CONDITIONS IN COASTAL WATERS

Bottom dynamic conditions (areas of accumulation, erosion or transport ation) in aquatic ecosystems influence the dispersal, sedimentation an d recirculation of most substances, such as metals, organic toxins and nutrients. The aim of the present work was to establish a simple and general method to predict sediment types/bottom dynamic conditions in Baltic coastal areas. As a working hypothesis, it is proposed that the morphometry and the absence or presence of an archipelago outside a g iven coastal area regulate what factors determine the prevailing botto m dynamic conditions. Empirical data on the proportion of accumulation bottoms (BA) were collected from 38 relatively small (1-14 km(2)) and enclosed coastal areas in the Baltic Sea. Morphometric data were obta ined by using a digital technique to transfer information from standar d bathymetric maps into a computer. Data were processed by means of mu ltivariate statistical methods. In the first model, based on data from all 38 areas, 55% of the variation in BA among the areas was statisti cally explained by five morphometric parameters, The data set was then divided into two parts: areas in direct connection with the open sea, and areas inside an archipelago. In the second model, based on data f rom 15 areas in direct connection with the open sea, 77% of the variat ion in BA was statistically explained by the mean depth of the deep wa ter (the water mass below 10 m) and the mean slope. In the third model , based on data from 23 areas inside an archipelago, 70% of the variat ion in root BA was statistically explained by the mean slope, the topo graphic form factor, the proportion of islands and the mean filter fac tor (which is a relative measure of the impact of winds and waves from outside the area). The model parameters describe the sediment trappin g capacity of the areas investigated.