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Abstract

Tideless estuaries are very common on the western, southern and eastern Baltic coast. They play an important role as buffers and filters for the Baltic Proper. These functions can vary, depending on discharge areas and the situation in the estuaries themselves. Our knowledge of the estuaries varies widely, ranging from more or less simple descriptions to a fairly complete understanding of the processes taking place in their ecosystems. So far, only one preliminary comprehensive study has been performed for the whole area (Baltic Sea Environment Proceedings No. 40, HELCOM 1991).Three different discharge areas connected to tideless estuaries are compared in some detail:-the shallow polytrophic Darss-Zingst Bodden Chain, Germany-the shallow eutrophic Puck Bay, Poland-the deeper mesotrophic Gulf of Riga, Latvia.Starting points are discharge areas, discriptions of the water bodies and main loads. The development of the ecosystems under the influence of anthropogenic impacts during the last 40 years is then described.Conclusions are drawn concerning:-the general behaviour of such systems-the benefits and drawbacks of the discharge areas, the loads, and the structures and functions of the estuaries-special problems regarding the buffer and filtering capacities of the systems in question-economic consequences.High variability and elasticity are the main characteristics of these tideless estuarine ecosystems. Multivalente economic utilization of these resources and functions is the best way to save such ecosystems and money as well.