The abiotic conditions of a deltaic lake ecosystem (on the example of the Druzno Lake catchment)

The water regime, location and origin are the features which make Lake Druzno an example of a unique water reservoir in every aspect. From the hydrographic point of view, it undergoes both natural (gravitational) and forced (polder) drainage. The authors believe that Lake Druzno did not use to be initially part of the Vistula Lagoon, and its origin is related to the formation of an end depression of a glacier lobe. Due to its situation, morphometric features and character of the bed, Lake Druzno is an environment of rich resources of organic life, which emphasises its unique character still more. The history of the development and present hydrological structure of Lake Druzno are crucial for an evaluation of the abiotic conditions influencing the state of the ecosystem.