Vertical distribution and seasonal changes in the number of bacterioplankton in the water of Lake Hancza, particularly in the period of reservoir summer stratification

The paper presents the results of the study on seasonal changes in the number of bacterioplankton, its vertical distribution and morphological composition in the waters of the deepest Polish lake, Lake Hańcza (108.5 m deep). The research was performed from 1997 till 2000. Water samples were collected at a research station placed at a location where the lake depth was maximum, at monthly intervals from May to October. Water was sampled along the following depth profile: from 0-1 cm layer, at 0.3 m and at the depth of 1m, 2m, 5m, 10m, deeper down at 10m intervals towards the bottom. Bacteriological analyses were completed with measurements of selected physico-chemical parameters such as temperature, pH, oxygen, nitrogen and phosphorus contents. Obtained results with regards both to the number of bacterioplankton and its morphological structure, namely 68% for cylindrical rods forms, and physico-chemical assays confirmed the purity of Lake Hańcza.