Sanitary and bacteriological survey of an artificially aerated eutrophic Lake Starodworskie, Poland
This paper presents the results of sanitary and bacteriological analyses of water and bottom sediments of an artificially aerated eutrophic Lake Starodworskie, Mazurian Lakeland, performed in 1986-1988. Analyses of water (in a vertical and horizontal profile) and of bottom sediments (from the 0-5 cm layer) were performed on five stations; samples were collected at monthly intervals: in 1986 when aeration was of low density; in 1987, when it was intensive; and in 1988, under the ice cover. The following indices were determined: TVC 20°C, TVC 37"C, TC, FC and FS. Numbers of micro-organisms belonging to these groups in water and bottom sediments were different in 1986 and 1987 and related to the intensity of aeration, distance from the lake shore, depth, and season, and atmospheric conditions. Bacteriological purity of water and bottom sediments was defined based on the usual water quality criteria, water suitability for recreational use, lake loading with organic matter easily decomposed by bacteria, and its loading with pollutants originating from humans and animals. The results suggest that the majority of water samples were clean or only slightly polluted, and loading of lake sediments with easily decomposed organic matter was relatively low, but they were fairly polluted with animal faeces. Pollution of water and of bottom sediments was higher in the first year of aeration than in the second one.