САНІТАРНО-ГІДРОБІОЛОГІЧНА ХАРАКТЕРИСТИКА ОЗЕРА ВЕРБНЕ ЗА МІКРОФІТОБЕНТОСОМ

Assessing ecological and sanitary state of aquatic ecosystems, including their trophic and saprobiological status and impact of human factors, is among key objectives in modern hydrobiology. Apart from common hydrobiological methods (identifying species compositions, calculating algae number and biomass etc), there are specific methods for the assessment of aquatic ecosystems. Bioindication, which is based on aquatic organisms’ response to environmental factors, including human factors, is the most important. Microphytobenthos is highly sensitive to changes in natural and human factors. Its bioindication capabilities are widely known, therefore studying them as part of sanitary and hydrobiological characteristics of various water bodies is of great interest. Water basins across the City of Kyiv are under diversified human impact including various factors and effects, which differ in pressure degree. Thus, using microphytobenthos for sanitary and hydrobiological assessment, even within one type of water basins, has certain aspects, which depend on the bottom algal communities’ stability or degree of transformation. It is often caused by trophic and topic competition between microphytobenthos, phytoplankton and higher aquatic plants, as the latter two can inhibit growth of bottom algae. In the view of the above, special attention should be paid to quantitative characteristics of benthonts, which may act as cenose-forming organisms. The paper examines the findings of the studies on microphytobenthos in Verbne Lake, which is affected by negative human factor – contamination by surface and ground flow from Kyiv City area and is intensively used for recreation. The objective is to study the sanitary and hydrobiological characteristics and ecological quality of Verbne Lake according to microphytobenthos’ biondication indices. Benthic algae were sampled with the MB-TE microbenthometer within the littoral zone in triplicate from the total area of 40 cm2. Algae number was calculated on a counting plate in a 0.1 cm3 drop, their biomass was calculated according to geometric similarity method. Trophic and saprobiological values were assessed in accordance with the scale, proven for microphytobenthos. Saprobity index was calculated according to the Pantle-Buck method in Sladecek modification on the grounds of traditional and modern data on saprobity indicator algae. Benthonts, planktonts and periphytonts were distinguished with consideration taken of their association with particular habitats. Ecological classification of water quality was performed on the grounds of saprobity bioindication (saprobity indices) according to microphytobenthos. For microphytobenthos’ structural components their role in species richness, number and biomass were analyzed. Proceeding from the obtained findings, sanitary and hydrobiological characteristics of Verbne Lake were presented according to microphytobenthos. On the whole, the lake can be classified as mesotrophic, β-mesosaprobic water body. Benthonts proved to play an essential part in forming microphytobenthos’ indicatory characteristics. Intensive phytoplankton growth in the water column and its sedimentation upon the lake bottom inhibit development of benthic algal forms. In accordance with the ecological water quality classification based on microphytobenthos saprobity bioindication results (saprobity indices), the water of Verbne Lake relates to Water Quality Class II, Water Quality Category 3. The most unfavorable situation within the lake’s littoral area was registered in summer, which signals that self-purification processes are becoming less intensive and the aquatic ecosystem state is getting worse.