Phytoplankton of Lake Bol’shie Shvakshty (Belarus) during the Shift of the Ecosystem from a Macrophyte-Weakly Eutrophic to a Phytoplankton-Hypereutrophic State
T. M. MIKHEYEVA1, B. V. ADAMOVICH1,2, T. V. ZHUKOVA1, I. V. SAVICH1, O. I. BELYKH3, E. G. SOROKOVIKOVA3, A. V. KUZMIN3, G. A. FEDOROVA3, R. Z. KOVALEVSKAYA1, I. N. SELIVONCHIK1,2, N. V. DUBKO1, E. V. LUKYANOVA1
1Belorussian State University, 220030, Minsk, Nezavisimosti ave., 4
2Institute of Fisheries, Belorussian NAS, 220024, Minsk, Stebeneva str., 22
3Limnological Institute, SB RAS, 664033, Irkutsk, Ulan-Batorskaya str., 3
Keywords: Беларусь, оз. Бол. Швакшты, эволюция трофического статуса, фитопланктон, цианобактерии, микроцистин, Belarus, Lake Bol’shie Shvakshty, trophic status, phytoplankton, cyanobacteria, microcystin
Abstract
Changes in the quantitative characteristics and functioning of phytoplankton in Lake Bol’shie Shvakshty have been assessed. The changes are evoked by the introduction of herbivorous fishes into the lake and the resulting disturbance of ecological balance in the ecosystem and the shift of the lake into a hypertrophic state from a weakly eutrophic state. Human interference has caused the cyanobacteria density (abundance) and biomass values in the overall phytoplankton composition to strongly exceed (3.5 x 109 cells/L and above 68 μg/L chlorophyll-а, respectively) the threshold value for safe recreational use of water bodies (20 million cells/L and 10 μg/L chlorophyll-а) established by the World Health Organization (WHO). The lake can be assigned to the third level of hazard to human health within the classification proposed by the WHO, as the cyanobacteria density is higher than 100 million cells/L and chlorophyll-а content is higher than 50 μg/L. MC-producing Microcystis species were identified among the cyanobacteria that has propagated in the lake in recent years, and five microcystin variants, including the highly toxic MC-LR, have been detected in the water.
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