Ecological condition of small reservoirs of different nature protection status (Samara region)

Currently, the conservation of the unique ecosystems of small water bodies located within cultural landscapes and/or in areas with limited nature protection status is of urgent issue. It is such hydrobiocenoses that are the most susceptible to increasing anthropogenic impact. Phytoplankton is a good indicator of the ecological situation in the reservoir. The aim of the work was to analyze the composition and structure of phytoplankton of some small urbanized lakes of Samara region with different levels of protection and degree of anthropogenic load. Here, this is the first time we present an analysis of the current ecological state of three small water bodies having various nature protection statuses: Lake Yaitskoe (53°10'85"N,50°17'46"E), the regional natural monument; Lake Gatnoe (53°14'93"N, 50°11'83"E), Samara region natural heritage site; and Lake Bolshoe Vasilievskoe (53°54'40"N, 49°53'24"E), the suburban lake located in the transition zone of the Middle Volga complex biosphere reserve (See Table 1). We collected samples for phytoplankton study and basic physical and chemical measurements in the growing season from 2013 to 2014 (See Table 2). We sampled the algae with a Ruttner bathometer. The material was fixed with 40% formalin solution. The cell count was carried out in the chamber “Uchinskaya” (Russia) with a volume of 0.01 ml. This chamber is a glass plate with low sides, the bottom of which is equipped with a special counting grid, optimized for counting plankton. Organisms are counted twice in 20 bands. Species identification of algae and counting of their cells were carried out on the microscope “BIOLAR PI” (limited liability company “Biolar”, Poland) with an increase of 600 times. To determine the species of algae, we used reference guides from the series “Determinants of freshwater algae of the USSR” and “Susswasserflora von Mitteleuropa”. The classification of Reynolds and co-authors was used to differentiate phytoplankton into functional groups. S₁-type (planktotrichete type) consisted of filamentous non-heterocyst forms of cyanoprokaryotes that previously belonged to genus Oscillatoria, M-type contained representatives of genus Microcystis, H₁-type contained representatives of genera Anabaena and Aphanizomenon. The similarity of the algae species composition of lakes was estimated with the Sorensen coefficient (Ks). The level of cenotic diversity and the degree of community alignment were assessed using Shannon (H) and Pielu (E) indices, respectively, taking into account the standard deviation. The dominant species were those whose number and biomass was 10% or more of the total value. The Simpson dominance index (S) was used to estimate the degree of dominance of individual species. Assessment of saprobity of waters was carried out by the method of Pantle and Bucc in the modification of Sladechek, using known indicator values of saprobity of individual species. The general state of ecosystems of the studied lakes was analyzed on the basis of the qualitative composition and quantitative development of phytoplankton from 2013 to 2014. In all lakes, the species richness of phytoplankton was quite high and contributed mainly by chlorophytes, diatoms and cyanoprokaryota species (See Table 3 and Fig. 1). Floristic analysis revealed signs of imbalance in lake ecosystems, probably caused by anthropogenic impact and/or lack of biogenic limitation (See Table 4). This situation is especially unfavorable for ecosystems of water bodies of protected nature areas. Ecological and geographical analysis did not reveal significant differences between the algal flora of the studied reservoirs (See Table 5). The level of similarity of the species composition of the studied reservoirs was quite high (See Table 6). Perhaps this was due not only to similar abiotic parameters of the environment, but also to a high level of identical anthropogenic load. Quantitative phytoplankton development was high in all water bodies, the highest one was observed in Lake Bolshoe Vasilievskoe, and the lowest in lake Gatnoe (See Fig. 3). According to average algal biomass over the study period, Lake Bolshoe Vasilievskoe corresponds to the hypertrophic state, while lakes Gatnoe and Yaitskoe are eutrophic. Phytoplankton species diversity and alignment were highest in lake Gatnoe, and smallest in lake Yaitskoe. According to saprobity, the studied water bodies were β-mezosaprobic which corresponds to the water quality class III. Analysis of the floristic composition, the ratio of taxonomic ranks, indicators of quantitative development and the structure of the dominant species complex revealed signs of an imbalance in ecosystems and the development of “oscillatory” disease in all studied lakes, regardless of their conservation status due to anthropogenic impact and lack of biogenic restriction. The paper contains 3 Figures, 6 Tables and 38 References. The Authors declare no conflict of interest.

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