Structure and dynamic of mollusk communities of small oxbow lakes and the determing factors (the Khoper river valley, Penza oblast)
I. V. Bashinskiy1, T. G. Stoyko2, V. A. Senkevich2, A. O. Svinin3, E. A. Katsman1, V. V. Osipov4,5
1A. N. Severtsov Institute of Ecology and Evolution of RAS, Moscow, Russia
2Penza State University, Penza, Russia
3Mari State University, Yoshkar-Ola,Russia
4The State Nature Reserve Privolzhskaya Lesostep, Penza,Russia
5Saratov branch of VNIRO, Saratov, Russia
Keywords: mollusks, envirmental factors, oxbow lakes, forest-steppe
Abstract
The structure and dynamic of mollusk communities, as well as environmental factors influencing them, were analysed under conditions of small oxbow lakes in the forest-steppe zone (a case of the Khoper river valley, Penza region). 19 species of mollusks were found in the studied water bodies. The oxbows were characterized by relatively low alpha-diversity (number of species 4 ± 2) with relatively high beta-diversity (Jacquard index 0.26 ± 0.18), which is typical for floodplain ecosystems. Lake communities was dominated by Planorbis planorbis (40 %), Lymnaea stagnalis (15 %), Anisus spirorbis (14 %), Lymnaea saridalensis (9 %), Anisus vortex (8 %). The results of our analysis showed that the group of factors that determined the type of water body (stability, light intencity, water temperature, oxygen concentrations) had the greatest impact on the structure of malacocenoses. The seasonal dynamics of mollusk communities was determined by the number of adjoining water bodies, water temperature, and dissolved oxygen concentrations. The number of adjoining oxbows influenced species diversity the most, as well as the total number and biomass - isolation was more favorable for mollusk communities. The factors influencing the highest number of mollusks species (seven) were the light intencity and the presence of fish. Other significant factors were the stability of lakes (five species of mollusks), the number of oxbows and the transparency of the water (four species). Aquatic vegetation positively correlated with only one species - Anisus vortex . Our data suggest that the presence of fish could influence the abundance of Lymnaea saridalensis . The mollusks themselves, apparently, had a positive effect on the number of leeches in water bodies. The most sensitive to the factors were Lymnaea stagnalis , Lymnaea saridalensis , Aplexa turrita , Anisus spirorbis and Anisus leucostoma , the most tolerant were Bathyomphalus crassus , Anisus vortex , Planorbis planorbis , Planorbarius corneus.
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