Vertical stratification of physical, chemical and biological components in two saline lakes Shira and Shunet (South Siberia, Russia)

• Published in: Aquatic Ecology
• Main Authors: Degermendzhy, A.G., Zadereev, E.S., Rogozin, D.Y., Prokopkin, I., Barkhatov, Y.V., Tolomeev, A., Khromechek, E.B., Janse, J.H., Mooij, W.M., Gulati, R.D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2010
• Subjects: Copepods; Siberia
• Online Access: https://pure.knaw.nl/portal/en/publications/ca055835-0d2c-4a6f-a03d-7c3e9849cbfb; https://doi.org/10.1007/s10452-010-9336-6; https://hdl.handle.net/20.500.11755/ca055835-0d2c-4a6f-a03d-7c3e9849cbfb; https://pure.knaw.nl/ws/files/484776/Degermendzhy_ea_4885.pdf

A feature of meromictic lakes is that several physicochemical and biological gradients affect the vertical distribution of different organisms. The vertical stratification of physical, chemical and biological components in saline, fishless meromictic lakes Shira and Shunet (Siberia, Russia) is quite different mainly because both mean depth and maximum depth of lakes differ as well as their salinity levels differ. The chemocline of the Lake Shira, as in many meromictic lakes, is inhabited by bacterial community consisting of purple sulphur and heterotrophic bacteria. As the depth of the chemocline is variable, the bacterial community does not attain high densities. The mixolimnion in Lake Shira, which is thermally stratified in summer, also creates different habitat for various species. The distribution of phytoplankton is non-uniform with its biomass peak in the metalimnion. The distribution of zooplankton is also heterogeneous with rotifers and juvenile copepods inhabiting the warmer epilimnion and older copepods found in the cold but oxic hypolimnion. The amphipod Gammarus lacustris which can be assigned to the higher trophic link in the fishless lake’s ecosystem, such as Lake Shira, is also distributed non-uniformly, with its peak density generally observed in the thermocline region. The chemocline in Lake Shunet is located at the depth of 5 m, and unlike in Lake Shira, due to a sharp salinity gradient between the mixolimnion and monimolimnion, this depth is very stable. The mixolimnion in Lake Shunet is relatively shallow and the chemocline is inhabited by (1) an extremely dense bacterial community; (2) a population of Cryptomonas sp.; and (3) ciliate community comprising several species. As the mixolimnion of Lake Shunet is not thermally stratified for long period, the phytoplankton and zooplankton populations are not vertically stratified. The gammarids, however, tend to concentrate in a narrow layer located 1–2 m above the chemocline. We believe that in addition to vertical inhomogeneities of both ...