Assessment of the Condition of Lakes in Southeastern Transbaikalia by the Chlorophyll a Content

The state of the lakes of Southeastern Transbaikalia is assessed. The formation of the hydrochemical and hydrobiological regime of water bodies in the study area occurs under semi-arid climate conditions. The existing cyclical climate fluctuations with a periodicity of 27–35 years cause their sequential filling and drying out. These works were carried out during the transition period between low-water and high-water years. The abiotic environmental factors and chlorophyll a concentrations of various phytoplankton divisions, such as green algae, cryptophytes, diatoms and cyanobacteria, are considered. This work was carried out using a FluoroProbe submersible probe (bbe Moldaenke GmbH, Germany). It was established that the observed fluctuations in the level regime of lakes affect abiotic indicators, causing changes in the content of chlorophyll a of phytoplankton. The principal component analysis showed that the chlorophyll content of green algae depends on the content of potassium and sodium, bicarbonates, and chlorides. The chlorophyll content of cyanobacteria depends on the concentrations of calcium and magnesium. The chlorophyll content of cryptophyte algae depends on the depth of water bodies. Thus, changes in water levels in lakes affect the hydrochemical composition, which determines the structure of phytoplankton communities. Consequently, changes in the abiotic conditions, influencing the development of primary producers, are manifested in changes in the pigment composition of phytoplankton. Currently, most of the studied reservoirs are passing through the stage of mesotrophic level of their development.