Primary production and destruction of organic matter in Lake Arakhley (Eastern Transbaikalia, Russia)

Abstract

Global climate changes affect water ecosystems. Long-term observations of climatic variables are indicative of cyclic climate changes. The fluctuations result in changes in water levels in lakes, which, in turn, alter primary production processes. Planktonic algae are the main drivers of primary production. This research continues long-term studies on hydroecology of Lake Arakhley. The lake is used for fishery and recreation. This work aims to estimate production and destruction processes in Lake Arakhley during the current transitional period between dry and wet years. To this end, we performed field studies on Lake Arakhley in August from 2016 to 2021, during the season of maximum precipitation, in the central and littoral zones of the lake. Primary production of phytoplankton in water was estimated by the oxygen light and dark bottle method. Sampling was carried out to assess physical and chemical parameters of water using a multiparameter water quality instrument. Lake Arakhley features the low level of mineralization under alkali conditions and relatively stable level of mineralization registered from 2016 to 2021. Macrophytes zone expanded after the massive flooding of the shore in 2021 hence alterating the values of such environmental factors as oxygen levels, total and mineral phosphorus, with destruction prevailing over organic matter production. Depth and transparency however contribute to significant production of organic matter in the lake. The findings can be used as the groundwork for the sustainable management of the lake.