Phytoplankton and zooplankton succession during the dry–refilling cycle: A case study in large, fluctuating soda lakes

Abstract Aquatic ecosystems in arid regions are important habitats for aquatic wildlife and also support species biodiversity. Soda lakes in endorheic drainage basins, so‐called amplifier lakes, are sentinels of climate change and are of scientific significance. Here we present the results of a long‐term study (20 years) of the Torey lakes, Transbaikalia, Russia, including the period from the maximum capacity of the Torey lakes through to aridification, and then to the initial phase of refilling. Our aim was to determine the response of planktonic communities in the lakes to environmental change over this period. We conducted our studies during various parts of the hydrological cycle, including three phases for Lake Zun‐Torey (high [1999, 2003], intermediate [2007, 2011] and low [2014, 2016] water levels) and two phases for Lake Barun‐Torey (high level [1999, 2003] and the initial refilling phase [2014, 2016, 2018, 2020]). Lake Barun‐Torey dried up completely in summer 2009, and since 2013 has been undergoing initial refilling. Lake Zun‐Torey dried up in the autumn of 2017. Temporal variation in planktonic communities differs for each lake. We identified four stages of changes in the planktonic associations during the aridification of Lake Zun‐Torey (the phytoplankton experienced a decrease in abundance and biomass, and was dominated by green algae and diatoms; the zooplankton underwent a decrease in species diversity and an increase in total abundance and biomass, which were caused by an increase in the abundance of some crustacean species) and three stages of changes as the lake level fell and during the initial refilling of Lake Barun‐Torey (the plankton communities increased in species richness and abundance in the transient pools). These results show the complexity of long‐term community dynamics in arid‐zone soda lakes. They have revealed how phytoplankton and zooplankton community diversity and structure can vary with changing environmental conditions and may pass between distinct states related to the stages of the hydroperiod.