LAUSR

Abstract Habitats of organisms in Lake Baikal have been comprehensively monitored for many years. In 2010–2015, we conducted 8 research expeditions to study ionic composition of the water and measure concentrations of dissolved oxygen, nutrients, organic carbon, and persistent organic pollutants in the entire pelagic area of Lake Baikal. Our data showed that the ionic composition was stable at all depths in the pelagic zone of the lake. We also recorded seasonal variability, vertical stratification, and spatial variations in the content of nutrients, organic matter, and gas components. The concentrations of major ions, nutrients, and dissolved oxygen were favourable for the growth of hydrobionts in the offshore pelagic zone. Concentrations of pollutants in Lake Baikal, such as persistent organic pollutants and heavy metals, were low and did not directly affect the biota. The water in specific areas of the littoral zone of Lake Baikal, however, was polluted near large settlements (Listvyanka, Severobaikalsk, Baikalsk, and Slyudyanka) and in bays because of unsatisfactory operations of sewage treatment plants, growing tourist activity, and intense ship traffic. Continuing investigations are needed to elucidate causes of eutrophication in the littoral zone of Lake Baikal.