Expedition aboard the RV “I.D. Papanin” from 18 to 29 September 2026

The work was carried out within the framework of the LIN SB RAS state project No. FWSR-2026-0015 “The influence of abiotic factors of Lake Baikal and adjacent areas of Eastern Siberia on the adaptation and biodiversity of aquatic organisms at the level of ecological, biochemical, and molecular genetic characteristics” (headed by A.P. Fedotov).

The expedition aimed to study hydrochemical parameters and phytoplankton distribution in the shallow zone of Lake Baikal. The average sampling interval along the perimeter of Lake Baikal was 30-50 km. Additionally, specimens of Spongillidae sponges were collected to determine their fatty acid composition. Both visually healthy and diseased sponges were sampled.

Overall, 68 quantitative and qualitative phytoplankton samples were collected at 54 stations from depths down to 50 m and at 3 pelagic stations. Water transparency was measured at each station using a Secchi disk. For hydrochemical analysis, 68 surface water samples were collected−both for immediate analysis and fixation, followed by laboratory determination of their ionic composition and content of biogenic elements. Temperature, pH, and electrical conductivity, as well as concentrations of bicarbonates and dissolved oxygen, were measured during the expedition in water samples. The minimum temperature of the surface water layer of 8.4 °С was recorded near the Tyya River, and the maximum temperature of 16.8 °С−near Cape Muzhinay. The mean temperature was 11.5 °С. Asterionella formosa, algae of the genera Dinobryon, Anabaena lemmermannii, and Rhodomonas pusilla dominated the phytoplankton.