Complex Circum-Baikal expedition on R/V Vereshchagin from September 16 to October 1, 2025
Field work was carried out within the State Assignments: № 0279-2021-0005 “Study of transformations of the state of water bodies…” (led by A.P. Fedotov); № 0279-2021-0004 “Study of advective and turbulent water exchange...” (led by I.A. Aslamov).
The purpose of the work was to carry out comprehensive monitoring of the abiotic and biotic components of the Baikal ecosystem during the period of direct temperature stratification, to identify the patterns of their spatial-temporal dynamics; experimental study of mechanisms and processes affecting the distribution and circulation of matter in the water column taking into account temperature-density anomalies of deep natural waters under current climate changes, study of the distribution and transfer of physical and chemical (oxygen, biogenic compounds) characteristics in the water column, gas exchange of water-atmosphere.
Samples were taken using a standard grid of stations on fixed horizons from the surface to the bottom using a Carousel SBE-32 sampler equipped with 24 5-liter bathometersWater samples were taken for chemical analysis and to study the distribution and species composition of phytoplankton. Zooplankton samples were taken using a Juday net. Work was carried out in three basins of the lake, as well as in the Barguzinsky, Chivyrkuisky bays and in theMaloye More Strait.
A total of 72 stations were covered, including:
- 27 stations of longitudinal section,
- 34 stations of transverse section,
- 4 stations in the bays.
Of these, water samples were taken at 18 stations, and zooplankton samples were taken at 37 stations.
Total number of samples for:
- hydrochemical analysis - 225;
- zooplankton - 99;
- phytoplankton - 49 (water).
Hydrophysical measurements were carried out at 72 stations with a high-precision CTD probe SBE-25 with additional dissolved oxygen and transparency sensors. The lowest surface temperature was noted at the central stations of Goloustnoye settlement - Babushkin settlement (9.06 °C), among others. B. Vorota Strait and Boldakova River recorded a temperature of 9.95 °C, while the highest temperature was measured 3 and 5 km away from the settlement of Maritui (13.98 °C). The mean surface temperature across the stations was 12.75 °C.
The average transparency measurement for the Secchi disk was recorded at 8.5 meters, with fluctuations ranging from 7 to 10 meters.
Simultaneously with the main work between stations on the way of the vessel, measurements were carried out with parallel recording in the subsurface layer of temperature, mineralization, pH and turbidity of water, as well as the concentration of dissolved methane. During the course of the expedition, bubble gas emissions (PGE) were monitored using a hardware and software system on the base of Furuno echo sounder with recording the echogram data.
At certain stations, upper layer (100m) soundings were conducted using the CTD probe JFE-Rinko equipped with additional sensors for oxygen, turbidity, fluorescence (chlorophyll-a), pH, and PAR.
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