Carbon dioxide in the atmosphere-water system and biogenic elements in the littoral zone of Lake Baikal during period 2004–2018

Abstract We report long-term comprehensive measurements of CO2 in the atmosphere, surface water and the major nutrients obtained for the period 2004–2018. The research was conducted at the Baikal Atmospheric and Limnological Observatory (BALO), which is located in the coastal zone of South Baikal (coordinates 51° 54′ N, 105° 05′ E). The seasonal variation of these characteristics was analyzed. For our site, during the open water period (May-December) we assessed average flux of CO2, which amounted to −155 mmol m−2 y−1 (sink from the atmosphere to the water surface). Carbon dioxide content in the near-water air of Lake Baikal rises with a rate of 2.46 ppm per year, which is in good agreement with the global trend. The common effect of many factors (often multi-directional), such as variability of weather conditions, hydrological processes and productivity cycles of aquatic plankton in the Baikal waters, cause strong variations in the water characteristics, which we observed in different seasons and years. Under these conditions of strong inter-annual and seasonal variability of all characteristics, trend calculations using our long-term observations did not allow us to reveal reliable tendencies of changes in surface water CO2 concentrations.