This paper continues the cycle of publications presenting analysis of the seasonal peculiarities of the carbon dioxide gas exchange process in the littoral zone of Southern Baikal and is devoted to the results obtained in summer. It is shown that photosynthetic activity of water biota at the end of July - the beginning of August causes the decrease of the content of biogenic elements in water in littoral zone of the lake, and minimum values of their concentrations are observed in the annual behavior. Diurnal behavior of CO2 and O2 in the near-surface water layer caused by the effect of water biota is well pronounced and prevails over other processes. In the littoral zone of the lake, the well pronounced diurnal behavior of CO2 is observed in the whole water column, including near-bottom layers. Photosynthetic activity of biota continuing in the period of transition from spring to summer and development of the summer population of plankton decrease the CO2 concentration. Strong flux of carbon dioxide from the atmosphere to the water surface in the daylight time, characteristic of this period, and the increase of duration of the sink during a day determine the maximum values.
carbon-dioxide, air - sea, gas exchange, Lake Baikal