Dissolved oxygen stratification in a small lake depending on water temperature and density and wind impact

The dissolved oxygen (DO) is one of the most important parameters in lakes ecosystem. Variability of DO in lakes is associated with the absorption of oxygen due to the decomposition of organic matter and chemical reactions and the release of oxygen as a result of photosynthesis. The DO concentration also depends on seasonal changes in water temperature and mixing regime. The aim of this work is to assess the influence of seasonal thermal and density stratification on the DO stratification in a small mesotrophic lake and to develop a regression DO model, with water temperature and density and characteristics of wind regime as independent variables. Long-term measurements of water temperature and DO in small Karelian Lake Vendyurskoe in 2007-2020 were used. At the stage of spring-summer heating, three periods are considered when the water column was in the state of homothermy (May 15-June 15), weak stratification (July 15-August 15), and strong stratification (July 15-August 15). The wind load (number of days with wind speed more than 3 m/s for each period) was analysed based on the weather station Petrozavodsk data. As a result of multiple regression analysis, taking into account the wind load, dependences of DO stratification on water temperature stratification (R² = 0.51) and water density stratification (R² = 0.61) are found. Obtained regression DO models can be used for solving various environmental tasks.