The impact of thermal regime on chlorophyll content in the southern part of the Kuibyshev reservoir

Institute of Ecology of the Volga Basin of the Russian Academy of Sciences – branch of the Samara Federal Research Center of the Russian Academy of Sciences, 10, Komzin St., Tolyatti, 445003, Russian Federation

^* Corresponding author: Seleznev53@mail.ru

Abstract

To assess the effect of water temperature on the concentration of chlorophyll “a”, regular observations were carried out in the southern part of the Kuibyshev Reservoir in the period 2016-2022. It was found that there is an exponential relationship between the concentration of chlorophyll and water temperature. The growth rate of chlorophyll concentration with an increase in temperature in the range of 15-22 ºC was 0.5 μg / dm³ per 1 ° C. With an increase in temperature above 22 ºC, the rate increased 5 times and was 2.5 μg / dm³ per 1 ° C. The different growth rates of chlorophyll are explained by the fact that at temperatures below 22 ºC, Bacillariophyta and Chlorophyta dominated in the phytoplankton structure, and at higher temperatures - Cyanophyta algae, which caused the process of “blooming” of the water. For prognostic calculations, the correlation between air and water temperature was studied. A very strong correlation was found for August with a coefficient of 0.90. Using the Student criterion, a conclusion was made about the statistical significance of the obtained linear trend of water temperature. It was concluded that under conditions of global warming, the content of chlorophyll “a” will increase due to the rapid development of Cyanophyta algae, which will lead to a deterioration in the state of the ecosystem of the Kuibyshev Reservoir.