The current hydrochemical regime of Lake Ladoga as an indicator of changes of its ecosystem

The changes in the regime of the most related to the balance of production and destruction of Lake Ladoga hydrochemical indicators were analyzed: the content of total and mineral phosphorus, pH and the oxygen concentration in water. The results obtained during the open water period over the last 20 years are compared with the modern period. A decrease in the average inorganic phosphorus concentration in the lake during the open water period is noted, as a result of its almost complete consumption in the hypolimnion of the deep-water zones of the lake in summer. These changes limit the phytoplankton primary production and are accompanied by a decrease in the average pH in the open water period, which in turn is expressed in a shift in the production-destruction balance towards an increasing predominance of the process of organic matter destruction.