Alkaline Phosphatase Activity and Phosphatase-Active Bacteria in Lake Baikal Water Column and Major Tributaries

Phosphorus is one of the major biogenic elements. Its inflow facilitates eutrophication of lake water. In aquatic ecosystems, phosphorus is present mostly in organic compounds. Ability of aquatic microorganisms to assimilate phosphorus from organophosphorous compounds results from activity of alkaline phosphatases; activity of these enzymes may be an indicator of the state of the ecosystem, phosphate load, and water quality. In the present work, alkaline phosphatase activity (APA) and abundance of phosphatase-active bacteria (PAB) in Lake Baikal pelagic zone and in the mouths of its major tributaries was studied. In the pelagic zone, APA and PAB abundance decreased with depth, indicating that the main processes of phosphate generation occurred in the trophic layer of the lake. In the main tributaries, both APA and PAB abundance were considerably higher than in the pelagic zone. These results indicate active biochemical processes of transformation of organophosphorous compounds occur in the estuarine zones of the rivers. The degradation processes result in regeneration of phosphates, which are completely incorporated in the biological turnover, providing for phytoplankton development.