Fluctuation of algal alkaline phosphatase activity and the possible mechanisms of hydrolysis of dissolved organic phosphorus in Lake Barato

Abstract

Fluctuation of algal alkaline phosphatase activity, and the possible mechanisms of hydrolysis of dissolved organic phosphorus by alkaline phosphatases that could be isolated from algae, were investigated seasonally at Lake Barato. The fluctuation of specific enzymatic activity was affected by algal species rather than by the concentration of external phosphorus and amount of phytoplankton. Most (more than 74%) of the organic phosphorus, extracted from phytoplankton, was hydrolyzed by the three variants of alkaline phosphatase purified from Melosira spp., Anabaena sp., and Escherichia coli. By contrast, the organic phosphorus in lake water and that extracted from sediment muds were only partially hydrolyzed (up to 32% and 20%, respectively) by the same enzymes. These results indicate that phytoplankton cannot utilize most of the dissolved organic phosphorus in the lake water and in the sediment muds through enzymatic hydrolysis by alkaline phosphatase, in spite of the high levels of activity of this enzyme in the organisms.