Phosphatase activities in sediments of subtropical lakes with different trophic states

Abstract

We characterized the vertical distribution of extracellular phosphatase enzymes; phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities in sediments of three subtropical lakes were characterized by different trophic states. We then explored relationships between phosphatase activities, phosphorus (P) compounds, and microbial biomass and activity. Sediment P compounds had been characterized previously by two different methods: sequential fractionation and solution 31P NMR spectroscopy. PMEase and PDEase activities declined with depth and were correlated strongly with microbial biomass and anaerobic respiration, indicating that bacterial phosphatase dominated in these sediments and is an important step in the anaerobic breakdown of organic matter. The oligo-mesotrophic lake had higher PMEase activity and the hypereutrophic lake had higher PDEase activity, while the eutrophic lake had the lowest activities of both enzymes. Principal component analyses showed that enzyme activities were related closely to concentrations of the P forms that they degrade: PMEase activity was correlated with phosphomonoesters, while PDEase activity was correlated with phosphodiesters (including nucleic acids and phospholipids). Enzyme activities were not related to the trophic state but with the concentration P forms found in the sediment. Overall, these results provide insight into the phosphorus cycle in subtropical lake sediments by demonstrating a link between phosphatase activity, P composition, and microbial activity.