Microbial Biomass and Community Composition Involved in Cycling of Organic Phosphorus in Sediments of Lake Dianchi, Southwest China

Abstract

ABSTRACTOrganic phosphorus (Po) was a major fraction of phosphorus (P) in sediments of lakes, and microbes were involved in most of its relevant biogeochemical cycling. Forms and quantification of Po were investigated by sequential fractionation in 18 sediments of Lake Dianchi, Southwest China. Microbial biomass and community structure in these sediments were determined by phospholipid fatty acids (PLFAs). Distribution of Po fractions were in the rank order that humic Po > nucleic acid and polyphosphate > residual P > Ca-Al-Po > Fe-Po > sugar Po > acid soluble Po > H2O-Po. The recoveries of Po and Pi in these detailed sequential fractions including residual P shows that the total contents of Po in sediments of lakes were overestimated by the Standards, Measurements and Testing (SMT) protocol (ignition method). Microbial biomass including Gram-positive bacteria (14.4–20.0%), Gram-negative bacteria (32.7–38.4%), microeukaryotes (14.9–24.4%), aerobic bacteria (43.6–55.8%), anaerobic bacteria (0–2.9%) and type І methanotrophs (17.6–24.4%) were assigned. Microbial mass and their composition were strongly correlated with H2O-Po, Fe-Po, nucleic acid and polyphosphate, and humic Po, though residual P was likely inert for microbes in sediments. The formation and degradation of Po was closely related with microbial activities in sediments. These findings have implications for understanding the role of microbes on cycling of Po and organic matter in sediments of lakes.