Seasonal distribution patterns of P-cycling-related microbes and its association with internal phosphorus release in the eutrophic Lake Chaohu, China

Understanding the coupling relationships among lake physicochemical properties, internal nutrient recycling, and related microbes is key for the control of freshwater eutrophication. In this study, seasonal variations in microorganisms at the sediment–water interface (SWI) of the eutrophic Lake Chaohu in China were analyzed, in order to reveal changes in phosphorus (P)-cycling-related microbes in the sediments and its association with internal P release during the cyanobacterial life cycle. The identified P-cycling-related microbes include phosphorus-solubilizing bacteria (PSB) (dominant of Bacillus, Thiobacillus and Acinetobacter), sulfate-reducing bacteria (SRB) (dominant of Sva0081_ sediment_ group, norank_ c__ Thermodesulfovibrionia and Desulfatiglans) and iron-reducing bacteria (FeRB) (dominant of Geothermobacter, Anaeromyxobacter, Thermoanaerobaculum and Clostridium_sensu_stricto_1). Increased PSB and reduced proportions of iron-aluminum–bound P (Fe/Al-P) and calcium–bound P (Ca-P) from the benthic stage to initial cyanobacterial growth indicated that internal phosphorus was released through the solubilization of Fe/Al-P and Ca-P by PSB. Growth of cyanobacteria was accompanied by cyanobacteria death, deposition, and degradation during early algal blooms, which increased SRB caused by high organic matter and the net deposition of phosphorus in the western lake. Conversely, phosphorus release in eastern lake was observed because of organic phosphorus mineralization. High linear discriminant analysis effect size of SRB and FeRB and the decreased Fe/Al-P in sediments indicated sulfide-mediated chemical iron reduction (SCIR) and FeRB-mediated microbial iron reduction mechanisms for internal phosphorus release during late algal blooms. The observed seasonal pattern of P-cycling-related microbes and its mediation on internal phosphorus release provides a foundation for internal P management in Lake Chaohu.