Periphytic biofilm: A buffer for phosphorus precipitation and release between sediments and water

The influence of periphytic biofilm on phosphorus (P) content and species between water and sediment interfaces was evaluated in a simulated experiment. Results showed that the concentration of all P species (TP, TDP, DIP, PP, and DOP) in overlying water decreased to significantly low levels (<0.05 mg L−1) in the presence of periphytic biofilms, while the TP increased (>1.8 mg L−1) in the control (without periphytic biofilm). Periphytic biofilm increased the water pH (maximal value at about 10) favoring co-precipitation between P and metal salt. The presence of periphytic biofilm also slowed the loss of P fractions such as Fe/Al-P and Ca-P from sediment. In addition, the P content of periphytic biofilms, mainly in forms of Fe/Al-P and Ca-P, increased by 100% after 60 d. These results suggested that periphytic biofilm was capable of entrapping P from water, attenuating P release, and storing P as a sink, thereby forming a buffer for P release and precipitation. This study not only offers some valuable insights into the role of periphytic biofilms or similar microbial aggregates in P biogeochemical processes in water-sediment interfaces, but also contributes to the management of water eutrophication from internal P loadings.