Effects of dissolved oxygen on phosphorus transformation in reservoir sediments: novel insights on bacterial community and functional genes

PurposeDissolved oxygen (DO) has important effects on microorganisms, phosphorus cycle genes, and phosphorus release from sediments. However, the mechanism by which DO affects the release of phosphorus through microorganisms and genes is not obvious. This paper aims to investigate how microorganisms and genes affect the release of phosphorus from sediments under different dissolved oxygen conditions.Materials and methodsSediment and water samples were collected and placed in incubators for 30 and 60 days of culture. Dissolved oxygen concentrations were maintained at 0.5 mg L−1, 1 mg L−1, 2 mg L−1, and 3 mg L−1. Fluorescence was used to quantitatively determine the number of functional genes, obtain microbial species through high-throughput sequencing, and analyze the correlation with phosphorus in sediments.Results and discussionAt the genus level, Pseudomonas has a greater contribution to mineralization. On the 30th day, as the concentration of DO increased, the number of functional genes (phoD, ppk, and qppC) increased significantly. The expression of phoD (alkaline phosphatase gene) and pqqC (pyrroloquinoline quinone) together promoted the release of phosphorus. After 60 days culture, the ReP (the release of phosphorus from sediments) content decreased from 53.5 to 14.2 mg kg−1 with increasing DO concentration.ConclusionsOrP (organic phosphorus) and AcP (acid extracted phosphorus) are converted to AlP (alkali extracted phosphorus) and thus lead to the reduction of ReP. The expression of ppk (polyphosphate kinase) gene was inhibited under low DO and promoted the release of phosphorus.