Ecological significance and phosphorus release potential of phosphate solubilizing bacteria in freshwater ecosystems

Abstract

Phosphorus (P) is a limiting nutrient in some freshwater ecosystems. Phosphate solubilizing bacteria (PSB) are candidates for enhancing P availability in rhizoplane, but their P release potential in freshwater environments needs further evaluations. This study conducted in floodplain wetlands correlated PSB abundance, decline in sediment pH, and natural mobilization of sediment Ca–P. PSB were abundantly present in floodplain wetland waters, sediments, and in river and ponds, showing low to moderate Ca–P solubilization activity; PSB from Churni River and Bhomra wetland sediments had comparatively higher activity than those from other environments. In laboratory sediment microcosms, PSB were effective in enhancing available P concentration in interstitial water indicating their P release potential. However, P-fractionation of incubated sediments showed only a short-term decline in Ca–P by PSB, suggesting that Ca–P might not be their sole or preferred metabolic target. Despite low to moderate activity in culture medium, high population density and efficacy in P release in sediment suggest significant role of PSB in P cycling in freshwater environments.