Historical changes of sedimentary P-binding forms and their ecological driving mechanism in a typical grass-algae eutrophic lake

With the transformation of lake ecosystem from clear water to turbid water, the residual phosphorus (P) accumulated in sediments may slow down the process of aquatic ecological restoration, and the related mechanisms are complex and need to be better understood. In this study, high-resolution systematic investigation and analysis of P-binding forms in the sediments showed that Lake Dianchi, the largest plateau lake in Southwest China, was enriched with NaOH-rP, HCl-P and Res-P, but depleted in NH4Cl-P, BD-P and NaOH-nrP. The BD-P, NaOH-nrP and NaOH-rP were the main contributors to potential P release from sediments, while the release potential of NH4Cl-P was relatively weak (<1%). When the external P loading gradually decreased, the internal P loading of Lake Dianchi was estimated to be 522 mg P/(m(2).a) in the past 30 years. The succession of grass-algae type in Lake Dianchi coincided with reduced absorption and transformation of potential mobile P and decreased accumulation of stable P, especially the Res-P. Meanwhile, the temporal variation of potential mobile P was a good predictor of ecological degradation and reduced ecosystem sustainability in Lake Dianchi.

Automated summary

The study found that the main forms of P binding in Lake Dianchi sediments are BD-P, NaOH-nrP, and NaOH-rP, with NaOH-rP contributing significantly to potential P release. As external P loading decreased, the internal P loading in Lake Dianchi decreased over the past 30 years, resulting in reduced absorption and transformation of potential mobile P in the lake ecosystem. This has implications for ecosystem sustainability and ecological restoration in Lake Dianchi.