The adsorption-release behavior of sediment phosphorus in a typical "grass-algae" coexisting lake and its influence mechanism during the transition sensitive period

In the early stage of eutrophication, the coexistence of "grass and algae" in lakes is obvious. Understanding the P sorption-desorption behavior in natural sediments during the ecologically sensitive transition period has important scientific value for predicting the deterioration of lake ecosystems and formulating restoration measures, but the related mechanisms are still unclear. In this study, the analysis results of sedimentary dissolved organic matter (DOM) fractions, extractable Fe (hydr)oxide fractions and P adsorption experiments showed that sedimentary DOM fractions, especially the tyrosine-like protein fractions and microbial humic-like fractions, played a part in determining the EPC₀ and K_d values of sediments in the plateau lake environment. The compound effect of amorphous Fe (hydr)oxides and sedimentary OM affected the increase of sedimentary P adsorption. Interestingly, these phenomena were strongly correlated with water depth. Furthermore, the distribution of water depth to aquatic plants indirectly regulated the values of sedimentary EPC₀ and K_d. Meanwhile, the ability of submerged plants to control the sedimentary EPC₀andK_d values will be forced to shift shallowly, thereby forcing a significant reduction of areas with low EPC₀ and high K_d values. This not only enhanced the risk of endogenous P release in lakes, but also accelerated the further deterioration of aquatic ecosystems. Therefore, studying the long-term scale changes of sedimentary EPC₀ and K_d values can help to understand the duration of the lake ecological transition period and prevent the transitional deterioration of ecosystem.