Climate change prior to human activity reduces the immobility of phosphorus in eutrophic alpine lake

Internal P loading (IPL) is a severe problem for the remediation of eutrophic lakes that the release of sedimentary P impedes the reduction of P in the lakes. To control the IPL, in-situ capping is a widely used remediation to improve the P burial efficiency. However, a lack of study has been done to investigate the long-term climate change effect on the P burial and release mechanisms. Thus, we thoroughly investigated the evolution of the P accumulation and release in the sediment of Dianchi Lake, a eutrophic plateau lake. The stability of sedimental P, which determines the internal P loading, is predominantly affected by climate change, anthropogenic activities, and the macrophyte-to algal-dominated ecosystem transition. The sediment core indicates more Ca accumulated in the 1930s caused by climate change and corresponding biological responses resulting in the transition of stable P fractions, which generates a vulnerable ecosystem from eutrophication. The self-clarification helps the lake accumulate anthropogenic P pollutants in the sediment as stable forms until the degradation of the ecosystem. It shows the NaOH extractable P (NaOH-rP) and HCl-extractable P (HCl-P) preservation capacity in an algal-dominated lake decreases from 780 to 700 mg cm(-2).a(-1) to 170 and 270 mg cm(-2).a(-1) respectively. The most stable P fraction (Res-P) is predominantly affected by climate change rather than human activities that a constant reduction from 730 mg cm(-2).a(-1) to 70 mg cm(-2).a(-1) after the climate change event that subdued the microbial activity producing Res-P in the 1930s. The spatial distributions of P fractions imply that the macrophyte-dominated area has more efficiency in preserving stable P in the sediment, thus the restoration of macrophyte as well as the benthonic microbe community should be considered in the remediation engineering.

Automated summary

The accumulation and release of phosphorus in the sediment of Dianchi Lake, a eutrophic plateau lake, were thoroughly investigated. The stability of internal phosphorus is influenced by climate change, anthropogenic activities, and the transition of the ecosystem. Self-clarification helps accumulate anthropogenic phosphorus pollutants in the sediment until the degradation of the ecosystem. Restoration of macrophyte and benthonic microbe communities should be considered in remediation engineering.