Constantly nitrogen and phosphorus input will increase methane and carbon dioxide emissions from global lakes

Due to the high nitrogen (N) and phosphorus (P) input and the weak self-cleaning ability of waterbodies, lakes are more prone to be eutrophication. The continuous input of N and P in enriched lakes regulates the carbon (C) cycle process, which affects the production of greenhouse gases such as CO₂ and CH₄. Therefore, we assessed the water CO₂ and CH₄ emission fluxes and their response to ongoing N and P inputs based on data from 707 globally distributed lakes. We found that CO₂ and CH₄ emission fluxes were higher in the tropics than in the temperate zone, with Antarctica acting as a methane sink. The emission fluxes of CH₄ and CO₂ increased with the increase in N and P concentration, and the effect of total phosphorus (TP) on the emission fluxes of CO₂ and CH₄ was the highest. When the TP load is increased by 3 times, the CO₂ emission reaches 443.99 mg m^-2 d^-1, and the CH₄ emission reaches 205.47 mg m^-2 d^-1, which is 1.48 and 3.85 times of the normal condition respectively. If the TP load is reduced by 3 times, it reduces 597.83 mg m^-2 d^-1 C emissions. This study shows that lake C emissions are highly dependent on continuous N and P input, which provides a scientific reference for the C cycle process of eutrophic lakes, and provides an important basis for the study of lake response to climate.