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

Abstract

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.