Re-estimating China's lake CO₂ flux considering spatiotemporal variability

The spatiotemporal variability of lake partial carbon dioxide pressure (pCO(2)) introduces uncertainty into CO2 flux estimates at the lake water-air interface. Knowing the variation pattern of pCO(2) is important for obtaining accurate global estimation. Here we examine seasonal and trophic variations in lake pCO(2) based on 13 field campaigns conducted in Chinese lakes from 2017 to 2021. We found significant seasonal fluctuations in pCO(2), with decreasing values as trophic states intensify within the same region. Saline lakes exhibit lower pCO(2) levels than freshwater lakes. These pCO(2) dynamics result in variable areal CO2 emissions, with lakes exhibiting different trophic states (oligotrophication > mesotrophication > eutrophication) and saline lakes differing from freshwater lakes (-23.1 +/- 17.4 vs. 19.3 +/- 18.3 mmol m(-2) d(-1)). These spatiotemporal pCO(2) variations complicate total CO2 emission estimations. Using area proportions of lakes with varying trophic states and salinity in China, we estimate China's lake CO2 flux at 8.07 Tg C yr(-1). In future studies, the importance of accounting for lake salinity, seasonal dynamics, and trophic states must be noticed to enhance the accuracy of large-scale carbon emission estimates from lake ecosystems in the context of climate change.
(c) 2023 The Authors. Published by Elsevier B.V. on behalf of Chinese Society for Environmental Sciences,Harbin Institute of Technology, Chinese Research Academy of Environmental Sciences. This is an openaccess article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).