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Greenhouse gases (GHGs) emitted or absorbed by lakes are an important component of the global carbon cycle. However, few studies have focused on the GHG dynamics of eutrophic saline lakes, thus preventing a comprehensive understanding of the carbon cycle. Here, we conducted four sampling analyses using a floating chamber in Daihai Lake, a eutrophication saline lake in Inner Mongolia Autonomous Region, China, to explore its carbon dioxide (CO 2) and methane (CH 4) emissions. The mean CO 2 emission flux (F CO 2) and CH 4 emission flux (F CH 4) were 17.54 ± 14.54 mmol/m2/day and 0.50 ± 0.50 mmol/m2/day, respectively. The results indicated that Daihai Lake was a source of CO 2 and CH 4 , and GHG emissions exhibited temporal variability. The mean CO 2 partial pressure (p CO 2) and CH 4 partial pressure (p CH 4) were 561.35 ± 109.59 µatm and 17.02 ± 13.45 µatm, which were supersaturated relative to the atmosphere. The regression and correlation analysis showed that the main influencing factors of p CO 2 were wind speed, dissolved oxygen (DO), total nitrogen (TN) and Chlorophyll a (Chl. a), whereas the main influencing factors of p CH 4 were water temperature (WT), Chl. a , nitrate nitrogen (NO 3 −-N), TN, dissolved organic carbon (DOC) and water depth. Salinity regulated carbon mineralization and organic matter decomposition, and it was an important influencing factor of p CO 2 and p CH 4. Additionally, the trophic level index (TLI) significantly increased p CH 4. Our study elucidated that salinity and eutrophication play an important role in the dynamic changes of GHG emissions. However, research on eutrophic saline lakes needs to be strengthened. [ABSTRACT FROM AUTHOR]

• The dynamics of CO 2 and CH 4 partial pressures are co-regulated by various nutrients. • CO 2 and CH 4 emission from lakes decreased and increased with longitude, respectively. • Freshwater lakes emit mainly CH 4 , while salt lakes are main contributor of CO 2. • NPP, NDVI and human activities enhance CH 4 emissions but reduce CO 2 emissions. Lakes are important component of the regional carbon cycle and a significant sources of greenhouse gases (GHGs) to the atmosphere. However, the regional variations in carbon dioxide (CO 2) and methane (CH 4) emissions, as well as the factors regulating these emissions are poorly constrained. To investigate the regional GHG emission from lakes and their potential influencing factors, we conducted field measurements in 13 lakes in Inner Mongolia from July to August 2020. We found that the studied lakes were predominantly sources of atmosphere CO 2 and CH 4. The CO 2 partial pressure (p CO 2) exhibited supersaturation in 80 % of samplings, but all samplings of CH 4 partial pressure (p CH 4) showed supersaturation. Moreover, the average p CH 4 is 40 times greater than that in the atmosphere. The lakes emitted substantial amounts CO 2 and CH 4 with average values of 25.8 ± 4.9 mmol m−2 d−1 and 2.1 ± 0.3 mmol m−2 d−1, respectively. At the regional scale, the dynamics of p CO 2 and p CH 4 are regulated by combination of various environmental factors. CO 2 emissions from studied lakes decreased with the catchment net primary productivity (NPP), normalized difference vegetation index (NDVI), and nighttime lights which is indicative of urbanization. Conversely, CH 4 fluxes increased with NPP, NDVI, and nighttime lights. We conclude that terrestrial carbon-cycling related variables and human activities significantly affect CO 2 and CH 4 emissions from lakes by transporting different nutrients, but they show opposite trends. Our results also exhibited that the freshwater lakes are the main contributors of CH 4 , while saline lakes are the main contributors of CO 2. We suggest that increased human activity leads to changes in terrestrial carbon-cycle related processes which affects lake carbon emissions by altering the amount of nutrients input to the lakes. [ABSTRACT FROM AUTHOR]