Terrestrial dissolved organic matter (DOM) can be highly reactive, and readily degraded into low-molecular-weight organic matter and dissolved inorganic substances such as CO₂ once it enters lake ecosystems. However, to date, there has been limited research into the links between long-term variations in the composition and fate of DOM and CO₂ emissions from lakes. Lake Taihu is a large, shallow, and highly eutrophic lake where DOM composition is influenced by inflow from surrounding rivers. Based on long-term seasonal observations from 2000 to 2022, we estimated the annual areal average CO₂ efflux (FCO₂) to be 470 ± 107 gC m^-2 yr^-1 corresponding to a summed flux of 1.1 ± 0.3 TgC yr^-1 from the lake. The FCO₂ decreased during 2005-2020, with higher values typically occurring in February, and we found lower FCO₂ values in August possibly explained by phytoplankton uptake. Aromatic compounds are typically associated with inputs of anthropogenic effluents from terrestrial environments and thus explain the increased FCO₂ in northwestern inflowing lake regions that co-varied with increasing nutrient and terrestrial DOM inputs. Ultrahigh-resolution mass spectrometry results revealed the link between FCO₂ and the biogeochemical processing of aromatic DOM molecules. Bioincubation experiments further confirmed the connection between the degradation of bio-labile DOM and the aerobic production of CO₂. We conclude that the input and subsequent degradation of terrestrial DOM, modulated by inflow discharge, drives CO₂ emissions from Lake Taihu.

太湖,千岛湖,二氧化碳,溶解性有机物,甲烷