Sustained deoxygenation in global flowing waters under climate warming

Dissolved oxygen (DO), as a vital material sustaining aquatic ecosystems, has declined markedly in oceans, lakes, and coastal waters, yet unbiased understandings of changing DO concentrations in each individual river segment globally remain a challenge. Here, we estimate DO concentrations in 21,439 rivers globally between 1985 and 2023, based on Landsat observations and climatic data, and examine their patterns and trends. We find sustained deoxygenation in global rivers, at a rate of -0.045 mg liter^-1 decade^-1, with 78.8% experiencing fluvial deoxygenation, driven mainly by oxygen solubility and temperature. Moreover, short-term heatwaves and dam impoundment exert non-neglecting influence on these changes. Future projections demonstrate that global fluvial DO concentrations decline by 1.1% ± 1.6% under SSP1-2.6 and 4.7% ± 2.7% under SSP5-8.5 throughout the 21st century. Our study provides an unbiased baseline for escalating deoxygenation in global fluvial ecosystems that underscores targeted measures to mitigate deoxygenation threats and protect ecosystem health.