What the study found
The study found that Lake Mai Ndombe, a humic tropical lake in the Democratic Republic of Congo, is highly supersaturated with respect to atmospheric equilibrium for all measured greenhouse gases across seasons, stations, and depths. The authors also report that greenhouse gas concentrations generally increase with water depth.
Why the authors say this matters
The authors conclude that carbon inputs, total water depth, and/or dissolved oxygen saturation are major drivers of the flux and composition of greenhouse gases emitted from Lake Mai Ndombe and potentially other tropical humic lakes. The study suggests this matters because mechanistic insight into greenhouse gas cycling in such systems has been limited, especially in understudied central Africa.
What the researchers tested
The researchers measured seasonal concentrations and isotopic compositions of the major dissolved greenhouse gases in Lake Mai Ndombe during high-water, falling-water, and low-water periods. They also used field measurements such as temperature and wind speed to estimate gas emissions from the lake.
What worked and what didn't
The lake water column was weakly to non-stratified, and all measured greenhouse gases were highly supersaturated across all seasons, sampling stations, and water depths. The study estimated emissions of 375 ± 32 Gg C yr−1 as carbon dioxide, 623 ± 136 Mg C yr−1 as methane, and 223 20 Mg N yr−1 as nitrous oxide, and isotope data suggested carbon dioxide came largely from respiration of bioavailable organic carbon while methane reflected sedimentary methanogenesis followed by aerobic methanotrophy in the water column. Bulk and position-specific nitrogen isotope compositions indicated a nitrogen cycle dominated by sedimentary denitrification, with near-quantitative reduction to dinitrogen before upward diffusion and outgassing.
What to keep in mind
The abstract does not describe detailed study limitations. The findings are specific to Lake Mai Ndombe and are presented as potentially relevant to other tropical humic lakes, but the abstract does not provide direct tests beyond this lake.
Key points
- Lake Mai Ndombe was highly supersaturated with greenhouse gases in every season, station, and depth sampled.
- Greenhouse gas concentrations increased with water depth in the lake.
- The study estimated lake emissions of carbon dioxide, methane, and nitrous oxide from field measurements and extrapolation.
- Isotope signals suggested carbon dioxide mainly came from respiration of bioavailable organic carbon.
- Nitrogen isotope data suggested sedimentary denitrification dominated the nitrogen cycle.
Disclosure
- Research title:
- Mai Ndombe lake emits greenhouse gases across all seasons
- Authors:
- Matti Barthel, T. W. Drake, A. de Clippele, L. W. de Groot, Michelle Engelhardt, N. Haghipour, Y. Hou, Nico Kueter, D. Lewicka‐Szczebak, A. Ludjwera Bahati, C. L. Tschumbu, K. Van Oost, J. N. Wabakanghanzi, R. A. Werner, J. Zambo Mandea, J. Six, J. D. Hemingway
- Institutions:
- ETH Zurich, ETH Zurich, ETH Zurich, ETH Zurich, ETH Zurich, ETH Zurich, Geological Institute, Geological Institute, Geological Institute, Geological Institute, Geological Institute, Ion Beam Applications (France), UCLouvain, University of Kinshasa, University of Kinshasa, University of Kinshasa, University of Wrocław, Westfälische Hochschule, Woodwell Climate Research Center
- Publication date:
- 2026-03-01
- OpenAlex record:
- View
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