What the study found
Lake Mai Ndombe, a humic tropical lake in the Democratic Republic of Congo, was found to be highly supersaturated with major dissolved greenhouse gases across all seasons, sampling stations, and water depths. The authors also report that greenhouse gas concentrations generally increased with water depth, and that the lake emits substantial amounts of carbon dioxide, methane, and nitrous oxide.
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. They suggest these observations may also help explain greenhouse gas emissions from other tropical humic lakes.
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 combined those field measurements with temperature and wind speed data to estimate gas emissions from the lake.
What worked and what didn't
The lake water column was weakly to non-stratified, meaning it was only weakly layered or not layered at all, and it remained highly supersaturated for all measured gases. Carbon-isotope signals suggested that one gas was largely sourced from respiration of bioavailable organic carbon, while methane reflected sedimentary methanogenesis followed by aerobic methanotrophy in the water column. Nitrogen-isotope measurements indicated a nitrogen cycle dominated by sedimentary denitrification, with near-quantitative reduction to nitrogen gas before upward diffusion and outgassing.
What to keep in mind
The abstract does not describe experimental limitations in detail. The study focuses on one lake in central Africa, so the results are directly shown for Lake Mai Ndombe and are only suggested to be potentially relevant to other tropical humic lakes.
Key points
- Lake Mai Ndombe was highly supersaturated with major dissolved greenhouse gases in every season, station, and depth sampled.
- Greenhouse gas concentrations increased with water depth.
- The study estimated lake emissions of carbon dioxide, methane, and nitrous oxide from field measurements and model-based extrapolation.
- Isotope evidence suggested one gas came largely from respiration of bioavailable organic carbon, while methane involved sedimentary methanogenesis and aerobic methanotrophy.
- Nitrogen-cycle measurements pointed to sedimentary denitrification and strong reduction to nitrogen gas before release to the water column.
Disclosure
- Research title:
- Lake Mai Ndombe is a strong greenhouse gas source
- 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, Johan 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
- DOI:
- 10.1029/2025jg009218
- OpenAlex record:
- View
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