Hydroclimate Drives Oxygen Output in Congo Peatlands for 10,600 Years

A groundbreaking new study reveals the dynamic oxygen release patterns of the Congo Basin peatlands over the last 10,600 years, shedding light on the complex interplay between hydroclimate and organic matter preservation. Researchers analyzed a 237-cm peat core extracted in 2017 from the Momboyo River region in the Democratic Republic of Congo, a site where peat accumulation began around 10.6 thousand years before present.

The data uncover a noteworthy “Ghost Interval” spanning 7,500 to 2,300 years ago, during which net peat accumulation significantly slowed. This intriguing phase suggests alterations in carbon cycling within this vast tropical carbon store. Notably, regional continental temperatures remained relatively stable at approximately 22.5 °C from 13,500 to 11,500 years ago, before gently rising by roughly 0.3 °C per millennium, stabilizing near 25 °C during the mid-Holocene onward. These subtle shifts in climate likely influenced organic matter decomposition and preservation dynamics within the peatland.

Utilizing high-temperature combustion with copper oxide at 900 °C, the team directly measured oxygen demand for organic matter oxidation, providing a precise burial-specific O₂:C ratio between 0.9 and 1.15 mol O₂ per mol of carbon. This approach surpasses traditional proxy uncertainties by avoiding cumulative isotopic aggregation and capturing early diagenetic degradation patterns. The results closely align with global terrestrial biosphere oxidative ratios derived from atmospheric budgets and soil incubation studies, underscoring the robustness of the new methodology.

Thermal and calorimetric analyses, including Rock-Eval pyrolysis, illuminated the preservation states of the peat’s labile and refractory organic fractions. Total organic carbon (TOC) measurements from the core matched previous Congo Basin peat studies, reinforcing the reliability of these findings.

To extrapolate net oxygen production across the entire central Congo Basin, researchers integrated core-derived oxygen demand values with basin-wide peat area and density data. Monte Carlo simulations yielded an estimate of roughly 83 petamoles of oxygen equivalent released, underscoring the vast scale of these tropical peat ecosystems in global carbon and oxygen cycles.

The study acknowledges inherent limitations, such as minor contributions from mobile hydrocarbons and heterogeneities within samples, which were rigorously addressed through statistical modeling. Additionally, the methodology accounts for reduced sulfur or iron components, enhancing applicability to more sulfidic or ferruginous environmental settings beyond freshwater peatlands.

This pioneering research not only quantifies peatland oxygen fluxes over millennia but also highlights the critical role of hydroclimate in modulating carbon turnover and atmospheric oxygen balance in tropical ecosystems. Its innovative techniques and basin-wide scaling provide an essential framework for understanding past environmental changes and predicting future impacts on carbon and oxygen cycles amid evolving global climates.