An excellent alternative to reduce potential atmospheric methane emissions: Anaerobic methane oxidation in freshwater wetlands

Freshwater wetlands (FWW) are characterized by high rates of methanogenesis, and although they occupy a small fraction of the Earth’s surface, represent one of the largest natural sources of methane. Is assumed that anaerobic methane oxidation is the dominant way of the methane consumption in FWW.  This assumption is because the sulfate has been considered the only oxidant for methane in anoxic environments but can be possible that other compounds are being used as electron acceptors, including nitrate/nitrite, iron and manganese.

This study provides the first constraints on both the magnitude and extent of anaerobic methane oxidation (AOM) in FWW, a critical first step to understanding the role of this process in freshwater environments. In this case were sampled three different bio-geographical provinces from Florida, Georgia and Maine, this sites were sampled in two different seasons to captured a range of in situ conditions to illustrate the broad relevance of AOM in FWW.

The measure parameters were the rates of AOM and sulfate reduction, pore water chemistry and stable carbon isotope geochemistry, including microbial lipid biomarker to     evaluate the magnitude of AOM and SR, their role in wetland carbon cycling and the microbial community potentially involved in AOM.

In the table 1 shows the most significant parameters measured to samples used in this study.

In the next figure shows the interaction between sulphate and AOM according to the depth.

Figure 2 sample the relation between SR and AOM in the same way to the previous figure according to the depth.

There is evidence that AOM in FWW is increasing but the rate of direct measurements is not usual so this study includes methanotrophy advances in FWW showing AOM in real time highlight. The potentially large role AOM plays in wetland methane cycling, the zone of maximum AOM activity was 0-3 cm corresponded to the lowest dissolved inorganic carbon values and the highest methane values. Alternative electron acceptors remain feasible sulphate-independent AOM is clearly indicated at some depth horizons in Georgia where rates of AOM exceeded rates of SR so its possible that iron and/or humic substances may play a role: experimental additions of humic substances may prove useful in future investigations.

As FWW ecosystems are responsible for a major portion of global emissions, a better constraint of methane cycling in wetlands is paramount to understanding past and future global methane budgets and the role of FWW in the global methane cycle.

-Segarra, K. E. A., Schubotz, F., Samarkin, V., Yoshinaga, M. Y., Hinrichs, K. U., & Joye, S. B. (2015). High rates of anaerobic methane oxidation in freshwater wetlands reduce potential atmospheric methane emissions. Nature Communications, 6.

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