Methane Emission in a Specific Riparian-Zone Sediment Decreased with Bioelectrochemical Manipulation and Corresponded to the Microbial Community Dynamics

Abstract

Dissimilatory metal-reducing bacteria are widespread in terrestrial ecosystems, especially in anaerobic soils and sediments. Thermodynamically, dissimilatory metal reduction is more favorable than sulfate reduction and methanogenesis but less favorable than denitrification and aerobic respiration. It is critical to understand the complex relationships, including the absence or presence of terminal electron acceptors, that govern microbial competition and coexistence in anaerobic soils and sediments, because subsurface microbial processes can effect greenhouse gas emissions from soils, possibly resulting in impacts at the global scale. Here, we elucidated the effect of an inexhaustible, ferrous-iron and humic-substance mimicking terminal electron acceptor by deploying potentiostatically poised electrodes in the sediment of a very specific stream riparian zone in Upstate New York state. At two sites within the same stream riparian zone during the course of 6 weeks in the spring of 2013, we measured CH4 and N2/N2O emissions from soil chambers containing either poised or unpoised electrodes, and we harvested biofilms from the electrodes to quantify microbial community dynamics. At the upstream site, which had a lower vegetation cover and highest soil temperatures, the poised electrodes inhibited CH4 emissions by ∼45% (when normalized to remove temporal effects). CH4 emissions were not significantly impacted at the downstream site. N2/N2O emissions were generally low at both sites and were not impacted by poised electrodes. We did not find a direct link between bioelectrochemical treatment and microbial community membership; however, we did find a correspondence between environment/function and microbial community dynamics.

Using Fixed-Potential Electrodes To Quantify Iron And Manganese Redox Cycling In Upland Soils

“…The results from SPVF show redox fluctuations between negative and positive currents at both 100 mV and 400 mV, and therefore indicate active redox cycling of both Fe and Mn. The only known previous installations of fixed-potential electrodes documented smaller magnitude positive currents in thawing permafrost soils where Fe reduction is known to account for over half of soil respiration, (Lipson et al 2010;Friedman et al 2012Friedman et al , 2013 or in riparian zones with active methanogen populations (Friedman et al 2016). Our results show that fixed-potential electrodes are useful for documenting redox dynamics (not just reducing conditions) in moderately well-drained upland soils that may not be predominantly reducing.…”

“…Our results show that fixed-potential electrodes are useful for documenting redox dynamics (not just reducing conditions) in moderately well-drained upland soils that may not be predominantly reducing. From our results and those reported by Friedman et al (2012Friedman et al ( , 2013Friedman et al ( , and 2016 fixed-potential electrode measurements can be applied to a diverse array of soils (permafrost soils, riparian floodplain soils, and upland soils) to document reduction and oxidation reactions across a range of redox potentials.…”

“…Recently, graphite electrodes fixed at a specific redox potential were used to track in situ anaerobic microbial metabolisms in organic permafrost (Friedman et al 2013) and riparian zones known for methanogenesis (Friedman et al 2016). These fixed-potential electrodes, long used by electrochemists, can be used for chronoamperometry to measure the current produced at the electrode surface over time.…”

Three promising applications of microbial electrochemistry for the water sector

“…101 Another application of microbial anodes buried in soils or sediments could be to mitigate methane emissions from such environments. 102 Recently, many researchers focus on using METs for production of chemicals. Microbial electrosynthesis 103 refers to the reduction of low-value carbon (e.g.…”

Novel method to immobilize phosphate in lakes using sediment microbial fuel cells

“…Studies show that the application of SMFCs favor oxidative processes such as iron and sulfide oxidation in reduced sediment (Tender et al 2002;Matturro et al 2017;Touch et al 2017), with consequent inhibition of Fe-S formation (Ryckelynck et al 2005), reduced methane emissions (Friedman et al 2016, Liu et al 2017) and increased sediment redox potential (Kubota et al 2019).…”