Patterns in Wetland Microbial Community Composition and Functional Gene Repertoire Associated with Methane Emissions

ABSTRACT Wetland restoration on peat islands previously drained for agriculture has potential to reverse land subsidence and sequester atmospheric carbon dioxide as peat accretes. However, the emission of methane could potentially offset the green-house gas benefits of captured carbon. As microbial communities play a key role in governing wetland greenhouse gas fluxes, we are interested in howmicrobial community composition and functions are associated with wetland hydrology, biogeochemistry, andmethane emission, which is critical to modeling the microbial component in wetlandmethane fluxes and to managing resto-ration projects for maximal carbon sequestration. Here, we couple sequence-based methods with biogeochemical and green-house gas measurements to interrogate microbial communities from a pilot-scale restored wetland in the Sacramento-San Joaquin Delta of California, revealing considerable spatial heterogeneity even within this relatively small site. A number of mi-crobial populations and functions showed strong correlations with electron acceptor availability andmethane production; some also showed a preference for association with plant roots. Marker gene phylogenies revealed a diversity of major methane-producing and-consuming populations and suggested novel diversity within methanotrophs. Methanogenic archaea were ob-served in all samples, as were nitrate-, sulfate-, andmetal-reducing bacteria, indicating that no single terminal electron acceptor was preferred despite differences in energetic favorability and suggesting spatial microheterogeneity andmicroniches. Notably, methanogens were negatively correlated with nitrate-, sulfate-, andmetal-reducing bacteria and were most abundant at sam-pling sites with high peat accretion and low electron acceptor availability, where methane production was highest