Aerobic and anaerobic methanotrophic communities in urban landscape wetland

Both aerobic methane-oxidizing bacteria (MOB) and nitrite-dependent anaerobic methane oxidation (n-damo) organisms can be important methane sinks in a wetland. However, the influences of the vegetation type on aerobic MOB and n-damo communities in wetland, especially in constructed wetland, remain poorly understood. The present study investigated the influences of the vegetation type on both aerobic MOB and n-damo organisms in a constructed urban landscape wetland. Sediments were collected from eight sites vegetated with different plant species. The abundance (1.19–3.27 × 107 pmoA gene copies per gram dry sediment), richness (Chao1 estimator = 16.3–81.5), diversity (Shannon index = 2.10–3.15), and structure of the sediment aerobic MOB community were found to vary considerably with sampling site. In contrast, n-damo community abundance (8.74 × 105–4.80 × 106 NC10 16S rRNA gene copies per gram dry sediment) changed slightly with the sampling site. The richness (Chao1 estimator = 1–11), diversity (Shannon index = 0–0.78), and structure of the NC10 16S rRNA gene-based n-damo community illustrated slight site-related changes, while the spatial changes of the pmoA gene-based n-damo community richness (Chao1 estimator = 1–8), diversity (Shannon index = 0–0.99), and structure were considerable. The vegetation type could have a profound impact on the wetland aerobic MOB community and had a stronger influence on the pmoA-based n-damo community than on the NC10 16S-based one in urban wetland. Moreover, the aerobic MOB community had greater abundance and higher richness and diversity than the n-damo community. Methylocystis (type II MOB) predominated in urban wetland, while no known type I MOB species was detected. In addition, the ratio of total organic carbon to total nitrogen (C/N) might be a determinant of sediment n-damo community diversity and aerobic MOB richness.