Abstract
Mangrove forests are key blue carbon ecosystems, but their net sink potential depends on methane oxidation in soils. In this study, DNA-based stable isotope probing was employed to decipher the changes of potentially active methanotrophic communities across five different mangrove forests along a 370 km coastline of Taiwan, with Kandelia obovata dominating the northern sites (Hsinchu and Miaoli) and Avicennia marina dominating the central and southern sites (Changhua, Tainan, and Pingtung). The results showed that the CH4 oxidation potentials ranged from 10 to 60 nmol CH4 g-1 hr1 in the mangrove forest soils. The pmoA sequencing of fresh soils revealed that unclassified Methylomonadaceae-affiliated methanotrophs, Methylomicrobium-jap-rel, Methylobacter, and Methylomonas were predominant in K. obovata forests. In contrast, unclassified Methylomonadaceae-affiliated methanotrophs and Methylomonas dominated in A. marina forests. Furthermore, Methylomonadaceae-affiliated methanotrophs were positively correlated to soil TOC and TN. DNA-SIP analysis further identified unclassified Methylomonadaceae-affiliated methanotrophs, Methylomonas, and Methylobacter as potentially active methanotrophs in K. obovata forests. In contrast, other unclassified Methylomonadaceae-affiliated methanotrophs and methanotrophs belonging to the deep-sea-1 and deep-sea-3 clusters were potentially active in A. marina forests. Overall, this study revealed distinct biogeographic patterns of methanotrophs in Taiwan's coastal mangrove ecosystems and highlighted the ecological role of Methylomonadaceae in mangrove CH4 cycling.