Horizontal and vertical distribution of nitrate-driven anaerobic methane oxidation process in coastal wetlands under different plant species cover across southeast China

Abstract

Coastal wetlands are an important methane emission source. Nitrate-driven anaerobic oxidation of methane (AOM), catalyzing via a novel clade of anaerobic methanotrophic archaea (ANME-2d), is a potentially important process for methane emission mitigation in coastal wetlands. However, the influence of regional and local environmental conditions, as well as plant species cover on this AOM process, remains unclear. Here, we investigated the horizontal and vertical distribution of nitrate-driven AOM activity and ANME-2d archaeal community in four coastal wetlands under both native and invasive plant species across southeast China. It was estimated that this AOM process could potentially reduce 5.7–9.5% methane emissions from the studied wetlands. Generalized linear mixed-effects model showed that sampling locations and sediment layers had greater impact on nitrate-driven AOM activity than plant species cover, and all these factors significantly affected the abundance of ANME-2d archaea. Nitrate-driven AOM activity was higher in low-latitude coastal wetlands than in high-latitude areas, and the activity positively correlated with mean annual temperature. Furthermore, both nitrate-driven AOM activity and ANME-2d archaeal abundance showed significant vertical variations along sediment profiles, with higher values in the slightly alkaline surface sediment. The plant species cover was found to impact the ANME-2d archaeal abundance and diversity by regulating the availability of substrates for the archaea. Overall, our study provides valuable insights into effects of regional and local environmental parameters and plant species cover on the horizontal and vertical distribution of nitrate-driven AOM activity and ANME-2d archaeal community in coastal wetlands.