Bacterial and methanogenic archaeal communities associated with Avicennia germinans in restored mangrove sites from the Yucatán Peninsula

Abstract Mangrove ecosystems are hotspots of microbial diversity, with bacterial and archaeal communities playing crucial roles in biogeochemical and nutrient cycles. Among these processes, methanogenesis is enhanced by anaerobic conditions typically induced by flooding and high organic matter accumulation. Despite extensive mangrove coverage on the Yucatán Peninsula, microbial communities in these sediments remain underexplored. This study aims to analyze, through 16S rRNA and mcrA gene sequencing, the structure and composition of microbial communities, particularly methanogenic archaea, in sediments associated with Avicennia germinans in restored sites with high (PH), medium (YM), and low (PL) mangrove recovery. While alpha diversity was consistent across sites, environmental variables —particularly total phosphorus (TP), total nitrogen (TN), total carbon (TC), sand, and silt content— varied significantly. Microbial community structure exhibited strong site-specific differences (R²=0.96, p = 0.004), primarily associated with TP, total carbon (TC), and sand content. LEfSe analysis showed 20 differentially abundant genera in the three sites. Analysis of mcrA gene sequences indicated a dominance of methylotrophic methanogens of the Methanosarcinales order in the three sites. Nevertheless, the PH site also exhibited hydrogenotrophic (Methanobacteriales), acetoclastic (Methanotrichales), and hydrogen-dependent methylotrophic (Ca. Methanomethylicales) sequences. Finally, two clusters of unassigned mcrA sequences, distantly related to methylotrophic groups, and one cluster, distantly related to a hydrogenotrophic group, were retrieved from this study, suggesting the presence of environmental clusters exclusive to the region. This study contributes to the comprehension of methanogenic communities in mangroves and provides a baseline for future research on methane emissions in mangroves of the Yucatán Peninsula.