Khairi, N.; Hamdan, N. H.; Rozaimi, M.; Md Zoqratt, M. Z. H.; Mohammad Nasir, M. A.; Abdella, B.; Tan, G. Y. A.; Eem, L. P.; Amir, A. A.; Akma, W. S.; Hazrin Chong, N. H.

Microbial communities are central to the biogeochemical cycling of nutrients, critically shaping ecosystem functioning and influencing climate change mitigation. Mangrove ecosystems are among the most important global carbon sinks that enable large amounts of carbon to be sequestered and stored. However, gaps persist in understanding the fundamental aspects of microbial-driven carbon cycling in these environments. This research explores the microbial taxonomic and functional diversity related to carbon cycling in tropical mangrove sediments of varying locations and depths. Sequencing data analyses based on the 16S rRNA gene revealed distinct microbial community composition but conserved predicted functions across the different mangrove locations. Depth was a strong influence on the functional composition, with carbon related pathways and metabolic strategies differing between top and bottom sediments. Putative functional gene abundance analyses revealed that carbon fixation processes were among the top carbon-related pathways, suggesting the key role of mangrove microbial communities in sustaining long-term carbon storage. Within these communities, Desulfobacterota appeared as a primary contributor to carbon fixation, while Chloroflexota played a significant role in carbon metabolism and methane cycling. Co-occurrence network analyses also revealed that these microbial groups were among the keystone taxa in mangrove sediments. Our study adds on to the body of knowledge on the mangrove microbiome and their carbon metabolic processes, which helps to improve strategies for managing and leveraging these vital carbon sinks.