The high carbon density of mangrove ecosystems is well established, however, the mechanisms governing sediment organic carbon (SOC) stability in mangroves remain ambiguous. In this study, a mangrove national nature reserve in Gaoqiao was selected to investigate the variations in SOC content, sub-component composition, and temperature sensitivity across mangrove communities. The underlying microbial mechanisms were elucidated using carbon-degrading enzyme assays, 16S rRNA sequencing, and metagenomic analysis. The results showed increased total SOC but decreased the ratios of labile to recalcitrant carbon and mineral-associated to particulate organic carbon in Rhizophoraceae forests compared to those in Avicennia marina and Aegiceras corniculatum community forests. The sediments of Rhizophoraceae forests also exhibited the lowest SOC mineralization rate yet the highest temperature sensitivity (Q10) of decomposition. The shift in SOC partitioning was accompanied by a transition of the microbial community toward K-strategist dominance, characterized by an increased ratio of K- to r-strategists, a higher ratio of recalcitrant-to-labile enzyme activity, and greater carbon allocation toward conservation versus reproduction. Multivariate modeling further revealed a significant linkage between SOC substrate (e.g., chemical recalcitrance and mineral protection) and microbial life-history strategies and functional traits, which in turn mediated SOC decomposition and Q10 across different mangrove communities. This study provides novel insights into the multi-stability of SOC in mangroves and the underlying ecological drivers, particularly under global warming.