Terrestrial inputs boost organic carbon accumulation in Mexican mangroves.

Despite their ability to mitigate climate change by efficiently absorbing atmospheric carbon dioxide (CO) and acting as natural long-term carbon sinks, mangrove ecosystems have faced several anthropogenic threats over the past century, resulting in a decline in the global mangrove cover. By using standardized methods and the most recent Bayesian tracer mixing models MixSIAR, this study aimed to quantify source contributions, burial rates, and stocks of organic carbon (C) and explore their temporal changes (∼100 years) in seven lead-210 dated sediment cores collected from three contrasting Mexican mangrove areas. The spatial variation in C burial rates and stocks in these blue carbon ecosystems primarily depended on the influence of local rivers, which controlled C sources and fluxes within the mangrove areas. The C burial rates in the cores ranged from 66 ± 16 to 400 ± 40 g m yr. The C stocks ranged from 84.9 ± 0.7 to 255 ± 2 Mg ha at 50 cm depth and from 137 ± 2 to 241 ± 4 Mg ha at 1 m depth. The highest C burial rates and stocks were observed in cores from the carbonate platform of Yucatan and in cores with reduced river influence and high mangrove detritus inputs, in contrast to patterns identified from global databases. Over the past century, the rising trends in C burial rates and stocks in the study sites were primarily driven by enhanced inputs of fluvial-derived C and, in some cores, mangrove-derived C. Despite their decreasing extension, mangrove areas remained highly effective producers and sinks of C. Ongoing efforts to enhance the global database should continue, including mangrove area characteristics and reliable timescales to facilitate cross-comparison among studies.