First assessment of organic carbon stocks and sequestration rates in soils of blue carbon ecosystems in Cuba

Blue carbon ecosystems are important carbon sinks that sequester large amounts of organic carbon in soils over time scales ranging from decades to millennia, offering high potential for climate change mitigation and adaptation strategies.  Cuba is considered as one of the world's blue carbon hotspots due to its extensive and well-preserved mangrove and seagrass habitats, as well as the high carbon densities found in its soils. However, quantitative assessments of organic carbon inventories and accumulation rates are still lacking. This study aimed to evaluate organic carbon stocks and sequestration rates through the evaluation of sediment profiles in seagrasses, mangroves and marshes in the Ciénaga de Zapata wetland and the Gulf of Batabanó, representative areas of these marine-coastal ecosystems in Cuba. Organic carbon content and dating by ²¹⁰Pb and ¹³⁷Cs were determined in the sediment profiles. Organic carbon stocks were highest in mangrove soils dominated by Avicennia germinans (mean value of 1014 ± 70 MgC/ha), compared to those dominated by Rhizophora mangle (mean value of 110 ± 3 MgC/ha), marsh soils (mean value of 179 ± 48 MgC/ha), and seagrass soils (mean value of 198 ± 62 MgC/ha). Sequestration rates were also generally higher in mangrove (mean value of 172 ± 132 g Corg m^-2 yr^-1) than in marshes (mean value of 33,8 ± 1,2 g Corg m^-2 yr^-1) and seagrasses (mean value of 26,5 ± 13,3 g Corg m^-2 yr^-1). This study represents a pioneering effort in Cuba, providing essential data on organic carbon stocks and sequestration rates within blue carbon ecosystems. Such information is critical for guiding future research, enhancing management and conservation strategies, and supporting regional climate change mitigation efforts.