Dataset: Increased Organic Carbon Burial in Northern Florida Mangrove-Salt Marsh Transition Zones

Salt marshes and mangroves are recognized globally as blue carbon habitats, burying large amounts of carbon with limited area, but they also are increasingly susceptible to current climate change. Rising temperatures and decreasing freeze frequencies are resulting in replacement of salt marshes along the southern United States by mangroves. Our results show surface soils from wetlands along northern Florida Atlantic and Gulf coasts had higher apparent sedimentation rates in mangrove-dominated sites (1.5-3.2 mm yr^-1) and where mangroves are migrating into the marsh (termed transition sites, 2.3-3.8 mm yr^-1). Average carbon burial rates were higher in transition sites for both coasts (27-47 gC m^-2 yr^-1) compared to the respective mangrove (10-22 gC m^-2 yr^-1) and salt marsh (4-7 gC m^-2 yr^-1) sites. Lignin biomarker data (_-6, _-8, C/V) indicated mangrove and transition sites had higher lignin inputs from woody vascular plants compared to salt marsh sites. Higher amino acid concentrations in mangrove soils relative to mangrove biomass (1.8-2.3 mmol gC^-1 vs. 0.2-0.9 mmol gC^-1) and lower C/N indicated these mangrove sites receive higher algal inputs than the transition and salt marsh sites and we attribute this difference to greater tidal inundation in the mangrove sites given their position near the shoreline.