Increased Organic Carbon Burial in Northern Florida Mangrove‐Salt Marsh Transition Zones. Issue 5 (11th May 2020)

• Record Type: Journal Article
• Authors: Vaughn, Derrick R.; Bianchi, Thomas S.; Shields, Michael R.; Kenney, William F.; Osborne, Todd Z.
• Is Part Of: Global biogeochemical cycles. Volume 34:Issue 5(2020:May)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-05-11
• Subjects: blue carbon -- carbon burial -- biomarker -- lignin -- amino acids -- mangrove migration; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1029/2019GB006334
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: Blue carbon habitats like salt marshes and mangroves bury large amounts of carbon with limited area; however, they also are increasingly susceptible to current climate change. Combined effects of rising temperatures, decreasing freeze frequencies, and increasing sea level rise rates are resulting in mangrove replacement of salt marshes along the southern United States. Surface soils analyzed here from wetlands along northern Florida Atlantic and Gulf Coasts showed 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 g C·m −2 ·yr −1 ) compared to the respective mangrove (10–22 g C·m −2 ·yr −1 ) and salt marsh (4–7 g C·m −2 ·yr −1 ) sites. Lignin biomarker data (Λ‐6, Λ‐8, and C/V) indicated that mangrove and transition sites had higher lignin inputs from woody vascular plants compared to salt marsh sites, which may slow decadal‐ to centennial‐scale decay. Higher amino acid concentrations in mangrove soils relative to mangrove biomass (1.8–2.3 mmol g C −1 vs. 0.2–0.9 mmol g C −1 ) and lower C/N indicated that these mangrove sites receive higher algal inputs than the transition and salt marsh sites, attributed to greater tidal inundation in the mangrove sites given their position near the shoreline. Overall, increased accretion, carbon burial, and lignin in mangrove transition sites indicate that this migration may increase carbon burial and increase the stability and residence time of buried soil carbon. Future studies on mangrove migration in northern Florida can verify this through replication and elevation analysis. Key Points: Mangrove migration increases lignin‐rich woody material in the soil that relates to increased organic carbon preservation Northern Florida sites with mixed mangrove and marsh vegetation had higher organic carbon burial than adjacent salt marshes and mangroves Among our mangrove sites, wave action and tidal pumping likely cause lesser organic carbon burial in shoreline mangroves