Tracing Mangrove Outwelling Provenance with Isotopes of Carbon

Objective

"Blue Carbon is defined by the guidelines of the Intergovernmental Panel on Climate Change (IPCC) as ""all biologically-driven carbon fluxes and storage in marine systems that are amenable to management"". The term was coined in 2009, when vegetated coastal ecosystems, such as mangrove forests, salt marshes, and seagrass meadows, started to be collectively known as blue carbon ecosystems. Mangrove forests are important blue carbon hotspots, holding ~1,93 Pg of organic carbon in the top meter of soil. In the Southwestern Atlantic Ocean, extensive mangrove systems account for 70-80% of annual organic carbon accumulation, with Brazil alone containing 95% of the mangrove carbon in the region. While it is well known that mangroves store large amounts of carbon in soils, recent research indicates that a significant amount of organic and inorganic carbon is also exported to the ocean, primarily through pore water exchange and tidal pumping. Evidence suggests that part of this carbon originates from organic matter buried centuries ago. The TROPIC (Tracing Mangrove Outwelling Provenance with Isotopes of Carbon) project will go beyond the quantification of the amount of stored carbon, applying a novel methodological approach that includes isotopic (e.g., radiocarbon) and molecular (lignin) analyses to resolve the age and origin of mangrove carbon and distinguish whether this carbon is recent and labile, or ancient and permanently sequestered. The project will focus on sediment, water and biomass samples collected from mangroves in the South Atlantic region (Amazon and Southern Brazil), where such a combined approach has never been applied. The results will provide the first isotopic fingerprinting of mangrove carbon outwelling in this region, advancing our understanding of carbon cycling in coastal ecosystems and informing conservation strategies and blue carbon policy frameworks. "