The objective of WP3 is to provide new insights on the mechanisms that lead to the preservation of mangrove soil blue carbon from the molecular to the global scale. Diagenetic reactions within the mangrove soils considerably modify organic and inorganic chemical species, also depending on local geomorphology and eutrophication. On the one hand, heterotrophic microbial activities in oxic, suboxic and anoxic conditions, decompose organic matter; on the other hand, associations with mineral phases stabilize organic molecules and prevent them from degradation.
We characterize diagenetic reactions involving carbon, oxygen, iron, nitrogen, and sulfur by coupling DET-2D gel, colorimetric methods and hyperspectral camera analysis. In soil cores, elementary (C,N,P,Mn,Fe,S) and isotopic (13C, 15N, 14C) composition and solid-state 13C NMR spectroscopy of soil bulk OM are analyzed, as well as OM sources with biomarkers, degradations state, and the microbial community (bacteria/archaea and fungi) assemblages growing in the soil belonging to six families of molecules: fatty acids, pigments, sterols, n-alcanes, sugars, and lignin. A specialized information on OM in mangroves surrounding coastal waters will also be assessed exploiting remote sensing information.
