Characterization and quantification of mangrove-derived extractable carbon

Blue Carbon, sequestered organic carbon from coastal ecosystems, is an integral part of the global carbon cycle that is stored in the preserved plant tissues and sediments of seagrass meadows, salt marshes, and mangrove forests for decades to millennia. Mangrove forests serve as nesting ground, home to a variety of fauna, and are important sources of food, traditional herbal medicines and other goods and services and the Philippine archipelago hosts 50% of the 65 known mangrove species worldwide. We aim to qualify the labile composition of “Blue Carbon” stored in mangrove plant tissues and sediments as we hypothesize that these are the types of compounds that are eventually transported and interact beyond the terrestrial zones. Extractable organic carbon from leaves, twigs, and roots of mangrove trees are compared to the molecular and stable carbon and nitrogen isotopic compositions in the sediments to trace the contribution of the mangrove plant and its transformations in the sediment. We analyzed the above- and below-ground components of Nypa fruticans and Rhizophora apiculata, the dominant mangrove species along Balingasay River, the least anthropogenically-altered mangrove forests in Bolinao, Philippines. The molecular compositions were identified using Gas Chromatography-Mass Spectrometer and Isotope Ratio Mass Spectrometer, and compared across species and parts. Known mangrove biological marker, Taraxerol, and other terpenoids were quantified and evaluated for their potential to track the burial and transport of mangrove components down to the molecular level, and how these can be used to refine Blue Carbon estimates, as well as determine adaptations of mangrove species to salinity stress from their lipid profiles. Linking the presence of these compounds with the specific functions, we showed the relationship of the compounds identified as well as map out their specific biosynthetic order. Close functional relationship between common compounds, such as Phytol, Campesterol, Sitosterol, Lupeol, and Stigmasterol, were observed for both species. Other compounds, such as steroidal sapogenins were found in N. fruticans roots which was linked to salinity tolerance.