Addition of Macromolecular Marine DOM Cycling to the Marine Biogeochemistry Library (MARBL)

The differential cycling of marine macromolecules, such as dissolved carbohydrates, proteins, and lipids play a fundamental role in marine microbial metabolisms, ultimately regulating the ocean's capacity to sequester carbon downwards via the biological pump or move carbon up the food chain, supporting marine food webs. To date, their representation in global scale models of marine biogeochemistry and ecosystems is lacking. Here we add explicit representation of marine macromolecular cycling for dissolved polysaccharides, lipids, amino polysaccharides, and proteins, within the dissolved organic matter pools of the Marine Biogeochemistry Library (MARBL) ecosystem model, implemented within the ocean circulation model of the Community Earth System Model. The resulting dissolved macromolecule distributions identify polysaccharide and amino polysaccharide accumulation within the upper ocean of the subtropics owing to longer lifetimes than dissolved lipids and proteins which are diagnosed with shorter lifetimes and accumulate in more biologically productive regions. Representation of marine macromolecules is found to better match observed constraints of dissolved organic carbon to nitrogen stoichiometry patterns with depth than its MARBL predecessor which considers only bulk pools. This implementation of macromolecular cycling within the marine dissolved organic matter pool represents an important next step in better characterizing the complexity of natural organic matter within the marine ecosystem.