Chemically unidentified dissolved organic carbon: A pivotal piece for microbial activity in a productive area of the Northern Patagonian shelf

The biochemical composition and fluorescence properties of DOM were assessed in relation to phytoplankton major aquatic bacterial clades a regenerative area the Argentine Shelf. was mainly autochthonous biological origin, containing humic- protein-like substances medium degree unsaturation diagenesis. Biochemical-DOM accounted for 25% total DOC, being dissolved combined amino acids (DCAA) dominant fraction followed by free carbohydrates. Phytoplankton main source serine, alanine, valine, particulate Gammaproteobacteria abundance correlated negatively with ammonium positively DCAA, suggesting coupling between consumption refractory acid production. A preferential utilization leucine threonine as nitrogen inferred from distribution Cytophaga-Flavobacteria-Bacteroidete (DFAA). Notably, Alpha- Betaproteobacteria large pool (75%) chemically unidentified DOC not DCAA or Particularly, Alphaproteobacteria (?40% EUB heterotrophic bacteria) either significantly contribute production “humic”, marine DOM, latter impairs resource control on their abundance. Spatial heterogeneity inherent coastal-shelf areas drives important regional variability DOM.