| Summary: | 2012 ASLO Aquatic Sciences Meeting: Voyages of Discovery, 8-13 July 2012, Lake Biwa, Shiga, Japan A dissolved organic matter (DOM) fraction absorbs ultraviolet and visible radiation that partially also emits fluorescence when irradiated with ultraviolet light. To identify the most relevant fluorophores present in deep waters, 429 excitation-emission matrixes (EEMs) from the bathypelagic layer of the Atlantic, Indian and Pacific oceans were recorded during the Malaspina 2010 circumnavigation. Parallel factor analysis (PARAFAC) modeling was applied and two humic-like fluorophores were identified in the dominant water masses of the deep world ocean: Antarctic Intermediate Water (AAIW), Circumpolar Deep Water (CDW), North Atlantic Deep Water (NADW) and Pacific Deep Water (PDW). Significant positive relationships were found between the humic-like fluorophores and AOU, suggesting the transformation of colorless bioavailable organic matter into chromophoric refractory DOM (RDOM) through microbial respiration. The RDOM/AOU ratio, a proxy to the efficiency of RDOM production, depended on the water mass. In the particular case of the NADW, terrestrial and in situ produced humic-like fluorophores were differentiated. These results will provide a basis for a better understanding of the role of microbial activity in the origin and fate of marine chromophoric dissolved organic matter Peer Reviewed
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