Turnover time of fluorescent dissolved organic matter in the dark global ocean

Abstract

Catalá, Teresa S. ... et. al.-- 8 pages, 4 figures, 1 table, supplementary information http://www.nature.com/ncomms/2015/150129/ncomms6986/full/ncomms6986.html#/supplementary-informationMarine dissolved organic matter (DOM) is one of the largest reservoirs of reduced carbon on Earth. In the dark ocean (>200 m), most of this carbon is refractory DOM. This refractory DOM, largely produced during microbial mineralization of organic matter, includes humic-like substances generated in situ and detectable by fluorescence spectroscopy. Here we show two ubiquitous humic-like fluorophores with turnover times of 435±41 and 610±55 years, which persist significantly longer than the ∼350 years that the dark global ocean takes to renew. In parallel, decay of a tyrosine-like fluorophore with a turnover time of 379±103 years is also detected. We propose the use of DOM fluorescence to study the cycling of resistant DOM that is preserved at centennial timescales and could represent a mechanism of carbon sequestration (humic-like fraction) and the decaying DOM injected into the dark global ocean, where it decreases at centennial timescales (tyrosine-like fraction). © 2015 Macmillan Publishers Limited. All rights reservedThis study was financed by the Malaspina 2010 circumnavigation expedition (grant number CSD2008–00077). C.R.-C. acknowledges funding through a Beatriu de Pinos postdoctoral fellowship from the Generalitat de Catalunya. M.N.-C. was funded by the CSIC Program ‘Junta para la Ampliación de Estudios’ cofinanced by the ESFPeer Reviewe