Does a general relationship exist between fluorescent dissolved organic matter and microbial respiration?-The case of the dark equatorial Atlantic Ocean

12 páginas, 9 figuras, 2 tablasThe distributions of humic-like fluorescent dissolved organic matter (at excitation/emission wavelengths of 340 nm/440 nm, F(340/440)) and apparent oxygen utilization (AOU) are determined from water samples taken at 27 stations along 7.5°N, in the equatorial Atlantic Ocean. The relationship between F(340/440) and AOU is evaluated. The influence of water mass mixing is removed through multiple regressions of both F(340/440) and AOU with salinity and temperature for the ocean interior. A general and significant relationship between the residuals of F(340/440) and AOU is found for the entire water column deeper than 200 m (R2=0.79, n=360, p-value <0.001), endorsing the idea that changes in fluorescence intensity are directly related to in situ oxidation of organic matter by microbial activity in the dark equatorial Atlantic Ocean. In addition, we analyse and discuss the relationships between the residuals of F(340/440) and AOU for all individual water massesFunding comes from the Spanish government through the MOC2 (CTM2008-06438-CO2), TIC-MOC (CTM2011-28867), and DOREMI (CTM2012-34294) projects of the R+D Spanish research program, and from the ECLIPSE project financed by Total Foundation. P. De La Fuente would like to thank the Agència de Gestió d׳Ajuts Universitaris i de Recerca de la Generalitat de Catalunya (AGAUR) for their financial support through a FI-AGAUR fellowship. A. Canepa was funded by CONICYT (PFCHA/Doctorado al Extranjero 4a Convocatoria, 72120016). C. Romera-Castillo was funded by a Beatriu de Pinós post-doctoral fellowship from the AGAUR of the Generalitat de CatalunyaPeer reviewe