Patterns and Drivers of UV Absorbing Chromophoric Dissolved Organic Matter in the Euphotic Layer of the Open Ocean
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Iuculano, Francesca; Alverez Salgado, Xose Anton; Otero, Jaime; Serrano Catalá, Teresa; Sobrino, Cristina; Duarte, Carlos; Agusti, SusanaEditorial
Frontiers Media
Materia
chromophoric dissolved organic matter Absorption spectroscopy euphotic layer tropical and subtropical ocean biogeographic provinces
Date
2019-06-18Referencia bibliográfica
Iuculano F, Álverez-Salgado XA, Otero J, Catalá TS, Sobrino C, Duarte CM and Agustí S (2019) Patterns and Drivers of UV Absorbing Chromophoric Dissolved Organic Matter in the Euphotic Layer of the Open Ocean. Front. Mar. Sci. 6:320.
Sponsorship
This study was funded by the Ingenio-Consolider project Malaspina 2010 Circumnavigation Expedition (MICINN CSD2008-00077). FI and JO were supported by a fellowship from the “Junta para la Ampliación de Estudios” (JAE-preDOC and JAE-postDOC programs 2011, respectively) from the CSIC.Abstract
The global distribution of chromophoric dissolved organic matter (CDOM) in the euphotic
layer of the Atlantic, Indian, and Pacific oceans (between 35 N and 40 S) was
analyzed by absorption spectroscopy during the Malaspina 2010 circumnavigation.
Absorption coefficients at 254 nm (a254) and 325 nm (a325), indices (a254/a365) and
spectral slopes (between 275 and 295 nm, S275--295) were calculated from the
dissolved fraction of the UV absorption spectra to describe the amount and quality
of CDOM. Generalized Additive Models (GAMs) were applied to evaluate the relevance
of physical and biogeochemical drivers for the variability of CDOM. Besides the low
CDOM values, a first division of our data following the Longhurst’s biogeographic
classification showed significant differences in CDOM levels among provinces. The
lowest values of a254 and a325 were found in the oligotrophic gyres, particularly in the
Indian Ocean, and the highest in the upwelling areas, particularly in the Equatorial Pacific.
Opposite distributions were obtained for S275--295 and a254/a365, indicative of higher
photobleaching in the gyres. The
GAM analysis also shows that a254/a365 and S275--295 exhibited inverse relationships with solar radiation, indicating that the biological production of CDOM counteracts
photodegradation as solar radiation increases. In summary, whereas photobleaching
dictates the vertical distribution of CDOM, Chl a explains the CDOM differences
among the photic layer of the tropical and subtropical ocean provinces visited during
the circumnavigation.