Characteristics of colored dissolved organic matter (CDOM) in the Western Arctic Ocean: relationships with microbial activities

• Published in: Deep Sea Research Part II: Topical Studies in Oceanography
• Main Authors: Matsuoka, Atsushi, Ortega-Retuerta, Eva, Bricaud, Annick, Arrigo, Kevin R, Babin, Marcel
• Other Authors: Takuvik Joint International Laboratory ULAVAL-CNRS, Université Laval Québec (ULaval)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'océanographie de Villefranche (LOV), Observatoire océanologique de Villefranche-sur-mer (OOVM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire océanologique de Banyuls (OOB), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Department of Marine Biology and Oceanography Barcelone, Institute of Marine Sciences / Institut de Ciències del Mar Barcelona (ICM), Consejo Superior de Investigaciones Científicas Madrid (CSIC)-Consejo Superior de Investigaciones Científicas Madrid (CSIC), Department of Earth System Science Stanford (ESS), Stanford EARTH, Stanford University-Stanford University
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [SDV.MP]Life Sciences [q-bio]/Microbiology and Parasitology; Arctic; Arctic Ocean; Chukchi Sea; Beaufort Sea; Chukchi; Phytoplankton
• Online Access: https://hal.sorbonne-universite.fr/hal-01120307; https://hal.sorbonne-universite.fr/hal-01120307/document; https://hal.sorbonne-universite.fr/hal-01120307/file/Matsuoka_Characteristics_of.pdf; https://doi.org/10.1016/j.dsr2.2015.02.012

International audience Colored dissolved organic matter (CDOM), a significant fraction of dissolved organic carbon (DOC), plays various roles in physical and biogeochemical processes in natural waters. In the Arctic Ocean, CDOM is abundant because of major input by large rivers. To better understand the processes that drive variations in CDOM, light absorption coefficients of CDOM [aCDOM(λ), m−1] were extensively documented together with temperature, salinity, chlorophyll a, nitrate concentrations, and bacterial production (BP) and abundance (BA) in the Western Arctic Ocean (WAO) from early to late summer as part of the MALINA and the ICESCAPE expeditions. The data set covered contrasting situations, from bloom to post-bloom conditions and from river-influenced to oceanic water masses. While CDOM photobleaching occurred in the surface layer (< 20 m), we observed significantly lower spectral slopes for CDOM absorption spectra (SCDOM) in addition to higher aCDOM(4 4 0) in the layer below (intermediate layer: 30.7<salinity<33.9). In particular, the low SCDOM values were found in the Chukchi Sea and the western part of the Beaufort Sea, which coincided with high BP and BA values. Considering the high primary production observed in these areas during our cruises ( Arrigo et al., 2012), we hypothesize that SCDOM variations reflect the degradation of phytoplankton that is associated with heterotrophic bacterial activity. In our datasets, a simple regression analysis showed that SCDOM was significantly correlated with BP and BA. A principal component analysis further supported this conclusion. From our field observations, it was shown that variations in aCDOM(4 4 0) and SCDOM result to a large extent from bacterial activity, at least in the WAO.