Tracing dissolved organic matter cycling in the eastern boundary of the temperate North Atlantic using absorption and fluorescence spectroscopy |
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| Institution: | 1. IIM–CSIC, Instituto de Investigacións Mariñas, Eduardo Cabello 6, 36208 Vigo, Spain;2. Centre for Sustainable Aquatic Research, Swansea University, Singleton Park SA2 8PP, United Kingdom;3. Australian Institute of Marine Science, PMB 3, Townsville MC, QLD 4810, Australia;1. LEGOS (CNRS/CNES/IRD/Université Paul Sabatier), Observatoire Midi-Pyrénées, 14 avenue Edouard Belin, 31400 Toulouse, France;2. Alfred-Wegener Institute for Polar and Marine Research, am Handelshafen 12, D-27570 Bremerhaven, Germany;3. Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA;4. LSCE/IPSL Laboratoire CNRS/CEA/UVSQ, Domaine du CNRS, Bat 12, Avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France;5. Institute of Marine and Coastal Sciences, Department of Earth and Planetary Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901-8521, USA;6. Vrije Universiteit Brussel, ESSC Research Group, Pleinlaan 2, 1050 Brussels, Belgium;1. MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str., 28359 Bremen, Germany;2. Geosciences Department, University of Bremen, Klagenfurter Str., 28359 Bremen, Germany;3. Helmholtz Young Investigator Group SEAPUMP, Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany;1. GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany;2. Dalhousie University, Halifax, Canada;3. ETH Zurich, Institute of Geochemistry and Petrology, Switzerland;4. Bedford Institute of Oceanography, NS, Canada;5. Max Planck Research Group for Marine Isotope Geochemistry, Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University Oldenburg, 26129 Oldenburg, Germany;1. Laboratório de Estudos dos Oceanos e Clima - LEOC, Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, RS 96203-900, Brazil;2. Laboratório de Oceanografia Física, Estuarina e Costeira - LOFEC, Departamento de Oceanografia, Universidade Federal de Pernambuco, Recife, PE 50740-550, Brazil;3. Rede Brasileira de Pesquisas sobre Mudanças Climáticas Globais – Rede CLIMA, São José dos Campos, SP 12227-010, Brazil;1. Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Department of Bioscience and Arctic Center, Aarhus University, Vejlsøvej 25, DK-8600 Silkeborg, Denmark;4. Sino-Danish Center for Education and Research, Beijing 100190, China |
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| Abstract: | Apparent oxygen utilization (AOU), dissolved organic carbon (DOC), coloured dissolved organic matter (CDOM) absorption spectra, and CDOM fluorescence characteristic of aromatic amino acids (excitation/emission 280 nm/320 nm; F(280/320)) and marine-humic like substances (320 nm/410 nm; F(320/410)) were measured in full depth during a cruise in the temperate Eastern North Atlantic (ENA). An optimum multi-parameter (OMP) inverse method was run to calculate water mass proportion-weighted average (archetypal) concentrations of these chemical parameters for all water masses and samples. Archetypal concentrations retain the variability due to water mass mixing and basin scale mineralization from the water mass formation sites to the study area. Conversely, the difference between measured and archetypal concentrations, retain the variability due to dissimilarities in mineralization processes within the study area. Our analysis indicates that DOC supported 26±3% of the AOU in the dark temperate ENA and that basin scale processes occurring at and from the formation area of the water masses explained 63% of the total DOC variability. Our data also suggests that DOC remineralized at the basin scale was of lower molecular weight, and with a lower proportion of fluorescent aromatic amino acids than found within the study area. The relationship between the absorption coefficient at 254 nm (aCDOM(254)) and AOU indicates that aCDOM(254) was consumed during organic matter remineralization in the dark ocean, with 55% of the variability being explained by basin scale processes. The relationships of F(320/410) with AOU and DOC confirmed that marine humic-like substances are produced by microbial degradation processes, at a rate of 6.1±0.9×10?3 mg equivalents of QS mol AOU?1. Our results also indicate that basin-scale remineralization processes account for 85% of the total variability of F(320/410), emphasizing that large scale processes control the formation of humic-like substance in the dark ENA. |
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| Keywords: | Apparent oxygen utilization (AOU) Dissolved organic matter (DOM) Coloured DOM (CDOM) Fluorescent CDOM (FDOM) Eastern North Atlantic (ENA) |
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