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Title: Deep-ocean dissolved organic matter reactivity along the Mediterranean Sea: does size matter?
Authors: Martínez-Pérez, Alba María
Álvarez Salgado, Xosé Antón
Aristegui, Javier 
Nieto-Cid, Mar
UNESCO Clasification: 251001 Oceanografía biológica
Keywords: High-Molecular-Weight
Cross-Flow Ultrafiltration
Coastal Upwelling System
Bacterial Utilization
Doc Dynamics, et al
Issue Date: 2017
Project: Zonas de Mezcla y Frentes en El Océano Oscuro Como ¿Hot-Spots? de Biodiversidad y Flujos Biogeoquímicos A Través Del Mar Mediterráneo y Atlántico Nordeste - I. 
Journal: Scientific Reports 
Abstract: Despite of the major role ascribed to marine dissolved organic matter (DOM) in the global carbon cycle, the reactivity of this pool in the dark ocean is still poorly understood. Present hypotheses, posed within the size-reactivity continuum (SRC) and the microbial carbon pump (MCP) conceptual frameworks, need further empirical support. Here, we provide field evidence of the soundness of the SRC model. We sampled the high salinity core-of-flow of the Levantine Intermediate Water along its westward route through the entire Mediterranean Sea. At selected sites, DOM was size-fractionated in apparent high (aHMW) and low (aLMW) molecular weight fractions using an efficient ultrafiltration cell. A percentage decline of the aHMW DOM from 68-76% to 40-55% was observed from the Levantine Sea to the Strait of Gibraltar in parallel with increasing apparent oxygen utilization (AOU). DOM mineralization accounted for 30 ± 3% of the AOU, being the aHMW fraction solely responsible for this consumption, verifying the SRC model in the field. We also demonstrate that, in parallel to this aHMW DOM consumption, fluorescent humic-like substances accumulate in both fractions and protein-like substances decline in the aLMW fraction, thus indicating that not only size matters and providing field support to the MCP model.
ISSN: 2045-2322
DOI: 10.1038/s41598-017-05941-6
Source: Scientific Reports [ISSN 2045-2322], v. 7, article number 5687
Rights: by-nc-nd
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