High particulate organic carbon export during the decline of a vast diatom bloom in the Atlantic sector of the Southern Ocean
Roca Martí, Montserrat (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Puigcorbé, Viena (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Iversen, Morten Hvitfeldt (Alfred Wegener Institute for Polar and Marine Research)
Rutgers van der Loeff, Michiel (Alfred Wegener Institute for Polar and Marine Research)
Klaas, Christine (Alfred Wegener Institute for Polar and Marine Research)
Cheah, Wee (Alfred Wegener Institute for Polar and Marine Research)
Bracher, Astrid (Alfred Wegener Institute for Polar and Marine Research)
Masqué Barri, Pere (Universitat Autònoma de Barcelona. Departament de Física)

Data:	2017
Resum:	Carbon fixation by phytoplankton plays a key role in the uptake of atmospheric CO2 in the Southern Ocean. Yet, it still remains unclear how efficiently the particulate organic carbon (POC) is exported and transferred from ocean surface waters to depth during phytoplankton blooms. In addition, little is known about the processes that control the flux attenuation within the upper twilight zone. Here, we present results of downward POC and particulate organic nitrogen fluxes during the decline of a vast diatom bloom in the Atlantic sector of the Southern Ocean in summer 2012. We used thorium-234 (234Th) as a particle tracer in combination with drifting sediment traps (ST). Their simultaneous use evidenced a sustained high export rate of 234Th at 100 m depth in the weeks prior to and during the sampling period. The entire study area, of approximately 8000 km2, showed similar vertical export fluxes in spite of the heterogeneity in phytoplankton standing stocks and productivity, indicating a decoupling between production and export. The POC fluxes at 100 m were high, averaging 26±15 mmol C m-2 d-1, although the strength of the biological pump was generally low. Only <20% of the daily primary production reached 100 m, presumably due to an active recycling of carbon and nutrients. Pigment analyses indicated that direct sinking of diatoms likely caused the high POC transfer efficiencies (~60%) observed between 100 and 300 m, although faecal pellets and transport of POC linked to zooplankton vertical migration might have also contributed to downward fluxes.
Ajuts:	Ministerio de Ciencia e Innovación CTM2011-14027-E Ministerio de Educación, Cultura y Deporte AP2010-2510 Ministerio de Educación, Cultura y Deporte AP2009-4733 Agència de Gestió d'Ajuts Universitaris i de Recerca 2014/SGR-1356
Nota:	Unidad de excelencia María de Maeztu MdM-2015-0552
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, i la comunicació pública de l'obra, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original. No es permet la creació d'obres derivades.
Llengua:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Matèria:	Biological pump ; Bloom ; Diatoms ; Export efficiency ; Particulate organic carbon export ; Sediment traps ; Southern Ocean ; Thorium ; Transfer efficiency
Publicat a:	Deep-Sea Research Part II: Topical Studies in Oceanography, Vol. 138 (April 2017) , p. 102-115, ISSN 0967-0645

DOI: 10.1016/j.dsr2.2015.12.007

Postprint 51 p, 11.3 MB

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