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| Titel |
Increased ocean carbon export in the Sargasso Sea linked to climate variability is countered by its enhanced mesopelagic attenuation |
| VerfasserIn |
M. W. Lomas, D. K. Steinberg, T. Dickey, C. A. Carlson, N. B. Nelson, R. H. Condon, N. R. Bates |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 7, no. 1 ; Nr. 7, no. 1 (2010-01-05), S.57-70 |
| Datensatznummer |
250004364
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| Publikation (Nr.) |
 copernicus.org/bg-7-57-2010.pdf |
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| Zusammenfassung |
| Photosynthetic CO2 uptake by oceanic phytoplankton and subsequent
export of particulate organic carbon (POC) to the ocean interior comprises a
globally significant biological carbon pump, controlled in part by the
composition of the planktonic community. The strength and efficiency of this
pump depends upon the balance of particle production in the euphotic zone
and remineralization of those particles in the mesopelagic (defined here as
depths between 150 and 300 m), but how these processes respond to
climate-driven changes in the physical environment is not completely
understood. In the Sargasso Sea, from ~1996–2007, we have observed a
decade-long >50% increase in euphotic zone integrated autotrophic
biomass (estimated from chlorophyll TChl-α), prokaryotic phytoplankton,
primary production and shallow (150 m) POC export coinciding with a shift in
the mean phase of the winter North Atlantic Oscillation (NAO) from
consistently positive to neutral but variable. During this same period
mesopelagic POC flux attenuation has doubled such that carbon sequestration
below 300 m, the maximum winter/spring ventilation depth, has not changed.
The increased mesopelagic POC attenuation appears mediated by changes in
plankton community composition and metabolic activity in both the euphotic
and mesopelagic zones. These changes are counter to extant hypotheses
regarding inter-relationships between phytoplankton community composition,
productivity and carbon export, and have significant impacts on how the
Sargasso Sea ecosystem, at least, is modeled. Moreover, these time-series
observations suggest that processes in the euphotic zone and mesopelagic are
tightly coupled and should be considered together in future research. |
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