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| Titel |
Upper ocean mixing controls the seasonality of planktonic foraminifer fluxes and associated strength of the carbonate pump in the oligotrophic North Atlantic |
| VerfasserIn |
K. H. Salmon, P. Anand, P. F. Sexton, M. Conte |
| 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 ; 12, no. 1 ; Nr. 12, no. 1 (2015-01-13), S.223-235 |
| Datensatznummer |
250117768
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| Publikation (Nr.) |
 copernicus.org/bg-12-223-2015.pdf |
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| Zusammenfassung |
| Oligotrophic regions represent up to 75% of Earth's open-ocean
environments. They are thus areas of major importance in understanding the
plankton community dynamics and biogeochemical fluxes. Here we present
fluxes of total planktonic foraminifera and 11 planktonic foraminifer
species measured at the Oceanic Flux Program (OFP) time series site in the
oligotrophic Sargasso Sea, subtropical western North Atlantic Ocean.
Foraminifera flux was measured at 1500 m water depth, over two
~ 2.5-year intervals: 1998–2000 and 2007–2010. We find that
foraminifera flux was closely correlated with total mass flux, carbonate and
organic carbon fluxes. We show that the planktonic foraminifera flux
increases approximately 5-fold during the winter–spring, contributing up
to ~ 40% of the total carbonate flux. This was primarily
driven by increased fluxes of deeper-dwelling globorotaliid species, which
contributed up to 90% of the foraminiferal-derived carbonate during late
winter–early spring. Interannual variability in total foraminifera flux, and
in particular fluxes of the deep-dwelling species (Globorotalia truncatulinoides, Globorotalia hirsuta and Globorotalia inflata), was related to
differences in seasonal mixed layer dynamics affecting the strength of the
spring phytoplankton bloom and export flux, and by the passage of mesoscale
eddies. As these heavily calcified, dense carbonate tests of deeper-dwelling
species (3 times denser than surface dwellers) have greater sinking rates,
this implies a high seasonality of the biological carbonate pump in
oligotrophic oceanic regions. Our data suggest that climate cycles, such as
the North Atlantic Oscillation, which modulates nutrient supply into the
euphotic zone and the strength of the spring bloom, may also in turn
modulate the production and flux of these heavily calcified deep-dwelling
foraminifera by increasing their food supply, thereby intensifying the
biological carbonate pump. |
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