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| Titel |
Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean |
| VerfasserIn |
G. Fischer, G. Karakaş |
| 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 ; 6, no. 1 ; Nr. 6, no. 1 (2009-01-16), S.85-102 |
| Datensatznummer |
250003317
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| Publikation (Nr.) |
 copernicus.org/bg-6-85-2009.pdf |
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| Zusammenfassung |
| The flux of materials to the deep sea is dominated by larger, organic-rich
particles with sinking rates varying between a few meters and several
hundred meters per day. Mineral ballast may regulate the transfer of organic
matter and other components by determining the sinking rates, e.g. via
particle density. We calculated particle sinking rates from mass flux
patterns and alkenone measurements applying the results of sediment trap
experiments from the Atlantic Ocean. We have indication for higher particle
sinking rates in carbonate-dominated production systems when considering
both regional and seasonal data. During a summer coccolithophorid bloom in
the Cape Blanc coastal upwelling off Mauritania, particle sinking rates
reached almost 570 m per day, most probably due the fast sedimentation of
densely packed zooplankton fecal pellets, which transport high amounts of
organic carbon associated with coccoliths to the deep ocean despite rather
low production. During the recurring winter-spring blooms off NW Africa and
in opal-rich production systems of the Southern Ocean, sinking rates of
larger particles, most probably diatom aggregates, showed a tendency to
lower values. However, there is no straightforward relationship between
carbonate content and particle sinking rates. This could be due to the
unknown composition of carbonate and/or the influence of particle size and
shape on sinking rates. It also remains noticeable that the highest sinking
rates occurred in dust-rich ocean regions off NW Africa, but this issue
deserves further detailed field and laboratory investigations. We obtained
increasing sinking rates with depth. By using a seven-compartment
biogeochemical model, it was shown that the deep ocean organic carbon flux
at a mesotrophic sediment trap site off Cape Blanc can be captured fairly
well using seasonal variable particle sinking rates. Our model provides a
total organic carbon flux of 0.29 Tg per year down to 3000 m off the NW
African upwelling region between 5 and 35° N. Simple parameterisations of
remineralisation and sinking rates in such models, however, limit their
capability in reproducing the flux variation in the water column. |
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