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| Titel |
Not all calcite ballast is created equal: differing effects of foraminiferan and coccolith calcite on the formation and sinking of aggregates |
| VerfasserIn |
K. Schmidt, C. L. De La Rocha, M. Gallinari, G. Cortese |
| 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 ; 11, no. 1 ; Nr. 11, no. 1 (2014-01-09), S.135-145 |
| Datensatznummer |
250117109
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| Publikation (Nr.) |
 copernicus.org/bg-11-135-2014.pdf |
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| Zusammenfassung |
| Correlation between particulate organic carbon (POC) and calcium carbonate
sinking through the deep ocean has led to the idea that ballast provided by
calcium carbonate is important for the export of POC from the surface ocean.
While this idea is certainly to some extent true, it is worth considering in
more nuance, for example, examining the different effects on the aggregation
and sinking of POC of small, non-sinking calcite particles like coccoliths
and large, rapidly sinking calcite like planktonic foraminiferan tests. We
have done that here in a simple experiment carried out in roller tanks that
allow particles to sink continuously without being impeded by container
walls. Coccoliths were efficiently incorporated into aggregates that formed
during the experiment, increasing their sinking speed compared to similarly
sized aggregates lacking added calcite ballast. The foraminiferan tests,
which sank as fast as 700 m d−1, became associated with only very
minor amounts of POC. In addition, when they collided with other, larger,
foram-less aggregates, they fragmented them into two smaller, more slowly
sinking aggregates. While these effects were certainly exaggerated within the
confines of the rolling tanks, they clearly demonstrate that calcium
carbonate ballast is not just calcium carbonate ballast – different forms of
calcium carbonate ballast have notably different effects on POC aggregation,
sinking, and export. |
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