Not all calcite ballast is created equal: the differing impact of coccoliths and foraminiferan tests on aggregate formation, character, and sinking velocity

Abstract : 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 700md−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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Article dans une revue
Biogeosciences, European Geosciences Union, 2014, 11, pp.135-145. 〈10.5194/bg-11-135-2014〉
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http://hal.univ-brest.fr/hal-00926400
Contributeur : Christina De La Rocha <>
Soumis le : jeudi 9 janvier 2014 - 15:17:45
Dernière modification le : jeudi 11 janvier 2018 - 06:22:24

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K. Schmidt, Christina De La Rocha, Morgane Gallinari, G. Cortese. Not all calcite ballast is created equal: the differing impact of coccoliths and foraminiferan tests on aggregate formation, character, and sinking velocity. Biogeosciences, European Geosciences Union, 2014, 11, pp.135-145. 〈10.5194/bg-11-135-2014〉. 〈hal-00926400〉

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