Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Biogeosciences, 7, 2613-2624, 2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
07 Sep 2010
Ballast minerals and the sinking carbon flux in the ocean: carbon-specific respiration rates and sinking velocity of marine snow aggregates
M. H. Iversen1,* and H. Ploug1,** 1Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
*now at: Faculty of Geosciences and Marum, University of Bremen, Klagenfurter and Leobener Strasse, 28359 Bremen, Germany
**now at: Stockholm University, Dept. of Botany, Lilla Frescativägen 5, 10691 Stockholm, Sweden
Abstract. Recent observations have shown that fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material) and organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. Hence it has been hypothesized that incorporation of biogenic minerals within marine aggregates could either protect the organic matter from decomposition and/or increase the sinking velocity via ballasting of the aggregates. Here we present the first combined data on size, sinking velocity, carbon-specific respiration rate, and composition measured directly in three aggregate types; Emiliania huxleyi aggregates (carbonate ballasted), Skeletonema costatum aggregates (opal ballasted), and aggregates made from a mix of both E. huxleyi and S. costatum (carbonate and opal ballasted). Overall average carbon-specific respiration rate was ~0.13 d−1 and did not vary with aggregate type and size. Ballasting from carbonate resulted in 2- to 2.5-fold higher sinking velocities than those of aggregates ballasted by opal. We compiled literature data on carbon-specific respiration rate and sinking velocity measured in aggregates of different composition and sources. Compiled carbon-specific respiration rates (including this study) vary between 0.08 d−1 and 0.20 d−1. Sinking velocity increases with increasing aggregate size within homogeneous sources of aggregates. When compared across different particle and aggregate sources, however, sinking velocity appeared to be independent of particle or aggregate size. The carbon-specific respiration rate per meter settled varied between 0.0002 m−1 and 0.0030 m−1, and decreased with increasing aggregate size. It was lower for calcite ballasted aggregates as compared to that of similar sized opal ballasted aggregates.

Citation: Iversen, M. H. and Ploug, H.: Ballast minerals and the sinking carbon flux in the ocean: carbon-specific respiration rates and sinking velocity of marine snow aggregates, Biogeosciences, 7, 2613-2624, doi:10.5194/bg-7-2613-2010, 2010.
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