ROBIN - Interaction between mineral and sinking organic carbon

Remineralization of Organic particles in presence of Ballast mINerals

In the deep ocean, fluxes of particulate organic carbon (POC) and calcium carbonate are positively correlated,suggesting that CaCO3 could increase sinking particle densities and/or protect the organic matterfrom degradation by prokaryotes, the so called ‘‘ballast effect”.

We showed that the calcifyers aggregates were found to be moresensitive to degradation with increasing hydrostatic pressure than previouls y thought. Increased hydrostatic pressure also had a positive effect on particle aggregation, which may compensate for the effect of increased cell lysis.

Our results imply that in coccolithophorid dominated sinking aggregates, the ballasting and protection effects of coccoliths may collapse throughout the water column. The increased aggregation potential with pressure observed in these controlled conditions, may balance the loss of mineral ballast to a certain extent, although this needs to be confirmed in situ.