Biologically mediated dissolution of calcium carbonate above the chemical lysocline?

We find a diverse but increasing amount of evidence to suggest considerable dissolution of calcium carbonate, perhaps as much as 60-80%, in the upper 500-1000 m of the ocean, well above the chemical lysocline. The same biolog ical processes that promote the rapid settling of carbonate particles (i.e. ingestion, digestion and egestion by zooplankton) as well as biologically mediated processes within flocculates and aggregates may be responsible - d irectly or indirectly - for much of this dissolution. The significance of s hallow-water dissolution of carbonate particles necessitates further resear ch into both its validity and, if true, specific causal mechanisms. (C) 199 9 Elsevier Science Ltd. All rights reserved.