Coccoliths: Production, transportation and sedimentation

Abstract

The presence of coccolith ooze on the deep-sea floor and the well preserved suspended coccoliths in the undersaturated water column is explained by accelerated and communal sinking of coccoliths and coccospheres in small zooplankton's fecal pellets. The community structure in the euphotic layer will be replicated in the underlying thanatocoenosis with high resolution without significant time-lag between the production and the deposition. The euphotic biocoenosis of coccoliths drift only a few hundred kilometers at the maximum while they descend at the rate of more than 150 m per day through 5,000 m of water column where the variance of advection is approximately 5 km a day. At an Equatorial Pacific station it was estimated that 92% of coccoliths produced in the euphotic layer were thus being transported to the deep-sea bottom. Coccolithophore production provides several grams of calcite to a square meter of sea floor per year. Coccoliths do not undergo significant change during passage through copepods and other planktonic grazers. The membrane which covers a copepod's fecal pellet is coherent particularly in cold water. It protects contents from spilling and from dissolution and accelerates sinking rates by providing a smooth surface. The membrane is biodegraded rapidly in warm water and its contents exposed. As such naked pellets sink, coccoliths are shed and suspended in aphotic water. The majority of freed coccoliths will be dissolved in the undersaturated water column before arriving at the bottom. Approximately 8% of coccoliths produced were estimated to be remineralized in the water column at the above-mentioned station if Peterson's dissolution rate of calcite is applicable.