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Three methods were used to collect living and recently dead radiolarians and fecal pellets containing radiolarians--plankton tows for those in the water column, and gravity cores and box cores for recovery from surficial sediments. Deep Sea Drilling Project cores were used to study radiolarians from fossil sediments. Our techniques differ from previous studies by the investigation of individual skeletons and suggest that radiolarian skeletons are removed from the water column primarily by dissolution and, secondarily, by settling as individuals or via fecal pellets. Laboratory experiments suggest that metallic coatings help to protect the skeletons from dissolution in the water column and in sediments. Other factors of extreme importance are differential rates of settling thickness of the "radiolarian dissolution zone," productivity of overlying waters, amounts and ratios of terrigenous and authigenic sediment, presence of different water masses in the water column and at the sediment-water interface, degree of bioturbation, and chemical conditions at and below the sediment-water interface.
Paleobiologic developments such as the evolution of diatoms appear to be related to radiolarian conservation. The use of silica by diatoms may be partly responsible for the preferential dissolution of some Neogene radiolarians. Major changes in oceanic circulation appear to be related to such changes as the cessation of radiolarian preservation in the middle and tropical Atlantic during the middle Miocene.
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