Destruction of radiolarian shells during sample drying and its effect on apparent faunal composition

Hokkaido University, Graduate School of Environmental Earth Science, Sapporo, Japan

Radiolarian concentration and faunal composition are compared between pairs of dried and wet sub-samples from 24 samples in sediment cores from the Japan Sea, in order to evaluate the alteration of radiolarian assemblages during the sample-drying process. Radiolarian shell count is reduced by nearly half after oven drying at 50 degrees C as well as at ambient room temperature. In contrast, the shell count is unchanged by freeze drying. The reduction in radiolarian test count is probably caused by contraction and consolidation of the sediment. The reduction in shell count is species-specific and results from the capacity of the shell to resist crushing owing to sediment contraction. Faunal composition definitely is altered by the drying process, especially in assemblages dominated by fragile species. The original faunal composition can be reconstructed from the observed faunal composition in dried material, based on the shell-strength of major species in a sample.

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