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Nannoplankton and foraminifera assemblages and their relations to bathymetry in Madura Waters


Nannoplankton and foraminifera assemblages were studied in eight surface sediment samples from Madura Strait and 33 surface sediment samples from open marine water north of Madura. Twenty-two nannoplankton taxa, 37 benthonic foraminifera taxa, and 16 planktonic foraminifera taxa were identified. Nannoplankton assemblages are very rare in water depths of less than 20 meters in the Madura Strait, being about 1 percent of the total sediment. These nannoplankton assemblages are made up of a single species, Gephyrocapsa oceanica. Planktonic foraminifera do not occur in these relatively shallow depths. However, benthonic foraminifera assemblages occur and are dominated by Florilus angulatus. In the neritic zone, which is indicated by accumulation of very fine-grained, nannoplankton assemblages are dominated by Gephyrocapsa oceanica, though Emiliania huxleyi and Florisphaera sp. are common components in the assemblages. Benthonic and planktonic foraminifera assemblages are increasingly more abundant and have higher diversity indices in the neritic zone. In shallow neritic open marine water, which is indicated by silt, nannoplankton assemblages are also dominated by Gephyrocapsa oceanica. The abundance and diversity index of both nannoplankton and foraminifera assemblages increase with increasing water depth. In water depths greater than 70 meters, neritic open marine foraminifera species are common. The occurrence of nannoplankton and foraminifera assemblages in the study area is closely related to bathymetry.

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