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Sediments and Foraminifera Distribution in Response to Environmental Changes of Jakarta Bay in Last +- 150 years

Abstrak

The research covered a study about sediments and microorganism content in marine sediment to find out the environmental changes of Jakarta Bay. This shallow marine northern Jakarta is marked by shell fragment. Seventy-five samples from twenty cores of + 30 cm in length were taken from the depth of 2.1 – 30.1 m. The actual research was started by the collection of secondary data and samples. Laboratory analysis upon sediment samples were conducted to describe sediment texture megascopically and microscopically adopted some basic method to identify foraminifera. The 210Pb dating on samples were carried out to determine the age of sediments. The sandy silt, clayey silt, silty mud and silty clay deposited during + 150 years generally contain abundant benthic foraminifera besides ostracods and mollusk shell. The 78 benthic foraminifera species were identified in sediment samples. Asterorotalia trispinosa was the most commonly found species in marine samples we collected. It was found that the assemblages, abundance and diversity of benthic changes in accordance with fluvial and marine influence during deposition. Less abundance and diversity of foraminifera assemblages as well as typical of some opportunistic genera (Ammonia, Asterorotalia, Elphidium, Nonion and Quinqueloculina) indicated high fluvial influence from Citarum and Cisadane rivers. In open marine, the assemblages were composed over 90%% calcareous benthic forms. This favorable condition was recorded by both high abundance and diversity as well. During the deposition of this sediment sequence, the relative environment changes frequently occurred due to anthropogenic affinity.

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