PLANKTONIC FORAMINIFERA ABUNDANCE AND ORIGIN POSSIBILITY ALONG THE INDONESIAN THROUGHFLOW

• Main Author: Romika Junita, Dynda
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69922
• Institution: Institut Teknologi Bandung

Foraminifera are a single-cell eukaryotic that forms a test during its life. After foraminifera dies, the test becomes fossilized in the sediment. Its high abundances and its distinctive shell morphology that is easy to be identified, resulting foraminifera is one of potential proxy for paleoenvironment, paleobiology, paleoceanography, and paleoclimate interpretation and analysis. Foraminifera are separated into two types following their life strategy, the planktonic and the benthic. Planktonic foraminifera live freely in the water column, and benthic foraminifera live attached to a substrate at the bottom of the water. Planktonic foraminifera, however, can be considered passive particles. Therefore, ocean currents carry their movement. Ocean currents influence planktonic foraminifera movements during the life and death phases before planktonic foraminifera are finally deposited in sediments. There have been many studies on the abundance of planktonic foraminifera in Indonesian waters, especially along the Indonesian Throughflow (ITF). However, an analysis of the origin possibility of planktonic foraminifera along the ITF has never been carried out. In general, an analysis of foraminiferal abundance will describe the ecological condition of the sample location where the foraminifera were collected. However, because the ocean currents influence planktonic foraminifera movements before its deposited in sediments, the abundance of planktonic foraminifera in sediment may originate from several thousands of kilometers away. Consequently, the analysis of planktonic foraminifera abundance may represent wider ocean regions according to the current pattern. Besides the analysis of the abundance and the origin possibility of planktonic foraminifera, the effect of water volume transport on the abundance of planktonic foraminifera is also interesting to be discussed. It is related to the life strategy of planktonic foraminifera, which is always in the water column during their life phase. A total of 6 surface sediment samples were used to analyze the abundance of planktonic foraminifera in the Sulawesi Sea, Makassar Strait, and Lombok Strait (2 samples from each location). The analysis was carried out quantitatively by calculating the total abundance (Ind/gr of dry sediment) and the relative abundance. The water volume transport was calculated using ocean current direction and velocity data integrated with depth. The origin possibility of iv planktonic foraminifera was estimated by associating the characteristics of planktonic foraminifera (morphology, habitat depth, lifespan, post-mortem sinking velocity) with the current velocity data. This analysis uses two decades (1992-2012) of ocean current simulated data from the Hybrid Coordinate Ocean Model (HYCOM). The planktonic foraminifera in this study were found abundant. A total of 18 species were identified. In the Makassar Strait, the abundance of planktonic foraminifera is 36.067 ind/gr. The abundance of planktonic foraminifera in the Sulawesi Sea and the Lombok Strait is not much different, it is 3.694 ind/gr and 3.235 ind/gr. Species Globigerinoides ruber has the highest percentage in all study areas. Based on the calculation of relative abundance, it can be seen that non-spinose planktonic foraminifera species are more abundant in waters with lower current velocities (>30%), while spinose planktonic foraminifera are abundant both in waters with higher currents velocity and lower current velocities. The effect of water volume transport on the abundance of planktonic foraminifera was analyzed by samples of the Makassar Strait and Lombok Strait. The results show that the greater the volume of water transport, the greater the abundance value of planktonic foraminifera. The origin possibility of planktonic foraminifera in the waters reaches hundreds of kilometers before being deposited in sediments (core site). The results show that the distance between the core site and the estimated origin location of planktonic foraminifera directly relates to the planktonic foraminifera lifespan and the average current velocity in the planktonic foraminifera habitat. The average current velocity shows that planktonic foraminifera in the Sulawesi Sea may be originated from 307 up to 782 km away from its recent location (core site). Planktonic foraminifera in the Makassar Strait may be originated from 313-789 km away, and in the Lombok Strait, which has the lowest current velocity, planktonic foraminifera may be derived from 129-258 km away from its current location.