[A-HW27] Biodiversity, nutrients and other materials in ecosystems from headwaters to coasts

[AHW27-P13] Variations in nutrients from Ciliwung River to the coastal Jakarta Bay, Indonesia

*Mitsuyo Saito¹, Shin-ichi Onodera¹, Anna Fadliah Rusydi², Iwan Ridwansyah², Aldiano Rahmadya² (1.Graduate School of Advanced Science and Engineering, Hiroshima University, 2.Research Center for Limnology and Water Resources, National Research and Innovation Agency (BRIN), Indonesia)

Keywords:Ciliwung River, Jakarta Bay, Nutrients, Spatial variation

Jakarta, located on a coastal alluvial plain in Indonesia, is one of the Asian megacities. According to previous studies, it is estimated that the load of biochemical oxygen demand (BOD) from lands to sea is so large in Indonesia. Therefore, it is necessary to conserve river and marine water environments by confirming nutrients characteristics from a river to the coastal area. However, species, seasonal and spatial variation, and sources etc. of nutrients have not been clarified. In this study, we aimed to confirm the present status and spatial variations of
nutrients in Ciliwung River which flows from volcanic mountains to Jakarta bay via central Jakarta. River water
samples were collected at 20 sites located from upstream to downstream in dry season and in rainy season in 2024. Water samples were analyzed for nutrients and particulate nitrogen and carbon. These results suggest that organic pollutants accumulated on riverbed during dry season were flushed out at a beginning of rainy season and organic decomposition occurred significantly in a rainy season due to increase of oxygen supply. Since flushing of pollutants at a beginning of rainy season would affect to coastal environments, it is necessary to estimate them.

Acknowledgement: This research was supported by Asia-Pacific Network for Global Change Research Project (No. CRRP2019-09MY-Onodera, PI: Shin-ichi Onodera), JSPS Fund for the Promotion of Joint International Research (Fostering Joint International Research (B)) (No. 21KK0192, PI: Shin-ichi Onodera) and JSPS Fostering Joint International Research (A) (No. 20KK0262, PI: Mitsuyo Saito).