The complex circulation for both atmospheric and ocean affects the pathways of floating marine debris (MD). The aim of this research was to define the MD trajectories in the Indonesian boundary seas. The Lagrangian particle method was applied with oceanographic factors and debris classes based on 1 to 3% windage class. The simulation was applied during the Northwest and Southeast Monsoon period. On the basis of the obtained findings, the debris trajectory patterns were indicated to vary in the two monsoons. In the northern part of Indonesia, all neighbouring countries were affected, especially those near the boundaries. In the southern part of Indonesia, most of the debris headed west towards the Indian Ocean. MD was mostly transported by the ocean currents and monsoonal wind and ended up in the coastal area. Some debris was also still floating in the open ocean after three months. This study concluded that marine litter not only polluted Indonesia water, but also the neighbouring countries.

Oil spill phenomena in the ocean possess a very serious threat to ocean health. On the ocean surface, oil slicks immediately start to spread and mostly end up in the ecosystem. Furthermore, it could threaten the organisms living in the ocean or impact nearby coastal area. The aim of this research was to investigate the trajectories of oil spill based on a real accident in the Java Sea. Tracking oil spills using satellite images is an efficient method that provides valuable information about trajectories, locations and the spread intensity. The objective of this study was to periodically track the trajectory of the oil spill from the Karawang incident using Sentinel-1 Synthetic Aperture Radar (SAR) images. Pre-processing of the images consisted of radiometric and geometric corrections. After the corrections, SAR images were mapped and plotted accordingly. To understand the oil spill trajectories in relation to the oceanic processes, the ocean current pattern map and surface wind roses were also analysed. The processed images from July to October 2019 show a trajectory dominated by the oil spill layers movement towards the west to northwest from the original location along with a decrease in the detected oil spill area over time. The identified trajectories of the oil spill followed the ocean current pattern and surface winds. Thus, these two parameters were considered to be the main factors responsible for the oil spill drift.

Marine Protected Areas (MPA) is an area that potentially poses stress from outside such as human activities and ocean pollution. One of the global issues that threat ecosystems include MPA is ocean debris. The aim of this paper is to assess vulnerability of MPA based on the trajectory of debris affected by oceanographic condition. Three MPAs were chosen in the Java Sea region including: Seribu Islands National Parks, Biawak Island Conservation Area, and Karimunjawa Islands National Parks. The data provided by The Hybrid Coordinate Ocean Model surface current and Global Forecast System surface wind were used to determine the trajectory of the debris. We simulate the ocean condition in two monsoons. The results showed that debris floating around the MPAs have a potential of reaching beaches inside the MPAs and have different patterns between the monsoon. Furthermore, in Seribu Islands and Karimunjawa Islands which are designated as National Parks, the debris managed to land in the most crucial zones, Core Zone and Buffer Zone. Modelling of marine debris, such as the one used in this study can be used to inform authorities regarding the landing points of floating debris to create better management decisions in battling global marine debris issues.

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