Mapping the sources and strands of marine debris via particle modelling and In-situ sampling approaches in archipelagic countries.

Marine debris (MD) is a global issue that remains unresolved in Indonesia where the accumulation of this kind of pollution poses a significant threat to the marine ecosystem and health of the ocean. Understanding the sources and locations of stranded debris is crucial in identifying the required regulations and mitigation strategies. This study used the hypothetical sources to identify the stranded debris along the coastline of Selayar Island and its surrounding seas. Using a combination of simulation and in-situ sampling methods, the simulation considered 13 hypothetical sources based on external factors such as river locations and surface ocean currents. This simulation result was then validated the simulation against beach litter observations and interview results with people. The results successfully mapped the sources and stranded MD in Selayar Island, indicating that the majority of MD originates from the island itself and the surrounding areas, influenced by oceanographic factors. The most frequently encountered locations of stranded MD are in the western coastal region including tourism areas and coastal ecosystem. Due to the oceanographic conditions, the stranded debris has varied quantities over the months, and higher in December represent the northwest monsoon (NWM) season, exceeding levels observed during the southeast monsoon (SEM). The study also identified that the main sources of debris are from Selayar Island and rivers from surrounding islands. This study also confirmed that oceanographic conditions such as surface ocean currents and wind pattern influenced the spreading of MD in Selayar Island. Due to the different ocean characteristics in different regions, a more detailed understanding and stranded of marine debris source which might provide more information for the explanation of the mechanism of marine debris pathways in Archipelagic Countries.