Land-derived litter load to the Indian Ocean: a case study in the Cimandiri River, southern West Java, Indonesia

The first study related to the characteristics of the riverine litter was carried out at the mouth of the Cimandiri River in the southern West Java to provide a national database, as mandated in the Indonesian Presidential Regulation 83/2018 concerning the handling of marine debris. We examined floating riverine litter entering the South Java Sea at Cimandiri River outlets four times between December 2020 and October 2021 using a Thomsea 1 T trawl-net. The amount of litter collected tended to rise throughout the sampling period. Daily floating riverine litter released into the South Java Sea was estimated to be 285,931 ± 133.70 items or 307 ± 192.69 kg. Our monitoring data revealed no sampling period differences in litter release into the South Java Sea with no correlation with rainfall. Our data indicate that plastics are the most single abundant type of floating riverine litter entering the South Java Sea from the Cimandiri River, accounting for 99.92% of abundance (285,701 ± 133,464.75 items per day) or 97.78% in terms of weight (300 ± 181.99 kg per day) of the total litter collected. As the Cimandiri River is one of the major rivers with an outlet in the south of Java, this land-derived litter information could be an archetype for riverine ecosystems in the nation and region.