Seasonal heterogeneity and a link to precipitation in the release of microplastic during COVID-19 outbreak from the Greater Jakarta area to Jakarta Bay, Indonesia.

To reduce microplastic contamination in the environment, we need to better understand its sources and transit, especially from land to sea. This study examines microplastic contamination in Jakarta's nine river outlets. Microplastics were found in all sampling intervals and areas, ranging from 4.29 to 23.49 particles m-3. The trend of microplastic contamination tends to increase as the anthropogenic activity towards Jakarta Bay from the eastern side of the bay. Our study found a link between rainfall and the abundance of microplastic particles in all river outlets studied. This investigation found polyethylene, polystyrene, and polypropylene in large proportion due to their widespread use in normal daily life and industrial applications. Our research observed an increase in microplastic fibers made of polypropylene over time. We suspect a relationship between COVID-19 PPE waste and microplastic shift in our study area. More research is needed to establish how and where microplastics enter rivers.

Additions to the Indonesian crab fauna of the genus Mariaplax Rahayu Ng, 2014, and notes on Hexapus timika Rahayu Ng, 2014 (Crustacea, Decapoda, Brachyura, Hexapodidae).

Hexapus timika Rahayu Ng, 2014 is redescribed based on newly collected male and female specimens from Papua, Indonesia. Three new species from Jakarta Bay and Sunda Strait, Indonesia, are added to the genus Mariaplax, the richest genus in the family Hexapodidae, hitherto having 14 species. Mariaplax pitrai n. sp. has the carapace covered by small, closely-spaced tubercles and long ambulatory legs, resembling M. chenae Rahayu Ng, 2014 but easily separated by the position of female vulvae. Mariaplax hispida n. sp. is unique for the presence of short stiff setae on the outer face of the chelipeds and pereopods 2-4. Mariaplax sundaica n. sp. is characterized by the broad carapace, covered entirely by tubercles, the longitudinal grooves present only on the meri of pereopods 2 and 3. A key to the species of Mariaplax is provided.