Spatial and vertical distribution of microplastics in mangrove sediment in the southern Philippines

Mangroves in the Philippines are essential ecosystems that support a diverse array of species. It also provides various ecosystem services, such as trapping of pollutants, including plastics. Microplastics are one of the pollutants that pose a significant ecological threat. These can be retained in mangroves and in the deeper layers of sediments. Thus, this study aimed to determine and characterize the microplastics in different areas and sediment depths in the mangroves in Misamis Oriental (Alubijid), Surigao del Norte (Siargao), and Lanao del Norte (Bacolod) in Mindanao, Philippines. The abundance of microplastics in Alubijid recorded the highest values (750.00-2250.00 items kg^-1), followed by Siargao (250.00-750.00 items kg^-1) and Bacolod (83.33-583.33 items kg^-1). Microplastics were prevalent in the landward zone of Alubjid (1150 items kg^-1) and Bacolod (216.67 items kg^-1). The microplastic morphology varied depending on the site, with fragments being predominant in Alubijid (42 %), fibers in Siargao (56 %), and films in Bacolod (41 %). The dominant color was green in Bacolod (32 %), blue in Siargao (34 %), and transparent in Alubijid (33 %). Prevalent polymers were polypropylene in Alubijid (45 %) and Bacolod (36 %), and polyester in Siargao (33 %). Moreover, there were no trends in microplastic abundance, color, shape, and polymer type with depth among all sites. The characteristics of microplastics at the site may be attributed to the plastic use, economic activities, and solid waste management practices in the area. Our findings serve as baseline data leading to the formulation of strategies for microplastic impacts on mangrove ecosystems.