Spatiotemporal variations in rural and urban beach microplastics accumulation in sediment along Sarangani Bay Protected Seascape, Mindanao, the Philippines.

This study evaluated the seasonal changes in the abundance and composition of microplastics in beach sands from urban and rural beaches along Sarangani Bay Protected Seascape, Mindanao, the Philippines. Sand samples were collected during the wet season (August) and dry season (December) using the quadrat-based protocol, and microplastics were extracted using the flotation method. A total of 110 microplastics were collected, with 87 found in the wet and 23 in the dry seasons. Urban beaches during the wet season (0.047 particles/g) exhibited significantly higher (p < 0.05) microplastics than during the dry season (0.015 particles/g). Microplastics are significantly influenced by seasonal changes, particularly during the rainy season when increased precipitation enhances water flow, facilitating the transport of plastic materials from land sources into aquatic environments, leading to higher microplastic concentrations. Fourier transform infrared spectroscopy (FTIR) analysis was employed to identify the chemical composition of the microplastics, revealing the primary polymers present, including polyester (23.1%) and polyethylene (23.1%). In urban areas during the wet season, both polyethylene and polyester were the most dominant polymer types, each comprising 37.5% of the total. In contrast, during the dry season, phenoxy resin emerged as the sole dominant polymer type. Rural areas displayed a more varied composition during the wet season, with three polymer types recorded: propylene, polyethylene terephthalate (PET), and butyl methacrylate, each at 33.3%. However, only PET was recorded during the dry season. The highest microplastic abundance was observed in urban beach sediments during the wet season, suggesting urban runoff sources. The findings highlight the influence of human activities on coastal plastic pollution, enhanced by erosion and wet deposition during the wet season. These are crucial to reducing the influx of microplastics, safeguarding the marine ecosystem, and ensuring sustainable coastal environments for future generations.