Microplastic contamination during the peak of upwelling in Maluku Sea, Indonesia

Microplastic pollution in marine environments has become a significant ecological concern. However, information on its presence in upwelling areas remains limited. This study investigates the concentration and characteristics of microplastics in both surface waters and deep-sea sediments of the Maluku Sea, a crucial upwelling zone in Indonesia. A total of 35 surface water and 5 deep-sea sediment samples were obtained during the Banggai Upwelling Dynamics and Ecosystem Experiment (BUDDE) cruise in September 2022 (peak upwelling period). Microplastics were recovered from surface water samples via vacuum filtering and from sediment samples through density separation, thereafter identified microscopically and analyzed for polymer composition using μ-FTIR spectroscopy. The results revealed widespread microplastic contamination, with an average concentration of 7.60 ± 3.18 items/L in surface waters and 304.23 ± 168.56 items/kg in deep-sea sediments. Microplastic concentration was higher in offshore sediments compared to coastal sediments, whereas surface water concentrations were greater near the mainland. Fragments (61.18 % in water and 50.67 % in sediment) and fibers (22.40 % in water and 49.33 % in sediment) were the dominant morphological shape, with polyethylene and tire-related polymers (ethylene propylene, chlorobutyl, and styrene-butadiene rubber) being the most prevalent. The study also documented a significant presence of small-sized microplastics (<1000 μm) and dark-colored microplastics (black and brown). These findings provide critical insights into microplastic pollution dynamics in upwelling regions, contributing to marine conservation efforts and informing sustainable fisheries management policies in Indonesia.