Microplastics in mangrove sediments of Northern Aceh, Indonesia: abundance, vertical distribution, characteristics, and their relationship with sediment grain size.

Mangrove ecosystems play a vital role in supporting aquatic organisms by providing food sources, shelter, and spawning grounds. However, microplastic contamination has emerged as a significant environmental threat that may disrupt the ecological functions of these ecosystems. Unfortunately, studies investigating the vertical distribution of plastics and their relationship with sediment grain size in mangrove environments remain limited. Hence, this study aimed to investigate the abundance, vertical distribution, and characteristics of microplastics, as well as their relationship with sediment grain size in the mangrove sediments of Northern Aceh, Indonesia. A total of 40 sediment samples were collected and analyzed from eight mangrove areas across five sediment layers. The results showed that the abundance of microplastics in the sampling areas ranged from 210 to 440 items/kg dry weight. Higher concentrations of microplastics were observed in the upper layer (0-10 cm) (p < 0.05). Particles smaller than 500 μm, predominantly black and fragment-shaped, were most common. Polyethylene and polypropylene were the dominant polymers identified, followed by nylon and polystyrene. Microplastic abundance showed a significant correlation with sediment grain size, particularly with granules, very fine sand, and clay fractions. In contrast, a significant negative correlation was observed between microplastic abundance and the percentage of clay.