Comprehensive assessment of microplastic contamination and ecological risks in mangrove sediments along the coasts of the Persian Gulf and Gulf of Oman

Despite the ecological importance of mangrove ecosystems, limited information exists on microplastic contamination along the Persian Gulf and Gulf of Oman coasts. This study investigated the occurrence, abundance, characteristics and risk assessment of microplastics in mangrove sediments along the coastlines of the Persian Gulf and the Gulf of Oman. Sediment samples were collected in 2023 from 24 stations across eight mangrove sites, with three replicates at each station. Microplastics were extracted by density separation, quantified, and classified by size, shape, and color. Microplastics were detected at all sampling stations, with abundance ranging from 38 to 1280 particle.kgdw. The mean microplastic abundance across all sites was 339.5 ± 19.1 particle.kgdw. Morphological characterization indicated that fibers and fragments were the predominant shapes of microplastics. Color analysis revealed that nearly half of the particles (49.0 %) were white or blue. Size distribution analysis showed that microplastics in the 100-500 μm size range were the most prevalent. Micro-Raman spectroscopy identified polyethylene as the dominant polymer type. Ecological risks were assessed using the Pollution Load Index (PLI), Polymer Hazard Index (PHI), and Potential Ecological Risk Index (RI), revealing a generally low to medium risk with significant spatial variability. This study highlights the widespread presence of microplastics in mangrove ecosystems of the Persian Gulf and Gulf of Oman and provides critical baseline data on ecological risks associated with microplastic contamination.