Microplastic pollution in the Indian Ocean: Fiber-dominated contamination and comparative bioaccumulation in Auxis thazard and Symplectoteuthis oualaniensis

Microplastics are minute particles that originate from the breakdown of large plastic materials or are put on as microbeads, creating critical hazards to ecosystems. Currently, there is a lack of research on microplastics (MPs) in the surface waters of the Indian Ocean and local marine organisms. This study investigates the abundance, composition, and potential ecological impacts of MPs in the surface waters of the Indian Ocean, and MPs in the bodies of two typical marine organisms in the local area were detected. The present study reveals significant spatial heterogeneity in microplastic (MP) characteristics across the Indian Ocean, with the Arabian Sea exhibiting notably higher abundances, greater lengths, and polymer-type diversity compared to surrounding waters. Results indicate a high detection rate of 93.75 % across 32 sampling sites, with an average abundance of 0.007 items/L, highlighting the widespread presence of MPs in marine environments. Rayon (RY), Polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) were identified as the predominant materials, likely linked to the extensive use of textiles and consumer packaging. The size distribution of MPs primarily falls within the 0-500 μm and 500-1000 μm ranges, with fiber-shaped MPs being the most prevalent, reflecting the release of synthetic fibers during washing processes. Analysis of MPs in biological samples revealed a high prevalence of RY, indicating potential bioaccumulation in marine organisms. Findings also showed that frigate tuna (Auxis thazard) exhibited a higher ingestion rate and MP content compared to purpleback flying squid (Symplectoteuthis oualaniensis), suggesting species-specific differences in feeding behavior and habitat utilization. Microplastic pollution negatively affects marine ecosystems and organisms by disrupting food chains, habitat contamination, and harming their health. These findings highlight the urgent need for improved monitoring and management strategies to mitigate the impacts of microplastic pollution on ecosystems and human health.