Characteristics and potential hazards assessment of microplastic pollution in the feces of spotted seals in Bohai Sea

Microplastics are emerging pollutants that have been extensively detected in various organisms. However, reports on the presence of microplastics in marine mammals, especially small-sized microplastics (>20 μm), remain limited. Laser direct infrared imaging spectroscopy (LD-IR) was employed to detect and identify the polymer types, particle abundances, and morphological characteristics of microplastics in the feces of spotted seals (Phoca largha) living in the Bohai Sea. Furthermore, the potential hazards index (PHI) of microplastic pollution was calculated based on the hazard score of each polymer monomer. The results showed that the average abundance of microplastics in the feces of spotted seals was (2.96 ±2.06)items/g. Moreover, polyethylene (40.1%), polypropylene (27.8%), and polystyrene (15.9%) were the predominant polymer types identified in fecal samples. From the perspective of morphology, microplastics were composed of fragments (59.5%), fibers (25.0%), films (8.3%), and particles (7.2%). It is noteworthy that microplastics of small size, specifically those measuring between 20 μm and 150 μm, accounted for over 80% of the identified microplastics. The PHI of microplastics in the feces of spotted seals reached a notably high value of 610.23, which was largely attributed to polyurethane and polyvinyl chloride with relatively high hazard scores. The findings from this study not only enhance the scientific knowledge regarding microplastic pollution in the Bohai Sea, but also serve as a valuable reference for evaluating the health risks faced by rare species as a result of their exposure to microplastic contamination.