Microplastics Contamination in Wild Fish Caught from Urbanised Sepanggar River of Kota Kinabalu, Sabah

Urban areas with high populations generate high levels of plastic waste from human activities, entering and raising microplastic levels in riverine systems. Microplastic contamination in rivers poses serious risks to fish through ingestion, toxicity, and bioaccumulation. Nevertheless, the paucity of previous studies on fish microplastic pollution in Sabah, Malaysia highlights the knowledge gaps in this area. Thus, this study aimed to assess microplastic pollution in fish from the urbanised Sepanggar River in Kota Kinabalu, Sabah. A total of 39 fish were caught from the river using gill nets (2-inch mesh), identified to the species level, and measured for total length, standard length, and wet weight. Samples were dissected into muscles and internal organs and digested with 10% KOH. Microplastics were then extracted using the density separation method in 5M NaCl and counted by type, colour, size, and polymer type. The present study demonstrated that microplastics were detected in 77% of fish (5.28 ± 6.51 items/fish) caught from the Sepanggar River. Small-sized microplastic fragments (54%), black (40%), and rayon (23%) were the dominant microplastics in fish. The Mann-Whitney U test revealed that microplastic abundance in internal organs (3.54 ± 3.63 items) was significantly higher than that in muscles (1.74 ± 5.10 items). The characteristics of ingested microplastics varied significantly by fish species, probably due to the different feeding habits and diets. Overall, fish in the Sepanggar River were moderately polluted by microplastics from domestic and industrial activities. Improved waste management is needed to monitor and reduce long-term microplastic contamination.