Microplastic load and distribution in the respiratory and digestive systems of some commercial fish species in the southwestern coast of Bangladesh

Microplastic (MP) pollution poses a growing threat to marine ecosystems and human health, particularly in coastal regions with intense fishing and commercial activities. This study investigated the occurrence, characteristics, and sources of MPs in three commercially important fish species, Otolithoides pama (Poa), Glossogobius giuris (Bele), and Euthynnus affinis (Little Tuna), collected from the Kuakata coast in the northern Bay of Bengal (BoB). A total of six individuals (two per species) were analyzed to provide a baseline understanding of MP contamination. MPs were identified in both gills and gastrointestinal tracts (GITs) using microscopy and characterized by size, color, shape, and polymer type. Descriptive statistical analysis revealed that the mean MP abundance was highest in G. giuris (0.54 ± 0.08 particles g-1), followed by O. pama (0.18 ± 0.03 particles g-1) and E. affinis (0.018 ± 0.005 particles g-1). Most MPs were small (0.05-0.25 mm) transparent fibers, likely derived from fishing gear and textile sources. Ten polymer types were identified using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy, where nylon, polystyrene (PS), and polyvinyl chloride (PVC) were most prevalent, indicating multiple pollution sources such as fishing activities, packaging materials, and household waste. Exploratory correlation analysis suggested a negative association between fish size and MP load (r = -0.84 to -0.94). Although limited by a small sample size, exploratory PCA and HCA revealed species-and tissue-specific patterns, indicating multiple pollution sources. The findings serve as an initial baseline for MP contamination in coastal fish from Bangladesh and underscoring the need for expanded, seasonally replicated monitoring and improved plastic waste management to safeguard aquatic biodiversity and food safety; however, the study's limitations, including a relatively small sample size and the omission of flesh (muscle tissue) analysis for MP contamination, mean the reported extent of the problem and potential risk to human consumers may be underestimated.