Abundance of Microplastics and Heavy Metals in the Riverine Shad (Tenualosa ilisha) from the Northern Bay of Bengal

Abstract

Microplastics (MPs) and heavy metals are significant pollutants affecting aquatic ecosystems in Bangladesh, with potential ecological and human health implications. This study investigates the occurrence and characteristics of MPs and heavy metal contamination in Tenualosa ilisha (riverine shad) from the Meghna River Estuary in the northern Bay of Bengal. MPs abundance varied from 17 to 38 particles/fish sample with a mean of 10 items/fish sample. MPs show variations in shape, size, and color. The occurrence of 189 MPs from the visually identified 210 microplastic-like particles were confirmed by µ-Fourier Transformed Infrared Spectroscope (µ-FTIR). In addition, 12 heavy metals, including arsenic (As), lead (Pb), cadmium (Cd), and iron (Fe), were quantified in different body parts (head, flesh, and bones). The concentration was found as As ˃ Fe ˃ Mn ˃ Cu ˃ Ni ˃ Pb ˃ Mg ˃ Se ˃ Co ˃ Zn ˃ Cd ˃ Hg in all parts (head, flesh and bones) of the fish samples. Significant differences in MPs and metal concentrations were observed based on fish size and body part. PCA analysis revealed distinct patterns of metal accumulation across different body parts and fish sizes, with larger fish showing higher levels of Pb and Cu, indicating prolonged exposure. Hierarchical clustering further highlighted similarities in metal distribution, grouping metals such as Pb and Cd due to common sources or pathways of accumulation. The results emphasize the potential health risks associated with consuming larger Hilsa fish due to the occurrence of elevated levels of heavy metal and MPs. To tackle this, the need for regular monitoring of both MPs and heavy metals in anadromous fish species in Bangladesh's aquatic environments is quite apparent.