Microplastic abundance, size distribution, spatial variation and ecological impact in Fenneropenaeus indicus across coastal regions of Sri Lanka

Abstract

Macroplastics generated from anthropogenic activities undergo degradation, breaking down into smaller particles, typically less than 5mm in size, known as microplastics (MPs). Microplastics are a significant contributor to ecosystem contamination by impacting both terrestrial and marine environments. Fenneropenaeus indicus (Indian white shrimp), a prominent seafood crustacean in the Indo-Pacific region, plays a crucial role in marine food webs and global seafood markets. The MPs in one hundred and fifty shrimp tissue samples were collected between December 2022 and January 2024 from ten coastal sites representing five major coastal regions of Sri Lanka: the Western, Northwestern, Northern, Eastern, and Southern coasts. MPs in the samples were initially characterised using a stereomicroscope, with subsequent polymer identification conducted using micro fourier transform infrared spectroscopy (μ-FTIR). A total of 292 MPs were identified in the gastrointestinal tract and gills. The mean abundance (±SD) of MPs in Indian white shrimp was 1.86±0.73 items/g, with respect to the weight of the gastrointestinal tract and gills. Based on the microscopic observation of MP colours, blue MPs were the most prevalent in both the gastrointestinal tract and gills, accounting for 62.3% and 60.4% of the total observed colours, respectively. A total of three polymer types were identified through μ -FTIR analysis, including rayon, polyester and cellulose. Rayon was identified as the predominant polymer type in the analysed samples. The identified rayon polymer particles commonly used in the textile manufacturing industry, are presumed to derive from laundry effluents in domestic wastewater, while other detected polymers likely originate from packaging materials and other anthropogenic sources. The findings of this study revealed a statistically significantly higher concentration of MPs in the gastrointestinal tract compared to the gills (Wilcoxon-Signed Rank test, p < 0.001). The study provides evidence of statistically significant variation of MP contamination in the Indian white shrimp, Fenneropenaeus indicus , across different sampling sites (ANOVA, p = 0.001). This issue raises serious concerns, with potentially grave implications for food safety and the delicate balance of the food web. The cascading effects could disrupt ecosystems, threaten the integrity of the food supply, and pose serious risks to public health.