Evidence of microplastics in commercially harvested anchovies (Stolephorus commersonnii) collected from Matara and Galle districts

Abstract

Microplastics are tiny plastic particles less than 5 mm in size. They pose a major environmental problem when contaminating ecosystems. This study was conducted to determine the presence of microplastics in commercially harvested anchovies (Haalmassa) (Stolephorus commersonnii) collected from Galle and Matara districts. Whole fish were digested using 68% nitric acid digestion protocols and filtered through 20µm filter papers to isolate microplastics. Filter papers with isolated microplastics were observed under a photomicroscope to identify the colour, shape, and size. Identified microplastics were confirmed using Nile red staining techniques and polymer types were identified using FTIR-ATR. All 40 samples tested positive for microplastics. Microplastic abundance was significantly higher in the Galle sample (36.55±6.9 MPs/individual) than in the Matara sample (26.80±10.6 MPs/individual). No relationship between morphometric characters (weight and length) of fish and microplastic count inside the fish. Fragment was the most dominant microplastic type (79.2%). Black was the most prominent colour in micro fragments (64% and 53% in Galle and Matara, respectively) and blue was the most prominent colour in microfibers (40% and 61% in Galle and Matara, respectively). All the microplastic films were transparent. Red, orange, yellow, green and purple microplastics were also observed in small quantities. Microplastics were categorized into three size classes based on length:small (<0.5mm), medium (0.5–1.0 mm), and large (>1.0mm) with small being the most dominant size class. According to FTIR-ART, microplastics found in anchovies included ethylene vinyl acetate, ethylene butyl acrylate, high-density polyethylene, low-density polyethylene, medium-density polyethylene and linear-density polyethylene. This study provides solid evidence that commercially important anchovies are highly exposed to microplastic-contaminated environment and further research is suggested to understand the health risk posed by consuming whole anchovies.