MICROPLASTIC CONTAMINATION IN SELECTED SHRIMP FARMS AND ADJACENT WATER BODIES IN PUTTALAM DISTRICT, SRI LANKA

Abstract

Microplastics (MPs) have emerged as a widespread environmental pollutant, posing significant threats to aquatic ecosystems and human health. This study investigated the prevalence, distribution, and characteristics of MPs in shrimp farms, and adjacent lagoons (Puttalam, Mundel, and Chilaw) in Puttalam District, focusing on water, sediment, and shrimp tissues of Litopenaeus vannamei. Samples were collected from six shrimp farms and their associated lagoons, with MPs isolated and analyzed using density separation, alkaline digestion, wet peroxide digestion, stereomicroscopy, and Fourier-transform infrared spectroscopy (FTIR). Results revealed significant spatial heterogeneity in MP concentrations. Chilaw Lagoon exhibited the highest MP levels in water (3294.7 ± 153.6 MPs/m³) and sediment (962.3 ± 58.9 MPs/kg), attributed to anthropogenic activities such as urbanization, fishing, and tourism, while Mundel Lagoon showed the lowest contamination (1637.3 ± 159.2 MPs/m³ in water; 521.0 ± 38.2 MPs/kg in sediment), likely due to lower human impact and efficient hydrodynamic dispersion. Shrimp farms mirrored these trends, with ponds exhibiting higher MP concentrations than water inlets, suggesting accumulation due to restricted water exchange and inputs from feed and plastic equipment. MPs predominantly were fragments (35–36%) and fibers (29–31%), with darker colors (e.g., blue, red, black) being more abundant. Smaller MPs (0.10–0.50 mm) dominated across all samples, particularly in shrimp tissues, where the gut showed the highest contamination (10.32 ± 1.80 MPs/g), followed by gills and muscles (0.67 ± 0.10 MPs/g). A strong positive correlation (R² = 0.9025) between shrimp muscle weight and MP abundance, indicated bioaccumulation over time. FTIR analysis identified common polymers, including polyethylene, polyvinyl chloride, and polyethylene terephthalate, originating from packaging, fishing gear, and industrial waste. Mainly MP pollutions have come to shrimp farms from water sources and plastic materials which are used for aquaculture practices. MPs can be minimized using ground water or purified water before aquaculture practices and substitute materials can be used instead of plastics. The study highlights the warning signs for the shrimp industry of Sri Lanka as farms showed considerable MP levels, with implications for food safety and export quality. The findings underscore the need for improved waste management, regulatory measures, and sustainable practices to mitigate MP pollution in aquaculture. Future research should prioritize long-term monitoring and the development of biodegradable alternatives to reduce environmental and health risks.