Occurrence of microplastics in commercially harvested shrimps (Penaeus monodon) captured from Madu Ganga Estuary, Sri Lanka.

Abstract

Microplastics (MPs), plastic particles smaller than 5 mm, are environmental pollutants and have become an environmental threat. This study investigated the abundance of MPs in Penaeus monodon (Tiger Prawn) in Madu Gaga Estuary for the first time in Sri Lanka. Three shrimp traps (Jakotu) were selected from the river mouth to upstream, at a distance of 500 m from each other. Ten shrimp, three water samples (5 L), and three sediment samples (1 kg) from each site were collected. The gastrointestinal tract (GIT), gills (GL), and hepatopancreas (HP) of the shrimp were acid digested separately to extract MPs. Sediment samples were density separated by air venting through a saturated CaCl2 solution. Water samples were filtered over a 10 μm mesh and treated with 30% H2O2. The total MP abundance/shrimp from site 1 (70.22±11.28) was significantly higher than from sites 2 (52.90±11.64) and 3 (43.82±8.60). Microplastics abundance was significantly higher in GIT and GL than in the HP of shrimp. The abundance of MPs (MPs/L) in water from site 01 (15.60±1.64) was significantly higher than that at sites 2 (11.33±1.10) and 3 (11.00±1.06). MP abundance in sediment (MPs/kg) from site 1 (153.77±11.93) was significantly higher than at the other two sites. Results suggest site 1, near the river mouth, was the most polluted site by MPs. Fibers were the most abundant MP type at all sites. Black was the predominant color in fibers and fragments, but transparent particles were predominant in films. Small (<250 μm) MPs were significantly high in all samples. Polypropylene was the only polymer type identified with enough accuracy using FTIR analysis; however, the identification of other polymers could not be confirmed as the accuracy was low. So further studies are needed to identify the sources of MP. As P. monodon is a vulnerable organism to MPs, further research is needed to determine the consequences of human consumption of P. monodon captured from wild environments that are contaminated with microplastics.