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.
