Microplastic Contamination of Four Important Commercial Fish in East Coast of North Sumatera Province, Indonesia

This study aims to identify microplastic pollutants of four important commercial fish (Johnius borneensis, J. macropterus, Osteomugil engeli, and Sardinella fimbriata) in the east coast of North Sumatra Province, Indonesia. The study was conducted from May to December 2022 in Langkat, Deli Serdang, Serdang Begadai and Batu Bara Regency, Indonesia. Microplastic analysis was conducted at the Biology Laboratory, Faculty of Mathematics and Natural Sciences, Universitas Negeri Medan, Indonesia. The microplastic extraction process was started by inserting the target fish organs into 10% KOH solution (1:10 ratio), then incubated for 12 hours at 60°C. Furthermore, the decomposed fish organs were filtered using Whatman No. 540, assisted by a vacuum machine; then the filter results were incubated at 50°C for 5 hours so that the liquid on the filter paper evaporated. The results of the analysis of microplastics in four fish species showed that the highest prevalence value was in O. engeli and J. borneensis reaching 98%, followed by S. fimbriata 92%, and J. macropterus 87%. Based on the total microplastics analyzed by species, J. borneensis had the highest value, reaching 513 particles, followed by S. fimbriata, 472 particles, O. engeli, 433 particles, and J. macropterus, 279 particles, where each intensity value reached 5.23, 5.13, 4.42, and 3.21 microplastics/fish. The results of microplastic analysis showed that the most dominant transparent color was found in O. engeli and J. borneensis, with values ​​reaching 35% and 30%, while in S. fimbriata, black color reached 33%, and in J. macropterus, brown color reached 38%. Furthermore, from a total of 1,697 microplastics from 4 fish species, the highest size found was in the size range of 105–500 μm reaching 55% with details of 31% film, 20% fiber, and 4% fragment.