Microplastics occurrence in water, sediment and edible small indigenous fish species in seasonal freshwater wetland ecosystems of Bangladesh.

Abstract

The widespread presence of microplastics (MP) in all matrices of the freshwater ecosystem is gaining attention globally due to their adverse impacts on the environment, wildlife, and human health. As the occurrence of MP in seasonal wetlands of Bangladesh remains unstudied, this study aimed to investigate the abundance, characteristics, and polymer types of microplastics occurring in water, sediment, and three small indigenous fish species (Puntius sophore, Mystus vittatus, and Channa punctatus, n = 480) in both fresh and dried conditions. The samples were collected from two locations within each of two selected wetlands (Chalan Beel: Boraigram and Gurudaspur, Haor: Mithamain and Astogram) in Bangladesh. The microplastics isolation procedure involved alkali digestion, wet peroxidation, density separation, and filtration. Polymer identification was carried out through FT-IR spectroscopy. The results revealed that microplastics were present in the gastrointestinal tract (GIT), gills, and muscle of all three fish species. The demersal fish, M. vittatus, had the highest number of MP in its GIT (both fresh and dried) in Chalan Beel, which was statistically higher than in Haor. Moreover, C. punctatus ingested the lowest amount of MP particles on a body weight basis. These findings indicated that the muscle of dried fish accumulated relatively higher microplastic content compared to fresh samples. Besides, the mean concentration of MP found in Chalan Beel was statistically greater than in Haor for both water and sediment. Among the three size classes, smaller MP (0.03-0.05 mm) were most frequently isolated from water, sediment, fresh, and dried fish. Additionally, a larger proportion of microfibers was found in all types of samples, particularly in fish. The MP detected in water and sediment were predominantly red and blue, whereas fish ingested the highest percentage of translucent MP. However, polyethylene (PE), polystyrene (PS), and polypropylene (PP) were the most common polymers present in these wetland ecosystems. Taken together, these results indicate that the seasonal inland wetlands of Bangladesh are polluted with microplastic contaminants.