Risk assessment of microplastics in fish assemblage based on ecological preferences in an interconnected and polluted river system

Abstract

Risk assessment of microplastics (MPs) contamination in the assemblage of 15 important fish species with different feeding habits and microhabitats was studied in the River Ravi, Pakistan. Fishes with different feeding habits (omnivore, herbivore, and carnivore) and microhabitat preferences (surface, column, and bottom dweller) were sampled at Balloki and Sidhnai barrages during the post-monsoon seasons of 2019–2020. The gastrointestinal tract (GIT) of fish samples were found to be contaminated with MPs, with an average of 28.1 ± 20.7 MPs/individual and 26.8 ± 15.9 MPs/individual at Balloki and Sidhnai barrages, respectively. The surface dweller fish exhibited the highest MPs abundance, followed by the bottom dweller and column dweller. In addition, the highest MPs recovered from the omnivore generalist feeding group as compared to herbivores and carnivores. The fibers were the most abundant shape and generally made up of polyethylene terephthalate (PET) and polyethylene (PE). These PET and PE (low-density MPs) exhibit low hazard level, whereas high-density MPs with high hazard level and rarely present in GIT of sampled fishes. Based on MP polymer toxicity assessment, nine fish species were categorized in minor risk, two species in medium risk, and four species in highrisk group. Bottom dwelling fishes were at the highest plastic polymer risk level III due to the presence of a high density of MPs with high toxicity hazards. The high-risk prone fishes are under direct threat from MPs pollution, which may disrupt the ecological integrity of the river ecosystem and human health. The findings of the current study highlight the urgent need to address plastic pollution issues in River Ravi, and will be helpful for managers, researchers, and fisheries experts to mitigate this emerging challenge.speciesspecies