Microplastic contamination in commercial goldfish (Carassius auratus) of Yuehai Lake via Laser Direct Infrared Imaging (LDIR)

Abstract

Freshwater ecosystems are increasingly threatened by microplastic (MP) pollution, which can bioaccumulate in aquatic organisms and pose ecological and human health risks. However, information on MP contamination in freshwater lakes of inland northwest China remains scarce, particularly in locally consumed fish species. This study examined the occurrence, characteristics, and ecological risks of microplastics (MPs) in goldfish (Carassius auratus) from Yuehai Lake, Ningxia, China. Fifty goldfish were collected, and their gills, intestines, and liver were dissected and digested with nitric acid. MPs were extracted, purified, and identified using Laser Direct Infrared Imaging (LDIR) spectroscopy. MPs were detected in all tissues, with an average abundance of 43.2 ± 30.2 particles per individual. The gills exhibited the highest MP abundance, averaging 8.56 ± 3.78 particles per fish, followed by the intestines (2.64 ± 1.02 particles) and liver (1.76 ± 0.48 particles). Across all tissues, 22 MP polymer types were identified, with nine polymers—such as polyethylene (PE), polyethylene terephthalate (PET), and polyvinyl chloride (PVC)—present in all organs. MPs predominantly ranged from 20 to 100 μm, accounting for over 89% of MPs in all tissues. Fibers were the most prevalent morphology, comprising 61.69% in gills, 41.67% in intestines, and 68.29% in liver. Contamination factor (CF) values indicated moderate MP contamination in intestines (2.43) and liver (1.98), and considerable contamination in gills (4.72). Pollution load index (PLI) values exceeding 1 confirmed a general MP pollution burden in goldfish from Yuehai Lake. These findings provide critical baseline data for understanding MP contamination in inland freshwater environments and highlight the urgent need for targeted mitigation strategies.