Microplastics contamination suppressed immune and health status in cage cultured Barramundi: An investigation on pollution sources, ecotoxicological impacts, and transcription of genes involved in detoxification

This study aimed to study the abundance and ecotoxicological consequences of microplastics (MPs) in cagecultured Barramundi from the Persian Gulf. The fish, water, sediment, and aquafeed samples were taken from 4 cage-culture sites and reference points in Bushehr and Hormozgan provinces. Gills showed the highest normalized, while muscles exhibited the lowest MPs concentration. Waters and sediments from cage-culture sites had significantly higher MPs than reference points. Raman spectrophotometry identified polyurethane, polyether, and polyolefin as prevalent MPs. Unexpectedly, larger fish had lesser number of MPs per unit of their weight. MPs contamination adversely affected fish health and immune. Specifically, fish with elevated MPs contamination exhibited significantly reduced levels of acetylcholinesterase and gamma-glutamyl transferase, and an increase in the activities of aspartate aminotransferase and alanine aminotransferase. The level of immune parameters including lysozyme, total immunoglobulin and complements were all decreased in fish with high MPs. A clear association was determined between MPs contamination and expression levels of cytochrome P450 1A1 and glutathione S-transferase in the liver. Low MPs biomagnification and hazard risk to the final consumer, but high threat to fish own health and immune were observed.