Multi-omics analysis reveals the toxic mechanism of ammonia-enhanced Microcystis aeruginosa exposure causing liver fat deposition and muscle nutrient loss in zebrafish

Microcystis aeruginosa and ammonia pollution are two important environmental stress factors in water eutrophication. Herein, we simulated environmental conditions to investigate the effects of chronic exposure (single and combined) to M. aeruginosa and total ammonia nitrogen (TAN) on lipid metabolism and muscle quality in zebrafish. Our results showed that M. aeruginosa and TAN significantly induced lipid deposition and tissue damage in the liver of zebrafish. Liver transcriptomic analysis revealed that M. aeruginosa and TAN disrupted the balance in lipid synthesis, decomposition, and transport, ultimately leading to hepatic lipid accumulation. Moreover, exposure to M. aeruginosa or TAN alone resulted in decreased crude protein content and increased lipid content in muscle, as well as disrupted muscle fatty acid composition. Metabolomic analysis of muscle revealed significant alterations in metabolites such as glycerolipids, glycerophospholipids and fatty acids. The co-exposure of M. aeruginosa and TAN had a more significant effect on liver lipid dysfunction and muscle quality deterioration in zebrafish. These findings provide valuable insights into the potential risks and hazards of M. aeruginosa and TAN in eutrophic water bodies subject to Microcystis blooms, and can help inform effective strategies for monitoring and managing these toxins in aquatic ecosystems.