Abstract
Understanding how crude oil exposure affects fish reproduction is essential for assessing the ecological risks of oil spills in Arctic ecosystems. We exposed polar cod (Boreogadus saida) to water-soluble fractions (WSF) of weathered crude oil during late vitellogenesis and monitore the fish until spawning, using an integrated multi-omics and biomarker approach.
Oil-derived compounds (naphthalene, cyclic monoaromatics, and PAHs) accumulated in brain, gonad, and liver tissues. Hepatic EROD activity showed a dose-dependent induction followed by a rapid decline post-exposure, confirming exposure and biotransformation. In contrast, PAH metabolites in bile remained elevated, suggesting persistent metabolic processing of accumulated compounds. WSF exposure advanced spawning by up to 20 days and reduced fertilized egg diameter at the highest dose.
Transcriptomic analysis revealed early upregulation of detoxification genes in liver and disruption of lipid metabolism pathways in gonads. Lipidomic and proteomic analyses of spawned eggs confirmed altered lipid composition, reduced triglyceride synthesis, and compromised protein metabolism. In spawning-active females, the strongest transcriptomic responses occurred in gonads with activation of signaling pathways involved in cellular stress and apoptosis, and with distinct gene regulation patterns across doses, suggesting differential mechanisms between doses. Finally, pituitary and liver showed an overweight of down-regulated genes.
These findings highlight molecular disruptions along the pituitary–gonad–liver axis and provide insights into how crude oil exposure can impair reproductive success in Arctic fish species.