Oil remains central to the global economy, with demand projected to peak around 2030 or continue growing toward 2050 depending on policy trajectories. Ongoing developments such as the Johan Castberg field in the Barents Sea highlight continued petroleum activities in Arctic regions. Accidental releases therefore remain a persistent threat to marine ecosystems. While early life stages of fish are highly sensitive to crude oil hydrocarbons, adults are generally considered more robust, and next-generational effects remain poorly understood. However, impacts of crude oil exposure on sensitive biological processes in adult fish, such as reproduction, may still have profound consequences for population viability.
This thesis investigated reproductive effects of exposure to the water-soluble fraction of crude oil during late gametogenesis and intergenerational consequences using two ecologically important Barents Sea gadids with contrasting reproductive strategies. Experiments demonstrated reproducible, dose-dependent advancement of the spawning window following parental exposure. In polar cod, earlier spawning occurred without detectable impairment of gonadal structure, gamete quality, fertilization success, or sperm performance. However, altered plasma sex steroid levels and expression of genes involved in ovarian steroidogenesis indicated endocrine modulation. Sustained polycyclic aromatic hydrocarbon metabolite levels suggested prolonged internal exposure. Intergenerational assessments using controlled in vitro fertilization in Atlantic cod revealed pronounced maternal effect with offspring exhibiting reduced egg size and transfer of crude oil related compounds, marked downregulation of genes essential for early development, and reduced viability depending on the progression of the spawning season. Paternal exposure caused, minimal effects on sperm motility parameters, limited transcriptional changes but reduced early larval survival, consistent with delayed or epigenetic mechanism.
Collectively, these findings demonstrate that crude oil exposure during a sensitive reproductive window can shift spawning phenology and compromise offspring viability. Incorporating maternal- and paternal-mediated intergenerational effects into ecological risk assessments is therefore essential for accurately evaluating consequences of crude oil toxicity.