Oil droplets are severely overlooked in risk assessments

Abstract Risk assessments of oil spills in the marine environment typically only address dissolved oil. However, oil droplets may adhere to some organisms and result in prolonged exposure not disrupted by diverging dispersal trajectories. Here, we present a framework for quantifying exposure of dissolved and droplet oil on adhesive fish eggs and implement the framework in a well-established numerical model for ocean, oil and fish eggs. Utilizing the model for a case study with an oil spill in the habitat of the world’s largest haddock stock, Northeast Arctic haddock, shows that droplets for a given concentration cover a much larger domain than dissolved oil. Impact assessments not taking oil droplets into account may therefore severely underestimate the impact of oil spills and result in decisions with inappropriate weighting of societal benefits to ecosystem impacts. Finally, our results call for more experimental work on the impact of oil droplets on marine species.