Ecological effects and mitigation strategies for underwater noise from shipping activities

In recent years, concerns about the harmful effects of underwater radiated noise (URN) on marine ecosystems have grown. Shipping activities are the most significant contributors to continuous low-frequency noise (<1000 Hz). This noise overlaps with the hearing range of marine organisms, disrupting vital processes like foraging, mating and predator-prey interactions. Over time, such disturbances may lead to population declines and shifts in community dynamics. Ship-generated noise dominates low-frequency sound pollution in marine environments due to its persistent and far-reaching nature, affecting more organisms over larger areas than other noise sources. Despite its critical impact, there are no mandatory regulations to limit ship noise, aside from non-binding guidelines by the International Maritime Organization (IMO). This article explores the ecological impacts of URN, emphasising the role of ship propulsion systems in noise generation and its effects on marine life. It reviews mitigation strategies, including quieter propulsion technologies and operational practices and highlights the need for noise limits on new ships and improved maintenance for existing vessels.