A global atlas of artificial light at night under the sea

The impacts of artificial light at night (ALAN) on marine ecosystems have emerged as a focus for ecological light pollution research in recent years, yet the global prevalence of ALAN in underwater marine ecosystems is unknown. We have derived a global atlas of ALAN throughout the marine water column that will accelerate our understanding of its sources and environmental impacts. At a depth of 1 m, 1.9 million km2 of the world’s coastal seas are exposed to biologically important ALAN, which equates to around 3.1% of the global exclusive economic zones. This area decreases to 1.6 million km2 (2.7%) at a depth of 10 m, and to 840,000 km2 (1.4%) at 20 m. The most heavily exposed regions are those that experience intensive offshore development in addition to coastal urbanization. The atlas highlights that ALAN as a global change issue is not exclusive to land but is also widespread in the world’s underwater habitats at irradiances that elicit biological responses in marine organisms.