The seas have always been dimly lit by celestial bodies, but today the world’s oceans blaze with the light from cruise ships, oil rigs, and coastal developments. To gauge the impact on marine habitats, researchers used satellite images to measure the amount of light pollution across the world's network of marine protected areas (MPAs). They found that 35% of the world’s contiguous MPAs were exposed to artificial light in 2012, and light pollution was both widespread and increasing in a larger percentage of protected areas. Although increasing illumination was more common in MPAs associated with human activity, even those designated as strict nature reserves or wilderness areas, which have limited human intrusion, experienced increasing light—about 9% are experiencing increases in artificial light intensity, the team reports online before print in Conservation Letters. Because many marine species such as squid and zooplankton are guided by natural light patterns, the introduction of artificial light is likely influencing their behaviors and restructuring communities. (Similar impacts have been seen in terrestrial protected areas.) To cut down on ill effects, the researchers suggest using less damaging lighting—like avoiding blue lighting, which penetrates deeper in seawater—to minimize ecological impacts, and establishing "marine dark sky parks," similar to what the International Dark-Sky Association has done for terrestrial parks.