A new study published in *Current Biology* reports that artificial light reaching coastal waters disturbs sleep in coral reef fish, with potential downstream effects for reef ecosystems. Researchers from Bar-Ilan University say the disruption occurs even at low levels of nighttime illumination, which spills into the sea from sources such as cities, ports, roads, and hotels. In experiments using blue-green damselfish, the fish exposed to artificial light sleep less and show more fragmented sleep. The study also finds changes in behavior that resemble a shift from night to day, including increased aggression and feeding at unusual hours. In addition to behavioral and sleep-pattern changes, the paper reports associations with biological markers linked to brain health, indicating cellular or physiological stress in the fish’s brains under artificial light exposure. The findings come with emphasis on locations such as the Gulf of Aqaba, where coastal development can increase light pollution. Together, the sources describe a pattern in which nighttime light alters both behavioral rhythms and brain-related indicators in reef fish, raising concerns about how widespread lighting could affect coral reef functioning.