Coral bleaching
When heat stress makes corals expel the algae that feed and colour them, leaving them white and starving.
Also: mass bleaching
When the sea stays too warm for too long, corals push out the algae living in their tissues, turn white and begin to starve. If the heat passes quickly they can recover; if it lasts, they die and the reef is overgrown by seaweed. Fish that depend on live coral for food or shelter, such as many butterflyfish and damselfish, decline after bleaching. Mass bleaching has become more frequent as the oceans warm. In April 2024 the United States agency NOAA confirmed the fourth global bleaching event on record.