Gray's Reef


Live-Bottom Reef

Not all reefs are formed through coral growth and the gradual accumulation of limestone layers over time. The term live-bottom reef refers to the myriad of invertebrates, such as sponges, corals, and sea squirts, that form a dense carpet of living creatures on hard-bottom areas such as the rocky outcrops in Gray’s Reef National Marine Sanctuary. This reef structure was formed by the cementing and consolidation of marine and terrestrial sediments, which were originally deposited as a blanket of loose grains between six and two million years ago. This vibrant reef habitat is home to many fish and invertebrate species and is a place for loggerhead sea turtles to forage and rest.

a sea star lies near a reef
Photo: Greg McFall/NOAA