NOAA National Ocean Service Education: Crown-of-thorns sea star

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In addition to severe weather, corals are vulnerable to attacks by predators. As sessile adults, corals spend their entire lives fixed to the same spot on the ocean floor. Certain predators have evolved to take advantage of this. Large sea stars like this Crown-of-thorns (Acanthaster planci) slowly crawl over coral reefs, consuming all of the living coral tissue that they come into contact with.