[ame=http://youtu.be/Pu0d101sMIk]Coral excavating itself after becoming buried in sediment (time-lapse #2) - YouTube[/ame]
Being buried alive is a major threat to immobile corals. Once buried, most corals die within a day. But it turns out that a few can actually save themselves from this otherwise certain death.
A new time-lapse video analysis published in the journal Coral Reefs, shows mushroom corals excavate themselves completely by rhythmically swelling up to five times their normal size.
Biologists buried this mushroom specimen under sand in an aquarium and then photographed it every 10 seconds for 20 hours. From their analysis of the shots, they determined that the pulses occurred every 10 to 20 minutes and that the coral inflated larger with each cycle.