Acting as the reef's 'gardeners,' the sea urchins feed on the algae that compete with ... both the corals and the sea urchin populations never fully recovered, with repeated mortality events ...

Sea urchins feed on the algae that compete with the corals ... following the notorious 1983 sea urchin population collapse there, which led to the catastrophic phase shift of the coral reef.

Sea urchin is a delicacy in many parts of the world ... where farmers are now feeding their urchins with greens.