(Long-Spined Sea Urchin)


Healthy Diadema by Larry FernandezLearn about Diadema studies and restoration efforts in the Caribbean.

Through all the millennia, the long-spined Diadema sea urchins, and other herbivores, grazed the reefs and maintained the balance between coral and algae growth that allowed the corals to flourish and build the vast calcium carbonate structures of the reef.

 Diadema antillarum was once the most abundant and important herbivore on the coral reefs of the western Atlantic and Caribbean basin (Lessios et al. 2001). Among all the grazers, however, it was the long-spined sea urchin, Diadema antillarum, that was the keystone herbivore- the grazer that maintained the balance of growth and production between the coral and the algae. The mass mortality of this keystone species is described as the largest known marine mortality which resulted in catastrophic long-term ecological effects (Lessios et al. 2001, Knowlton 2001). Caribbean wide, D. antillarum mortality was greater than 97% (Lessios et al. 2001) and as a result, many Caribbean reefs have been dominated by macro-algae thereby smothering corals and inhibiting scleractinian recruitment (Edmunds and Carpenter 2001). These urchins have no commercial importance and their presence on the reefs was usually viewed as detrimental since their long sharp spines often caused injuries to scuba divers and complicated the activities of lobster divers. Once they were gone, however, and algae and coral disease decimated the reefs, it seems that only the reef ecologists have connected the loss of this keystone herbivore with the rapid decline of the tropical western Atlantic coral reefs.

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