Coral Reef Restoration in the Bahamas

Many coral reefs throughout the Caribbean region are in poor shape due to overfishing, disease, smothering by algae and other factors. In some places, a coral reef exists in name only, as most if not all of the hard or stony corals have disappeared. These reefs are still beautiful, covered in soft corals, sponges and fish, but their long-term future is at risk unless hard corals return.

Shallow coral reef dominated by soft corals

Conservation efforts undertaken by Disney’s Animals, Science and Environment team is helping to reverse this trend for some coral reefs in the Bahamas. (All work has been authorized by the Bahamian government). The research capitalizes on the ability of corals to regrow from fragments or broken branches generated by storms. These coral fragments, found unattached on the seafloor, are collected and grown in a nursery for several months and then glued using epoxy onto a clear part of the reef. This ensures that no living, attached corals are harmed. Each coral fragment has a numbered tag so growth and survival can be monitored over time. Within a year, the coral will overgrow the epoxy and securely attach itself to the reef. This research focuses on two coral species: Acropora cervicornis or the staghorn coral, and Acropora palmata or the elkhorn coral.

Fragments of Acropora cervicornis (top) and A. palmata (bottom) glued onto the reef

Both Acropora corals are large branching species, important for the coral reef ecosystem by providing structure, food and nursery habitat. Both species used to dominate the shallow zone of Caribbean coral reefs, but these days are uncommon on most reefs.

Acropora palmata growing on a reef. This individual is relatively small, about 50 cm tall

All this good research is fruitless, however, unless environmental and biological conditions are right for coral growth and survival. One important animal that helps “protect” corals is Diadema antillarum or the long-spined sea urchin because it’s the main herbivore or grazer of algae. Without Diadema urchins, algae can overgrow corals killing them. Unfortunately, disease decimated Caribbean urchin populations in the 1980’s, and may reefs now have few if any urchins.

Algae are rare where urchins are common

An important component of this coral reef restoration research is to move urchins from reefs where they are common to neighboring reefs where they are not. Only a small number of urchins are moved from a “donor” reef so that it still has sufficient numbers of grazers. All moved urchins are placed in crevices so they’re protected from predators like triggerfish; urchins typically feed at night when most of their predators are asleep.

Diadema urchins are collected (top) and moved to reefs (bottom) where they are uncommon

Coral reefs throughout the Caribbean and elsewhere provide food, protection from storms and employment (e.g. tourism) for millions of people. But coral reefs need our help. Good management, sustainable fishing and responsible coastal development can all help conserve and protect coral reefs. On reefs where corals are rare or absent, coral reef restoration is needed.

Alan Duckworth, research scientist at Blue Ocean Institute, helped out with this research in June 2012.

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