by Thomas J. Goreau

Restoring the health of damaged reefs is a priority wherever possible. The steps required will vary according to the specific nature of the damages and site, but in general require speeding up coral growth and settlement and reducing stresses which have damaged the reef such as sewage and sediment. Some reefs needing restoration may have been damaged by forces not easily controlled such as crown of thorns starfish, hurricanes, typhoons, cyclones, tidal waves, earthquakes, volcanoes, or ships running aground on reefs. In this section we discuss how reefs can be restored from chronic stress from sewage and sediment, or from episodic damage such as hurricanes, ship damage, and crown of thorns starfish.

There have been many efforts to transplant corals into areas where reefs have been damaged. Success is very variable, but generally not very high. Corals which are not adequately attached will be damaged in storms. Corals transplanted into areas where water quality is inadequate will die just as the orginal reef did. For hurricanes, crown of thorns, or clean coral reefs hit by ships not carrying polluted cargo, natural recovery may be best, but where reefs are chronically stressed, natural recovery may be impossible. In general transplantation is too expensive to be practical except in very small areas.

The new technology of mineral accretion is unique because it creates conditions which speed up coral growth and promote settlement of young corals onto natural substrate. This advantage is sufficient to allow exceptionally healthy coral growth even in areas where surrounding reefs are dying or dead due to inadequate water quality. Mineral accretion allows restoration of reefs for the first time in areas where habitat is degraded, but requires continuous electrical power. GCRA has developed such projects in islands in the Indian Ocean, Caribbean, and Pacific. GCRA is actively developing projects to restore damaged reefs in cooperation with local environmental management groups in many countries, especially using solar panels or tidal current driven turbines.

In recent work in the Maldives we have developed methods to speed up the growth of living reef without transplanting or building artificial reefs. Wires used to stimulate coral growth were quickly overgrown by rapidly growing corals. This method will soon be used to speed up growth of a whole section of reef in order to protect beaches from erosion. Further details on reef restoration projects can be accessed in material in this section. Photographs and video showing dramatic results on artificial reefs in the Maldives, Seychelles, and other places will be accessible on this web site later this year. These clearly show that mineral accretion is the most successful method of restoring coral reef habitats known.

At sites where nutrients are excessively high and weedy algae have killed the reef, recovery will be possible (without mineral accretion) only in places where the nutrients are reduced below the excessive limits (see Water Quality page). After nutrient supplies are cut off, weedy algae rapidly die back and the freshly exposed rock beneath can now become a site for young corals to settle and grow. Evidence shows results are quick and effective but management must be sustained. There are two places known where algae overgrowth of reefs has been reversed. At the first, Kaneohe Bay in Oahu Island, Hawaii, corals were overgrown and killed by dense masses of weedy algae in the 1970s in a large bay into which raw sewage was discharged. After sewage discharge from cities and suburbs covering much of the watershed above the bay ended, nutrients declined, algae died back, and corals recolonized old reef areas again gradually over the next 20 years. Now, however, even though the large nutrient "point" sources of the sewage outfalls have been eliminated, the expanding population in the watershed now causes increasing levels of nutrients from "non-point" sources (running off fertilized golf courses, farms, and lawns, pavement and road runoff, etc) flowing into the bay, and now the same algae are begining to spread and kill corals all over again. We will provide a link to more information on this case by coral researchers in Hawaii.

The second case shows how rapid the effect of stopping a single nutrient source can be. Dragon Bay in Jamaica was cleaned up of excess algae in 1996 by effective management steps recommended by the Global Coral Reef Alliance and the Portland Marine Park Program. The area lies along the rough windward side of the island, where very high rainfall, lush rainforests, steep mountain slopes, and poor roads keep the area isolated and lightly populated. When first surveyed nutrients were only a few times above the minimum limits, and coral reefs and seagrasses were being killed by masses of weedy algae. Nutrient studies showed that there were two sources of nutrients in the bay, which were traced back to the sewage and laundry of a single large hotel which surrounded the small bay. Lack of animals which eat algae was not the problem because there were large schools of algae-eating fish in the bay because the hotel did not allow spearfishing and dense populations of spiny black algae-eating sea urchins, both rare in many other Jamaican reefs, yet these were unable to control the algae while nutrient inputs were high. GCRA recommended that sewage and laundry effluents, after secondary sewage treatment, should be used to water land plants, which by absorbing the nutrients as fertilizer, would prevent nutrients flowing into the sea and killing corals by overfertilizing algae. Instead of killing their reef and causing ear infections to their guests, the hotel now uses the treated effluent to water their lush landscape lawns, ornamental plants, bright flowers, leafy foliage plants, and flowering trees, while water lilies, water hyacinths, and other aquatic plants bloom in ponds, causing the minimum possible nutrients to enter the sea. When the nutrient flow was diverted from coral reef to land plants the results were immediate. Within weeks the dive shop noticed that the algae masses in the reef were dying back, and a few months later they were practically gone. A search for weedy algae then found only a few traces, mostly decaying clumps at the base of seagrasses mats. The reef, which previously had masses of algae overgrowing and killing the remaining corals, had become free of weedy algae, with corals in good health and recovering. Areas covered with dense weeds were replaced by a thin pink crust of good limestone algae, which cement-over dead coral and provide the best surface for young corals to settle and grow on. This area is now prime for reef recovery, and if nutrients can be kept low new corals will settle and grow and within a decade it may begin to look as luch as it had in the past. Although full recovery will take years because corals grow very slowly, this case shows that a reef which is steadily declining can be turned around and placed on the road to recovery almost immediately by ending excessive nutrient inputs to it. Details of this case can be accessed in the paper on Water Quality in the Port Antonio Area on the Water Quality page of this web site, and in Practical Reef Restoration, in this section. It shows that other algae overgrown reef can be cleaned up as long as excess human nutrient sources are eliminated and water quality is restored to levels safe for corals. This case only required a single source of pollution to change their waste management and clean up their environmental effects, but in most other reef areas far more, up to millions of separate sources, are contributing to the problem, so much larger scale action will be needed. Since algae overgrowth is a problem in every reef near more than a few people, these two successful examples need to be repeated in thousands of more localities before most human affected reefs can begin to recover on their own from any of the stresses they face, whether man-made or natural. If the water quality is not restored to clean reef conditions, natural restoration will be impossible, and only mineral accretion methods will be able to help restore corals and reef habitat.