The health of the coral reefs has been steadily declining over the past few decades. Environmental pollution and rampant destructive fishing practices damage the delicate corals. Nutrients seeping into the sea from agricultural areas cause the algae in the sea to increase in volume. This causes smothering of the corals and leads to decrease in size of coral reefs. Quite recently, the decrease in the coral populations has been attributed to a dozen or more deceases that attack corals. Many of these diseases were unknown until recently.
Coral reefs have also been affected by bleaching. Bleaching is the discoloration or loss of symbiotic zooxanthellae. In 1979 and 1980, several incidents of coral bleaching occurred at reefs around Okinawa, Easter Island, northeast Australia, and the Caribbean Sea. Outbreaks of bleaching also occurred in 1982 and 1983, including reefs off east Africa, Indonesia, and the west coast of Central and South America, and from 1986 to 1988 in areas such as Taiwan, Hawaii, Fiji, Mayotte Island, and the entire length of the Great Barrier Reef. The most extensive bleaching episode ever documented occurred in 1998 and affected reefs in the Indian Ocean, Pacific Ocean, Red Sea, Persian Gulf, and Caribbean Sea. In some areas 100 percent of the corals were bleached and more than 70 percent of the corals died. (Smith 2003)
Taking the rapidly declining coral population and the vulnerability of corals various measure are being taken in many countries to prevent further damage to the corals. Some of these steps include strict vigilance on fishing practices, artificial plantation of corals etc. Methods of coral community rehabilitation included coral transplantation and translocation, reattachment of coral fragments, providing artificial substrata, coral cultivation, prevention measures, and mitigation of damaged coral reefs. (Yeemin No date)
Artificial plantation of corals
There are two methods of artificially cultivating corals. The first one involves reattachment of fragmented corals to the sub-stratum using special cement. Fragmentation is a significant process of asexual reproduction in many scleractinian corals, especially branching corals. Due to fragmentation the corals are unable to get a holding on the sub-stratum and so they get dispersed. The dispersal causes a substantial decrease in the population. Though this method is in experimental stages, according to Yeemin and Chunabundit (No date), "The methodmay be applied in certain areas in order to rehabilitate coral communities and facilitate coral reef development."
The second method involves transplantation of corals. In the area where the corals are to be transplanted, an initial survey is carried out to ensure that the conditions are suitable for growth of corals. Corals from other coral reefs are transplanted to the area. The primary objectives of coral transplantation are to improve reef quality in terms of live coral cover, biodiversity, and topographic complexity. Stated reasons for transplanting corals have been: 1) to accelerate reef recovery after ship groundings, 2) to replace corals killed by sewage, thermal effluents or other pollutants, 3) to save coral communities or locally rare species threatened by pollution or land reclamation, 4) to accelerate recovery of reefs