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Do not let the coral reefs become just part of the history lesson material for our children and grandchildren's generation
The incidence of coral bleaching or coral bleaching has actually been recorded since 1870. This phenomenon often occurs in some coral colonies or clusters of reefs in the tropics. The first report on mass coral bleaching took place in 1979, when the bleaching phenomenon actually occurred simultaneously across coral reefs in various regions. Global mass coral bleaching occurred again in 1997/1998 on an unprecedented scale. Almost every coral reef on earth is experiencing white. Furthermore, the frequency, scale and intensity of mass coral bleaching events have increased sharply over the last few decades. This phenomenon has been studied and is known to be triggered by a rise in global temperatures, which of course raises concerns about the future of coral reefs. In fact, coral reefs that have survived more than 1000 years, which has been able to survive the effects of floods, storms, and cyclones suddenly died from this phenomenon.
In some areas, 95% of the coral reefs are dead, while the Great Barrier Reef (GBR) loses nearly five percent of the entire coral reefs. In the following year it was only investigated and known how the coral bleaching mechanism and its interaction with the increasing trend of sea water temperature. A book written by Professor Ove Hoegh-Guldberg entitled Coral Bleaching, Climate Change and The Futures of the Worlds Coral Reefs provide a definite answer to what scientists have long been looking for that climate change is a key factor indicated as the cause this phenomenon
Coral is an animal that is ektotermik, that is living in isothermal condition with global temperature between 18-30C. During the summer, most corals are exposed to temperatures that are at the upper limit of their thermal tolerance. The coral metabolism rate and zooxantela (symbiotic algae on coral) will increase with temperature rise. Under normal circumstances, zooxantela will be able to photosynthesize using coral reef products (nitrogen and inorganic phosphorus) and convert them into sugars and proteins.
Furthermore, 95% of the photosynthesis proceeds are returned to the coral, so corals can grow, reproduce and form carbonate skeletons. The main problem is that one of the side effects of this process is oxygen. If the sea temperature exceeds the coral limits in full sunlight conditions, there will be an uncontrolled rate of reaction. In this condition the ability of zooxantela to process the energy of sunlight will come down sharply, so that eventually this energy is converted into dangerous oxygen radical. This molecule is highly reactive and begins to damage the host coral tissue.
Under these conditions, of course, the corals will experience pressure up to the point of damage and make the zooxantela break away from the reef into the surrounding waters. The first symptom of coral reef depression is the removal of algae from the polyps, and the changing color of the coral becomes more pale due to reduced or lost algae. If this condition occurs consistently within 24 hours, the entire coral tissue can whiten and the corals will certainly die if the zooxantela does not come back again.
The loss of zooxantela has a significant long-term effect on corals. The rate of coral growth declined markedly and its reproductive ability will not necessarily recover within two to four years. After bleaching, the coral is able to survive for several months without its symbiotic algae. However, its survival depends on how long the corals are exposed to rising temperatures, and on the quality of the surrounding water after the incident. Quite often small amounts of zooxantela are still alive in coral tissue or some return after their normal environment returns, so gradually recolonization takes place and over time, the corals can re-color and healthy.
Massive coral mortality can occur if corals do not recover after turning white, coral covered by algae or disease. The loss of zooxantela as the primary producer in this ecosystem has widespread implications in the long run. Initially resulted in the extinction of various fish species in the vicinity, and then impacted on other species at higher trophic levels such as sea birds. The corals live in a large geographical area and experience large temperature variations, providing evidence of reef adaptation to temperature.
In extreme places such as the Arabian Gulf, coral can survive in summer sea temperatures up to 36C, while in cooler areas of Lord Howe Island, Australia, the same coral species can whiten at or slightly above