A research project in eastern Australia, conducted by a team that included Israeli scientists, has produced the first-ever evidence in a natural setting that greenhouse gases damage the development of corals. The results of its experiment, the first on corals in their natural environment, reinforced the hypothesis that increased acidity in sea water, caused by increased emissions of carbon dioxide into the atmosphere, may significantly damage coral reefs and even cause them to disappear.
The new study, published recently in the journal Nature, was carried out at the most important coral reef in Australia, the Great Barrier Reef. Among the participants were scientists from Australia, the United States and Germany, as well as three Israeli scientists: Tanya Rivlin and Dr. Kenneth Schneider of the Hebrew University of Jerusalem and Dr. Jack Silverman of the Israel Oceanographic and Limnological Research Institute in Haifa.
About a quarter of the carbon dioxide released every year from human activity reaches the oceans and makes ocean water more acidic. In recent years research carried out in laboratories has shown that increased acidity makes it difficult for corals to build their skeletons, which are made of calcium carbonate. The result is that coral reefs cannot develop and maintain the habitats they provide for a wide variety of other species.
The new research took advantage of the unique natural conditions in three lagoons of a coral island on the Great Barrier Reef. At low tide, these lagoons empty of sea water, but water continues to flow between two of the lagoons relatively slowly because of height differentials.
For 60 minutes a day over 22 days, at the lowest ebb of low tide during the daylight hours, the team drew sea water out of the high lagoon and added to it a small quantity of the strong base material sodium hydroxide. They channeled the new mixture toward the reef separating the two lagoons to simulate the acidic conditions in the sea before the beginning of the industrial revolution. They used florescent dye to follow the water and were able to estimate how much calcium carbonate was created by the corals while the water was flowing.
The team discovered that the rate at which the reef was being built rose by 7 percent with the addition of base to the water, which led the scientists to confirm that a rise in acid in the water impacts the rate of coral growth. According to Israeli team member Silverman, the rise in acidity impairs chemical processes that cause the creation of calcium carbonate in the corals’ bodies.
The team noted following publication of the article that acidity is not the only factor that can influence the growth of coral skeletons. Another important element is water temperature, which was lower before the beginning of the industrial revolution. Oceanic warming since then has badly impacted the corals and caused the widespread deaths of many reefs.
Coral reefs are known as the tropical forests of the ocean. They serve as a habitat and provide shelter and food for many species of marine plants and animals. A significant rise in acidity could cause serious damage to these ecosystems, which provide a livelihood to industries such as fishing and tourism. These new findings stress even more the immediate need to reduce greenhouse gas emissions in order to curb future damage to the reefs, perhaps allowing them to rejuvenate in the long term.