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November 30, 2023

Coral reefs may survive changes in climate

By ANNE MCGOVERN | April 27, 2012

The future of the world's coral reefs may not be as grim as we think. A recent study conducted by researchers at the James Cook University in Australia took a look at the composition of various corals in the Great Barrier Reef and determined that the flexibility across species may allow corals to adapt to future changes in the ocean due to climate change.
A global increase in temperature as a result of the increase of greenhouse gases in the atmosphere (mainly carbon dioxide), is projected to cause not only a warming of the world's oceans, but also an increase in ocean acidification. The oceans act as carbon sinks, which means they absorb carbon at a faster rate than they emit it. Currently, oceans remove about 30 percent of anthropogenic carbon dioxide from the earth's atmospheres each year.
However, with ever increasing rates of carbon dioxide emissions, the oceans can only swallow so much. A side effect of carbon sequestration is the production of carbonic acids, and the more carbon dioxide oceans take up, the quicker the acid is formed. As a result, the overall oceanic pH level decreases, which in turn decreases the calcium carbonate production of many coral forming organisms. Acidification affects both the organisms building reefs, as well as the reefs themselves.
Originally, the health of a coral reef was determined by "total coral cover." However, the study's detailed look into the coral composition of 35,000 different colonies within the Great Barrier Reef discovered another factor that influences the overall ability for corals to survive: the distribution and number of adaptable species.
The yearly temperature fluctuations within the Great Barrier Reef occur on the same scale as predicted changes in conditions due to climate change. Between winter and summer, the ocean temperature fluctuates between 14.4 and 16.2 degrees Fahrenheit. The continual existence of corals within this region supports the claim that corals will be able to adapt to changing water conditions. However some special types of adaptation are what scientists consider to be their main saving mechanisms.
The presence of "warm genes" is one instance of an effective coral adaptation strategy. A study done on the same species of coral in Florida and Mexico found a genetic difference that allowed those in Mexico to survive unharmed in warmer waters. In short, the same species of coral was able to alter its genes to survive.
Another example involved the ability of some corals to survive in extremely acidic "submarine springs," which are areas with naturally low pH levels that mirror those of projected climate change levels.
Though we may rest assured that corals will not entirely disappear, the natural selection process will cause future reefs to look very different from those we are used to today. For example, the projected increase in mound-shaped coral types, and decrease in branch-like types, will make a much smoother and less elaborate looking reef. This change may also decrease the types and amount of marine fauna present in the reefs because of a decrease in nooks and crannies in which small creatures can hide.
Though the world's reefs may survive climate change, there are many other factors that threaten their survival. The most current and pressing issues to address include pollution and overfishing.

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