Mythbusters: The Great Barrier Reef

Stella Cao November 16, 2011 1

Imagine the picturesque Great Barrier Reef, one the Seven Natural Wonders of the World, as a desolate wasteland of pale, white coral exoskeletons wrapped in muggy green algae. Though this may seem shocking, some scientists project that non-coral organisms will dominate this reef as early as 2050. Coral reefs experience natural dips in their populations but are biologically programmed to be resilient; they compose the backbone of tropical marine ecosystems. So how is it possible that these reefs are going to disappear?

Unfortunately, the reality is that unfavorable ocean conditions are likely to cause the eradication of persisting coral reefs. One factor contributing to these problems is global warming, which is causing a rise in ocean temperatures and disrupting the natural processes of the reefs. Coral reefs depend on a symbiotic relationship with zooxanthellae, photosynthetic microorganisms that live within the reefs and provide up to 90% of the energy required by them. These organisms also sequester carbon in the ocean and display the vibrant colors that we associate with coral reefs. However, stresses such as disease, acidification, or the slight rise in temperature cause coral reefs to expel the zooxanthellae and lose their pigmentation, resulting in a phenomenon known as coral bleaching. During this disruptive process, reefs will expose their white calcium carbonate skeletons, which are more susceptible to breaking and snapping. Mass coral bleaching has already occurred with an increase of only 1°C above the maximum temperature range. Though coral reefs are capable of recovering if temperatures return to normal levels, global warming has produced sustained changes; thus coral reefs have already started to disappear.

Although temperature fluctuations have caused the death of many coral reefs, the true risk of extinction comes from ocean acidification. Since the ocean is a large “sink” for carbon dioxide, an increase in greenhouse gases will directly influence the amount of carbon dioxide in the water. In turn, an increase in carbon dioxide increases the acidity of the oceans. Unfortunately for the reefs, the world’s oceans have absorbed about 30% of the excess CO2 that has been released to the atmosphere. With this increase in acidity, coral reefs are incapable of producing calcium carbonate to form their exoskeletons. This poses a significant problem as the hard calcium carbonate skeleton provides necessary protection and is the only means by which the coral reef can grow. To perpetuate this vicious cycle, the death of coral reefs actually exacerbate the ability of new coral to form since the decay of the skeletons release even more carbon into the oceans.


(Top) Healthy coral reefs support thriving and diverse marine life. Photo courtesy of coralcoe.org.au. (Bottom) In this photo, a once-thriving coral reef has transformed into rubble due to coral bleaching. Photo courtesy of Australian Institute of Marine Science.

So what will help preserve the remaining reefs? In Australia, the Great Barrier Reef Water Quality Protection Plan was created to protect a pocket of the Great Barrier Reef. The goal was to sustain a level of water quality in which the Great Barrier Reef can be preserved for a longer period of time. However, these organizations have not had a significant impact, especially when compared to the anthropogenic disturbances to the reefs. For example, fishermen use dynamite and cyanide to stun the fish that live in coral reefs, and tourists have also taken parts of the reef as souvenirs. In addition, coastal development has also destroyed this ecosystem by flooding the environment with cement and sediment.

Perhaps a new wave of attention drawn to coral reefs will encourage the public to protect the coral reef. Recent ecotourism has developed around observing and learning about the coral reef while not harming the dynamic ecosystem. In fact, a coral monitoring organization, Reef Check, has even begun to enlist volunteer scuba divers to collect data on coral reefs around the world. However, despite these efforts, coral reef populations will inevitably continue to decline with environmental fluctuations. Unless coral reefs somehow develop an instantaneous ability to adapt to the rise in temperature and acidification of the oceans, it is likely that the same thriving marine ecosystem will not exist in 2050. So if observing this natural beauty is on your bucket list, now is not the time to put off the visit because the Great Barrier Reef is likely to disappear in our lifetime.

One Comment »

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