There are over 400 species of corals on the Great Barrier Reef. Together they provide the foundations of the greater structure of the Reef. Living within these corals are microscopic organisms called zooxanthellae that nourish the coral host through photosynthesis and give reef building corals both life and colour. They are the life-blood of a healthy coral reef.
However, we now know that corals and their zooxanthellae live in delicate balance with their environment. Even the smallest changes in water chemistry can cause the zooxanthellae to be expelled from the coral, leaving the coral skeletons looking white or bleached (coral bleaching). Unless conditions return to normal, usually within 4-6 weeks, the coral will die.
The important link between increasing sea temperatures and coral bleaching has been known for more than a decade. However, scientific research has recently identified that increasing levels of carbon dioxide in the atmosphere from rising emissions are exacerbating coral bleaching. The absorption of carbon dioxide into the ocean is a natural process but excessive amounts of carbon dioxide in the atmosphere are pushing ocean acidity levels well beyond normal. Unfortunately, even the smallest change in the acidity of the water is enough to stress corals, causing them to expel the zooxanthellae.
Bleaching not only significantly impacts our coral populations; it also endangers many other organisms in larger reef ecosystems; invertebrates like starfish and anemones, fish, turtles and sea birds all depend on the corals for food and protection. On a larger scale, entire industries and communities rely on healthy reef systems to sustain them; the Great Barrier Reef alone is, even on the most conservative of measures, said to contribute over $6 billion to the national economy each year.
Coral bleaching events have been increasing in frequency over the last 20 years and are predicted to become still more frequent as water temperatures and carbon dioxide levels continue to rise. The predictions of the Intergovernmental Panel on Climate Change (IPCC) are grim at best, with forecasts that if nothing is done, as much as 97% of the Great Barrier Reef will bleach every year by 2050. We must take action now to protect the Great Barrier Reef.
To learn more about coral bleaching and the effects of climate change on the Reef, visit www.climateshifts.org