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Warmer seas will stress coral

  • 05 September 2007

While the need to protect vulnerable people around the globe is widely recognised, people are less aware of the need to protect the vulnerable areas of the earth itself, including its rivers and oceans. 

Climate change is perhaps the greatest challenge confronting the international community. The study of oceans and reefs offers us insight into the consequences of not taking immediate action to combat this challenge.

On a recent trip to Heron Island, I visited the Heron Island Research Station (HIRS) and met with Dr Selina Ward, a scientist at the Centre for Marine Studies (CMS) at the University of Queensland, which operates the station.

Research from the CMS and the Australian Research Council Centre for Excellence for Coral Reef Studies (CoECRS) reveals that there are two main threats facing reefs around the globe: rising sea temperatures, which leads to coral bleaching, and increasing ocean acidification. The Great Barrier Reef is estimated to contribute $5.4 billion and over 60,000 jobs to the Australian economy. Worldwide, reefs support up to 200 million people. Dr Ward explained that the level of symbiosis between different inhabitants of the Great Barrier Reef is incredible. There is a high level of mutualism between the fish and the coral, and the HIRS has undertaken substantial research on symbiosis and climate change. Dr Ward explained: 'The most important symbiosis that we work on as a laboratory is the symbiosis between corals and single celled organism called zooxanthellae'. The zooxanthellae, which lives inside the coral is vital to the coral because the zooxanthellae photosynthesise, that is, they convert the sun’s light into energy, and then give the corals 95 percent of that energy. Dr Ward adds: 'They also provide glycerol to make fats and corals can’t get by without fats, and they assist with calcification that lays down the coral skeleton. And for the zooxanthellae, they get somewhere safe to live, they are protected within the cells of the coral, and they also get the nitrogen and phosphorus from the coral excretion. It’s wonderful tight mutualism that goes on.' However, warming sea levels, which cause coral bleaching, are threatening this relationship. Dr Ward explains: 'When the corals bleach [it] is due to zooxanthellae loss. If a coral undergoes some kind of stress, the photosynthetic apparatus of the zooxanthellae breaks downs and the zooxanthellae disappear from the coral tissue…Even when a coral is bleached completely white it will generally have at least 10 percent