The announcement of unprecedented coral bleaching in the Great Barrier Reef has rightly raised concern over the long term health of an Australian icon, but there may be cause for optimism which should support growing calls for regulatory reform at the state and federal level in Australia.
New research published by scientists from the UK and the Middle East has found that natural selection of existing biodiversity is vital to rapid adaption of coral reef ecosystems to climate change. The scientists made this discovery by analysing coral in the Persian/Arabian Gulf, which are able to survive in waters with high salinity levels and temperatures up to 35 degrees Celsius, conditions that corals in temperate areas could not. A symbiotic algae called Symbiodinium thermophilum was found to be present, having not been seen anywhere else before (symbiotic algae are crucial to coral ecosystem health). By analysing the DNA of the coral symbionts along 5000km of the Persian/Arabian Gulf coastline, it was found that one genetic variation of Symbiodinium thermophilum was exclusively present which had enabled coral growth to occur in that environment.
What is fascinating is that that particular population of Symbiodinium thermophilum was not always dominate in the area, only doing so around 15,000 years ago as a result of rising sea levels after the last ice age (and therefore warmer sea temperatures). The scientists suggest that that particular heat tolerant coral symbiont may have existed in small numbers due to the colder conditions which enabled other variants of the Symbiodinium thermophilum to prosper.
The key take away from this study is that maintaining genetic diversity in coral reef systems is vital for maximising the opportunity for adaption to something like climate change. This is a challenge for policy makers in Australia as the Australian and Queensland governments have previously been criticised for its management of the reef, culminating with the threat by the UNESCO world heritage committee to list the reef as ‘in danger’. While the Reef 2050 Plan was created as a response, the Australian Institute of Marine Science has stated that the Australian and Queensland Governments will not meet targets it has set for 2018 and also that there has only been modest changes in agricultural management practices, practices that have such an impact on the water quality in the rivers and coastal waters of the reef. To encourage change from the damaging agricultural management practices, appropriate legislative change and subsequent regulation is crucial to give the reef the best possible chance to adapt to climate change.
Paper citation: Hume et al (2016), Ancestral genetic diversity associated with the rapid spread of stress-tolerant coral symbionts in response to Holocene climate change, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1601910113
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