Corals spread south as oceans warm


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Corals along the western coast of Australia may head south as water temperatures rise, a new study suggests.

Scientists Benjamin Greenstein and John Pandolfi predict that global warming could trigger the diverse array of corals found in warmer, northern waters to spread and inhabit cooler waters in the south, currently home to just a small range of species.

Eventually, rich and diverse coral communities such as those found on the Ningaloo Reef could be seen in more temperate zones off the coast of Perth, 1200km to the south.

Coral movement

The authors report that species of the genus Acropora were recorded as far south as Rottnest Island, near Perth, for the first time in 1993; the sighting has been attributed to increased water temperatures in the area.

As global warming causes further increases in water temperatures, even more tropical-adapted corals could make the journey south into these temperate regions, and cause further diversification of the coral taxa found there.

Fossil evidence

The study compared the fossilised evidence of reefs from the late Pleistocene period with the coral composition of modern reefs along the coast of western Australia. This fossil evidence allowed the authors to make predictions as to the changes that could occur as a result of global warming.

During that warmer period, approximately 125,000 years ago, there was little difference between the composition of corals found in northern and southern reefs, and both would have hosted a diverse array of corals.

With the on-set of the most recent ice age, however, this composition changed.

The modern reefs currently found in the north continue to host a diversity of corals similar to those found during the Late Pleistocene period; meanwhile, the more temperate reefs in the south, where temperatures cooled, host a significantly lower diversity of species.

The future

The authors do warn that that the movements of corals south could only happen if an appropriate environment, other than just an increased temperature, can be found there.

They state that it is important to protect potential habitats from pollution and disease, while light and carbonate saturation levels, along with ocean acidification, could also impact.

For more information, see the paper: Greenstein, B.J. and Pandolfi, J.M (2008) - Escaping the Heat: Range Shifts of Reef Coral Taxa in Coastal Western Australia. Global Change Biology (OnlineEarly Articles).