Warming Oceans May Push Australia's Coral Reefs South To Cooler Water - DPA

[hatrack]

Sydney - Global warming could send Australia's corals migrating south to where the waters are cooler, scientists said Wednesday. Researcher John Pandolfi looked at the fossil record and found evidence that coral reefs shifted south along Australia's west coast during a warm spell 125,000 years ago.

"Back then there used to be rich coral reefs dotted all along the West Australia coastline, from south of Perth to north of Dampier," Pandolfi said in a statement. "When the seas cooled with the onset of the most recent ice age, many of the corals contracted north."

Pandolfi, a researcher at the Centre of Excellence for Coral Reef Studies in Perth, said that there would be no similar migration on the continent's east coast because there was no suitably shallow water south of the Great Barrier Reef.

EDIT

Two million tourists visit the Great Barrier Reef in Queensland each year. According to Ray Berkelmans, a coral bleaching expert with the Australian Institute of Marine Science, all of Queensland's coral could be gone by 2025 if global warming keeps pushing up the water temperature. "Background temperatures have reached the level where every summer we are getting to dangerous conditions," he said.

EDIT

http://www.earthtimes.org/articles/show/167488.html

[RaleighNCDUer]

1. The problem is that it takes thousands of years to build a coral reef.

With the rapid warming we have today, extinction is liklier than migration.

[malakai2]

2. Yes and no

Reefbuilding corals can grow very quickly. Species that tend to exhibit branching or plating growth forms (some species exhibit various forms adapted to various current and light regimes) can grow on the order of 6 inches per year per branch. Other organisms also contribute to the formation of reef structure-coraline algae and sponges add mass, parrotfish scrape chunks of coral and algae off the reef to get at zooxanthellae and excrete the skeleton as sand.

If you were starting from scratch, with very little suitable substrate for embryonic coral, coralline algae, and so forth to attach and grow, temperatures deviated from the 72F-85F range in which calcium deposition exceeds erosion, and local currents were insufficient to bring food to sedentary organisms while carrying their waste products away, it would probably not be possible for reefs to arise in new areas. However, if you do have rocky substrates, preferably within the photosynthetic zone, with adequate temperatures and currents, all you'd need to grow a new reef would be embryonic colonies to settle out of the plankton. The expansion of these reefs toward higher latitudes would be reasonable. Seems like the biggest problems would be seasonal fluctuation in water temperatures and acidification of the oceans.

At the same time, there are a few genera, I'm thinking of Heliopora in particular, that reached their highest diversity during very warm geologic periods (also with high atmospheric CO2 concentrations and probably more acidic oceans) and in fact favor high water temperatures that would severely stress the more common contemporary reefbuilding species. I'd think that as large areas on continental shelves warm, Acroporids and the like would give way to Heliopora (currently monotypic), and that species would split into several new species to occupy the niches vacated by those moving poleward. There is probably a point at which even more thermophilic species would give way to a hot, dead sea, but I imagine selective pressures would quickly produce some organisms that could take advantage of the photosynthetic zone.