Saturday, February 4, 2012

Shocking News - Tropical Corals Like Warm Water

Butterfly Fish on Great Barrier Reef
A GOVERNMENT-run research body has found that the past 110 years of ocean warming has been good for the growth of corals spanning more than 1000km of Australia's coastline. The findings undermine predictions that global warming will devastate coral reefs, and add to a growing body of evidence showing corals are more resilient than previously thought - up to a certain point.

The study by the Australian Institute of Marine Science, peer-reviewed findings of which were published today in the leading journal Science, examined 27 samples from six locations from the West Australian coast off Geraldton to offshore from Darwin. At each site, scientists took cores from massive porites corals - similar to a biopsy in humans - and counted back to record their age in much the same way tree rings are counted. Although some cores extended to the 18th century, they focused on the period from 1900 to 2010.
Giant Clam (Tridacna) on Great Barrier Reef

The researchers found that, contrary to their expectations, warmer waters had not negatively affected coral growth. In fact, for their southern samples, where ocean temperatures are the coolest but have warmed the most, coral growth increased most significantly over the past 110 years. For their northern samples, where waters are the warmest and have changed the least, coral growth still increased, but not by as much.

"Those reefs have actually been able to take advantage of the warmer conditions," said Janice Lough, a senior AIMS research scientist and one of the study's authors.
Of course, at some point between the current temperatures, and 100 C is a temperature at which increasing temperatures will lead to a decline in growth.  Most temperature vs growth curves show an exponential ramp up with temperature (often expressed as a Q10) up to an optimum, and a fairly steep decline above that point.  Other things that could be going on is increased food from nutrient enrichment as Australia has become more developed.  Many corals are filter feeders (in addition to being photosynthetic by virtue of their zooxanthellae), and up to a point, nutrient enrichment could increase their food supply.

The pictures above are from our trip to Australia in 2009.  The last one, with the Giant Clam, was the last picture taken before my supposedly water proof point and shoot camera filled up with seawater.  I managed to rinse it out with freshwater and dry it, but it was never quite the same afterwards...

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