Some coral reefs growing in a warming world
Cooler, marginal reefs don’t mind warmer water
While Austraia’s iconic Great Barrier Reef has been suffering bleaching and damage, the combined impact of warmer oceans agricultural runoff, a few thousand kilometers to the west, coral growth seems to be enjoying the changing climate.
The research, published on February 3 in Nature, shows that the Porites coral – so stressed in the Great Barrier Reef that a 2009 study showed its growth slowed by 13 percent – is growing at the same rate or even somewhat faster at sites offshore from Western Australia.
Researchers took core samples from the Western Australian corals covering a 110-year span, from 1900 to 2010. Corals lay down annual growth rings, making measurement of their performance year-to-year a relatively straightforward exercise.
Their research covered a 1000 km north-south stretch, giving them a wide sample of ocean temperatures.
And yes, according to the research team led by Dr Tim Cooper, “in the southeast Indian Ocean, marginal reefs have taken advantage of warmer conditions”.
The effect, the researchers found, is greatest in sites furthest from the equator, which lines up with what we already knew about corals. Porites isn’t all that viable in waters cooler than 19°C, so as warmer water moves further south, corals in formerly-marginal climates are starting to expand their colonies.
Interestingly, the research also suggests that temperature, rather than ocean acidification, has more influence on coral health. However, at some point Cooper believes acidification (so far not observed in the Western Australian waters) is likely to take hold and slow down coral growth rates.
The next challenge will be working out just what ocean temperatures become “critical” for corals. Great Barrier Reef researcher Professor Maria Byrne of Sydney University’s One Tree Island Research Station, told The Conversation that “all of a sudden it hits the wall and becomes too hot”.
Some of that research, according to the Australian Institute of Marine Science, will be conducted at a $AU35 million National Sea Simulator under construction in Townsville, Queensland. ®
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