Coral growth in Western Australia found to be thriving in warmer water

Feb 03, 2012 by Bob Yirka report
Coral Reefs

(PhysOrg.com) -- As most people are well aware, global warming isn’t just about the atmosphere, it’s about rising ocean temperatures as well. And like increases in the atmosphere, scientists aren’t really clear on what impact such temperature increases will have on the oceans. One such impact most researchers thought was well understood was the bleaching of coral reefs. As ocean temperatures rise and become more acidic, coral reefs tend to slough off the algae that grows on them, causing them to slowly die. Now however, new research by a team from the Australian Institute of Marine Science, has found that coral reefs off the western shores of the Australian continent are not only not suffering from the increased temperature, but are apparently thriving, as the study they’ve published in Science describes, they have actually been growing faster in the past hundred years than prior to that time.

Research has shown as air temperatures rise, so too do ocean temperatures and as more carbon dioxide is released into the air, more of it is soaked up by oceans the world over, where it reacts to make carbonic acid. That in turn causes the water to have lowered pH levels which causes lowered levels of dissolved carbonate, which is what corals use to create their skeletons. The result seen thus far has been slowed coral growth.

It was those skeletons that the team looked at in the waters off Australia’s west coast, specifically those of Porites. As corals grow over time, they create layers of skeleton material that can be read like tree rings to discern not just their age, but how much the coral grew each year. By drilling into some of the larger , the team was able to trace the corals back hundreds of years. But it was the record of the last hundred that surprised them. Rather than finding slowed growth, such as has been seen with the Great Barrier Reef on the eastern part of the country, the growth in some areas of the southern sections had actually been growing at a faster rate than prior to the start of global warming.

After more thought, the team has come to the conclusion that what they’ve found makes sense. The increased growth rates were found only in the more southern corals where water temperatures are generally cooler than in the north, thus, an increase in temperature would be more conducive to coral growth. But only up to a point. They believe once temperatures reach those of the north, the same slowed growth patterns seen elsewhere will appear.

Interestingly, the team did not sample the ocean water at the sites where the coral samples were taken, and because of that, it’s not known if acidity levels in those areas that saw high growth rates had higher acidity levels or not.

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More information: Growth of Western Australian Corals in the Anthropocene, Science 3 February 2012: Vol. 335 no. 6068 pp. 593-596. DOI: 10.1126/science.1214570

ABSTRACT
Anthropogenic increases of atmospheric carbon dioxide lead to warmer sea surface temperatures and altered ocean chemistry. Experimental evidence suggests that coral calcification decreases as aragonite saturation drops but increases as temperatures rise toward thresholds optimal for coral growth. In situ studies have documented alarming recent declines in calcification rates on several tropical coral reef ecosystems. We show there is no widespread pattern of consistent decline in calcification rates of massive Porites during the 20th century on reefs spanning an 11° latitudinal range in the southeast Indian Ocean off Western Australia. Increasing calcification rates on the high-latitude reefs contrast with the downward trajectory reported for corals on Australia’s Great Barrier Reef and provide additional evidence that recent changes in coral calcification are responses to temperature rather than ocean acidification.

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User comments : 8

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mtc123
2.6 / 5 (10) Feb 03, 2012
Wow! Algorean 'scientists' won't like this.
Don't look for this story on the state run media.
kaasinees
2 / 5 (8) Feb 03, 2012
Wow! Algorean 'scientists' won't like this.
Don't look for this story on the state run media.

The jokes is on you, the title contradicts the article:
The increased growth rates were found only in the more southern corals where water temperatures are generally cooler than in the north, thus, an increase in temperature would be more conducive to coral growth. But only up to a point.

Second of all:
and because of that, its not known if acidity levels in those areas that saw high growth rates had higher acidity levels or not.

Thus a very inconclusive article.
more of it is soaked up by oceans the world over

They forgot to include that because of ocean pollution (including thermal pollution) and drying up of rivers by irrigation; the oceans chemistry and environment changes and as a result we have learned that ocean absorbs less carbon which is one of the many factors the ocean becomes more acidic.
JRi
1 / 5 (1) Feb 03, 2012
If it is the temperature that determines whether corals grow faster or slower, one would think that globally, the total coral growth rate would increase. Only the relatively narrow belt around equator being too hot would suffer.
DrSki
1 / 5 (4) Feb 03, 2012
Higher CO2 absorption by the ocean = increased BUFFER (bicarbonate) which is in constant equilibrium with the CO2. Acid added to the buffer will be neutralized, while the dissolved CO2 then adjusts (chemically) and MORE bicarbonate then becomes available.

LOGICALLY - more dissolved CO2 may be a good thing. If the coral are directly using the CO2 to then form carbonate-complexes 'shell', then MORE dissolved CO2 may be a good thing. If the coral are indirectly utilizing CO2 in the form of bicarbonates, then MORE acid should be beneficial as more bicarbonate will be available for the structure.

Measurements of dissolved CO2 and bicarbonate (pH, Temp., etc.) are EASY to perform, but should be PROSPECTIVE in order to answer the fundamental questions in the survival of the coral reefs. Having more questions after research has been published is good - but having fundamental questions unanswered is just poor research.
NotParker
1.6 / 5 (7) Feb 03, 2012
DUH! At the beginning of the Holocene the oceans were 130 meters lower than they are now. It didn't kill off the coral when oceans rose over the last 10,000 years, why would anyone think it would now ... except for brain dead climatologists.
pauljpease
5 / 5 (2) Feb 03, 2012
If it is the temperature that determines whether corals grow faster or slower, one would think that globally, the total coral growth rate would increase. Only the relatively narrow belt around equator being too hot would suffer.


Considering temperature only, that might be true. What we might see is a shift in coral reefs from tropics to higher latitudes. Unfortunately the death rate of the old reefs is much higher than the growth rate of the potentially new reefs, so ocean ecosystems will still collapse over timescales humans care about. Plus, this article didn't study acidification, which should increase all over the ocean and will probably ultimately become the dominant factor that affects coral growth. So the most probably scenario is a near complete loss of coral reefs within 100 years or so. Possibly within 30-50 years based on more recent acidification studies (it's worse than previously thought... climate change deniers won't like that).
NotParker
1 / 5 (6) Feb 03, 2012
Did coral reefs die out during the Holocene Optimum? The Minoan Warming? The Roman Optimum? The Medieval Warm Period?

No. And those periods were warmer than today.

As for acidification ... the oceans are not acid, won't be acid, and will drop 130m during the next ice age. Which is overdue.
DarkWingDuck
1 / 5 (3) Feb 04, 2012
This is a perfect example of how mainstream media distorts science and masks truth. Even as a science media, the writer misses the mark.

I think this "science writer" had issues translating. First, with increased CO2 uptake by the ocean, the dissolved carbonates would increase, not decrease.

Aragonite is a calcium salt which is by definition "insoluable" in water but does exist in very low amounts. The abstract, appearently misinterpreted by the writer here, suggests that the calcium salt solution would increase as the CO2 absorption increses thus lowering the pH to make the ocean more acidic and thus disolving more aragonite or increasing the dissolved CO2 mineral.

The Absract suggest that as the aragonite (dissolved CALCIUM carbonate) "saturation drops" as with lower temperature and higher pH. The writer communicated the right message with the wrong interpretation.