Thread: Ocean acidification effects on coral

A study documents the fertility problems of a common coral as ocean acidity rises in response to future rises in atmospheric CO2:

To determine whether OA threatens successful sexual recruitment of reef-building corals, we tested fertilization, settlement, and postsettlement growth of Acropora palmata at pCO2 levels that represent average ambient conditions during coral spawning (∼400 μatm) and the range of pCO2 increases that are expected to occur in this century [∼560 μatm (mid-CO2) and ∼800 μatm (high-CO2)]. Fertilization, settlement, and growth were all negatively impacted by increasing pCO2, and impairment of fertilization was exacerbated at lower sperm concentrations. The cumulative impact of OA on fertilization and settlement success is an estimated 52% and 73% reduction in the number of larval settlers on the reef under pCO2 conditions projected for the middle and the end of this century, respectively.

http://oceanacidification.wordpress....opora-palmata/

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Acropar palmata, commonly known as Ekhorn coral, is one of the most abundant and an essential species for reef building in the Caribbean.

We recently saw the Imax movie Under The Sea, (which in 3 D was stunning - highly recommended) and toward the end there was a segment on reefs and coral bleaching in which the narrator said it was due to the rising seawater temperature. No mention of acidicfication. I understood that the higher water temperature actually partly offsets (due to lower solubility) the increase in CO2 partial pressure in the atmosphere above the surface, so that acidification may not be as severe as it would have been if the temperature remained the same. If correct then the movie is misleading in attributing coral bleaching to higher water temperatures. Both are the result of increased CO2 concentration, but one is not the result of the other. Or do I have it wrong?

I think just about everything I've read attributes recent wide scale coral die-offs, usually called "bleaching," to water temperature increases.

Though surface acidity has increased by roughly a 30% in the past hundred years I haven't read much about the effects so far. Even with lower solubility, most models project surface water acidity to more than double sometime this century.

Yes, you're right. I should have checked my facts.

I understand there are in-situ experiments being conducted that add CO2 to water flowing over corals on the Great Barrier Reef off Australia's coast that seek to answer some of the questions around warming and acidification. I think one of the questions being pondered is whether they can colonise new locations that will have suitable temperatures in a warming ocean; acidification is looking likely to make that difficult. It doesn't look good for coral reefs or for a whole lot of marine life. Or for the viability of fisheries that depend on them.