[Coral-List] From a Keys farmer

Mark Eakin Mark.Eakin at noaa.gov
Tue Apr 3 12:27:34 EDT 2007

While temperature has an impact of carbonate ion availability, the  
far greater impact is from ocean acidification.  At the same time as  
CO2 is rising in the atmosphere, it is also being absorbed into the  
oceans.  In fact, just less than half of the anthropogenic carbon has  
gone into ocean waters.  As pCO2 (the partial pressure of CO2 in  
water) rises, the pH drops and carbonate ion availability drops.  We  
have already seen a pH drop of around 0.1 pH units and perhaps as  
much as a 10-15% drop in calcification since the start of the  
industrial revolution.

If anything, the warming will increase the availability of carbonate  
ions for coralline algal growth.  However, rising CO2 has a much  
larger effect.

Two general reports on the topic are the British Royal Society report:

and the US report on the Impacts of Ocean Acidification on Coral  
Reefs and Other Marine Calcifiers


On Mar 31, 2007, at 1:55 PM, terrasubaqua at peoplepc.com wrote:

> I would add a personal observation to the global warming discussion  
> based on ten years (~4 one week visits /yr) at the same spot off  
> Plantation Key.
> There is a fundamental chemistry link between the solubility of  
> calcium salts and water temperature, and we can see the local  
> biochemical link to crustose coralline algae (CCA) growth rate at  
> work each Fall. During this seasonal change, our aquaculture  
> substrate coquina rock gathers a nice coating of CCA over a period  
> of several weeks, commencing just as the water temperature drops.  
> The CCA appears to cover substrate much more rapidly in the Fall  
> months than at any other time of year, it's a very colorful  
> phenomenon and one we watch closely because CCA means added value  
> to our live rock products. We see that, with other variables held  
> to a (roughly) narrow range, the rate of CCA coverage growth seems  
> largely related to the degree of saturation of the calcium salts in  
> the seawater.
> This may have global ramifications, with global water temperatures  
> rising and considering the significance of calcium carbonate  
> deposition to the global sequestration of carbon dioxide. I wonder  
> how rising water temperatures affect the global deposition of  
> calcium carbonate? Though we might assume from controlled  
> experiments it would be detrimental, some biological factors such  
> as faster overall growth, reproduction rate, and/or coverage of CCA  
> in warmer water, or over water temperature changes spanning  
> particular ranges, might control natural feedback mechanism(s)  
> assisting CCA (and possibly other calcium carbonate 'bio- 
> consumers'?) in global- scale sequestration. Even though CCA seems  
> to grow much more slowly (if at all) in mid-winter at our site, the  
> warmer global water temperatures we encounter may also enhance  
> reproduction or otherwise benefit overall growth over the span of a  
> year. It would be interesting to see some large scale/long term  
> field research on this topic as
>   we struggle with the questions surrounding globally rising  
> temperatures and CO2.
> Tim Birthisel
> terrasubaqua.com
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C. Mark Eakin, Ph.D.
Coordinator, NOAA Coral Reef Watch
National Oceanic and Atmospheric Administration
Center for Satellite Applications and Research
Satellite Oceanography & Climate Division
e-mail: mark.eakin at noaa.gov
url: coralreefwatch.noaa.gov

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Silver Spring, MD 20910-3226
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The contents of this message are mine personally and do not  
necessarily reflect any position of the Government or the National  
Oceanic and Atmospheric Administration.

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