So I missed all the initial discussion, but apparently the New Scientist published a critique of a recent book by Matt Ridley called “The Rational Optimist”, who amongst other things believes that ocean acidification is ‘greatly exaggerated’. You can read his response to the critique over at his website. It’s an entertaining dialogue, but here’s where his argument starts to fall down:
My source was the Herfort et al 2008 paper, which Ridgwell says is irrelevant, because of its experimental design. That’s his opinion, which others in the field do not share (Read more)
His opinion? As Chris Langdon pointed out, the Herfort paper it is not relevant to predicting what will happen in the future. What Ridley misunderstands is that it isn’t based opinion. Journalism is based upon opinion, science is based upon fact. Here’s what Chris Langdon had to say about the Herfort paper:
In their experiments, they increased both the bicarbonate and the carbonate concentration. This is what happens when you add sodium bicarbonate to seawater. They have no way of knowing if the increase in coral calcification was due to the increase in the bicarbonate or the carbonate.
In the real world, and in the experiments that I and others have performed, the bicarbonate concentration is increased by 13 per cent and the carbonate concentration is decreased by 40 per cent. When you do this the calcification of the corals is observed to decrease.
Here’s what we had to say about the Herfort paper back in June 2008:
Herfort’s experiment focused on the effects of increasing bicarbonate concentrations on rates of photosynthesis and calcification of coral reef organisms. I hear some of you ask: “But, is that not the same as ocean acidification?” Well, in a nutshell – no. Ocean acidification is the result of declining pH caused by the uptake of atmospheric CO2. Herfort et al. kept their pH (the parameter that determines acidity) constant at 8.2 across all treatments. This also means that Herfort’s results are totally irrelevant to the major problems of ocean acidification – (1) carbonate saturation state and (2) acidosis of cellular mechanisms such as photosynthesis.
The lowered pH from ocean acidification leads to low concentrations of carbonate ions, the building blocks of all marine calcifying organisms, which can lead to critically low rates of calcification and even shift to net rates of calcium carbonate dissolution. Also, the proper functioning of cellular mechanisms such as photosynthesis are sensitive to pH change, so keeping pH constant would not capture those stresses.
Bottom line, Herforts’ experiment did the opposite of any realistic future scenario: by keeping pH constant while increasing bicarbonate (HCO3-) concentrations they boosted carbonate ion (CO3=) concentrations and thereby rates of calcification, and ignored any effects of acidosis. Idso et al (2008) is another sad example of uninformed propaganda, running with one of two sentences from a study they do not comprehend – and then leaping to their own naive conclusion that the overwhelming amount of good science predicting negative effects of ocean acidification, is simply alarmist (Read more)
Matt Ridley concludes with:
In conclusion, I rest my case. My five critics have not only failed to contradict, but have explicitly confirmed the truth of every single one of my factual statements. We differ only in how we interpret the facts.
Interpreting the facts? Oh well. I guess opinion sells books! See this paper released today in Science (Ocean Acidification Unprecedented, Unsettling) by Richard Kerr:
As hydrogen ion concentrations go up, more and more of the ocean’s carbonate ions—the building block of all carbonate shells and skeletons—combine with hydrogen ions to form bicarbonate, driving down the concentration of the essential carbonate. Organisms have a harder time extracting the carbonate they need from the surrounding water. In a compilation of controlled acidification studies, marine chemist Scott Doney of the Woods Hole Oceanographic Institution in Massachusetts and his colleagues found that all 11 species of tropical coral studied under falling pH slowed their aragonite production. Among noncoral calcifiers, most also slowed their carbonate building, though a few, such as certain coralline red algae and echinoderms, increased it.
It’s also worth pointing out that there are LOTS of similarly poorly argued points in Ridley’s rebuttal. Just a few that really made me shake my head:
There are reefs in the Persian Gulf, which proves that corals can stand high temperatures already if given time to acclimatize.-
This completely ignores the diversity of corals and symbionts in the Persian Gulf vs. the center of reef diversity. It also assumes a continuous gradual increase in temps, rather than an increasing frequency of extreme events that we’re actually seeing.
Reefs will just expand to where it’s warmer-
There’s lots more to the patterns of reef distribution than just temperature. He’s assuming there are larvae to recruit and that other parameters like aragonite saturation and nutrient loads are also suitable in these cooler areas, which often isn’t the case.
In acidic water mussels just grow slower-
That’s great to know but irrelevant to what will happen to coral reefs. Experiments have clearly shown that at pHs much higher than those found where the mussels were growing, corals stop calcifying altogether. Even if they did still manage to calcify at half the current rate, net reef growth would be negative, which would be a death sentence for coral reefs.
The pH of the oceans was lower in the past-
Yes, and those periods of low pH also tend to coincide with the disappearance of reef builders for a few million years and often with the extinction of the dominant reef builders altogether. How much lower has the pH been during the reign of modern scleractians? Not much, except for the ~12-16 million year gap in reef building.
…I could go on, but I won’t