Ocean acidification update

It's been a while since ocean acidification has been mentioned here. There have been more studies reported, often with confusing or uncertain results:

* it was reported a month ago that tank studies with fish indicate that they grow bigger ear bones in more acidified water. This is the opposite of what was expected. Does it matter? No one knows, but there is speculation it might affect affect their navigation and orientation. Presumably, the studies to look into that are underway.

* The latest studies for coral are quite mixed. One tank study on a species of Mediterranean temperate coral indicates that it is not particularly sensitive to more CO2. (Although it is noted that this might be because it is relatively slow growing coral.) Yet, another study shows a mechanism for how a Hawaiian species can suffer more erosion under higher CO2. A third study, this time on an Atlantic species, indicated that it was indeed sensitive to decreased aragonite saturation (which is a consequence of increased acidification.) The overall picture then: still not good seems a fair conclusion.

Update: overnight, another paper has turned up indicating that coral around Bermuda:

...will experiences seasonal periods of zero net calcification within the next decade.... The Bermuda coral reef is one of the first responders to the negative impacts of ocean acidification, and we estimate that calcification rates for D. labyrinthiformis have declined by >50% compared to pre-industrial times.

* So, what about phytoplankton?, I hear you say. (Assuming you are still awake.) Well, this seems unexpected, but it seems some tank tests in coastal waters off Norway indicate that higher CO2 can lead to a phytoplankton bloom which then leads to more dissolved iron being in the water. (I don't quite follow how that works.) Anyhow, the abstract notes that this may be a good thing:

"If applicable to the open ocean this may provide a negative feedback mechanism to the rising atmospheric CO₂ by stimulating marine primary production."

Of course, whether this happens out in the deep ocean is not known. And are phytoplankton blooms in shallow areas necessarily a good thing? Certainly, some algal blooms are not good.

* On a related issue, if AGW does increase water temperatures, it seems that it will cause a significant shortening of the lifespan of many cold-blooded creatures:

“We were intrigued by the fact that that pearl mussels in Spain have a maximum lifespan of 29 years, while in Russia, individuals of the same species live nearly 200 years,” said Dr. Munch....

For the study, the researchers looked at lifespan data from laboratory and field observations for over 90 species from terrestrial, freshwater, and marine environments.

They studied organisms with different average longevities-from the copepod Arcartia tonsa, which has an average lifespan of 11.6 days, to the pearl mussel Margaritifera margaritifera, which has an average lifespan of 74 years.

They found that across this wide range of species, temperature was consistently exponentially related to lifespan.

“It is interesting to consider how cold-blooded species are likely to react in the face of global warming. Because of the exponential relationship between temperature and lifespan, small changes in temperature could result in relatively large changes in lifespan. We could see changes to ecosystem structure and stability if cold-blooded species change their life histories to accommodate warmer temperatures but warm-blooded species do not,” said Salinas.

It surprises me that a consistent relationship between temperature and life span was not noticed before.

* Someone should tell scientists how to write more clearly. There is a lengthy paper here about pH testing of the ocean near Hawaii over a number of years, but I have trouble working out exactly what it concludes. I think it indicates that ocean surface pH is dropping as expected (subject to seasonal variability), but the picture at depth was more complicated than they expected.