How does rising atmospheric CO2 affect marine organisms?

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Effects of Ocean Warming and Acidification on Jellyfish
Winans, A.K. and Purcell, J.E. 2010. Effects of pH on asexual reproduction and statolith formation of the scyphozoan, Aurelia labiata. Hydrobiologia 645: 39-52.

The authors write that "scyphozoans have two main stages in their life cycles, the benthic polyps and pelagic jellyfish." The polyps reproduce asexually by budding polyps and through the process of strobilation, in which ephyrae (juvenile jelly fish) are produced by transverse fission." And, as they continue, "like many other marine invertebrates, jellyfish have statocysts, balance organs that enable them to sense gravity," and they say that "inside these statocysts are numerous statoliths of trigonal crystals of calcium sulfate hemihydrate that are formed during strobilation."

What was done
Polyps produced by medusae collected from the moon jellyfish (Aurelia labiata) in Dyes Inlet, Washington (USA) were arbitrarily assigned (18 each) to one of six treatments comprised of all combinations of two water temperatures (9 and 15°C) and three pH levels (7.2, 7.5 and 7.9), where they were allowed to develop under controlled conditions for 122 days.

What was learned
The two researchers report that "polyp survival was 100% after 122 days in seawater in all six temperature and pH combinations;" and because few polyps strobilated at 9°C and "temperature effects on budding were consistent with published results," they say they "did not analyze data from those three treatments further." At 15°C, there were also no significant effects of pH on the numbers of ephyrae or buds produced per polyp or on the numbers of statoliths per statocyst." However, they state that "statolith size was significantly smaller in ephyrae released from polyps reared at low pH."

What it means
Winans and Purcell conclude that "A. labiata polyps are quite tolerant of low pH, surviving and reproducing asexually even at the lowest tested pH," which degree of "acidification" is not expected to occur (even by climate alarmists) until about AD 2300. But to not come up empty-handed with respect to potential bad news, they note that "the effects of small statoliths on ephyra fitness are unknown," which means that the phenomenon could bode poorly for earth's jellyfish. On the other hand, they acknowledge that many organisms "may be able to acclimate or adapt to slowly changing pH conditions." And in this context they report that in Puget Sound "pH fluctuates from 7.2 to 9.6 in 2.4-meter deep water over the span of a couple of days," stating that "with such large pH fluctuations due to plant photosynthesis during the day and respiration at night, many organisms may be exposed to low pH conditions routinely." And, obviously, they are also successfully dealing with those low pH conditions routinely, as are an enormous amount of other marine organisms.

Reviewed 28 July 2010