1 Jan 2010, 10:58pm
Salmon and other fish
by admin

Carbon Dioxide, Acidification of the Oceans, and Tropical Marine Fish

Some folks contend that additional atmospheric CO2 will lead to “acidification” of the world’s oceans.

The word “acidification” has to taken with a grain of salt. The worlds oceans have a pH of ~8.2. That’s alkali, not acid. Neutral is pH 7.0. If the pH went down to 8.0, that would be still be alkali, but less so. That’s what the word “acidification” means in this context.

At any rate, some folks contend that it would be a grave thing to lessen the alkalinity of the oceans because all the fish would die, not to mention coral reefs and whales.

However, all those animals evolved in and do better in oceans that are less alkali than today, perhaps as low as pH 7.4 in Carboniferous times.

Most animals, in fact, are much less alkali than sea water of today, inside their bodies. Human blood has a pH of ~7.4, for example. So has dolphin blood. So has fish blood. Look it up.

Aquarium and pond owners know about testing and buffering the water pH for their fish. From The FishDoc [here]

Each species of fish has its own very narrow range of pH preference and levels outside of this range will cause health problems. For example, koi prefer a range between 7 and 8.5, while some tropical fish prefer water that is slightly acidic. There are several ways that pH can affect fish health.

But carbon paranoia being what it is these days, scientists decided to do the litmus test, scientifically, as part of the tens of $billions spent on “climate change” research every year. We could spend that money on something else, or not spend it at all, but… And to be fair to researchers, they can’t get any funding if their proposals don’t have a global warming hook.

So anyway, some scientists altered the pH in some fish tanks to see how tropical marine fish reacted to “acidification” — some tanks at pH 8.2 like the oceans, and some tanks at pH levels lower than that.

Basically, they replicated the experiment aquarium owners have been performing ever since Robert Boyle invented litmus paper (or perfected the idea) around 1650. But the scientists did it scientifically.

And what did they find?

The punchline is coming…

They found that the fish did better in “acidified” sea water. Yup. No difference in the egg hatching rate but the little fish grew larger faster. They liked it! Tropical marine fishes like their water a little less alkali than 8.2!

Whodda thunk it? Besides all those aquarium owners keeping their aquariums at pH 7 to 8, I mean?

But anyway, the following excellent science review was lifted whole from CO2Science [here], the website of the Center for the Study of Carbon Dioxide and Global Change:

The Center for the Study of Carbon Dioxide and Global Change was created to disseminate factual reports and sound commentary on new developments in the world-wide scientific quest to determine the climatic and biological consequences of the ongoing rise in the air’s CO2 content. It meets this objective through weekly online publication of its CO2 Science magazine, which contains editorials on topics of current concern and mini-reviews of recently published peer-reviewed scientific journal articles, books, and other educational materials. In this endeavor, the Center attempts to separate reality from rhetoric in the emotionally-charged debate that swirls around the subject of carbon dioxide and global change. In addition, to help students and teachers gain greater insight into the biological aspects of this phenomenon, the Center maintains on-line instructions on how to conduct CO2 enrichment and depletion experiments in its Global Change Laboratory (located in its Education Center section), which allow interested parties to conduct similar studies in their own homes and classrooms.

CO2 Effects on Tropical Marine Fish Embryos and Larvae

Science review by the Center for the Study of Carbon Dioxide and Global Change, 9 December 2009 [here]


Munday, P.L., Donelson, J.M., Dixson, D.L. and Endo, G.G.K. 2009. Effects of ocean acidification on the early life history of a tropical marine fish. Proceedings of the Royal Society B 276: 3275-3283.


The authors say “there is concern that continued increases in atmospheric CO2 over the next century could have significant impacts on a wide range of marine species, not just those with calcified skeletons.” In the case of fish, however, which “control their tissue pH by bicarbonate buffering and the exchange of ions, mostly across the gills,” they say that “small changes in internal or external pH can readily be compensated (Heisler, 1989; Claiborne et al., 2002).” Fish embryos and young larvae, on the other hand, are said by them to be “more sensitive to pH changes than are juveniles and adults,” citing the work of Brown and Sadler (1989). Therefore, they indicate that “significant effects of ocean acidification are most likely to be detected in these early life stages,” which possibility they thus go on to explore.

What was done

Working with a 70,000-liter recirculating sea water system at James Cook University’s experimental marine aquarium facility, Munday et al. grew wild-caught pairs of the orange clownfish (Amphiprion percula) in 70-liter tanks containing sea water simulating a range of ocean acidification scenarios for the next 50-100 years — 390 (current day), 550, 750 and 1030 ppm atmospheric CO2 — while documenting various aspects of egg, embryo and larval development.

What was learned

The four researchers, all from the School of Marine and Tropical Biology of Australia’s James Cook University, determined that “CO2 acidification had no detectable effect on embryonic duration, egg survival and size at hatching.” In fact, they say that it actually “tended to increase [italics added] the growth rate of larvae.” Eleven days after hatching, for example, they observed that “larvae from some parental pairs were 15 to 18 per cent longer and 47 to 52 per cent heavier in acidified water compared to controls,” further noting there was a “positive [italics added] relationship between length and swimming speed,” and that “large size is usually considered to be advantageous for larvae and newly settled juveniles.”

What it means

In discussing current concerns over potential effects of the ongoing rise in the air’s CO2 content on marine fish, Munday et al. state that “the most common prediction is that ocean acidification could [negatively] affect individual performance (e.g. development, growth, survival, swimming ability),” especially during the early life history of such fish. However, they indicate that “contrary to expectations,” their findings indicated that “CO2-induced acidification up to the maximum values likely to be experienced over the next 100 years had no noticeable effect on embryonic duration, egg survivorship and size at hatching for A. percula, and tended to have a positive effect on the length and weight of larvae.”

As for adult fish, the Australian scientists note that “most shallow-water fish tested to date appear to compensate fully their acid-base balance within several days of exposure to mild hypercapnia [a deleterious condition produced by having more than the normal level of carbon dioxide in the blood due to exposure to elevated CO2 concentrations],” citing the work of Michaelidis et al. (2007) and Ishimatsu et al. (2008) in this regard. Hence, it would appear that climate alarmism over this issue is significantly overblown.


Brown, D.J.A. and Sadler, K. 1989. Fish survival in acid waters. In: Morris, R., Taylor, E.W., Brown, D.J.A. and Brown, J.A. (Eds.). Acid Toxicity and Aquatic Animals. Cambridge University Press, Cambridge, United Kingdom, pp. 31-44.

Claiborne, J.B., Edwards, S.L. and Morrison-Shetlar, A.I. 2002. Acid-base regulation in fishes: cellular and molecular mechanisms. Journal of Experimental Zoology 293: 302-319.

Heisler, N. 1989. Acid-base regulation in fishes. I. Mechanisms. In: Morris, R., Taylor, E.W., Brown, D.J.A. and Brown, J.A. (Eds.). Acid Toxicity and Aquatic Animals. Cambridge University Press, Cambridge, United Kingdom, pp. 85-96.

Ishimatsu, A., Hayashi, M. and Kikkawa, T. 2008. Fishes in high CO2, acidified oceans. Marine Ecology Progress Series 373: 295-302.

Michaelidis, B., Spring, A. and Portner, H.O. 2007. Effects of long-term acclimation to environmental hypercapnia on extracellular acid-base status and metabolic capacity in Mediterranean fish Sparus aurata. Marine Biology 150: 1417-1429.



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