How does rising atmospheric CO2 affect marine organisms?

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Will Burning Fossil Fuels Reduce Baltic Cod Reproduction Rates?
Frommel, A.Y., Stiebens, V., Clemmesen, C. and Havenhand, J. 2010. Effect of ocean acidification on marine fish sperm (Baltic cod: Gadus morhua). Biogeosciences 7: 3915-3919.

Climate alarmists are worried that continued business-as-usual CO2 emissions from the burning of fossil fuels will lead to increases in CO2 absorption by the ocean from the atmosphere that will cause an under-saturation of calcium carbonate in seawater, which phenomenon may have major negative effects on calcifying marine organisms. In addition, Frommel et al. say that "elevated CO2 concentrations can disturb the acid-base regulation, blood circulation, and respiration, as well as the nervous system of marine organisms, leading to long term effects such as reduced growth rates and reproduction," especially in fish, because the majority of them, as they describe it, "are external fertilizers, and sperm are activated by seawater as they are expelled into the open ocean during a spawning event," citing the work of Westin and Nissling (1991).

What was done
To explore this subject further, the four researchers collected sperm from ripe adult male cod fish (Gadus morhua, that they had caught during an August cruise through their spawning grounds in the Baltic Sea's Bornholm Basin), which they exposed to seawater that had been brought into equilibrium (by bubbling) with air of either 380 or 1400 ppm CO2 (leading to seawater pH values of 8.080 and 7.558, respectively), during which exposure period sperm swimming behavior was recorded using a digital camera.

What was learned
In the words of the scientists who conducted the experiment, "we found no significant effect of decreased pH on sperm speed, rate of change of direction or percent motility for the population of cod analyzed."

What it means
In light of their careful and meticulous observations, Frommel et al. conclude that "future ocean acidification will probably not pose a problem for sperm behavior, and hence fertilization success, of Baltic cod."

Westin, L. and Nissling, A. 1991. Effects of salinity on spermatozoa motility, percentage of fertilized-eggs and egg development of Baltic cod (Gadus morhua), and implications for cod stock fluctuations in the Baltic. Marine Biology 108: 5-9.

Reviewed 30 March 2011