How does rising atmospheric CO2 affect marine organisms?

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CO2-Enriched Seawater: A Menace to Marine Meiofauna?
Kurihara, H., Ishimatsu, A. and Shirayama, Y. 2007. Effects of elevated seawater CO2 concentration of the meiofauna. Journal of Marine Science and Technology 15: 17-22.

Meiofauna are small benthic invertebrates that are larger than microfauna but smaller than macrofauna, which basically means they are metazoan animals that can pass through a 0.5 - 1 mm mesh but are retained by a 30 - 45 Ám mesh. In marine environments, they typically are found between grains of damp sand on the seashore or in muddy sediments at the bottoms of water bodies.

What was done
The authors extracted sedimentary mud from the seafloor of Tanabe Bay on the Kii Peninsula of Japan and incubated it in marine microcosms that were continuously aerated for 56 days with air of either 360 or 2,360 ppm CO2 -- the latter of which concentrations has been predicted by some to be characteristic of the real world in the year 2300 -- while they periodically measured the abundance and biomass of different members of the meiobenthic community contained in the sediments.

What was learned
Kurihara et al. report they "observed no significant differences in the abundance of total meiofauna, nematodes, harpacticoid copepods (including adults and copepodites) and nauplii by the end of the experiment." In addition, they say there "may have been successful recruitments under elevated CO2 conditions," and, therefore, that "elevated CO2 had not impacted the reproduction of nematodes and harpacticoid copepods."

What it means
In the words of the three researchers, "these results suggest that the projected atmospheric CO2 concentration in the year 2300 does not have acute effects on the meiofauna."

Reviewed 3 June 2009