From my own personal aquariums, I know that this is absolutely false.
I was hoping that other Freepers would help explain why this was impossible.
Correction: increasing atmospheric CO2 concentration has measurably changed the pH of surface waters and the saturation state of surface waters with respect to calcium carbonate.
You need to find and read this reference:
Feely, R.A., C.L. Sabine, K. Lee, W. Berelson, J. Kleypas, V.J. Fabry, and F.J. Millero (2004) Impact of anthropogenic CO2 on the CaCO3 system in the oceans. Science, 305, 362–366.
Abstract: Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO3) particles. Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell-forming species. CaCO3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO3 dissolution rate for the global oceans is approximately 0.5 ± 0.2 petagrams of CaCO3-C per year, which is approximately 45 to 65% of the export production of CaCO3."
Here's a complete list of Dr. Feely's publications:
You might also want to check out Contribution 2726.