The Impact of Anthropogenic CO₂ in the Oceans. (July 6, 2006)

At risk. Microscopic marine snails will lose their shells and disappear if the oceans become too acidic, robbing fish of a key food source.  From ScienceNow - Photo courtesy Victoria Fabry, California State University, San Marcos

    A new report from a workshop sponsored by the united states' National Science Foundation, the National Oceanic and Atmospheric Administration, and the U.S. Geological Survey cautions, "The uptake of anthropogenic CO₂ by the ocean, changes the seawater chemistry and will significantly impact biological systems in the upper oceans."

Quite simply the ocean's, not uniformly it must be said, are becoming acidified by the increasing amount of CO₂ that is dissolving in them. studies of ice cores indicate that the ocean's chemistry had been stable for about the past 650,000 years. But in the past 150 years, excess carbon dioxide dissolving into the water has caused the average ocean pH to drop from 8.2 to 7.9.

Looking to the future the report concludes:

Estimates of future atmospheric and oceanic CO2 concentrations, based on the Intergovernmental Panel on Climate Change (IPCC) emission scenarios and general circulation models indicate that atmospheric CO2 levels could exceed 500 ppmv by the middle of the 21st century, and 800 ppmv by 2100. Corresponding models for the oceans indicate that by 2100, surface water pH will decrease by approximately 0.4 pH units relative to the preindustrial value, lower than it has been for more than 20 My. The carbonate ion concentration will also decrease by almost 50% relative to preindustrial levels. Such changes will significantly lower the ocean’s buffering capacity and, therefore, reduce its ability to accept more CO2 from the atmosphere...

    The calcification rates of most calcifying organisms studied to date decrease in response to decreased carbonate ion concentration... The decreased carbonate ion concentration
significantly reduces the ability of reefbuilding corals to produce their CaCO₃ skeletons, affecting growth of individual corals and the ability of the larger reef to maintain a positive balance between reef building and reef erosion.

The report goes on to point out, "The effects of reduced calcification on individual organisms and on ecosystems have not been investigated, however, and have only been inferred from knowledge about the role of calcification in organism and ecosystem functioning," and calls for significantly more research to be undertaken in order to gain a more thorough understanding of the effect of the increasing anthropogenic generation of CO₂ on the oceans' ecology. "It is largely unknown if, or how, various organisms will adapt to the large-scale pH changes that are anticipated over the next two to three centuries," the report concludes while  Robert Byrne a University of South Florida marine chemist based in St. Petersburg told Science such studies, "are going to become extremely important," as the problem worsens, because the organisms dependent on CaCO₃ for skeletal formation are part of the marine food web, "it's going to be a problem that you are eventually going to have on your dinner plate [and] the public needs to know about it."