A team of researchers from the US, Canada and Mexico found evidence of the acidification of the ocean caused by the ocean’s absorption of carbon dioxide less than 20 miles off the west coast of North America during a field study from Canada to Mexico last summer. This was the first time “acidified” ocean water has been found on the continental shelf of western North America.
Ocean acidification is an issue of basic chemistry: atmospheric CO2 is absorbed by and reacts with seawater to form carbonic acid (H2CO3). This reaction of CO2 with seawater reduces the availability of carbonate ions required for calcium carbonate (CaCO3) skeleton and shell formation. The effect on organisms depends upon the state of calcium carbonate (CaCO3) saturation. In regions where the concentration is high, formation of shells and skeletons occurs. In regions where it is low, the water becomes corrosive, and the dissolution of shells begins to occur.
Thus, increasing acidity resulting from increasing concentrations of atmospheric CO2 could have profound affects on basic marine life. Concern about this began to accelerate in 2003 with the publication of a short paper in Nature by researchers at Lawrence Livermore National Laboratory who suggested that unabated anthropogenic increases in CO2 in the atmosphere may drive changes in ocean pH values greater than any experienced in the past 300 million years. (Earlier post.)
Acidification of the Earth’s ocean water could have far-reaching impacts on the health of our near-shore environment, and on the sustainability of ecosystems that support human populations through nourishment and jobs. This research is vital to understanding the processes within the ocean, as well as the consequences of a carbon-rich atmosphere.—Richard W. Spinrad, NOAA assistant administrator for oceanic and atmospheric research
The report on the upwelling on the Pacific Continental Shelf is published online in the journal Science. The report was written by Richard A. Feely and Christopher Sabine, both oceanographers at NOAA’s Pacific Marine Environmental Laboratory in Seattle, Wash. Their co-authors are J. Martin Hernandez-Ayon of the Instituto de Investigaciones Oceanologicas from the University of Baja California, Mexico; Debby Ianson of Fisheries and Oceans Canada in Sidney, British Columbia, and Burke Hales, of Oregon State University College of Oceanic and Atmospheric Sciences, Corvallis, Ore.
Our findings represent the first evidence that a large section of the North American continental shelf is seasonally impacted by ocean acidification. This means that ocean acidification may be seriously impacting marine life on our continental shelf right now.
While this absorption provides a great service to humans by significantly reducing the amount of greenhouse gases in the atmosphere and decreasing the effects of global warming, the change in the ocean chemistry affects marine life, particularly organisms with calcium carbonate shells, such as corals, mussels, mollusks, and small creatures in the early stages of the food chain.—Richard Feely
The study was the first in what is planned to be a biennial sequence of observations and studies of carbon along the west coast of North America. The researchers participated in the North American Carbon Program West Coast Cruise on the R/V Wecoma, owned by the National Science Foundation and operated by Oregon State University. The international scientific team plans to continue their studies of ocean acidification in follow up cruises in late 2009.
Previous studies found ocean acidification at deeper depths farther from shore. The researchers said that the movement of the corrosive water appears to happen during the upwelling season during the spring and summer, when winds bring CO2-rich water up from depths of about 400-600 feet onto the continental shelf. The water that upwells off of the North American Pacific coast has been away from the surface for about 50 years.
The field study collected samples from Queen Charlotte Sound, Canada, to San Gregorio Baja California Sur, Mexico. The closest they found corrosive water was about four miles off of the northern California coast.
We observed seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of approximately 40-120 m along most transect lines and all the way to the surface on one transect off northern California. While seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area.
...These observations clearly show that seasonal upwelling processes enhance the advancement of the corrosive deep water into broad regions of the North American western continental shelf. Since the region experiences seasonal periods of enhanced aragonite undersaturation, it is important to understand how the indigenous organisms deal with this exposure and whether or not future increases in the range and intensity of the corrosiveness will affect their survivorship.
Presently, little is known about how this intermittent exposure to corrosive water might impact the development of larval, juvenile and adult stages of aragonitic calcifying organisms or finfish that populate the neritic and benthic environments in this region and fuel a thriving economy. Laboratory and mesocosm experiments show that these changes in saturation state may cause significant changes in overall calcification rates for many species of marine calcifiers including corals, coccolithophores, foraminifera and pteropods, which are a significant food source for local juvenile salmon. Similar decreases in calcification rates would be expected for edible mussels, clams and oysters.
Other research indicates that many species of juvenile fish and shellfish of significant economic importance to coastal regions are highly sensitive to higher-than-normal CO2 levels such that high rates of mortality are directly correlated with the higher CO2 levels.—Feely et. al.
Richard A. Feely, Christopher L. Sabine, J. Martin Hernandez-Ayon, Debby Ianson, Burke Hales. (2008) Evidence for Upwelling of Corrosive “Acidified” Water onto the Continental Shelf. Science DOI: 10.1126/science.1155676