“The ocean is warmer, more acidic and less diverse … we are seeing corrosive waters coming onto the continental shelf right now.”
~ Dr. Richard Feely of the Pacific Marine Environmental Laboratory
National Oceanic and Atmospheric Administration, at Living Oceans Climate and Oceans Think Tank 2009
Under normal conditions oceans absorb huge amounts of carbon dioxide (CO2). Since the start of the Industrial Revolution the oceans have absorbed more than 550 billion tonnes of CO2 from the atmosphere due to the increasing atmospheric concentrations of CO2 associated with industrial activity. Since then there has been about a 0.1 percent decrease in pH in the Pacific Ocean. This translates into about a 30 percent increase in acidity.
When CO2 dissolves in seawater, carbonic acid is formed. This reduces the pH level of the ocean in a process called ocean acidification. The effect on marine life is not completely understood, however impacts on some species can be determined through lab experiments and observations.
Lab experiments have shown a dramatic effect on calcification for coral and shell producing species. Carbonic acid reduces carbonate concentrations, and if surface seawater becomes under-saturated in carbonate minerals the seawater will begin to dissolve calcium carbonate shells.
For fish, squid and shellfish, acidification causes increased juvenile mortality and reduced growth, metabolism, and tolerance to fluctuating temperatures.
What can we expect?
The oceans of the world are becoming acidic at an alarming rate and corrosive water is coming closer to the surface where the impact on species and ecosystems is strongest.In the North Pacific the pH of the water is decreasing at a faster rate than has been previously predicted by scientists. Corrosive water is closest to the surface (100 to 200 meters) in this part of the Pacific Ocean. If we do not reduce carbon dioxide (CO2) emissions the consequences will be unequivocal as upwelling waters continue to bring corrosive water up onto the continental shelf where it could destroy the extraordinarily rich ecosystem of Canada's Pacific coast.
According to the IPCC, over the 21st Century an average reduction of between 0.14 and 0.35 pH units is expected for global ocean surface water. Historically, the average decrease in pH has been 0.1 units.
There is still much to be learned about the impacts of ocean acidification; genetic responses, effects on other stress factors, and ecosystem responses are a few examples. Drastic reduction of CO2 emissions is the only way to mitigate the consequences and continued progression of acidification.
