Oceans off acid: Another reason why we must succeed in Copenhagen

The global ocean has buffered the effects of increasing CO2 levels by absorbing approximately 25% of all the CO2 that has been emitted. While the ocean has protected us by absorbing this excess CO2, it has come at a cost. As CO2 dissolves in water it creates a weak carbonic acid. As greater volumes of CO2 are absorbed by the ocean it progressively turns the relatively alkaline sea water more acidic. Scientists estimate that the oceans have become 30% more acidic since the beginning of industrial activity. If current rates continue then, by 2060 the oceans will have become 120% more acidic! Such a rate of ocean acidification is unprecedented and has not been seen in the past 55 million years. The evolutionary history of marine organisms present in the sea today has been restricted to a narrow range of PH that has not changed much over several million years. Simply, there is little or no genetic memory of more acidic conditions, and it is doubtful if marine organisms will be able to adapt to this change in PH.

What does this matter if you live in the sea? If you’ve ever owned a pair of pearls you know you should never make the mistake of soaking them in vinegar. If you do, they will disappear, quite literally corrode away. More acidic seawater is expected to have drastic effects on marine life. Many marine organisms including various types of plankton that form the base of the marine food web form shells, and contain calcium carbonate in their structures. Organisms from tiny snail like pteropods to large shellfish and mollusks will have to work harder and expend more energy in acidic waters to build and maintain their shells. Their rates of calcification will decrease and make them more venerable, affecting their survivorship, particularly in their young and larval stages. Laboratory experiments have already shown this response in organisms. It’s like an osteoporosis in the ocean, only at a massive scale! Such changes would affect entire food webs, especially since many calcareous marine organisms form the base of food webs. The entre marine ecosystem would change, likely collapse, become less diverse and reduce many fisheries and negatively affect those who depend on them. Tropical coral reefs, the most biodiverse habitats on earth are already threatened by increased water temperatures from climate change are now being affected by acidification. Decreases in calcification rates of tropical coral reefs attributed to acidification have already been documented in tropical coral reefs.

Temperate and polar oceans are already experiencing greater rates of acidification. This is not good news for Canada. Our three oceans are particularly vulnerable. More acidic water in the Pacific coast of North America that naturally rises from the deep annually is now moving more into shallower coastal waters each year. In Oregon, of the west coast of the U.S., it is suspected that acidification has caused poor survival of oyster larvae, resulting in losses in that seafood industry. Cold water corals found off all our coasts in Canada will likely be affected in the very near future. It is anticipated that 10% of Arctic waters are already affected by acidification, and up to 80% of Arctic waters may be acidified by 2060! The new frontier, an ice-free Arctic may very well be devoid of marine life!

Furthermore, we already have a large store of CO2 in the atmosphere such that it will continue to dissolve over many more decades, continuing to make the seawater more acidic, simultaneously reducing the capacity of the ocean to absorb CO2. The natural process of de-acidification in the oceans is anticipated to take in the order of tens of thousands of years, and will only happen when atmospheric levels of CO2 have stabilized and returned to lower levels. In short, once we go acid we don’t go back anytime soon, there are no quick ways out! If our leaders needed it, here is another compelling reason why we need to have immediate and ambitious reductions in GHG emissions, and why we must succeed in Copenhagen. We need to keep our oceans off acid!

Hussein Alidina
Senior Officer, Marine Planning