Since the industrial revolution, levels of carbon dioxide, in the atmosphere have continued to increase from human activities.
About a quarter of these emissions enter the oceans, which dissolve and react with water. This chemical reaction creates carbonic acid which lowers the pH of the ocean; making it more acidic and reducing the availability of shell-building materials.
This process is called ocean acidification, or OA for short.
Worldwide, OA affects ecosystems and the communities that rely on the ocean for livelihoods. As atmospheric CO2 continues to increase, so will OA especially in colder oceans.
- Year 2000: average ocean pH levels of 7.8 to 8.2
- Year 2050: projected ocean pH levels of 7.7 to 8.1
- Year 2100: projected ocean pH levels of 7.5 to 7.9
The effects of OA are felt by many marine organisms.
- Sea Urchin
Ocean acidification reduces how much calcium carbonate is available for shell formation. It can also cause a range of biological effects.
Some species may thrive in a more acidic environment, while others may adapt over time by changing their diets, or moving to more favorable environments. Some populations may decline or disappear.
When small species that form the basis of food webs are affected by OA, then the whole food web can be affected.
Canada's cold oceans are vulnerable to the impacts of OA – because CO2 is absorbed more easily in colder waters.
OA is taking place in all 3 of Canada's oceans. There are conditions in each region which further contribute to OA.
- Seasonal upwelling, or the mixing of deep and surface water in the Pacific, increases OA.
- Increased ice melt from glaciers and decreasing sea ice from warming temperatures in the Arctic, cause OA to happen more quickly.
- In the Atlantic, OA is influenced by the flow from the Arctic, uptakes of large amounts of CO2 in the Labrador Sea caused by deep mixing, and a combination of surface freshwater inputs and low oxygen sea water at the bottom of the Gulf of St. Lawrence.
Fisheries and Oceans Canada Scientists monitor and study changing ocean conditions such as ocean acidification and conduct research to understand its effects on Canada's fisheries and ecosystems. This contributes to increasing global knowledge on OA.
To learn more about ocean acidification and the important work DFO is doing, please visit our website.