Question: How will sequestered carbon dioxide gas affect ocean life?

Carbon dioxide will not affect ocean life while it remains trapped well below the sea floor, and there are few worries that the gas will escape in large quantities. The Utsira formation, a layer of sandstone in the North Sea about 1 kilometer (0.62 miles) below the sea bed where this CO₂ is currently being stored, is thought by scientists to be very suitable because of the dense rock layer that’s on top of the formation. Estimates for the likely leakage rate are very low – less than 1 percent over 1,000 years.

However, ocean life could be impacted in the event of an unexpected release of CO₂ through the sediments into the North Sea. Increasing carbon dioxide in seawater changes the water’s chemistry by making it more acidic and by reducing the amount of chemicals that organisms like local corals and shellfish need to make their skeletons and shells. Such changes in seawater pH also could reduce how well certain organisms reproduce.

Storing carbon under the seabed may be an important tool in the efforts to slow global warming. If this CO₂ were not being stored in the Utsira formation, it would already have been released into the atmosphere. At least a third of it would then have dissolved into the ocean and making it more acidic, although to a much lesser extent than were it to be added in one spot.

-- Andrew Dickson, marine chemist, Geosciences Research Divsion