Ocean Acidification

About one third of the anthropogenic carbon dioxide (CO2) released since the start of the Industrial Revolution in the 1800s has been taken up by the oceans. This excess CO2 is altering the basic ocean chemistry, specifically the marine carbonate system. Carbon dioxide that dissolves in the surface water forms carbonic acid. The increased concentrations of CO2 in the atmosphere and the surface ocean have led to a decrease in ocean pH by 0.1 units over the past 200 years. And the surface ocean pH will keep decreasing as the CO2 release to the atmosphere by human continues.

The most direct impact of a lower pH on the biota arises from lowered carbonate ion concentration in seawater. This affects organisms that form calcium carbonate (CaCO3) shells and skeletons (called calcifying organisms).

Calcium carbonate saturation state (Ω) will give you an indicator of how corrosive the seawater is for organisms with CaCO3 skeleton and shell. Ω is calculated from the carbonate ion concentration, calcium ion concentration and the stoichiometric solubility product. When Ω is smaller than 1, the seawater is corrosive to the calcifying organism and dissolution of their shells and skeleton can begin without protective mechanisms. Furthermore, biological impairment can occur at Ω as high as 3.1 for some organisms such as reef building corals.

Ocean acidification is predicted to occur first in polar oceans and will have profound socioeconomic consequences. Effects of ocean acidification may propagate from individual organisms up through marine food webs and biodiversity, which could affect multi-billion dollar commercial fisheries and shellfish industries. We investigate the ocean acidification in the Canadian Arctic Archipelago (CAA) and the Northwest Atlantic. Since the shelf regions of Canada's east coast are both biologically active and support important commercial fisheries, continued monitoring and investigations of biological responses to ocean acidification in these regions are urgently needed.