When you think of carbon dioxide emissions, what comes to mind? For most people, that is probably something along the lines of fossil fuels, greenhouse gases, and global warming. But for me, I think about ocean acidification. Often referred to as “the other carbon dioxide problem”, ocean acidification, or OA for short, is a lesser-known by-product of excess carbon dioxide being released into the atmosphere. Between 25 – 30 % of the carbon dioxide produced since the Industrial Revolution has been absorbed by our oceans. This buffering capacity of the ocean has actually helped reduce some impacts of global warming and greenhouse gases, but, as we’ve discovered in the last decade or two, it has come at a great cost to our oceans.
When carbon dioxide (CO2) enters the ocean, it reacts with seawater to form excess hydrogen (H+) and bicarbonate ions (HCO3–). Increases in hydrogen ions are what makes liquids more acidic and reduces their pH, hence the term “ocean acidification”. But the main consequence of increases in hydrogen ions in seawater is that hydrogen ions bond readily with the carbonate ions (CO32-). Carbonate is naturally occurring in seawater, and it is a crucial building block for organisms that build calcium carbonate hard parts, like clams, oysters, lobsters, corals, and even the tiny plankton that serve as the base of the ocean’s food chain. The less carbonate ions available in seawater, the harder it is for organisms to make their hard parts. In the past 15 years or so, there has been considerable research demonstrating the negative effects of OA on calcifying organisms. These calcified structures can take more energy for organisms to form, grow smaller, slower, and/or weaker, or even start to dissolve! Increased seawater acidity can also affect organism survival, particularly in early life stages. On the west coast of the U.S., there have already been several seasonal mass die-offs events of oyster crops that have caused significant and repeated financial losses to the aquaculture industry, most likely attributed to OA.
As most societies, particularly coastal communities, depend on the oceans for both food and livelihoods, monitoring and mitigating OA has become a global priority. The UN has declared the next decade (2021 – 2030) the Decade of Ocean Science for Sustainable Development. Many countries, including Canada, have committed to the Ocean Decade and its Sustainable Development Goals (SDGs). OA is directly addressed in the Ocean Decade plan under SDG 14.3 – to “minimize and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels”. To this end, the Global Ocean Acidification Observing Network (GOA-ON) has created a database where researchers can make sure their data adheres to SDG 14.3.1 methodologies and then contribute their data to this global OA database. There are also many other national and international OA groups that have been created in recent years to help create and share OA knowledge and research.
Canada and Ocean Acidification
Canada faces several unique challenges with respect to OA. First, we have the largest coastline of any country in the world. Second, Canada is more vulnerable to OA given our latitude and colder ocean temperatures, as carbonates are naturally more soluble in colder waters. Thirdly, Canada is surrounded by three connected ocean basins, each with unique properties that make them vulnerable to the effects of OA. In the Pacific, OA is exacerbated by seasonal upwelling, where deep, naturally acidic ocean waters are forced to the surface by wind patterns. The Arctic is vulnerable due to rapidly increasing freshwater input from melting sea ice and glaciers from warming temperatures (freshwater is more acidic than seawater). In the Atlantic, OA is exacerbated by ocean mixing patterns and freshwater input from the Arctic. Finally, Canada’s coastal communities, of which there are many given our extensive coastline, are socioeconomically vulnerable to OA.
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Kristina Barclay, Time Scavengers, 28 April 2021. Article.
