Acidification and the Arctic Ocean

The sea’s absorption of carbon dioxide lowers the pH of seawater, corroding the calcium carbonate shells that corals and many other marine creatures build. (Australian Institute of Marine Science)

Natural ecosystems exist in a delicate balance of biotic and abiotic factors, intertwined through billions of years of evolutionary progression and reliance on each other. As global climate change continues to escalate and impact a myriad of aspects of the natural world, this has never been more important to understand — that the impacts of one action, be it drilling or greenhouse gas emissions or overharvesting, can cascade through the biosphere for centuries to come. One of the more serious side effects of climate change is ocean acidification, which will change our oceans forever if action is not taken — and soon.

Ocean acidification occurs when carbon dioxide (CO2) is absorbed by the ocean from the atmosphere. Since the industrial revolution, humans have emitted 40 billion metric tons of CO2 into the atmosphere, of which 30% has been absorbed by the world’s oceans. When CO2 dissolves into water it creates mild carbonic acid which in turn lowers the pH of the water.  Bivalves, such as oysters and clams, are most at risk from acidification as the acidic water prevents them from building their calcium carbonate shells. Not only are bivalves valuable seafood for commercial and indigenous harvest in the Arctic, but they are also prey for a variety of marine animals, including, but not limited to: fish, walruses, seals and certain species of seabirds. Bears living along the coast have also been observed foraging for clams. Ocean acidification doesn’t only pose a threat to these shell building invertebrates, but to everything above them on the food chain.

Nowhere on Earth is ocean acidification seen as severely as it is in the Arctic Ocean, which has absorbed the largest quantity of CO2 due to the gas’s solubility with cold water. Ocean acidity in the present day is rising faster than it has in 55 million years, and without intervention it will only continue to rise, leading to dire consequences for marine organisms and humans alike. And in Alaska, climate change has raised temperatures at twice the rate of the continental United States, which has already thrown off the balance of this unique and awe-inspiring environment. 

It’s not just bivalves or the creatures that eat them that are at risk. Warming and acidifying Arctic waters are decreasing populations of fish as well, with the Environmental Protection Agency predicting that within the next forty to eighty years, as many as half of today’s salmon and trout could vanish from Alaska. Fish are incredibly sensitive to changes in pH, and acidifying waters can slow growth and alter the behavior of fish.

Many regions in the Arctic are considered food deserts — description of food deserts — and Native Peoples will be significantly impacted by losing subsistence fish species. Without nutritious and affordable food in groceries stores, traditional sources of food are the only option. As shellfish and fish populations decline in the Arctic due to acidification and warming, Indigenous communities will likely be hit the hardest

While the interconnectedness of nature might mean that one negative action, such as high CO2 emissions, leads to a thousand negative impacts around the world, the inverse can also be true. One action, such as lowering these emissions, can send a cascade of positive change across the biosphere. The most important action that can be taken to help protect the Arctic Ocean from acidification is continuing the push for clean energy and the lessening of CO2 emissions on a large scale. Increasing resource availability and protecting current subsistence resources for Native Peoples in the Arctic is also critically important as climate change and ocean acidification compromise their food security and ancestral lands. Promoting research into mitigation efforts could also provide crucial information to guide our response to this growing environmental catastrophe.

Research has shown that sea plants such as kelp and eelgrass can prove effective in dramatically reducing the levels of dissolved CO2 in water. In the past, the idea of fertilizing the ocean with substances such as Iron in order to induce CO2 absorbing algal blooms has been proposed but consistently shut down due to the ecological and financial concerns. However, on a small scale — in the vicinity of prominent oyster beds, for example — creating meadows of seagrasses or kelp farms can help lower acidity and help bivalves build their shells because of all the CO2 they extract from the water. In order for kelp to be useful, however, it must be harvested, thereby removing the extracted carbon from the entire ecosystem. Raising kelp and oysters harmoniously could provide an economic boost to coastal communities and help the environment. In Alaska, it is expected that brown kelp forests will expand their range northward in the coming years due to climate change.

One of the most promising ways that we can help protect bivalves and other organisms against ocean acidification is through oyster reef restoration efforts. By returning the shells of bivalves that have been eaten to the ocean, a buffer against acidity can be created for the living bivalves. Additionally, the shells provide shelter for young oysters that are vulnerable to predation. Limestone and concrete have also been used to create shelters in these barren reefs.

We are living in ever changing times as human activity continues to threaten the stability of the biosphere. Warming temperatures, acidifying waters, plastic pollution, overfishing and oil drilling all threaten the fragile Arctic Ocean. Without a drastic change in humanity’s course of action, the Arctic’s unique marine ecosystems could cease to exist in the coming decades, and many traditional ways of life and traditional sources of food in the Arctic will be lost unless action is taken. By reducing greenhouse gas emissions and working to understand the problem better we can work to stop further acidification of the oceans and support those most at risk.

Madison Shea, Alaska Wilderness League, 7 October 2020. Article.

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