Changing Ocean Chemistry
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At least one-quarter of the carbon dioxide released by burning coal, oil, and gas doesn’t stay in the air, but instead dissolves into the ocean. When carbon dioxide and seawater mix, they combine to form carbonic acid. The ocean is becoming more acidic, which is having a harmful effect on many forms of life.
As seawater becomes more acidic, shellfish, crabs, seastars, and sea urchins find it more difficult to build their calcium carbonate shells. Oysters in Puget Sound and off the east coast of Vancouver Island have already experienced reproductive failure because of acidic waters. Scientists predict mussels and oysters to grow less shell by 25 per cent and 10 per cent respectively by the end of the century. For good reason, ocean acidification has been called “climate change’s evil twin.”
In Kwilákm, the loss of mussels, clams, oysters, and other species would have a large effect in the food web, as shellfish are food for many marine bird species. River otters love to feast on shellfish, as do octopi. Oyster and mussel beds create refuges and habitat for juvenile salmon, other small fish such as stickleback, crabs, and many very small creatures.
While the chemistry is predictable, the details of the biological impacts are not. For instance, new calculations made by scientists from the Monterey Bay Aquarium Research Institute suggest that low-oxygen “dead zones” in the ocean could expand significantly over the next century as more and more carbon dioxide dissolves into the ocean. Fish and other marine animals may find it harder to breathe as water becomes more acidic and the dissolved oxygen essential for their life becomes increasingly difficult to extract.
Some Kwilákm natural systems absorb carbon, thereby reducing the effects of climate change. Like plants on land, seaweeds and eelgrass use photosynthesis to absorb carbon dioxide from the water.