Ocean acidification is caused by the dissolution of atmospheric carbon dioxide into the oceans, which results in a decrease in seawater pH and increased acidity . Since the pre-industrial era, the oceans have absorbed approximately one-third of human produced carbon dioxide emissions, resulting in an increase in acidity of more than 26%, the lowest levels in 20 million years [46–49]. The impacts of acidification on marine ecosystems are complex and serious, especially for calcareous and planktonic organisms as it impacts the ability of those organisms to produce and maintain their calcium carbonate shell structures [46,50] as well as potentially increases metabolic stress.
In the Northeastern Pacific Ocean, ocean acidification is one of the most urgent threats to both marine ecosystems and human communities. These waters are already among the most acidic of the world’s ocean regions, due to ocean currents and upwelling of deep ocean waters [5,51,52]. Upwelling waters already have relatively low pH, and organic matter production driven by upwelling currents further lowers the pH of those waters by remineralization.