Ocean Acidification

Ocean acidification, or OA, is caused by CO2 from the atmosphere combining with sea water, which both changes the pH of the water and robs many marine animals of the essential chemicals they need to survive. A little over a third of human-emitted CO2 winds up in the ocean, where it has detrimental effects on all the plants, animals and people who rely on those ecosystems. Despite only having 15 percent of the global species, the world’s oceans contain 78 percent of the world’s animal biomass and 40 percent of the global population (including 100 percent of Hoonah) lives within 60 miles of the coast. HIA currently works in conjunction with the SEATOR network to monitor OA in Hoonah, while federal level monitoring is conducted by NOAA.

Figure 3 Near-surface measurements of salinity and chlorophyll along the BC and Southeast Alaskan coast. The M/V Columbia takes water quality measurements every three minutes during the sailing from Bellingham to Skagway to monitor environmental changes. Figure from Evans et al. (2022)


While creatures lower on the food chain face the largest direct threat from ocean acidification, negative impacts to them will end up affecting the entire marine food web. Shellfish and crabs face an immediate threat from OA because in acidic conditions they lose the ability to grow their shells, while salmon can have their skeletons damaged and become disoriented. In turn, other animals that eat those species (including humans) then face risks to their food supply and may struggle to find enough to eat. [1] Since shellfish, crabs and salmon are among the most important traditional foods in Hoonah, community members are likely to lose access to important nutritional and cultural resources.

ACIDIFICATION IS EXPECTED TO INCREASE 150 % BY THE END OF THE CENTURY. The ocean is already about 30 percent more acidic now than it was before the industrial revolution and it’s expected to get much worse, especially in Alaska. Alaskan waters naturally hold more carbon dioxide than waters at lower latitudes and are already more acidic than water from temperate latitudes. Increased freshwater input, from heavy rains and glacial meltwater, decrease the ocean’s ability to resist acidification, meaning as precipitation patterns in Southeast change and the glaciers melt, the ocean will become increasingly vulnerable to CO2 absorption.

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