Ocean Acidification

Shells from crabs, mussels, sea snails, and sea urchins are seen on the seafloor
Photo: NOAA

Human activities are changing the ocean, including protected national marine sanctuaries. The burning of fossil fuels, such as coal, oil, and natural gas, are releasing too much carbon dioxide (CO2) into the atmosphere

The ocean has absorbed more than a quarter of human-generated carbon emissions to date. As the ocean absorbs carbon dioxide, it reacts with seawater to form carbonic acid, which further breaks down into bicarbonate and carbonate ions that each generate a hydrogen ion--a chemical reaction that lowers ocean pH. Globally, ocean pH has declined 30% since the beginning of the industrial revolution. The West Coast is particularly vulnerable to ocean acidification due to seasonal upwelling along the coast.

Ocean acidification makes it more difficult for animals like oysters, crabs, and deep-sea corals to create and maintain shells and skeletons and may affect the development and behavior of some fish. Ocean acidification can also affect marine food webs by impacting prey species, such as krill and copepods, that support the rest of the ecosystem—everything from seabirds to salmon to southern resident killer whales. Research suggests that harmful algal blooms become more toxic due to ocean acidification, exacerbating negative effects on resources critical to coastal communities for ceremonies, subsistence, and economies.

Olympic Coast National Marine Sanctuary was designated as a sentinel site for ocean acidification in November 2019. An Ocean Acidification Sentinel Site (OASeS) on the Olympic Coast of Washington state focuses on related science and identifies trends in carbonate chemistry and hypoxia through collaborative monitoring, research, outreach, and public engagement efforts.The sentinel site will help ensure that the Olympic Coast is well prepared for changing ocean conditions, with research and information that supports management responses and actions.