“The global extent of ocean acidification, its complex social–ecological dynamics involving potential tipping points, the clear role of anthropogenic CO2 emissions to worsen it, the large uncertainties associated with most of its dimensions, and the potentially very large impacts, all together speak for a precautionary approach to address ocean acidification”

Source:  Jagers, S.C., Matti, S., Crépin, A.S., Langlet, D., Havenhand, J.N., Troell, M., Filipsson, H.L., Galaz, V.R. and Anderson, L.G., 2018. Societal causes of, and responses to, ocean acidification. Ambio, pp.1-15. Societal causes and responses to ocean acidification

pH has declined by about .11 units, equivalent to about a 28.8% increase in acidity, relative to pre-Industrial era baseline. (NOAA pH) (See the three figures below)

…(C)omputer re-creation of surface ocean pH from 1895 to the present and a forecast of ocean pH between now and 2100 under business as usual emission scenarios. Purple dots show cold-water coral reefs. Red dots show warm-water coral reefs. The pH scale is shown on the right. Increasing acidity is a relative shift in pH to a lower value. https://pmel.noaa.gov/co2/story/OA+Educational+Tools

CO₂ And Seawater Chemistry:  “Ocean Acidification”

Fundamental changes in seawater chemistry are occurring throughout the world’s oceans. Since the beginning of the industrial revolution, the release of carbon dioxide (CO₂) from humankind’s industrial and agricultural activities has increased the amount of CO₂ in the atmosphere. The ocean absorbs about a quarter of the CO₂ we release into the atmosphere every year, so as atmospheric CO₂ levels increase, so do the levels in the ocean. Initially, many scientists focused on the benefits of the ocean removing this greenhouse gas from the atmosphere.  However, decades of ocean observations now show that there is also a downside — the CO₂ absorbed by the ocean is changing the chemistry of the seawater, a process called OCEAN ACIDIFICATION.  NOAA Ocean Acidification

Significance:  Ocean acidification is expected to impact ocean species to varying degrees. Photosynthetic algae and seagrasses may benefit from higher CO₂ conditions in the ocean, as they require CO₂ to live just like plants on land. On the other hand, studies have shown that lower environmental calcium carbonate saturation states can have a dramatic effect on some calcifying species, including oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton. Today, more than a billion people worldwide rely on food from the ocean as their primary source of protein. Thus, both jobs and food security in the U.S. and around the world depend on the fish and shellfish in our oceans. NOAA Ocean Acidification