The current concentration of atmospheric carbon dioxide (CO2) surpasses 400ppm, resulting in increasingly higher levels of this gas being absorbed into the ocean and reacting with ocean water. This process is changing the acidity of the global ocean, with increases already observed in higher latitudes and more changes expected in the future. Historically, ocean pH has averaged near 8.1, with historical changes occurring gradually. However, over the past few decades, the rate of change has increased dramatically, lowering pH by about 0.1 (a 30% increase in acidity) and affecting the buffering capability of the ocean. Many studies have found negative physiological effects on a wide range of calcareous organisms, from phytoplankton to shellfish to predators. Ecologically, potential trophic cascades have been observed in laboratory experiments. These studies usually utilize the lower pH predictions derived from the International Panel of Climate Change (IPCC) evaluations of the continued rise in atmospheric carbon dioxide content. Owing to the well-understood physico-chemical processes of ocean acidification, future pH predictions are especially robust, relying chiefly on the amount of CO2 entering the atmosphere and the rate of oceanic absorption by the ocean.
Macko S. A. & Fantasia C. M., 2018. An overview of ocean acidification: relationships. In: Nordquist M. H., Moore J. N. & Long R. (Eds.), The marine environment and United Nations Sustainable Development Goal 14, pp 391-417. Koninklijke Brill NV, Leiden. Chapter (restricted access).
