Ocean acidity increasing faster than expected
November 25th, 2008 by Jim JustA new study conducted in the Pacific Ocean at Tatoosh Island off the coast of Washington finds that ocean acidity has increased more than 10 times faster than had been predicted by climate change models and other studies. The new study is based on 24,519 measurements of ocean pH spanning eight years, which represents the first detailed dataset on variations of coastal pH at temperate latitudes where the world’s most productive fisheries are found.
This increase will have a severe impact on marine food webs and suggests that ocean acidification may be a more urgent issue than previously thought. Many sea creatures have shells or skeletons made of calcium carbonate, which is dissolved by acid. The increased acidity of the ocean could interfere with many critical ocean processes such as coral reef building or shellfish harvesting. The study documented that the number of mussels and stalked barnacles fell as acidity increased. At the same time, populations of smaller, shelled species and noncalcareous algae increased.
The ocean plays a significant role in global carbon cycles. When atmospheric carbon dioxide dissolves in water it forms carbonic acid, increasing the acidity of the ocean. During the day, carbon dioxide levels in the ocean fall because photosynthesis takes it out of the water, but at night, levels increase again. The study documented this daily pattern, as well as a steady increase in acidity over time.
The study, “Dynamical Patterns and Ecological Impacts of Declining Ocean pH in a High-Resolution Multi-Year Dataset,” will be published in the Dec. 2 issue of PNAS.