Ocean Acidification

image of oregon coast by Allie Barner

As the level of carbon dioxide in the atmosphere rises, oceans worldwide are become increasingly acidic. Even small changes in ocean acidity make it more difficult for marine organisms to form the shells and other hard parts they need to survive and function normally.


Ocean acidification is a global phenomenon, but it is especially marked on the west coast of the United States where acidic deep ocean waters well up close to the surface. Ocean acidification, in combination with warming waters and shifting ocean currents, has the potential to drastically affect the distribution and ecology of marine resources. Using a combination of newly advanced genomics tools, oceanography, and traditional ecology, PISCO scientists are revealing the impacts of ocean acidification on important early life stages of marine species and its possible consequences for marine ecosystems. 



The combined effect of a warming climate and anthropogenic carbon emissions is the lead cause of ocean acidification, according to numerous researchers and the International Panel on Climate Change. Throughout earth’s history, oceans have buffered climate change by absorbing nearly one-third of atmospheric carbon dioxide. But absorbing all this CO2 comes with a price; CO2 dissolved in the ocean reacts with other components of seawater to decrease ocean pH. Since the industrial revolution, oceans have become 30% more acidic (from a pH of 8.3 to 8.1).  Experts estimate that if atmospheric CO2 levels remain the same, by the end of this century, the ocean pH will decrease by 0.4 pH units, which will leave the ocean 150% more acidic than it is today.

The biological impacts of these trends are uncertain. Research thus far indicates that organisms such as corals, mussels, algae, and plankton that make calcium carbonate shells will be negatively impacted. These calcifying organisms normally rely on a healthy abundance of carbonate ions in the ocean water. With increased acidity, less of these precious ions are available and calcification rates decrease, making it more difficult for the organisms to form their protective shells and skeletons. The effect of thinner shells and weaker skeletons is not yet known, but it could have serious ecological consequences.


In the lab and the field, scientists use a combination of approaches to study the biological effects of ocean acidification and ocean warming. For example:

  • CO2 systems in laboratories that allow researchers to experiment with effects of low pH conditions that mimic the predicted future ocean conditions.
  • Genomics allows researchers to investigate the impacts of ocean acidification on important cellular growth processes.
  • PISCO community surveys in the intertidal and subtidal are integrated with this work, providing personnel already in-place for field collections and unique long-term biological data about species distributions, growth, and interactions.
  • Oceanographic moorings and ship-based work contribute to PISCO studies of climate change and ocean acidification.
  • Coordinated ecosystem studies with scientists along the US West Coast have helped to develop new understanding about the patterns of ocean acidification in the coastal ocean and some impacts on key species such as mussels. Coming soon: work by the “Ocean Margin Ecosystems Group for Acidification Studies”.




To learn more about PISCO's long-term studies, check out summaries about our work in the coastal oceankelp forests, and rocky intertidal. Also access our sampling protocols and data.