Ocean Acidification

small pteropod in ocean water


Each year, oceans absorb about a quarter of the carbon dioxide (CO2) that humans add to the Earth's atmosphere. While this absorption process has helped to remove this potent greenhouse gas from the atmosphere, it has also led to an increase in the acidity of the ocean at a faster rate than has ever previously occurred.

Cause of Ocean Acidification
Ocean acidification occurs at the global scale, and is largely caused by human carbon emissions. Since the Industrial Revolution (when fossil fuels were first burned to create energy), ocean pH (an acidity measurement where a “low” pH indicates an increase in acidity) has dropped, and acidity has increased by 30%. Ocean acidification is occurring dramatically faster than any time in approximately the last 300 million years.

Effects on Ocean Life

When carbon dioxide dissolves in the ocean, it creates carbonic acid. This reaction increases the amount of carbonic acid present in seawater and decreases the amount of a compound called calcium carbonate. Many invertebrate species (such as corals, oysters, sea urchins, and some types of plankton) use calcium carbonate to build their shells and plates. Without this compound, they lose one of the most important building blocks for their survival and are left vulnerable – not only is it harder for these species to make their shells and other structures, but increased ocean acidity also breaks down the calcium carbonate present in their bodies, threatening the structures they have already formed.

As these animals are affected, so are the species that consume and are consumed by them. The science of ocean acidification and its effects on marine species and the larger food web are only beginning to be understood, but resource managers in many ocean and coastal parks are taking steps to document and lessen impacts, where possible. In Olympic National Park, a pilot project is monitoring ocean acidification to track local variation in acidity levels and develop a baseline for long-term monitoring within the park.

How the Park Service is Adressing Ocean Acidification

Many other parks across the country are engaging in research and monitoring to better understand ocean acidification. In the US Virgin Islands National Park, the National Park Service and US Geological Survey scientists have been monitoring coral reefs for over 20 years. Channel Islands National Park has one of the longest monitoring efforts in the world. Bright yellow ocean pH sensors measure acidity off of Anacapa Island and San Miguel Island in a joint project with University of California at Santa Barbara to study natural changes in pH. This monitoring effort is part of a large-scale United States National Science Foundation west coast monitoring initiative that analyzes the changes in ocean pH in relation to other natural ocean processes.

Parks ranging from National Park of American Samoa to Alaska’s Glacier Bay National Park and more are trying to protect invertebrate species threatened by ocean acidification. Ultimately, to protect these species and the food webs that depend on them, we need to try to reduce the amount of carbon dioxide we are sending into our atmosphere and our oceans, while also learning more about the causes and effects of ocean acidification. National parks are living laboratories that can help teach our children and inspire our communities to learn about, care for, and advocate on behalf of our threatened oceans.

For Further Reading

Climate Change and Corals

Ocean Acidification

Learn More

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