Ocean Acidification

Ocean Acidification

Ocean acidification is devastating marine environments and economies

Ocean acidification threatens the marine food web and as a result, the health and stability of coastal economies. Without concerted action to reduce global carbon dioxide emissions, oceanic pH could drop to 7.8 by the end of this century. That would be a huge change, representing a 150 percent increase in acidity. Such an alteration in the marine environment could have devastating results, for any marine species that extracts calcium carbonate to build its shell or skeleton, and for the people who depend upon them.

Human-caused carbon dioxide emissions is the main driver for ocean acidification

The ocean has absorbed an estimated 26 percent of the carbon dioxide released into the atmosphere since the start of the Industrial Revolution in 1750. This uptake of carbon dioxide from the atmosphere is a major contributor to the decline in seawater pH known as ocean acidification. 

Since the beginning of the industrial era, the pH of surface seawater has decreased from about 8.2 to 8.1. While the ocean is “basic” because it is above a 7 on the pH scale, dissolved carbon dioxide acidifies the ocean by increasing the concentration of hydrogen ion. The pH change from 8.2 to 8.1 corresponds to a 26 percent increase in acidity (or hydrogen ion concentration) and is likely the fastest acidification rate in 300 million years.

Both human-caused ocean acidification and human-caused climate change are due to rising carbon dioxide concentrations in the atmosphere. The world’s ocean’s absorption of carbon dioxide may have slowed several of the impacts of climate change that humans would have otherwise experienced on land due to a warmer atmosphere, but this “buffering” service comes at a heavy cost.

The U.S. is already seeing the economic impacts of acidification

Acidification is having a significant impact on the chemical composition of seawater, especially in colder basins like the Arctic where carbon dioxide dissolves more readily. This change in ocean chemistry is threatening the health and development of many marine species, posing risks to humans who depend on oceans for their livelihoods. The U.S. is no exception: in the Pacific Northwest, acidification has already cost the farmed oyster industry almost $110 million, jeopardizing 3,200 jobs, and 16 more coastal regions are expected to experience rapid acidification by mid-century.

According to the study, U.S. coastal communities earn over $1 billion in revenue from mollusks, but 16 out of 23 of these coastal regions will face “rapid acidification” by mid-century. Other analyses show that large areas of the oceans along the U.S. west coast, the Bering Sea and the western Arctic Ocean will also become difficult for calcifying animals within the next 50 years. For example, a recent study found that even crustaceans in their larval and juvenile stages, such as New England lobster and Alaskan red king crab, may soon be affected by rapid declines in seawater pH, which has implications for lucrative U.S. seafood exports.

Coral reefs, in particular, provide essential ecosystem services to countless marine species. If they decline due to accelerating acidification, destructive fishing practices, pollution and warming waters, other marine life will weaken with them, resulting in less vibrant and less productive oceans. Dead and dying coral reefs, in turn, will result in increased economic hardship for coastal populations. Decreased skeletal growth in reef-building corals and coralline algae is one of the best-known consequences of ocean acidification. Read more about coral bleaching here.