Scientist Describes Ocean Acidification Risk

Rising Carbon Dioxide Levels Threaten Ocean Food Webs Worldwide

Sep 7, 2008 R.H. Sheldon

Dr. Richard A. Feely told a U.S. government subcommittee that predicted changes in ocean chemistry from the absorption of carbon dioxide could pose significant risks.

During the past 200 years, billions of tons of carbon dioxide (CO2) have been emitted into the atmosphere, with global warming being the most telltale consequence. Another consequence has attracted the attention of scientists like Feely, an oceanographer with the National Oceanic and Atmospheric Administration (NOAA), affiliate professor at the University of Washington, and winner of the Nobel Peace Prize, shared with Al Gore and other members of the Intergovernmental Panel on Climate Change (IPCC).

Dr. Richard A. Feely's Evidence on Ocean Acidification

On June 5, 2008, Feely testified in a hearing on ocean acidification before the U.S House of Representatives Subcommittee on Energy and Environment, part of the Committee on Science and Technology.

According to Feely’s written testimony, the oceans have absorbed about 525 billion tons of CO2, one-third of the total CO2 emitted in the last 200 years.

Currently, the oceans absorb 22 million tons of CO2 daily, resulting in changes to the seawater’s chemistry. Feely says these changes are evidenced by dropping pH levels, which indicate that the oceans are becoming more acidic. “Scientists have estimated that the pH of our ocean surface waters has already fallen by about 0.11 units from an average of about 8.21 o 8.10 since the beginning of the industrial revolution.”

Feely believes that, if emissions output follow the IPCC's predictions, the surface water pH will decrease by about 0.4 pH units by the end of the century. “To put this in historical perspective, the resulting surface ocean pH would be lower than it has been for more than 20 million years.” The increased acidity could significantly affect the chemistry and biology of the oceans.

Calcifying Organisms at Risk from Lower pH of Ocean Water

When the oceans acidify, organisms with calcium carbonate shells, such as the pteropod and coral, have difficulty surviving. Feely cautions that, if these types of organisms die out, the ocean’s entire food web could be affected.

The pteropod, for example, is a free-swimming mollusk that is eaten by a wide range of organisms, from krill to whales. “In particular, pteropods are a major food source for North Pacific juvenile salmon, and also serve as food for mackerel, Pollock, herring, and cod.”

Coral reefs provide a home for thousands of species of sea creatures. In addition, people who fish rely on coral reefs to support the food webs that make the fish available. If the oceans continue to acidify, coral growth will slow and their shells will weaken, making them more susceptible to predators, disease, and stress.

Non-calcifying Organisms and Ocean Acidification

Feely also points out that ocean acidification can have a direct impact on non-calcifying organisms. For example, ongoing research shows that in CO2-enriched, low pH waters, king crab and silver seabream larvae exhibit high mortality rates; fish experience decreased respiratory rates, changes in blood chemistry, and changes in enzymatic activity; Pacific oyster populations decline; squid experience respiratory and blood-oxygen transport problems; and sea urchins show evidence of inhibited growth.

Continuing Research on the Effect of Carbon Dioxide on Ocean Ecosystems

Feely acknowledges that ocean acidification is a new scientific frontier and more research and monitoring are of critical importance. He also believes that the results seen so far from laboratory, field, and modeling studies, as well as evidence from the geological record, clearly indicate that ocean ecosystems are highly susceptible to the increased CO2.

As Feely warns, if CO2 emissions are allowed to increase as predicted by the IPCC, humankind may be responsible for making the oceans more acidic than any time in the last 20 million years: “The decisions we make about carbon dioxide emissions over the next several decades will probably have a profound influence on the makeup of future marine ecosystems for centuries to millennia.”

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CO2 Absorption in the World's Oceans