University professor advances research on ocean acidification

Wei-Jun Cai, a professor in the School of Marine Science and Policy, discovered his love for marine science when he was in middle school and watched an educational movie about how Mount Everest originated in the ocean. This opened his eyes and immediately attracted him to science. He described his career in marine science as “an accident,” but one he really loves.

Cai has been a professor at the university since 2013, after spending 18 years teaching at the University of Georgia, and was named the Mary A.S. Lighthipe Chair of Earth, Ocean and Environment in 2015. He has been conducting research on marine carbon cycling for 20 years.
His most recent published research is about how the Arctic Ocean has become more acidic in terms of its area and depth.

The paper was a collaborative effort with many other scientists and based off observations of subsurface carbon dioxide in the Arctic Ocean in 2010. They found the water in the Arctic Ocean became much more acidic in comparison to previously recorded observations.

“We found the acidified water spread way north and deeper compared with 1994 results,” Cai said. “We found that the acidified water before was at south of 80 degrees and now it goes all the way to north of 85 degrees, so it’s like 350 miles further north…Also, it’s a lot deeper. It was 100 meters and now it’s 250 meters.”

Ocean acidification is caused by an increase in carbon dioxide in the atmosphere. When CO2 dissolves in the ocean, it decreases the pH levels making the water more acidic. Fossil fuels are a major cause of CO2 in the atmosphere, and therefore a major cause of ocean acidification. Coal, fuel oil and natural gases are the primary components of fossil fuel (and when burned it produces CO2).

The ocean taking carbon dioxide out of the air relieves the pressures of global warming. Since the ocean is such a large reservoir, it can handle CO2 intake. However, the speed of uptake is so fast that the water is rapidly acidifying and affecting the surrounding ecosystem.

The arctic ecosystem is extremely vulnerable to acidification because of its low temperatures, so it significantly affects marine life. Smaller organism like zooplankton are food for the larger organisms like fish, and zooplankton are dying due to the higher acidity of the water, affecting all of the food chain. Fisheries are greatly affected by the increasing acidity, as well as the indigenous people who rely on fishing for food.

Cai has participated in other research projects including an earlier trip he took to the Arctic Ocean in 2008 with a group of scientists studying surface carbon dioxide. Their observations were published in a scientific journal in 2010.

“In the summer of 2008, when the ice was melting all the way to the Arctic Ocean basin, we were there,” Cai said. “We were the first.”

He also conducted research in the Gulf of Mexico after the 2010 Deepwater Horizon oil spill. Cai looked into how ocean stresses relate to ocean acidification. After the oil spill, much of the surrounding area outside of the Mississippi River was experiencing low oxygen levels, also known as hypoxia. The decomposition of organisms uses oxygen and releases carbon dioxide which adds to the carbon dioxide from the atmosphere. This causes the water to acidify much faster.

His current focus is on how environmental stressors such as hypoxia work together with atmospheric carbon dioxide to make the coastal waters even more vulnerable to acidification. He participated in studies in the Chesapeake Bay and Delaware Bay to measure how much carbon dioxide is released from the coastal water to the atmosphere.

“CO2 is a main currency for biological production and respiration,” Cai said. “I use CO2 to measure the rate of biological production or respiration and I measure the flux of CO2 because it is important to know the flux for the climate change model.”

Jessica Liebman, The Review, 17 march 2017. Article.

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