Study finds acidic oceans may produce more nitrous oxide

The increase in carbon dioxide in the atmosphere not only alters the climate of the Earth’s surface but also makes the ocean more acidic, foreign media reported. Now, scientists have also discovered an unfortunate feedback loop that could make things worse. Ocean acidification appears to increase the amount of nitrous oxide (N2O), a greenhouse gas, and release it into the atmosphere, according to a new study.

Study finds acidic oceans may produce more nitrous oxide


As a side effect and contributor to climate change, ocean acidification has become a major problem. More carbon dioxide in the air means that the ocean also absorbs more carbon dioxide, which makes the sea more acidic. This, in turn, alters the climate of marine ecosystems, leading to the bleaching of coral reefs, the destruction of the natural food chain, the disruption of fish survival instincts and even the dissolution of the sea floor.

Now, researchers from EPFL, the Tokyo Institute of Technology and Japan’s Bureau of Ocean and Earth Science and Technology (JAMSTEC) have discovered a new effect. According to the team, more acidic seawater releases more N2O into the atmosphere. Once it rises into the atmosphere, it produces almost 300 times the greenhouse gas effect of carbon dioxide, which depletes the ozone layer.

The team collected water samples from five different locations off the coast of Japan from 2013 to 2016. To test the amount of N2O produced at different acidity levels, the team reduced the pH of the samples to make them more acidic. The goal is to trigger a chemical process in which microorganisms in the water begin to convert ammonium salts into nitrates and produce by-products, N2O.

The team found that in a specific area of the Pacific Ocean, the sub-Arctic region near the northern island of Hokkaido, Japan, the more acidic the sea water significantly increased N2O production.

Interestingly, in the sample, the team recorded a decrease in the actual rate at which ammonium salts were converted to nitrates, but N2O production increased. The team isn’t sure what’s causing this, but it’s possible that changes in pH affect other biochemical mechanisms in unexpected ways.

The new study supports previous research that found that ammonium salts are decreasing in rate of nitrates, but the difference is that earlier studies concluded that N2O levels also decline — the opposite of what the new study found.

The team acknowledges that for the time being, these conclusions are valid only for the part of the water they tested. Further research is needed to determine whether this phenomenon also applies to other sea areas.

The study was published in Nature Climate Change.

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