And, she added, because the high carbon dioxide levels were found to affect the nose and at least two parts of the brain, adaptation would have to take place at multiple levels, which would make it hard to predict how the fish would adapt — if they even had time to do so.
The changing acidity of the ocean, measured in pH, has implications far beyond the sense of smell, including a possible deficit in reproduction, said Mary Hagedorn, a senior research scientist at the Smithsonian Conservation Biology Institute who studies fish, coral and climate change.
And while some species will find ways to adapt, “we don’t know the limits of those adaptations,” she said. “There will definitely be winners and losers.”
Carbon dioxide levels have been increasing over the last 200 years because of the burning of fossil fuels, car emissions and deforestation, all of which have resulted in more acidic oceans, according to the National Oceanic and Atmospheric Administration. That’s because the oceans absorb about 30 percent of the carbon dioxide released into the atmosphere, and when carbon dioxide is dissolved in ocean water it turns to carbonic acid.
Since the start of the Industrial Revolution, surface ocean waters have experienced a 30 percent increase in acidity, the agency says.
“We should take all of this extremely seriously,” Dr. Hagedorn said.
Dr. Porteus said her future research would aim to determine if fish are already being affected by the rise in carbon dioxide compared with preindustrial levels. She also hopes to find out the level of carbon dioxide that starts to affect the sense of smell of fish.
“It’s likely that this will become a problem at a lower CO2 concentration than that tested in our study,” she said.
While the outlook might seem dour, there is still time to take preventive measures and reduce carbon emissions, Dr. Porteus said.