Fish depend on olfaction for a plethora of things, including food discovery, predator evasion, navigation, and recognition. But what happens when fish suddenly lose their sense of smell? The short answer is: it's not pretty.

Image Credit: Cosima Porteus/Nature Climate Change

Reporting in the journal Nature Climate Change, researchers from the University of Exeter call attention to the rising carbon dioxide levels in our planet’s vast oceans and how it impacts fish’ ability to smell out their surroundings in an unfavorable manner.

"Our study is the first to examine the impact of rising carbon dioxide in the ocean on the olfactory system of fish," study lead author Dr. Cosima Porteus said in a statement.

In the lab, the researchers subjected sea bass to varying levels of carbon dioxide and analyzed their behavior throughout the experiment. It became evident that fish with impaired olfaction exhibited higher vulnerability to potential dangers.

"First we compared the behavior of juvenile sea bass at CO2 levels typical of today's ocean conditions, and those predicted for the end of the century. Sea bass in acidic waters swam less and were less likely to respond when they encountered the smell of a predator. These fish were also more likely to "freeze" indicating anxiety."

Related: Reef fish offspring demonstrate above-average tolerance to climate change

The results also showed how the fish became less efficient at hunting and displayed sub-par performance while conducting usual routines or tasks when carbon dioxide levels were cranked up above what is considered normal.

"The sense of smell of sea bass was reduced by up to half in sea water that was acidified with a level of CO2 predicted for the end of the century," Porteus added.

"Their ability to detect and respond to some odors associated with food and threatening situations was more strongly affected than for other odors. We think this is explained by acidified water affecting how odorant molecules bind to olfactory receptors in the fish's nose, reducing how well they can distinguish these important stimuli."

Related: Walleye fish populations appear to be declining

With oceanic carbon dioxide levels rising at an exponential rate, the researchers expect downward trends in not only sea bass populations but in other fish as well. The findings imply horrific consequences for the delicate underwater ecosystem unless we find a way to stunt the progression of said trends.

More research could teach us more about how our ways impact the fish in our oceans, and furthermore, help us discern ways to mitigate the side effects imposed on the environment.

Source: Phys.org