Smells fishy: acidic oceans are bad for shark noses

dogfish shark
CC BY 2.0 Dogfish Shark || NOAA

The ocean is vast and meals can be hard to come by. That's why sharks evolved an excellent sense of smell. Some sharks, like the lemon shark, can smell one drop of blood in an Olympic sized pool.

But a new study shows that ocean acidification, the result of atmospheric carbon being absorbed by the ocean, might rob sharks of the sense they most depend on.

Scientists placed dogfish sharks into water treated with levels of carbon that are expected by mid century and by 2100. They found that sharks' sense of smell was impaired.

"The sharks' tracking behavior and attacking behavior were significantly reduced," Danielle Dixson, an assistant professor in the School of Biology at the Georgia Institute of Technology in Atlanta, said in a press release. "Sharks are like swimming noses, so chemical cues are really important for them in terms of finding food."

Instead of swimming towards the odor of a squishy squid meal, the sharks tended to avoid the squid smell completely - even when squid odor was pumped through their waters. Sharks from the control group, who were not exposed to acidic waters, tended to swim towards the source of the smell and spend 60 percent of their time basking in it.

The scientists used odor only so that they could make sure the sharks weren't using any other senses to detect prey. Dixson says they hope to observe other senses in the future.

This is not the first study to show the effect of higher levels of ocean carbon on predator-prey relations. In a previous study, Dixson observed that fish living near areas where carbon seeped through the ocean floor struggled to detect the odor of predators compared to fish who lived in areas without added carbon.

Though sharks have been around for almost 450 millenion years and have adapted to changes in ocean carbon levels, the rate at which ocean acidification is occurring as a result of climate change is alarming. Scientists are concerned that they, and many other species of marine life, may not be able to adapt quickly enough.

Smells fishy: acidic oceans are bad for shark noses
Sharks' sense of smell may get turned off as ocean acidification intensifies.