Fish follow their noses to navigate the world, but that may soon be tricky. As the climate warms and oceans hold more carbon dioxide, fish will have to get 42 per cent closer to an odour source to find mates, hunt prey, or make their way to spawning grounds.
That鈥檚 what Cosima Porteus at the University of Exeter found when she and her colleagues subjected European sea bass to elevated CO2. They observed sea bass in water that mimics the level of ocean acidification predicted by the year 2100, and measured changes in their olfactory nerve.
Porteus and her team exposed the fish to 10 odours: amino acids found in protein, which produce odours fish use to find food; bile acids, which help fish recognize whether another fish of their species is male or female, or sexually active; and a chemical alarm cue that helps them detect predators.
Advertisement
The nerve activity was lowered in response to three of the amino acids and the bile, which meant the fish would have to be two to five times closer to the source to smell it. The team found that less information was being taken in by the olfactory nerve, and from there, less information was being transmitted to the brain centre for processing.
Nose blindness
Finding your way through an acidified ocean would be like walking through the world with foggy glasses. 鈥淭hey would have a hard time finding suitable habitats and finding mates,鈥� Porteus says. Some species need to travel long distances using their sense of smell to navigate, which would get trickier.
There could be a trade-off here, though. It would be harder to hunt, but also harder to be hunted.
These findings may apply to many other fish, as well as invertebrates like crabs or lobsters, Porteus says. And if so, the seascape could change drastically. Depending on the species, populations could plummet, she says.
鈥淭here are going be some winners and some losers when it comes to climate change,鈥� says Danielle Dixon at the University of Delaware, who was not involved in this work. 鈥淓els, for instance, are notorious for having pretty bad eyesight, but they鈥檙e very good at chemical recognition. They may be disadvantaged if CO2 levels rise.鈥�
