Predicting climate change risks for commercial fisheries and aquaculture using genetic and physiological approaches in early life stages of fish

Sound and Smell in an Acidified Ocean

Climate change is everywhere, its effects seen in the air, on land and in the sea. The increasing levels of carbon dioxide on Earth interact with seawater, making it more acidic. This change in water chemistry affects both organisms’ sense of smell—predator odors were even found to attract some fish—and the way sound travels through the water, causing low frequency sounds to travel farther. Both sounds and smells are key carriers of information for animals seeking to avoid predators, find food or identify a mate. Dr. Cosima Porteus wondered, then, how an increasingly acidic ocean would affect the behavior of one fish that is important for our food supply, the European sea bass. The consequences she observed could affect their survival.
First, she found that, in acidic seawater simulating predicted future conditions, their sense of smell was only half as sensitive and some odours had to be four times more concentrated to be detected by these fish. This means the bass would need to be much closer to the source of the smell before noticing, say, a predator closing in. Sea bass are also familiar with the sounds made by species that prey on them. Haddock, for example, make noise when communicating or looking for a mate. Though this might alert the bass to the presence of a predator, it should not affect their behavior much, since they can be sure the haddock isn’t hunting. That was true under today’s ocean conditions; however, in the acidic environment, Dr. Porteus found that juveniles became less active upon hearing haddock sounds. It is not yet clear how ocean acidification could lead sea bass to react in what looks like an overly cautious way. Nonetheless, the result could be less time spent on vital activities like finding food and mates. Dr. Porteus now aims to uncover what happens at the genetic level to create such behavior changes, all of which could become a matter of life or death for sea bass and other marine creatures that ecosystems, and we humans, rely on.

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