A growing sensory smog threatens the ability of fish to communicate, navigate, and survive

Ocean acidification can confuse how a clownfish reacts to predators.

An 11-day-old clownfish, pale orange and about as long as a grain of rice, searches for a place to settle down on a reef. Its keen sense of smell helps it both navigate to a safe home and steer away from the mouths of predators.

In the wild, clownfish inhabit living coral reefs. But in behavioral ecologist Danielle Dixson’s laboratory at the University of Delaware in Lewes, the habitats beckoning the fish are made mostly of wires. Dixson will use the experimental setup to study how ocean acidification could alter how fish perceive and respond to their world.

The laboratory—a converted garage with black bags taped over the windows to block bright light—holds two bays of fish tanks. A network of densely draped cables connects sensors in the aquariums to a black box on the wall, which researchers call “the brain.” It helps them monitor and control water temperatures and acidity levels in each tank.

In some tanks, Dixson will keep clownfish and other species in seawater with the acidity levels found now in the ocean. In other tanks, the water will be more acidic, to mimic the ocean chemistry that’s forecast for later this century if humans do not curb CO2 emissions. In both cases, conditions fluctuate during the day, as on a real reef. The researchers will look at how pH levels affect the way fish behave, interact, and respond to olfactory cues.

Elizabeth Preston, 20 July 2019, Science Magazine. Press release.

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