As kelp forests decline, scientists worry sensitive sea creatures are losing a sanctuary from sonic overload
The sea is calm and, for the moment, relatively quiet. But marine ecologist Kieran Cox is about to change that. He hits play and suddenly the deep hum of a large ship surging through ocean swells emanates from a waterproof speaker. Sound waves ripple toward a lush underwater forest off the west coast of Vancouver Island.
Cox, a postdoctoral fellow at Simon Fraser University, has a theory that kelp forests may offer sea creatures a quiet refuge from a growing barrage of ocean noise. As they disappear, destroyed by hungry urchins and thinned out by warming seas, he and other scientists are racing to understand what could soon be lost. “We’re losing kelp forests at a pretty alarming rate in some places,” Cox said.
It’s early September and nearing the end of Cox’s field season in Barkley Sound. Today is a demonstration of the noise experiments he’s been running all summer, usually with underwater recorders to measure any shifts in volume as the sound travels through the stand of giant algae. Suddenly, a seal pops its head above water, and Cox, wanting to protect it from the noise, halts the experiment. “Oh no, let’s pull that up,” he says, and the speaker is lifted from the water.
Sea creatures’ sounds are being drowned out by human noise
Drenched in dew, the Bamfield Marine Sciences Centre glimmers under the pastel skies of a late summer morning. Recreational fishing boats are already on the move, puttering out through the inlet by the time Cox wanders into the kitchen of his shared cabin.
He starts each day with a quad shot americano and has another coffee in hand as he heads out the door with his colleagues, past the seaweed drying on the porch railing. It’s a short trek downhill to the dive shed. Here, the team readies their dry suits, air tanks, life jackets and totes of various scientific equipment. Then a black bear ambles onto the scene — and sound erupts. There’s clapping, yelling and the sharp blasts of a whistle.
Not all noise humans create is meant to affect wildlife, but a lot of it does. Zebra finch chicks, for instance, struggle to learn their melodies against the constant drone of traffic, which can also make bats less effective hunters. For humans, noise is a known stressor. It can make it impossible to sleep, damage our hearing and is even linked to high blood pressure, a risk factor for heart disease. Underwater, the impacts of noise can be even more intense — sound waves travel faster and farther through water than they do through air.
In the dim underwater world, marine animals rely heavily on sound to communicate, find food and protect themselves from predators. The ocean reverberates with their clicks, squeaks, whistles, wails, grunts and groans. The sounds dolphins, sea lions and whales make are familiar by now, but fish make noises too. “They’re bubbling at each other, they’re singing to each other, they’re humming to attract their mates,” said Cox, whose research is supported through a Liber Ero Fellowship and the Natural Sciences and Engineering Research Council of Canada.
Fish don’t need external ears to hear because their bodies are roughly the same density as water. “The sound wave literally just … goes right into the side of their head,” Cox explained. And as it passes through their bodies, it strikes the otolith, a small bone that helps fish hear.
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