'They get blinded' How underwater noise pollution is posing a threat to Norway's whales

From the moment that the biologist Dr Heike Vester presses play, sounds of static from the fjord fill the room. First comes the constant, steady rumbling of a boat engine. Then, every eight seconds, like a foreboding bass drum, comes the explosion of seismic airguns - extremely loud blasts used in oil and gas exploration that can travel vast distances underwater. And finally, dancing above it all - and at times drowned out by it - are the soaring vocalisations of whales.

- Miranda Bryant

"Here, we have sperm whales clicking, pilot whales and seismic airguns," Vester says. During another recording playback, she points out the sound of a tourist boat's gears shifting as it follows a group of feeding orcas. Suddenly, as the engine sound becomes overwhelmingly loud, the whales' calls become almost inaudibly faint.

"It really affects their feeding," Vester says. "As soon as there's boat noise, they can't feed any more. Whale-watchers should be aware of that."

These underwater recordings, playing from Vester's laptop at her home near Bodø, in the Norwegian Arctic Circle, are among hundreds she has made over decades in Vestfjorden.

Every year from April to October, whenever the weather allows, she lies for hours in a little boat with headphones on, listening to what her hydrophone picks up from 20 metres below the surface.

The fjord, which is passed by the Gulf Stream coming up from Scotland, is visited by orcas, minke, humpback, sperm and long-finned pilot whales. Blue whales have recently made a return.

But noise pollution now threatens all that, she says. It comes from cruise liners and tourist boats (many of which do not turn off their engines even when whale-watching), cargo ships, oil and gas exploration, and the military - along with issues posed by commercial fishing nets and pollution - and is growing in frequency and volume, she says.

Unlike the majority of humans, who see with their eyes, in the darkness of the ocean whales and dolphins see with sound. It is like going into a dark room and scanning the room with a torch, she says, only for somebody to suddenly turn on a big light.

"You get blinded. And that's how it is for the whales with noise - they get blinded. It's not just a masking of the communication," Vester says.