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August 2018    Download the Entire Issue (PDF) Available to the Public Vol. 44, No. 8   RSS Feed for Undercurrent Issues
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Quiet, Please! Marine Noise is Making Fish Deaf

from the August, 2018 issue of Undercurrent   Subscribe Now

Jacques Cousteau first sold us the idea of the "silent world," but it patently isn't. Use a closed-circuit rebreather and you'll realize how noisy a busy coral reef can be. Yes, fish make noise (around 800 different species are thought to produce sound), and the noises they make are crucial to their way of life.

But civilization, as usual, gets in their way. You only have to be underwater near a busy shipping lane to understand that -- the noise a ship makes is a veritable din. It's estimated that since the 1950s, the ambient noise level in the ocean has risen about three decibels per decade, making a four-fold increase.

It's difficult to state the scale of the problem, because scientists have only begun exploring the ecological impact of such noise pollution. But now a systematic review of 42 research papers by scientists from 11 different countries reveals that human-generated noise has a significant negative effect on fish behavior and physiology.

In this summary, titled "A Meta-analysis of the Effects of Marine Noise on Fish," researchers at Hakai Institute and the University of Victoria in British Columbia found that in the presence of increased noise pollution, both volume and frequency, fish move faster, dive deeper and change direction more frequently. They are also less able to respond to predatory attacks. Foraging ability also takes a hit. In short, we're deafening them.

It's not only mechanical noises. A data analysis of sound signatures published in Acoustics Australia reveals that human activities like swimming, canoeing and scuba diving can even be heard underwater by marine life.

Steve Simpson, a marine biologist at the University of Exeter in the United Kingdom, agrees. "Recent studies have proved that even plankton are sensitive to noise," he says. "Fortunately, marine noise can be controlled. There are technologically-driven ways to reduce human--produced noise in the ocean."

Does this mean that we noisy air bubbling divers should avoid grouping together underwater, or should we opt to train to exclusively use close-circuit rebreathers for "silent diving"? As for the sounds of generators, compressors and engines from our dive boats, this might be a lost cause.

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