Scientists search for ‘acoustic wilderness’ in the oceans

ship
A supply ship lumbers through the biodiverse waters of the Antarctic Sound. @bberwyn photo.

Staff Report

Ocean scientists are advocating for the designation of quiet zones to help gain a better understanding of how noise pollution affects marine life.

Creating areas where ship traffic is limited would help researchers find the best way to protect marine life from harmful noise, according to a new study published in the journal  Marine Pollution Bulletin. By assigning zones through which ships cannot travel, researchers can help find the best way to protect marine life from harmful noise.

Almost all marine organisms, including mammals like whales and dolphins, fish and even invertebrates, use sound to find food, avoid predators, choose mates and navigate. Chronic noise from human activities such as shipping can have a big impact on these animals, since it interferes with their acoustic signaling. Increased background noise can mean animals are unable to hear important signals, and they tend to swim away from sources of noise, disrupting their normal behavior.

Loud sound like underwater blasts and sonar testing has also been shown to have direct impact on marine mammals. Such high intensity sounds are suspected as the cause of whale and dolphin strandings.

The number of ships in the oceans has increased fourfold since 1992, increasing marine noise dramatically. Ships are also getting bigger, and therefore noisier. In 2000 the biggest cargo ships could carry 8,000 containers; today’s biggest carry 18,000.

“Marine animals, especially whales, depend on a naturally quiet ocean for survival, but humans are polluting major portions of the ocean with noise,” said Dr. Christopher Clark from the Bioacoustics Research Program, Cornell University. “We must make every effort to protect quiet ocean regions now, before they grow too noisy from the din of our activities.”

The researchers identified high- and low-noise areas around Canada by assessing existing ship traffic and measured noise with a network of hydrophones, helping to locate potential noise conservation zones.

“We tend to focus on problems in conservation biology. This was a fun study to work on, because we looked for opportunities to protect species by working with existing patterns in noise and animal distribution, and found that British Colombia offers many important habitat for whales that are still quiet,” said Dr. Rob Williams, lead author of the study. “If we think of quiet, wild oceans as a natural resource, we are lucky that Canada is blessed with globally rare pockets of acoustic wilderness. It makes sense to talk about protecting acoustic sanctuaries before we lose them.”

Although it is clear that noise has an impact on marine organisms, the exact effect is still not well understood. By changing their acoustic environment, we could be inadvertently choosing winners and losers in terms of survival; researchers are still at an early stage of predicting who will win or lose under different circumstances. The quiet areas the team identified could serve as experimental control sites for research like the International Quiet Ocean Experiment to see what effects ocean noise is having on marine life.

So far, the researchers have focused on marine mammals – whales, dolphins, porpoises, seals and sea lions. With a Pew Fellowship in Marine Conservation, Dr. Williams now plans to look at the effects of noise on fish, which are less well understood. By starting to quantify that and let people know what the likely economic effect on fisheries or on fish that are culturally important, Dr. Williams hopes to get the attention of the people who make decisions that affect ocean noise.

“When protecting highly mobile and migratory species that are poorly studied, it may make sense to focus on threats rather than the animals themselves. Shipping patterns decided by humans are often more predictable than the movements of whales and dolphins,” said Erin Ashe, co-author of the study and co-founder of the Oceans Initiative from the University of St Andrews.

Keeping areas of the ocean quiet is easier than reducing noise in already busy zones, said the study authors. However, if future research that stems from noise protected zones indicates that overall marine noise should be reduced, there are several possible approaches to reducing noise.

The first is speed reduction: the faster a ship goes, the noisier it gets, so slowing down would reduce overall noise. The noisiest ships could also be targeted for replacement: by reducing the noise produced by the noisiest 10 percent of ships in use today, overall marine noise could be reduced by more than half. The third, more long-term, option would be to build quieter ships from the outset.

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