Blue Noise

The effects of noise pollution in the ocean may not be immediately obvious but they could nonetheless be profound.

AsianScientist (July 14, 2017) – The first thing I do when I walk past a construction site is cover my ears. After watching friends struggle with hearing loss, I decided to do everything possible to remove from my orbit any noise exposure that could jeopardize my hearing. As someone who loves music, the thought of losing my ability to hear is a sobering one.

The world I know today is loud, and not just for city-dwellers like me. Creatures that live far away from me, underwater, where I cannot see them unless I don my diving gear, are also encountering loud noise. Like me, they live in a noisy world. Unlike me, they do not have the luxury of hands that act as makeshift earmuffs.

The ocean has long been awash in ambient noise. Waves, wind and earthquakes contribute to a lively acoustic environment in the ocean. The vocal repertoire of marine mammals like dolphins includes high-pitched whistles and squeaks that resemble a creaky door. And many animals, even the tiniest ones, make noise as they go about their lives underwater.

Humans are increasingly adding their own sounds into the mix. High-traffic areas like the Strait of Malacca—a waterway through which nearly half of yearly global seaborne trade passes—are full of ship noise, which can be as loud as a rock concert.

Daia Husein, a marine and coral curator at The Andaman resort in Langkawi, Malaysia, said that the many speedboat companies operating around Langkawi also contribute noise to the water. So does a fishing method that local fishermen use: hitting shallow reef floors with a rod to attract their catch.

“It gives a shock to the fish,” Daia said. “It really works.”

Not-so-silent screams

Add noise from offshore oil and gas drilling, sonar and overflying aircraft into the mix, and the din can be formidable. For marine animals, it can be a game-changer. Some are modifying their behavior in the face of auditory masking, which occurs when a sound prevents animals from hearing important signals.

One response is to simply ‘talk louder,’ just as humans might if a noisy restaurant kept them from hearing their dining partner. Right whales, for example, make louder calls in high background noise. Others avoid areas with non-ideal noise levels, like the harbor porpoises that a 2001 Marine Ecological Progress Series study observed keeping a few hundred meters between themselves and an acoustic pinger. Some creatures stop making noise altogether.

At face value, these responses seem benign. After all, we suffer few dire consequences from raising our voices in a crowded bar or skipping a deafening sports event. But the exact costs of the coping strategies to marine animals are still fuzzy, and it is unlikely that they do not exist. We also do not know whether animals have an infinite capacity to compensate for unwelcome noise.

“There has to be a biological limit—you can’t just scream louder and louder,” Curtin University Centre for Marine Science and Technology Director Christine Erbe said. “How much energy does it take for you to constantly repeat what you are saying at a higher level?”

For some animals, behavioral change is not an option or does not work. In 2016, scientists discovered that motorboat noise makes damselfish twice as likely to be eaten by predators than they would be in their normal acoustic environment. What would happen if a chimpanzee released smoke bombs into the air as an airplane was trying to take off from a runway?

Other consequences of noise can be sneakier, but are no less concerning.

“You don’t have to deafen an animal or cause tissue trauma to cause them harm,” scientist John Potter, who founded the National University of Singapore’s Acoustic Research Laboratory, told me.

Instead, you could mask their ability to hear just enough such that they were unable to find mates or socialize as they normally would. You might never see a straightforward ‘reaction’ from an animal, yet—“If it was persistent enough, you could drive a species to extinction,” Potter said.

Far-reaching consequences

Sound in the ocean is too important not to take seriously. The ‘talking animal’ trope in movies like The Lion King has its roots in reality: many marine animals rely on sound to survive, using it to attract mates, find food and navigate. And unlike light, sound travels well underwater. Swimming in the ocean, you would be hard-pressed to see something tens of meters in front of you, but you could certainly hear a speedboat from a far greater distance.

“Sound just goes,” Erbe said. “The geographic area over which you can affect animals [with sound] is humongous.”

Experts have suggested that noise could have contributed to the functional extinction of China’s Yangtze river dolphin. The dolphins, which are almost blind and depend heavily on sound, may have collided with boat propellers as a result of confusion from boat noise.

Southeast Asia, where I first discovered my love for the ocean, has a lot at stake if external stressors like noise deteriorate its waters too much. The region’s oceans house some of the world’s most precious marine treasures. The world’s center of all centers for marine biodiversity is the Coral Triangle, a six-million-square-kilometer area that covers the waters of the Philippines, Indonesia, Malaysia, Papua New Guinea, Timor-Leste and the Solomon Islands.

This swathe of ocean hosts three quarters of all the coral species in the world and is home to blue whales, dugongs and over 2,000 varieties of reef fish, among other inhabitants. By some estimates, it is a source of food and income for 120 million people who live in the region, and many more outside of it.

Sound in the ocean is too important not to take seriously.

Marine gold though they are, the waters and coasts within the Coral Triangle buzz with noise-generating industries that are key to the region’s economies. The oil and gas industry, which makes noise via drilling and seismic surveys, contributes 20 percent of Malaysia’s gross domestic product, for instance. Constellations of ships used in maritime trade dot the waters around the region’s ports.

Meanwhile, worrying numbers of small-scale fishers, who face competition from industrial operations and sometimes lack adequate fishing equipment, rely on fish ‘bombing’ to make their catch. Fish bombing involves homemade contraptions constructed from bottles, fertilizer and gasoline that blow up underwater, killing the life around them—and, of course, creating a big, explosive noise.

Unknown but not innocuous

In a 2011 article for Oceanography magazine, Erbe and her colleagues described the relationship between sound and marine organisms as “one of the big unknowns of current marine science.” Today, she stands by this description. “There’s still so much we don’t know,” she said.

Studying marine animal behavior is a challenge at the best of times—it takes considerable resources to follow any population in the wild around enough to observe what it is doing. And it is tough to pin down definite cause-and-effect relationships between noise and animal behavior in the oceans. The wild is full of influences apart from acoustic exposure that can stress marine animals on multiple different axes at the same time, with each individual influence aggravating the others. That sound does not necessarily have an immediate impact on animal survival complicates matters further.

“When a bunch of whales beach on a popular bathing spot, that’s clear, obvious, dramatic,” Potter said. “But if you don’t have an observable, direct, individual response, it’s very hard to explain.”

In Southeast Asia, the unknowns are particularly unknown. Biologists have examined how noise affects marine life since at least the 1970s, but much of the existing work on how oceanic noise affects animal behavior focuses on other parts of the world—though many of the species that have been studied also live in the Coral Triangle.

As the region’s oceans continue industrializing in the midst of economic and population growth, it is unclear how noise in the ocean will affect those who do not live in it. The ocean is far from a vacuum. In a part of the world that is at once politically complex and extremely reliant on healthy oceans, oceanic noise and its consequences for marine life could affect areas from food security and income inequality to migration and cultural integrity.

Though it supports life, directly or indirectly, for so many, the ocean remains largely an abstraction for a lot of those who spend little time interacting with it for work or recreation. And oceanic noise exceptionally so.

Daia said she has encountered little awareness of oceanic noise during her time as a conservationist in Malaysia.

“People don’t really talk about noise pollution—they talk about trawling and fish bombing,” Daia said, adding that she hopes to see more efforts to educate the public about the issue.

Many people, according to Erbe, are not aware that marine creatures—even invertebrates like shrimp and urchins—make or use sound at all.

“It’s not photogenic, it’s not obvious,” Potter said. “What’s in the ocean is largely unseen.”

This article won first place at the 2017 Asian Scientist Writing Prize.

Click here to see photos of the the prize presentation ceremony held on July 7, 2017.
Also, look out for the other winning entries to be published in a compilation coming out later this year.


Copyright: Asian Scientist Magazine; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Tara Thean is a research associate at the Lee Kuan Yew School of Public Policy. She received an MPhil in Biological Science from the University of Cambridge.

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