The underwater world is full of natural sounds produced by the motion of the atmosphere, water, and seafloor as well as animals. These sounds form a rich soundscape of rumbles, grunts, bubbles, and clicks, which allow marine animals not only to communicate but also to survive. However, noise from human activities has increased along our coasts, offshore, and deep-ocean environments, disrupting marine life in many serious ways.
Ocean Noise Fundamentally Disrupts Marine Life
Previous studies revealed that an increase in ocean noise levels reduces the ability of animals to communicate with their offspring, feeding partners, potential mates, or other group members. It also reduces their ability to hear environmental cues that are vital for survival, including those key to avoiding predators, finding food, and navigating to preferred habitats. One of the latest examples of how humans initiate activities that encourage ocean noise is underwater sonic tests.
In 2019, the US administration allowed offshore drilling for gas and oil exploration. Over five companies sought permits to use seismic air guns across the Eastern Seaboard, the most common method companies use to map the ocean floor which can produce the loudest noise that humans use regularly underwater. “They fire approximately every 10 seconds around the clock for months at a time. They have been detected 4,000 kilometers away. These are huge, huge impacts,” Douglas Nowacek, a professor of marine conservation technology at Duke University, said.
According to The New York Times, an American newspaper based in New York City with worldwide influence and readership, experts fear that ocean noises from air guns, ship sonar, and general tanker traffic can fundamentally disrupt the marine ecosystem. Not only can it diminish populations of some species but also it can also cause the outright death of sea creatures, from the giants to the tiniest — whales, dolphins, fish, squid, octopuses, and even plankton. At the same time, high ocean levels can cause brain hemorrhaging, impairing animals’ hearing. and the drowning out of communication sounds important for survival.
While there’s no global map of ocean noise, researchers agree that ship traffic approximately doubled between 1950 and 2000. According to Nature, a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology, this has increased sound contributions by about 3 decibels per decade, which translates to a doubling of noise intensity every 10 years.
A 2017 study, for instance, revealed that nearly two-thirds of the zooplankton in three-quarters of a mile was killed due to a loud blast — softer than the sound of a seismic air gun. “Researchers saw a complete absence of life around the air gun,” said Michael Jasny, director of marine mammal protection for the Natural Resources Defense Council, one of several environmental groups suing the federal government to stop the seismic surveys.
Several reports have also shown masses of dead beaked whales found on beaches. The researchers recorded seven mass strandings of marine species in the five decades before 1950. But from then to 2004, there were more than 120. A 2016 study conducted by the US National Oceanic and Atmospheric Administration suggested that the pulses of sound above 160 dB cause marine mammals to change their behavior. The best evidence that shows how ocean noise impacts marine life came from data on killer whales off the Pacific coast of Canada.
The researchers said that while only 75 southern resident killer whales remain in this area, they still battle for food. They also reported that the whales spent 18% to 25% less time feeding when surrounded by boat noise than when bathed in quiet. “We’re not talking about a quality of life issue; we’re talking about something with real impacts,” Rob Williams, co-founder of the cetacean-conservation group Oceans Initiative in Seattle, Washington, said.
Quieter Oceans Amid Coronavirus Lockdowns
As countries enforced lockdowns to contain the spread of coronavirus, everything has become a lot quieter. Declines in the economy have slowed exports and imports by around 20%, causing a dramatic decrease in ocean noise. Oceanographer David Barclay of Canada’s Dalhousie University and his team recently revealed a significant drop in low-frequency sound associated with ships. “Generally, we know underwater noise at this frequency has effects on marine mammals,” Barclay said.
According to The Guardian, a British daily newspaper, the researchers examined real-time sound signals from seabed observatories run by Ocean Networks Canada. The two research locations, which experienced decrease levels of ocean noise, include a deep-ocean site approximately 60 kilometers (37 miles) from the Vancouver port in 3,000 meters (9,842 feet) of water and a more shallow inland site. “There has been a consistent drop in noise since 1 January, which has amounted to a change of four or five decibels in the period up to 1 April,” Barclay said.
One of the sources of the decline of ocean traffic is the drop in tourism due to coronavirus lockdowns. Usually, cruise ship season in southeast Alaska begins in late April. However, the pandemic has halted them this year. “What we know about whales in south-east Alaska is that when it gets noisy they call less, and when boats go by they call less,” Michelle Fournet, a marine acoustician at Cornell University, who studies humpback whales in south-east Alaska, said.
According to Daily Mail, a British daily middle-market newspaper published in London in a tabloid format, the last time the oceans fell quiet was in the wake of the terrorist attacks of 9/11. Previous reports showed that the reduction in shipping allowed experts to determine that ship noise is connected to chronic stress in baleen whales. “We are facing a moment of truth. We have an opportunity to listen – and that opportunity to listen will not appear again in our lifetime,” Fournet said.
The researchers see this as an opportunity to further understand the impact of ocean noise on marine life. Ocean scientists across the world are eager to collect data from this once-in-a-lifetime opportunity to listen. Nathan Merchant, a bioacoustics expert at the UK government’s Centre for Environment, Fisheries and Aquaculture Science (Cefas) in Lowestoft, and his team are already discussing how they could conduct an experiment to make the ocean quieter. Their goal is to find out what benefit it would have.
“We have this natural experiment going on. Of course, it is a terrible crisis, but we may as well get on and look at the data, to find out what effect it is having,” Merchant said.