Oil spills, rising sea levels, temperature increases, and plastic contamination continue to disrupt marine ecosystems and animals, but most people are unaware of the effects of ocean noise pollution.
Since 2001, human activity in the oceans, including merchant shipping, seismic testing, and military drills, has increased significantly. Although the problem seems to be getting worse, government officials, shipping industry executives, and military leaders have been slow to address the issue. Unless the noise level is decreased, marine animals will continue to suffer and perish.
What Causes Ocean Noise Pollution?
Any loud sound caused by humans can contribute to noise pollution, but the activities that harm the ocean the most are sonar testing from the military, industrial shipping (primarily container ships), and seismic testing for oil production.
Since water is denser than air, sound can travel four times faster in the ocean. Underwater visibility is limited in the sea, and marine creatures have adapted to the murky water by relying on sound for hunting, defending territories, communicating with others, selecting mates, navigating, and avoiding prey.
When a disruptive noise interferes with an animal’s hearing, it can become disoriented and attempt to flee the sound. Unfortunately, escaping the noise can be as deadly as staying in place. In 2008, a group of narwhals changed course during their southward migration after being subjected to nearby seismic testing in Baffin Bay, Canada.
Over 1,000 whales died when they became trapped in the ice. Navy sonar and seismic blasts affect numerous marine species, including beaked whales. When the high-decibel sounds spook the whales, they alter their dive patterns, and some die from decompression sickness when surfacing.
What Are the Different Types of Ocean Noise Pollution?
The primary contributors to ocean noise pollution are seismic air guns, military sonar, and merchant ships. Marine animals with enhanced hearing don’t have to be right next to the noise for it to affect them, but close proximity to a loud sound can have a devastating effect.
A nearby blast from a seismic gun or sonar can force a whale or other marine species to swim toward the surface frantically. If the creature ascends too quickly, it can become overwhelmed with decompression sickness. Gas bubble lesions and tissue damage can result from decompression sickness, which can invariably lead to death.
An unfortunate result of underwater sonar testing is that it leads to beaching. North Carolina’s Outer Banks were notorious for sinking ships during the colonial period, but the area was just as deadly for whales in 2005. When the U.S. Navy conducted sonar training near the coast, 34 whales became trapped after moving to shallow water and died.
How Disruptive Are the Sounds?
Marine creatures have several harmful sounds to contend with, but seismic air guns are the most disruptive and detrimental.
Seismic Air Guns
The air guns are mounted on massive ships and used to map the ocean floor and detect oil deposits. Although an air gun can create 260 decibels of noise on its own, seismic mapping operations involve multiple ships and guns that slowly creep along the ocean in uniform rows.
Around the world, up to 40 seismic surveys occur at the same time for geological studies and gas and oil exploration. If you heard a seismic gun fire above the water (in the atmosphere), the sound would register 200 decibels. For comparison, an incredibly loud rock group registers 130 decibels, and a space shuttle launch generates 160 decibels.
When whales, fish, and invertebrates are subjected to deafening sounds, the underwater environment becomes a stressful nightmare. In 2017, a study proved that air guns could also disrupt the primary food source for whales and shrimp. When an intense blast, slightly less noisy than an air gun, occurred near a colony of zooplankton, it killed two-thirds of them.
Initially, Navy sonar (sound navigation and ranging) was developed to detect enemy submarines, but it’s always been used for navigation and to detect mines. At 235 decibels, the sound from sonar can send the marine life fleeing for their lives; some escape harm, but others die from decompression sickness or suffocate from beaching. Mass strandings of whales and other large marine animals have occurred near Navy sonar drills, and the sounds can also cause hearing loss in several aquatic creatures.
Although the sound generated from a large ship’s propellers registers fewer decibels (190) than air guns or sonar, the substantial number of merchant vessels operating at one time create an unlivable underwater atmosphere for nearby marine life. The noise masks other sounds that whales, dolphins, and fish depend on for survival. Container shipping noise can cause marine animals to alter their communication; bottlenose dolphins began using higher-pitched whistles and simpler calls to compensate for nearby shipping noise. Marine scientists worry that the changes to the mammal’s communication could reduce reproductive success since it could make it more challenging to connect with mates.
What Are the Solutions to Ocean Noise?
In 2011, the World Health Organization designated anthropogenic (human-created) noise to be a global pollutant. Although that seems admirable, the 20,000 marine fish and 170,000 species of multicellular invertebrates affected by noise pollution require more than official declarations. The author of 2018’s “The Impact of Ocean Noise Pollution on Fish and Invertebrates,” Dr. Lindy Weilgart, had several recommendations to reduce ocean noise and protect marine life.
Frequently Asked Questions (FAQs)
Which types of studies will help scientists determine the severity of our ocean noise pollution problem?
Although it seems like several studies have been conducted on noise pollution in the ocean, scientists still know little about the exact effect of noisy devices. Government agencies, marine organizations, and private firms need more funding to conduct extensive studies. More research and funds also need to be directed toward improving technology for marine vessels, seismic equipment, and ocean-mapping techniques.
Which human activities cause the most noise?
Seismic air guns have the highest decibel level (260 decibels) of any underwater devices. Since 10-decibel increases are an order of magnitude, an air gun blast is 10 times more powerful than the noise from a large ship. An electronic sensor can detect an air gun noise from 4,000 kilometers away, and since sound travels quickly in water, marine creatures do not have to be nearby to be affected.
Besides whales and fish, which marine animals are most affected by noise pollution?
Invertebrates can also be harmed by seismic testing, sonar, and shipping noise. They have an organ, the statocyst, that’s responsible for controlling balance and orientation. When a loud blast disrupts the statocyst, the invertebrate becomes confused and vulnerable to nearby predators.
A Quick Reference Guide
Here is a breakdown of the noise level of sounds that disrupt marine life
|Noise Type||Level of Noise (in decibels)|
|Seismic air gun||260|
|Industrial propeller (from ships)||190|
Although the U.S. Navy, marine shipping officials, and fishing industry executives have minimized the risk of noise pollution to marine life, the research conducted in the last 30 years has established a connection with marine fatalities and injuries to seismic air guns, sonar, and shipping vessels. Until more studies are initiated on a massive scale to find solutions, marine animals will continue to live in an agonizing underwater environment overwhelmed by life-altering noise.
Featured Image Credit: alex pixel, Unsplash