Protecting Ocean Ecosystems
Navigating a Noisy Ocean
Daily life is loud: cars honking, planes flying, and doors slamming. But we often do not think about how human-generated sounds can travel below the ocean’s surface. Our everyday activities fill the underwater seascape with a chaotic clamor of “ocean noise” that can be detrimental to marine life.
Sources of ocean noise
Four major noise sources pollute the ocean: explosives, seismic air guns, military sonar, and ship traffic.
- Explosives are detonated in the ocean by the military, oil and gas industry, and scientific researchers during demolition, seismic exploration, and equipment testing. These explosives create sudden bursts of high noise levels.
- Seismic air guns are commonly used to locate oil and gas beneath the seafloor by shooting air into the water at very high pressure. Twenty air guns can be firing at once, every ten seconds for 24 hours a day. At any time, anywhere from 20 to 40 seismic air gun surveys are happening around the world.
- Military sonar is used by military vessels to locate objects in their path. This sonar system deploys 100-second-long pulses of sound for hours at a time, saturating miles of ocean with noise.
- Ship traffic is the most prevalent ocean noise source. It gives off low-frequency sounds that travel far distances in every direction. Noise from ship traffic increases with increasing vessel speed—the faster the ship, the louder the sound.
In addition to these sources, other human activities affect the soundscape of the ocean including pile driving for offshore wind, “pingers” to repel marine mammals from fisheries activities, and industrial activities along the shoreline.
Ocean noise disrupts marine life
Generally, human-generated ocean noise can range anywhere from 116 to 279 decibels—that is twice as loud as a jet engine from 100 feet away. Ocean noise is particularly harmful because sounds travel faster and farther underwater. The density, salinity, and depth of the water determine the frequency of the sound, and even sounds at low frequencies can travel across entire oceans.
Ocean noise greatly impacts marine life. Over 20,000 fish species can hear, and many use sound to hunt, navigate, communicate, and mate. Fishermen report a 40 to 80 percent decrease in landings when there is nearby use of explosives and seismic air guns. Blasts from explosives and air guns can also damage invertebrates’ orientation and balance, making them especially susceptible to predators.
Ocean noise also impacts the health and welfare of marine mammals. Disruptive human-generated sound can temporarily or permanently impair a marine mammal’s hearing, affecting its ability to communicate, avoid predators, find mates, avoid vessels, and hunt prey. In some cases, ocean noise can displace marine mammals from foraging habitat, migratory pathways, and pods. In other cases, ocean noise can cause hemorrhaging around the brain, air cavities, and lungs, often leading to severe injury and death.
North Atlantic right whales, for example, face considerable impacts from ocean noise because they rely on a variety of low frequency sounds to survive. For instance, right whales use an “up call”—a short “whoop” sound—that brings whales together.
Mitigating the harmful impacts of ocean noise
Fortunately, federal laws like the Endangered Species Act (ESA) and the Marine Mammal Protection Act (MMPA) exist to mitigate or prevent these harmful impacts on marine mammals.
The ESA requires federal agencies to assess how their actions may impact threatened or endangered species. Agencies must ensure that their actions do not “jeopardize the continued existence” of an ESA-listed species or result in “destruction or adverse modification” of the species’ critical habitat.
The MMPA limits the number of marine mammals that can be disturbed or injured by human activities. Under this act, regulators must ensure that human-generated noise has no more than a minimal impact on endangered species such as the North Atlantic right whale.
Beyond these laws, additional actions can be taken to mitigate the harmful impacts of ocean noise on marine life. For example, offshore developers can utilize acoustic monitoring to detect the presence of marine mammals and halt harmful activities if an animal is in the vicinity. Additionally, vessels could have trained observers aboard to watch for whales and other protected species ahead. Then, a vessel could slow down or be redirected – reducing sound and the risk of vessel strikes.
Regulations and laws that require mitigation of ocean noise and other harmful activities can protect marine life like the critically endangered North Atlantic right whale. With increasing globalization and technological innovation, we must aim to strengthen protections for all life under the sea to ensure a healthy marine ecosystem.