Imagine you’re at a rock concert without earplugs. Your head hurts and you’re pretty sure the noise is damaging your eardrums. You decide to leave but realize all the doors are locked. Then, you wake up with your hands clenched over your ears, hearing intact – it was only a bad dream.
Unfortunately, this dream is a reality for several marine creatures. Human activity like cargo ships, oil drilling and military sonar sends major sound waves through the ocean. Like concertgoers in a bad dream, these marine animals can’t escape the noise because it pervades their home.
Increased noise levels in the ocean negatively impact orca populations by interfering with their ability to communicate and hunt. In combination with reduced fish populations, noise pollution is a threat to the survival of these apex predators.
Sound and Water
The human ear can detect sound waves between roughly 20 and 20,000 Hertz. This includes noises ranging from the deep punch of a bass to the high-pitched chirp of a cricket. In the air, sounds travel at about 344 meters per second. Temperature and altitude can influence the speed of sound through air.
However, differences in compression and density mean sound behaves a bit differently underwater. It travels about four times faster here than in the air, at around 1,493 meters per second. The distance it can travel depends on temperature and pressure. The ocean works to channel sound over vast distances at a certain level.
This means underwater sounds can travel for thousands of miles while staying very loud. Research shows that human activity such as boat motors and oil exploration adds a lot of noise to the natural ocean soundscape. The energy of these sound waves impacts ocean life even when the sound can’t be heard.
Killer Whales and Sound
Many different marine species are affected by noise pollution, but orcas are particularly at risk because the rely on sound. Although they’re called killer whales, orcas are related to dolphins. They’re highly social mammals that live in maternal pods and hunt cooperatively. Each pod in the Northern Pacific has its own dialect and communicates through a series of whistles, clicks and pulses.
Because light doesn’t go far underwater, orcas also rely on sound to locate prey. Pods use echolocation to find and round up their food together. Scientists have realized that these mammals even use sound to discern different species of prey. For example, Southern Resident killer whales specifically seek Chinook salmon.
Research shows that intense sounds can disorient marine mammals like orcas, causing abnormal behavior. For example, after the navy started using high-power sonar, there was a spike in the number of beached whales – 126 were reported from 1950-2004.
Underwater, the sounds caused by ships falls directly into the frequencies orcas use to hear and communicate. This constant background noise puts pressure on an already stressed animal – several species of killer whales are already endangered because of pollution, overfishing and loss of habitat.
Noise and Killer Whales
Over 70% of the Earth’s surface is covered in water. Because ocean transportation is an essential part of the human economy, it’s not going anywhere soon. However, researchers have been working on reducing noise pollution caused by boats to protect marine species.
One of the tools marine researchers rely on is called a hydrophone. These machines collect information about sound deep underwater within a certain region. Scientists can then listen to marine creatures and determine how human sounds might be interfering with or overpowering their communication.
Some groups are starting to take action as mounting research shows noise pollution’s negative and sometimes deadly effects. However, the response to protect marine life has been slow compared to the exponential growth of disruptive sound in the ocean. Between 1950 and 2000, the noise level underwater doubled every 10 years.
Turn Down the Noise
Noise pollution can be easy to ignore since people rely on sight instead of sound. However, it poses a major threat to marine life, putting particular stress on orca populations. Many scientists and researchers are working hard to understand the effects and devise strategies to reduce it.
Quieter propellers and informed drilling can protect orca populations without disrupting human activity. Some countries have banned arctic ocean drilling to protect marine animals. Becoming aware of the effects of noise pollution is the first step toward turning down the noise so ocean creatures can thrive.