Confronting Underwater Noise Pollution

What is UNP?

UNP, otherwise known as Underwater Noise Pollution, is the rising issue of anthropogenic (human-generated) noise that contaminates our oceans and its habitats. It is mainly caused by heavy use of explosives, oceanographic experiments, geophysical mapping, underwater construction, ship traffic, sonar signals, and seismic air guns used for locating oil and gas reserves.

Why is UNP a Problem?

The main concern of UNP is that cumulation of these noise sources over time poses a significant threat to marine mammals, fish, and other ocean wildlife. Growing amounts of research confirms that the intense soundwaves produced by these noise sources are detrimental to the wellbeing of many marine mammals and corals. They can cause death or serious injury caused by brain hemorrhages or other tissue trauma; temporary or permanent hearing loss or impairment; displacement from their habitats and disruption of feeding, breeding, communication, sensing, and other behaviors vital to the survival of these marine species. Cornell University marine bioacoustics expert Christopher Clark asserts that “we are injecting so much noise [into our oceans] that we are effectively acoustically bleaching the world’s oceans’.”

One of the largest contributions to underwater noise pollution comes from ocean exploration for oil and gas, which is done by seismic air guns. The explosions caused by these air guns are six or seven times louder than the loudest ship sounds. “They are so loud that when someone is surveying off northern Brazil, I can hear that explosion on a small piece of instrumentation that I deploy 60 miles off the coast of Virginia.” says Clark. “Image that every 10 seconds there is an explosion that is rattling grandma’s china out of the cupboard and it is falling on the floor.” When the sound from the explosion travel throughout the ocean, it becomes one big fuzzy ball of resonating sound that fills the water with noise.

One animal that is especially prone to the adverse effects of UNP are whales. Whales see the ocean through sound and are highly acoustically oriented. Their consciousness and sense of self is based on sound, not sight. One species of whales, the Baleen whale, broadcast complex songs and sound patterns over long distance underwater to communicate, but maritime noise pollution is interrupting this ability. Research shows that in Cape Cod Bay near the Boston harbor that Baleen whales lose 50 to 70 percent of their opportunities to communicate due to routine ship traffic. As shipping traffic increases, the ocean area over which a whale can communicate, and listen has shriveled to a small fraction of what it was less than a century ago. What we are doing to these whales is essentially tearing their social fabric continuously over and over again. When it comes to seismic surveys, researchers have noticed whales attempted to hide behind rocks to escape in a sound shadow when surveys were being conducted along the California coast.

However, many researches are hoping that over time the whales will be able to adapt and change their vocalizations to overcome the cacophony. Even though physical adaptations can take eras, behavioral adaptations can occur much quicker. For example, captive whales have been able to lower the threshold of sound that they can receive, and wild whales tend to distance themselves from loud, unnatural noises. Additionally, humpback whales have been shown to increase their call volume to overcome elevated noise levels in the water, similar to humans speaking louder in crowded rooms. 

What Can Be Done About UNP?

There are some operational and technological tweaks that can be made to reduce ships’ noise footprint. For example, ships can slow down and operate outside of breeding grounds and periods, and can also modify their own propellers, hulls, and onboard machinery to become quieter. One way is to mount boat engines so that they are not in direct contact with the hull. Additionally, quiet zones were recently implemented in British Columbia to protect a population of orca whales.

Concluding Remarks

Humans rely on the ocean for its biodiversity and natural resources. They play a fundamental role in regulating atmospheric temperatures and gases. If today’s seas continue to face threats such as UNP, as well as habitat destruction, warming and ocean acidification, we may permanently lose a defining part of our planet as well as thousands of species. By threatening the ocean and its inhabitants, we are effectively threatening the wellbeing of humans as well.

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