Noise nuisance out at sea isn’t necessarily something most people would think of as being a problem – but they’d be wrong! Humans are causing different types of noise pollution in the ocean that are having a detrimental effect on marine life.
While excess noise can cause health hazards for people living in the vicinity, similarly, noise pollution can cause problems for sea life too. Developments in technology have undoubtedly enhanced the marine industry but at the same time, there’s a price to pay, in terms of the environmental impact.
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More than half a century ago, the famous marine explorer, Jacques Cousteau, released his ground-breaking documentary, The Silent World, telling the story of his underwater explorations. After the film was released in 1953, generations of scientists were inspired into studying the world’s oceans.
Today, scientists have realised the ocean is anything but silent! Researchers are expressing increasing concerns that noise pollution is confusing, distracting and even destroying aquatic life. While natural sounds (such as bubbles produced by the motion of the water, marine life and the creatures on the seabed) pose no threat, additional noise created by humans is taking its toll.
The underwater soundscape now includes the “ping” of military sonar systems, the roar of motors, the blasts and bangs of offshore development, seismic airgun noises from gas and oil exploration, commercial shipping traffic and even coastal leisure pursuits, such as jet skis and motor boats.
According to scientists, the effects on marine life can be disastrous. Research has shown that the frequency used in military sonar testing can harm some marine creatures. Dolphins and whales, in particular, can be affected by underwater sonar, which was originally developed by the United States Navy as a defence mechanism to detect submarines.
The sonar systems can generate sound waves of around 235 decibels. When you consider that the loudest rock bands in the world peak at 130 decibels, it’s easy to imagine how loud the sonar can seem to marine creatures living in its path. These sound waves commonly travel under water for hundreds of miles and up to 300 miles away, they can still retain an intensity of 140 decibels.
Early scientific evidence suggests that whales are swimming hundreds of miles out of their normal region to escape the sonar. In addition, they will change their depth rapidly on encountering loud sonar noises, which can cause bleeding from their ears and eyes.
Research has also shown that the population of dolphins and whales has declined in areas where there’s noise pollution from ships. Researchers use a hydrophone to record and measure the noise from boats to find out where it is loudest.
Breakdown in communication
While the noise from shipping or construction may not kill marine life directly, it can disrupt the sea creatures’ ability to hunt for food, avoid predators and find a mate.
Many marine species rely on acoustic signals to communicate with one another. In particular, marine fish have their own language, consisting of sounds such as chirps, pops and grunts, using their mouth, swim bladder or fins.
When human-made noise interferes with their day-to-day life, it reduces their ability to hear the normal sounds of other sea life. This means they are unable to communicate with each other as they would normally.
The noise can interfere with cognitive processing of normal sounds. A serious consequence is that a fish’s ability to understand what’s happening when the shoal is attacked by a predator can be impaired by excess noise. This can lead to mass deaths.
Research was carried out into the effects of motorboats near Lizard Island research station, at Australia’s Great Barrier Reef. It was discovered that damselfish reacted in different ways to their natural predator, the dottyback, depending on whether boat noise was present or not.
Fish used to the ambient, natural ocean sounds were scared when they sensed a dottyback in the vicinity and would stop foraging and other activities. However, the fish used to boat sounds didn’t appear to be scared at all when in the presence of the dottyback – again exposing them to danger and even death.
Scientists monitored the fish in their natural habitat and noted that in just three days, only 20% that were exposed to boat noises had survived. This compared to a survival rate of 70% of fish not exposed to noisy boats.
Protect the environment
While people tend to think of over-fishing, climate change and refuse pollution as the major threats to marine life, noise pollution is becoming just as big a danger, with a growing body of evidence showing excess noise is killing our fish.
The human race relies on the ocean for its natural resources and biodiversity. It plays a vital role in regulating atmospheric gases and temperatures. Yet the ocean is continually under threat from the pollution caused by people. As a species, humans must protect the marine environment, rather than destroying it.
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