The Effect of Sound Pollution on Marine Animals

Over 100,000 thousand sea mammals die each year due to marine pollution. Marine pollution can vary from plastic to oil. A form of pollution that is often overlooked and might prove to be a big problem in the coming future is sound pollution, also known as noise pollution. Sound pollution is noise negatively impacting human and animal life. The main source is outdoor noise such as automobiles and machines. It can be found anywhere in the world, even underwater. Underwater noise pollution is caused mostly by commercial trawlers. It is possible that this affects marine life. A few ways it can affect marine life is by shortening their lifespans, damaging their ears and interrupting their mating calls. Firstly, to thoroughly understand this topic, one must know the basics of what sound is.

Sound is created when objects vibrate, as a result, sound-pressure waves are created. A sound wave consists of 3 main parts; frequency, wavelength, and amplitude. Frequency is practically the number of waves that pass by a certain point per unit time. It's measured by Hertz, Hz, or cycles per second. Humans can usually only hear 20 to 20,000 Hz. Sounds that are below 20 Hz are called infrasonic and sounds that are above 20,000 Hz are called ultrasonic. Wavelength is how far apart to waves are. In other words, it is the distance between the peaks of 2 sound waves. Wavelength is related to frequency because the lower the frequency of a sound wave is, the longer the wavelength. Lastly, the amplitude of a wave is the length of it. It is the loudness of a sound. Amplitude is usually measured using the decibel(dB) scale. For example, small variations in amplitude, short waves, result in weak or quiet sounds.

Large variations, tall pressure waves, result in strong or loud sounds. The speed of a wave is talking about how fast vibrations move through a certain medium. For instance, in water, sound moves at 1500 meters per second, while in the air it moves at a speed of about 340 meters per second. Underwater acoustic pollution is caused by various things. They consist of energy exploration, recreational boating, shipping, and seismic testing. Out of these, shipping and seismic testing are the major causes. Thanks to the increasing demand for oil, seismic airgun surveys are often performed to locate oil and gas reserves. The exploration companies that carry out these surveys usually deploy 30 to 40 air guns that all go off simultaneously. The surveys typically go off every 9 to 12 seconds. The pressure created by these surveys results in bubbles that generate a large amount of sound energy where they expand and contract. This testing can last weeks. Ships are very harmful too because their propulsion releases many sound waves that have low frequencies. Low frequencies have the ability to go a long way without losing a lot of energy. Ships usually have frequencies between 20 and 200 Hz.

While these are certainly not the only causes, they are the major ones. Along with decreasing their life spans, noise pollution has an additional effect on marine animals. Noise pollution causes extensive damage to the ears of marine animals such as fish and disturbs the mating calls and echolocation of animals such as whales. Whales are highly affected because they rely greatly on echolocation due to highly turbid, dirty, waters. Echolocation is being able to locate an object by using the reflection of sound. Most whale feed along shallow coastlines where noise pollution is in the greatest capacity. The immense amounts of sound disturb the process and can disorient a whale. If they can't communicate with other whales, they can miss opportunities to feed and can starve to death. Since their mating calls are interrupted, they miss breeding opportunities. This would result in a whale population decline. Additionally, fish are affected too. Their ears are highly damaged by all the immense amounts of sounds created.

The concern of most scientists has shifted from whales onto smaller marine animals such as fish and shrimp. This is because while whales are pretty robust and have the ability to take the damage, fish and shrimp are not. The results of a study conducted by Norwegian scientists showed that the fish are moving out of noisy areas and the survival rate of their new-born offspring greatly decrease when they're in areas with high noise levels. In summary, the amount of underwater sound pollution increases in number each year. This is because of the increasing oil industry and demand for oil. When looking for oil reserves, large amounts of sound are released into the water. The sound is low in frequency, making it more harmful. Low frequency sounds are more harmful because they can affect larger areas. They can do this because they can go long distances without losing much of their energy.

While these sounds are created by the seismic air gun surveys being used to find places where oil is abundant, they are also created by ships and their propellers. When the propellers use force to push the ship forward, immense amounts of sounds with low frequency are released into the water. These sounds affect different species of marine animals in different ways. For example, whales are affected differently than fish. Whales are affected because their mating calls and echolocation are disturbed. While there isn’t much research on how fish are affected, it is known that their ears are damaged. It is predicted that marine animals near or in water that has sound pollution created by low frequency sounds will experience negative effects. Their life spans will greatly decrease. This hypothesis is strongly supported by the research provided.

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