For millions of years, the oceans have been filled with sounds from natural sources such as the squeaks, moans and clicks of whales and dolphins, the snapping of shrimp, the sound caused by wind upon the surface and even the occasional rumble from earthquakes. Over millions of years, the ocean’s marine species have developed into what they are today, with their own specialized acute hearing abilities, communication skills and echo location abilities at natural sound levels.
Hearing is generally as important to many marine creatures as sight is for humans. The oceans once referred to as the “The Silent World” by Jacques Cousteau, has now become an increasingly noisy place since the industrial age. According to Wikipedia, Noise Pollution is excessive, displeasing human, animal or machine-created environmental noise that disrupts the activity or balance of human or animal life. Noise pollution could also be defined as a type of energy pollution in which distracting, irritating, or damaging sounds are freely audible.
As with other forms of energy pollution (such as heat and light pollution), noise pollution contaminants are not physical particles, but rather waves that interfere with naturally-occurring waves of a similar type in the same environment. Thus, the definition of noise pollution is open to debate, and there is no clear border as to which sounds may constitute noise pollution. In the narrowest sense, sounds are considered noise pollution if they adversely affect wildlife, human activity, or are capable of damaging physical structures on a regular, repeating basis.
Hearing is the universal alerting sense in all vertebrates. Sound is extremely important because animals are able to hear events all around them, no matter where their attention is focused. Sound travels far greater distances than light under water. Light travels only a few hundred meters in the ocean before it is absorbed or scattered. Even where light is available, it is more difficult to see as far under water as in air, limiting vision in the marine environment It is similar to looking through fog on land.
So, the best opportunity for long-range vision underwater especially in murky water is to swim beneath objects and see their silhouettes. In consequence, most marine animals rely on sound for survival and depend on unique adaptations that enable them to communicate, protect themselves, locate food, and navigate underwater. Animals change the rate of sound production and the structure of the sounds to send different messages. Underwater sound allows marine animals to gather information and communicate at great distances and from all directions.
The speed of sound determines the delay between when a sound is made and when it is heard. The speed of underwater sound is five times faster than sounds traveling in air. Sound travels much further underwater than in air. Thus marine animals can perceive sound coming from much further distances than terrestrial animals. Because the sound travels faster, they also receive the sounds after much shorter delays (for the same distance). It is no surprise that marine mammals have evolved many different uses for sounds. Marine mammals, such as whales, use sound to identify objects such as food, obstacles, and other whales.
By emitting clicks, or short pulses of sound, marine mammals can listen for echoes and detect prey items, or navigate around objects. This animal sense functions just like the sonar systems on navy ships. It is clear that producing and hearing sound is vital to marine mammal survival. Whales and dolphins are celebrated for their sounds, but many species of fish and marine invertebrates also use sound. Fish produce various sounds, including grunt, croaks, clicks, and snaps, which are used to attract mates as well as ward off predators.
For the toadfish, sound production is very important in courtship rituals. Sound is produced by the male toadfish to attract the female for mating and is especially important in the murky waters that toadfish inhabit where sight is limited. Fishes also produce sound when feeding. When a fish eats hard food, such as coral, it will produce a sound. Fishes sometimes gnash their teeth without the presence of food, which may be a way to scare away predators. As you can see, sound is very important to its underwater inhabitants.
It allows them to navigate, to hear approaching predators and prey, and is a way of communicating with other members of the same species. There are a lot of sources of noise in the marine environment. Naturally occurring noises include underwater volcanic eruptions and storms. Background noise in the ocean is produced by breaking waves, wind and rain, and by the huge number of small crustaceans and other animals. A typical background noise level is about 100 decibels (dB), which is about the same in energy terms as 40 dB in air.
Wind and waves in storms, and choruses from fish and invertebrate can increase this level to about 120 dB. Measurements show that the Pacific Ocean is still relatively quiet and that most of its background noise is produced by wind and by marine creatures. This is in contrast to the Atlantic Ocean, where most of the background noise is from the churning propellers of ocean-going ships. There are also several man-made (anthropogenic) sources of ocean noise, some of which are the unintended by products of human activity (e. g. essel propulsion), while others are produced for a specific purpose (e. g. military sonar). Whales, dolphins and porpoises today face a wealth of man-made threats including hunting, ship strikes, entanglement in fishing gear and issues arising from climate change. However, one man-made threat that is not as commonly acknowledged as others is ocean noise pollution. This is partly due to the fact that it is not a visible threat, so can be easily overlooked. The noise becomes problematic and highly hazardous when it is man-made.
In the past several years many studies have shown that man-made ocean noise emanating from such sources as are military sonar equipment, ship traffic, and underwater drilling, commercial shipping seismic surveys for oil and gas exploration, mineral and aggregate extraction, construction (e. g. drilling, dredging and explosions), acoustic deterrent and harassment devices(e. g. pincers on fishing nets used to deter predators) and recreational activities(e. g. boating). Noise pollution in the oceans has been shown to cause physical and behavioral changes in marine life, especially in dolphins and whales, which rely on sound for daily activities.
However, low frequency sound produced by large scale, offshore activities is also suspected to have the capacity to cause harm to other marine life as well. It can also cause hemorrhage or other trauma to the marine mammal’s auditory system, sometimes leading to permanent hearing loss, and, indirectly, death. It also causes displacement from their natural habitat, disruption of feeding, breeding, nursing, and other behaviors vital to the species survival. Some of the sounds produced by these man-made sources can travel for hundreds of kilometers in marine environment, potentially affecting many marine animals over a huge are.
The growing amount of human noise pollution in the ocean could lead fish away from good habitat and off to their death, according to new research from a UK-led team working on the Great Barrier Reef. Noise pollution might also severely affect the distribution of fish, and their ability to reproduce, communicate and avoid predators. For example, some studies have reported that Atlantic herring, cod and blue-fin tuna flee sounds and school less coherently in noisy environments. That could mean that fish distributions are being affected, as fish avoid places polluted by man-made noise.
Not only can squids and octopuses sense sound, but as it turns out, these and other so-called cephalopods might be harmed by growing noise pollution in our oceans—from sources such as offshore drilling, ship motors, sonar use and pile driving. Giant squid, for example, were found along the shores of Asturias, Spain in 2001 and 2003 following the use of air guns by offshore vessels and examinations eliminated all known causes of lesions in these species, suggesting that the squid deaths could be related to excessive sound exposure.
The effects of noise pollution on whales depend, among other things, on the distance the whales are from the source of the noise. If the sound is very powerful and close to the animals it could well bring about permanent ear damage, internal injuries, and even death. Even sounds less powerful can induce temporary deafness, as was shown by studies carried out on seals, dolphins and belugas in captivity. Knowing just how dependent whales are on sounds, there is much cause for concern.
During March of 2000, at least 17 whales stranded themselves in the Bahamas and the population of beaked whales in this region disappeared. A federal investigation identified testing of a U. S. Navy active sonar system as the cause. There are many things we can do to decrease ocean noise,” Ocean Link, an organization dedicated to ocean education, says on its website. “The first would be to simply recognize that there is a noise problem in the oceans, which some governments have begun to do. With formal recognition, it may be possible for national and international agencies to work together to help reduce this problem.
For any new policies regarding ocean noise, scientists should follow the precautionary principal to ensure that no further harm will come to marine mammals. From this perspective, governments should adopt legislation with the habitats of marine mammals in mind, ensuring that important areas would receive the least impact possible. ” While these may come too late for hundreds of sea animals that have already been damaged by underwater noise, with the right and concerted action, the seas may resonate with the sounds of whale songs, not the human-produced lethal noises of engines and machinery.