In 2006 April, 28 Zanzibar villagers were in shock after their coastline was covered with 400 dead dolphins. Zanzibar government went on imposing warning to the villagers and fishermen not to consume the dead dolphins as the reason of their death is not know.
From that peace of story from my country which happened about two year ago, rises my eyebrow when I was thinking what should I write concerned the effects of military vessels on the whales. Soon after that incident in Zanzibar, different comments on what might be the cause of their death were discussed. For example, some scientists believe that, the death may be a result of loud burst of sonar, from miles away and can be heard in water therefore scare marine mammals causing them to surface too quickly. This type of movement is known as bends whereby is occur to the people who dive for feeling severe pains and difficulty in breathing as result come to the surface too quickly. Shortly is when sudden decompression forms nitrogen bubbles in tissue. Other speculates the death to be caused by U.S. Navy task force which patrols the coast of East Africa as part of counterterrorism operations. The villagers themselves were thinking that the cause of death was disoriented of those animals which lead them to shallow water and died. Later on the U.S Navy acknowledged that sonar is likely to contribute to the death of those dolphins.
According to Oxford Advanced Learner’s Dictionary, Sonar is described “as a device or system for finding objects under water by means of reflected sound waves.” The history of sonar goes back after the World War I where Britain and U.S develop the technology of navigating by sound in the sea. In the World War II sonar were used to counter attack the German ship. It was until the cold war era where the sonar technology was improved and was much used. In Word War II sonar was passive: essentially big microphones that listened for the distinctive sounds emitted by large submarines. Nowadays there are mid frequencies active sonar designed to find a new generation of smaller, stealthy submarine. Active sonar is working by sending out sound waves and listening for the reflections of the objects, as this provide the location of object detected.
This improvement and advanced system of sonar have been designed and used despite the knowledge of its effects to sea mammals. Even after the end of cold war, sonar has been used in military testing causing whales and dolphins to stranded and dead. The exercise of Navy using mid-frequency sonar which operates from 2,000 to 10,000 hertz has resulting in increasing to the numbers of mammal stranding. As this technology seem not enough to the military, they have now develop the new technology of sonar known as low – frequency sonar which is believed to cause wide range of sound travel. Environmentalists explain fear to this new technology as it will increase the number of whales and dolphins to stranding. Up to date there are numbers of cases which have been reported due to the effect of sonar, as will be mentioned in the following paragraphs.
In September 2002, fourteen beaked whales were stranded in the Canary Island close to the site of international naval exercise. This happened four hours after the mid frequency sonar was deployed. The effect of this tragedy is lost of ability to navigate for the whiles which force them to strand.
In 2003 US Navy Sonar in Pacific Northwest was direct linked to the number of death of whales. This blast draws attentions to many institutes. One of them was Natural Resources Defense Council (NRDC) which went on to stop US Navy of using the powerful active sonar system known as SURTASS LFA. NRDC was also involving other countries on restriction of using the sonar as to prevent the life of marine mammals.
The battle of protecting marine mammals with sonar have take a new look this January 2008, when President G.W Bush allow US Navy ships to use sonar during exercises off the California coast. The exercises is planned to take place in San Diego, where aircraft carries have been permitted to use sonar on detecting submarines. This decision of President Bush is opposing the court order of stopping the uses of sonar in the vicinity of whales.
Going back to my country four hundred dolphins were dead after beached, there is a need of positive thinking this effects which are caused by sonar. Further studies show that there even more effects to these sea mammals such as the reproduction of this endangered species; to disrupt the feeding of orcas; and to cause porpoises and other species to leap from the water, or panic and flee.
Nevertheless there is other dangerous noise which may also contribute on disturbing marine life. These dangerous sources of noise in the sea are manmade. There is ship traffic; the world is now witness increase of ships due to the increased of global business. These ships generate noise from their propeller, engine, generator and bearing. The propeller is one part of ship which provide a noise pollution to undersurface of sea. Propeller can provide noise from frequency range from 20Hz - 300Hz throughout the sea. Sea mammal such as whales whom they use frequency for navigating and communicating can be direct effected with this kind of noises which are traveling hundred of kilometer in the sea.
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