Hums and hoots, purrs and grunts, clicks and drums –a mellifluous orchestra plays underneath the surface of the sea. Marine animals like fish, whales, dolphins use sound i.e. high-frequency echolocation to forage, navigate through the water and to communicate with each other. They produce sound to locate their prey or predators in their vicinity. Even for reproduction, sound and sound detection is vital for these animals. However, since the last century, the underwater noise has increased multifold which has started to disturb this perfect symphony and thus now threatens the longevity of these aquatic animals.
Human activities within the freshwater and marine realm have grown over the years. Oil and gas exploration requires technologies for oil drilling which produce a loud sound, equivalent to launch of a rocket in the air. Seismic surveys and air gun blasting to explore oil may affect the behaviour of whales and fish. The thundering noise of engines of the ships may sound like a rock concert. Sometimes the noise is so loud that it can be heard from hundreds of kilometres. Dolphins and toothed whales use echolocation to call at a frequency which is similar to the frequency of the sounds of the engines of the ships. This may well interfere with their communication with the other members of their species. A study says that ship traffic has almost doubled between 1995 and 2000 which has boosted 3 Decibels per decade. Dredging activities, the process of excavating and clearing of materials from the bed of water bodies, can affect seagrasses, affecting the food chain of several sea animals. Military sonar exercise can result in considerable stress and loss of health in marine wildlife too.
Anthropogenic noise can interfere with the sound animals produce. These loud sounds can mask the sound they emit and it affects their ability to locate food, predators and find a mate, accurately. Sometimes, the sudden loud sound can trigger a panic deep dive among Cetaceans, like whale and dolphins, into the sea, where the pressure is relatively higher, causing decompression sickness leading to haemorrhage in brains and hearts and, eventually, the death of these creatures. A study shows that a single whale in its lifetime can absorb carbon from the atmosphere equivalent to a thousand trees. In 2018, bodies of dead beaked whales on the beaches of Ireland attracted the attention of ecologists. This may have been a repercussion of military exercises when warships use active sonar to locate enemies submarines.
For us terrestrial living beings, the underwater noise may not sound a bigger threat but a loss of marine life would affect us indirectly too. Unlike other environmental issues, marine noise pollution can be curbed rather quickly. While there has been an increasing awareness of the marine issues (for example, Emmy award-winning documentary Sonic Sea which showcases the deleterious effects of the sonar waves on marine life), we need stricter regulations on and within the sea; dredging should be banned and airguns could be replaced with marine vibrators; propellers of the ships should be made efficient and noiseless; the sea traffic should be controlled and further reduced; navy operations impact on the sea life should be made minimal. Like us, our marine friends need some peace too!