MARINE NOISE POLLUTION
For many species of whale and dolphin sound is the primary sense, and is used to navigate, find food and communicate in an environment where smell is useless and sight nearly so, and sound is greatly enhanced compared with in air.
Until little over 100 years ago the oceans were almost unaffected by human related noise. Modern propeller driven ships and smaller vessels are very noisy and increasingly abundant in many parts of the world, especially in highly populated areas like around European, southeast Asian or USA coasts. Here shipping noise is constant and intense, and is considered likely to interupt communication and food-finding in cetaceans.
Recent developments in anti-submarine measures that generate very loud short pulses of sound have been implicated in some mass-strandings of particularly, but not only, beaked whales. Some animals have suffered damage to brain and other tissue associated with hearing and sound transmission, as well as other organs. Meanwhile others have suffered 'the bends' (nitrogen bubbles in the bloodstream) as a result of overly rapid surfacing from great depth, presumably as a panic response to the noise. Less acute, but nonetheless serious, is the displacement of animals during these operations, forcing them to abandon important foraging habitats. Marinelife has noted during systematic surveys, periods following naval exercises in Biscay when cetaceans are absent from a large area around where the exercise took place, which possibly points to significant displacement levels.
Oil, gas and other under-sea mineral exploration commonly uses seismic surveys (creating pulses of intense noise and recording its transmission through the rock strata) to find new mineral reserves. Cetaceans are known to be displaced by seismic survey activity, which can last for several weeks in a given area.
Offshore construction is rapidly increasing, particularly the construction of large wind farms, but also building of bridges and other structures, which require prolonged pile-driving and even underwater use of explosives. This can cause behavioural changes in marine mammals up to 10km distance.