Underwater Noise: Consequences
An overlooked catastrophe
Marine animals depend on their hearing to navigate, communicate and catch prey. But sound levels in the oceans are rising constantly. Military sonar used to locate submarines is particularly dangerous, as its sound waves can interfere with hearing within a radius of about 3,000 kilometres. Shipping, offshore oilrigs and the use of airguns in seismic oil explorations all add to the ear-battering noise.
Internal injuries and strandings
The most striking consequence of ocean noise pollution is the stranding of whales and dolphins. Strandings have been observed to be particularly frequent after naval sonar manoeuvres. Extreme sound events like these inflict vascular damage on the brain, lungs and other organs. Further, animals may panic and surface too fast which causes nitrogen bubbles to form in the blood – the so-called bends (decompression sickness). The resulting embolism may cause death. Dead animals end up sinking to the seabed or getting beached on the coast.
As is the case for humans, extremely loud sound may cause hearing damage in marine animals. This is a grave problem for the many marine creatures that depend on their hearing for communicating, sensing danger, finding a partner and hunting prey. Other physical consequences of ocean noise pollution include disruption of the schooling structure of fish or impaired growth of shrimp. Even cell changes have been detected in lobsters. Noise means stress and impairs the animals’ immune system which makes them more susceptible to illness in general.
Fleeing valuable habitats
Ocean noise pollution also causes marine animals to flee and abandon valuable habitats, either because of direct impact or because they have to follow their fleeing prey. Ocean noise pollution has a disruptive impact on mating, finding food and nursing young – with grave consequences in populations that are already weakened by other environmental impacts.