Man-made noise is a danger to marine fauna and the conservation of endangered species, including marine mammals. Researchers are trying to learn more about this form of noise pollution and its effects on wildlife in order to recommend solutions and improve regulations surrounding the issue.
It is no surprise that in these more hectic, technology driven times that sound underwater comes in various forms and travels further than ever before. Boats, wind turbines, seismic studies, drilling, use of explosives and sonar are some of the key examples. The most common sources, such as maritime traffic, can be heard continuously due to increasing trade systems and holiday-goers. This underwater noise is not without consequences for the marine fauna.
This invisible and, above all, almost inaudible pollution for humans has long led people to believe that it does not pose a threat to wildlife. But the beaching of twelve beaked whales on the Greek coast on May 12, 1996 calls this into question. Scientists formally identified the culprit: a NATO naval exercise with powerful sonar, conducted the day before in the Mediterranean. This research led scientists to focus on cetaceans, some 80 species.
The impacts on marine fauna
In marine mammals, such as whales and manatees, reactions to noise pollution differ according to species, individual, age, sex and condition. The avoidance or total abandonment of certain habitats is the main environment-based factor, but the health problems associated are numerous.
It results in behavioural disorders, damage to bodily tissues not just related to hearing, reduced reproductive capacity and increased susceptibility to disease. Acoustic-induced stress can also lead to death, for example through diving accidents. This is true of beaked whales, which are very sensitive to the sounds of military sonar or mine prospectors. They flee to the surface upon hearing these sounds without any decompression time and die from a lethal embolism.
But these mammals are not the only ones affected…
In the last decade or so, effects have also been discovered on invertebrates, from species as small as shrimp all the way to octopus and jellyfish. Although deprived of their sense of hearing, they maintain their sense of direction and stability with organs sensitive to water pressure. As with mammals and fish, the impact is therefore potentially fatal. The hum of ships unfortunately masks the animals’ vital communications.
For scientists, one of the challenges now is to establish a comprehensive data set of the health of underwater fauna exposed to this type of pollution.
Management, conservation and regulation
The numerous research projects carried out aim to establish a “sound identity card” for species in order to establish a diagnosis of which possible disorders can be caused and why. This will lead to the development of a map in real time of maritime travel noise pollution to increase the protection and conservation status of Mediterranean marine areas. The quietMED project has produced this noise prediction map containing data on the effects of certain species, as well as an intelligent acoustic buoy capable of detecting and identifying certain species in real time. This instrument can also warn ships to change course and avoid a collision with an animal.
ACCOBAMS, an organisation which works on the conservation of marine mammals in the Mediterranean, the Black Sea and the Atlantic, is carrying out multiple initiatives to implement a basin-wide monitoring programme on underwater noise. They have also proposed regulations aimed at balancing human activities at sea and cetacean conservation, and the production of a “Guide to Underwater Noise Mitigation Measures” to assist industries in implementing such procedures.
By Nadège Delalieu