Man-made noise in the world's seas and oceans is becoming an increasing threat to whales, dolphins and turtles who use sound to communicate, forage for food and find mates, wildlife experts said on Wednesday.
Rumbling ship engines, seismic surveys by oil and gas companies, and intrusive military sonars are triggering an "acoustic fog and cacophony of sounds" underwater, scaring marine animals and affecting their behavior.
"There is now evidence linking loud underwater noises with some major strandings of marine mammals, especially deep diving beaked whales," Mark Simmonds, Science Director of the Whale and Dolphin Conservation Society, told a news conference in Rome.
Simmonds, who was speaking on the sidelines of a December 1-5 United Nations Environment Program's Convention on Migratory Species conference, said there are also growing indications that certain tissue damage in cetaceans is linked to noise.
Experts suspect that startled animals may tend to dive erratically and suffer something similar to human divers getting the "bends" -- illness symptoms experienced when divers do not carry out proper decompression stops after a long or deep dive.
According to "Ocean Noise: Turn It Down," a new report by the International Fund for Animal Welfare, the distance over which blue whales can communicate has been cut by 90 percent as a result of higher noise levels.
Over the past 50 years, low frequency underwater noise has doubled every 10 years over the previous decade, while the number of ships has tripled, the report also said.
It added that sound produced by air guns used for seismic surveys in oil exploration can travel more than 3,000 km (1,864 miles) from their source.
The rising number of vessels, and their increasing speed, has led to more ships striking marine animals already threatened by hunting and climate change.
Experts say there are also concerns that rising levels of carbon dioxide are pushing water acidity levels up and contributing to noisier oceans, because when acidity rises, water absorbs less noise.
"If there is a lot of background noise, the animals can't hear the boat coming," said Simmonds. "It's the cocktail party effect."
Marine conservationists at the Rome conference are urging governments and industry to adopt quieter ship engines, tighter rules on seismic surveys and less disrupting sonar technologies by navies.
The European Union has submitted a draft resolution to the convention calling on members to consider a wide range of measures to reduce underwater noise.
But Simmonds said conservationists were concerned that pressures from the military and energy industry as well as the need for more research into marine noise pollution may lead to the resolution being substantially weakened.
"We simply don't know at this stage how many animals are affected by noise pollution, but the lack of full scientific evidence should not be a reason to delay action, said Simmonds."