ROME, Italy - Oceans and seas are becoming noisier with more vessels, increased seismic surveys for oil and gas, off-shore construction and recreation, and a new generation of military sonars, an alliance of wildlife groups said today. They warn that the cacophony is intensifying threats to marine mammals that use sound to communicate, forage for food and find mates.

The largest animals on Earth, blue whales are vulnerable to noise and ship strikes. This blue whale died in September 2007 in the waters off Santa Barbara, California. (Photo courtesy Santa Barbara Museum of Natural History) The groups, attending the United Nations Environment Programme's Convention on Migratory Species conference in Rome, are urging governments and industry to adopt quieter engines for ships, tighter rules on the use of seismic surveys, and new, less intrusive sonar technologies by navies.

At the conference, the International Fund for Animal Welfare issued a report, "Ocean Noise: Turn it Down," showing that the distance over which blue whales can communicate is down by 90 percent as a result of intensified noise levels.

Ship noise in the Pacific Ocean has doubled every decade over the past 40 years and the global shipping fleet is expected to double in size by 2025, after doubling between 1965 and 2003, the report calculates.

Airguns used in seismic surveys generate "colossal" sounds peaking at up to 259 decibels and can be repeated every 10 seconds for months. These sounds travelled more than 3,000 km from the source. There are 90 seismic survey ships in the world, the report states, and a quarter of them are in use on any given day.

In addition, there are an estimated 300 naval sonar systems worldwide able to generate pressure sound waves of more than 235 decibels. Pings this loud are over one billion times more intense than the 145 decibel upper limit deemed safe for humans.

Veronica Frank, an attorney with the wildlife group, said, "We are calling for wide-ranging action, including a requirement that builders and owners of all vessels, from super-tankers down, working with the competent international body, factor noise reduction measures into vessels' design and operation at the outset."

The news of noisier oceans is emerging alongside new concerns that rising levels of the greenhouse gas carbon dioxide may be aggravating underwater noise levels.

Researchers at the Monterey Bay Aquarium Research Institute in the United States published a study in October showing that rising ocean acidity can make the marine environment noisier.

Conservative projections by the Intergovernmental Panel on Climate Change suggest that by 2050 the chemistry of seawater could increase in acidity by 0.3 pH units.

In the October 1, 2008 issue of "Geophysical Research Letters," Monterey Bay's Keith Hester and his co-authors calculate that by 2050 this change in ocean acidity would allow sounds to travel up to 70 percent farther underwater.

The more acidic the seawater, the less low-frequency and mid-frequency sound it absorbs, said Hester and his team. The changing chemistry of seawater may mean that currently it is 10 percent less absorbent of low frequency sound than it was prior to the Industrial Revolution.

Unless greenhouse gases emissions are cut - the key issue this week in Poznan, Poland at the annual UN climate conference - the rising ocean acid level will increase the amount of background noise in the oceans and could affect the behavior of marine mammals, said Hester.

Mark Simmonds, science director of the Whale and Dolphin Conservation Society, who is attending the Convention on Migratory Species meeting in Rome, said, "Underwater, man-made noise, is already triggering a kind of acoustic fog and a cacophony of sound in many parts of the world seas and oceans."

There is now evidence linking loud underwater noises with some major strandings of marine mammals, especially deep diving beaked whales, Simmonds said.

When cetaceans are startled by loud noise, they exhibit unusual diving behavior and suffer something similar to a human diver getting the bends, he said.

"Now we are confronted with cutting-edge evidence that fossil fuel burning and the buildup of C02 may pose a new and even louder threat unless urgent action is taken to cut emissions over the coming years and decades," said Simmonds. "There clearly needs to be a comprehensive and joined-up response to noise pollution in the underwater world."

Robert Hepworth, executive secretary of the UNEP-Convention on Migratory Species, said climate change is set to make parts of the ocean that were once relatively tranquil and inaccessible, much noisier.

"The retreat of the ice in the Arctic is leading to a scramble for drilling and oil and gas exploration which is likely to increase underwater noise exposure for species such as the beluga whale and the bowhead whale," warned Hepworth. "This increase does not include the rise in noise as passages around the Arctic open up to ship traffic."

The European Union and its 27 member states submitted a draft resolution to the governments attending the Convention on Migratory Species this week, which urges consideration of a wide range of measures to quiet underwater noise.

Suggestions include noise protection areas in enclosed seas and sea basins, greater monitoring of noise levels, noise databases that list where man-made sounds originate, and a set of guidelines on better managing noise sources.