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 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.
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Environment News Service, 3 December 2008. Full article.
The definition of “acidic” in the Oxford English dictionary is “having the properties of an acid; having a pH of less than 7”. This definition does not apply to un-manipulated seawater now nor in the foreseeable future. Hence, the adjective “acidic” or the noun “acid” should not be used. Note that there are some exceptions, for example in the immediate vicinity of CO2 vents.