Yahoo News 23 Sep 09;
PARIS (AFP) – Seismic surveys used for oil and gas prospecting on the sea floor are a disturbance for blue whales, the world's biggest animal and one of its rarest species, biologists reported on Wednesday.
Lucia Di Iorio of Zurich University, Switzerland, and Christopher Clark, an acoustics specialist at the Cornell Laboratory of Ornithology in New York, recorded the calls of blue whales at a feeding ground in Canada's St. Lawrence estuary in August 2004.
The 11-day experiment was conducted during a period when a survey vessel was using a "sparker", a low-to-medium power device that sends an acoustic pulse to the sea floor and picks up the reflected signal to get a picture of the topography.
"On the days when the vessel was operating, the whales called more than two and a half times more frequently than on days when the vessel was not operating," Di Iorio told AFP.
For humans, "it would be the same as if you were next to a roadworks hammer and have to shout or repeat what you say," she said.
Di Iorio said further work would show whether blue whales suffered stress or other problems from the acoustic kerfuffle.
"Blue whales are rather solitary whales which swim all the time, are highly dispersed and always travelling, and feeding areas are places where they have the chance to get together in a small range and with a lot of social activity as well.
"Being disturbed during social interactions that don't occur very often could have an influence, perhaps in mating, but we can't really say for sure, or what kind or if it is short term or long term."
One concern is that oil and gas prospecting is venturing out into ever-deeper water, and little is known about the impact this might have on whales' feeding and migratory patterns.
The paper appears in Biology Letters, a journal of Britain's Royal Society.
In April, an experiment reported in the same journal found that very loud, repeated blasts of sonar caused an Atlantic bottlenose dolphin to temporarily lose its hearing.
Numerous beachings of whales, dolphins and porpoises have occurred over the past decade, prompting a finger of blame to be pointed at warship exercises.
Measuring up to nearly 33 metres (100 feet) and weighing as much as 180 tonnes, the blue whale (Balaenoptera musculus) was hunted almost to extinction until it was given international protection in 1966.
Estimates of this species' population today vary widely. A 2002 Canadian study put the global numbers at between 5,000 and 12,000.
Before large-scale whale hunting, there may have been more than a quarter of a million of the giant mammals.
Seismic bangs 'block' whale calls
Richard Black, BBC News 23 Sep 09;
Scientists have turned up new evidence showing that ocean noise can affect the communication of whales.
Studying blue whales off the eastern Canadian coast, they found the animals changed their vocalisations in response to an underwater seismic survey.
The survey was conducted using gear considered to have a low impact.
Writing in the journal Biology Letters, the researchers say this is the first evidence that whales will increase calls in response to underwater noise.
At this site, on a feeding ground, the whales make frequent calls of just a few seconds' duration, rather than the long "songs" that can be heard across vast tracts of ocean.
"The calls are used for short-range communication within a range of a few hundred metres," said Lucia Di Iorio, based at the University of Zurich in Switzerland.
"And the frequency band they use is exactly where the main energy of those seismic pulses is located," she told BBC News.
Initially, Dr Di Iorio's group tried to persuade the Canadian university conducting the seismic survey to co-operate in the research, and to give details of where and when the underwater bangs were being produced.
That attempt failing, the scientists recorded the pulses with an array of detectors mounted on the sea bed in the St Lawrence Estuary.
The detectors also recorded the blue whales' calls, which are thought to be associated with feeding and socialising.
Information gap
On days with seismic surveys, the whales made two-and-half-times more calls than on days without.
The ratio was the same when the recordings were analysed in blocks of 10 minutes; survey noise induced more than a doubling of calls.
The researchers suggest the whales are having to "repeat information", as some of the calls are blocked or degraded by the seismic bangs.
"Our research doesn't say anything about whether this increase in call rate is negative for the animals, but of course it's not positive and it may be stressful," said Dr Di Iorio.
This survey was carried out using "sparkers", devices that generate a bang from an electrical discharge between two electrodes.
Sparkers produce sounds quieter than the ones generated by airguns, another technique engineers use for underwater surveys.
"It's used [here] because it's thought to have a lower impact on marine life," said Dr Di Iorio.
"But we should definitely reconsider these things, because clearly it's not only the sound level that's important; and one thing might be not to do the test when there are lots of whales around."
Gray area
A number of recent reports have highlighted the increase in ocean noise brought about by humanity's use of the oceans, in particular shipping.
One study indicated that the level of background noise from ships' propellers was doubling every decade in the Pacific Ocean.
Conservation groups are raising the issue because many marine animals, including whales and dolphins, use sound to communicate and to hunt.
The sharp sounds of seismic surveys are a particular concern. Engineers use very sharp, very loud bangs because these produce the clearest images of geological structures below the sea floor.
The surveys are typically used to map oil and gas deposits.
Earlier this year, companies involved in the Sakhalin Energy consortium agreed to suspend seismic work after seeing evidence that it was driving the critically endangered western gray whale, of which only about 130 remain, away from its summer feeding ground.
