The Department of Conservation will carefully review a study which has described a constant underwater racket created by seismic airguns.

In a new blog post, US scientists Dr Leigh Torres, of Oregon State University, and Dr Holger Klinck, of Cornell University, have aired their concerns over the oil and gas industry's use of the instruments, which they say are having a harmful impact on marine life.

They shared underwater recordings made in the South Taranaki Bight capturing an oil survey ship letting off seismic blasts every eight seconds.

When sped up, the recordings showed how the sound was enough to drown out the call of a blue whale - a species known to feed in the area.

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The researchers said whales used sound to communicate, find food, and navigate, and seismic blasting meant their lives were "disturbed and dramatically altered".

A consistent, repetitive boom was what whales living in a region of oil and gas exploration heard, as seismic surveys often lasted several months.

Industrial seismic airgun arrays were among the loudest man-made sources and the noise emitted by these arrays could travel thousands of kilometres, they said.

Noise from a single seismic airgun survey could blanket an area of more than 300,000sq km, raising local background noise levels 100-fold.

"Imagine someone operating a nail gun for three months in your kitchen and you have nowhere else to eat," they wrote.

Consistent, repetitive boom was what whales living in a region of oil and gas exploration heard, as seismic surveys often lasted several months, researchers say. Photo / File
Consistent, repetitive boom was what whales living in a region of oil and gas exploration heard, as seismic surveys often lasted several months, researchers say. Photo / File

"You would stay to feed yourself, but your stress level would elevate, health deteriorate, and potentially have hearing damage.

"The evidence has mounted. There is no longer a scientific debate: seismic airguns are harmful to marine animals and ecosystems."

The researchers said the impact could be reduced, among other ways, by restricting their use around sensitive environmental areas, such as marine mammal feeding and breeding areas.

The release of the recordings came as the world's largest seismic oilfields company, Schlumberger, waited for the Government to approve an application to seismic blast across 19,000 sq km of the Taranaki Basin this summer.

The data would be on-sold to Austrian oil company, OMV.

Greenpeace climate campaigner Kate Simcock argued that the study's findings should mean the survey does not go ahead.

"The impacts on blue whales in this area are likely to be torturous, interfering with their communication and feeding."

Torres and Klinck noted some oil and gas representatives point towards their adherence to seismic survey guidelines and use of marine mammal observers to reduce their impacts on marine life.

But in New Zealand, these measures only stopped airgun blasting when animals were within 1km of the vessel, or 1.5km if a calf was present - and seismic airgun blasts were so intense that the noise travelled much farther, they said.

"So, while these guidelines may be a start, they only prevent hearing damage to whales and dolphins by stopping airguns from blasting right on top of animals."

Dr Karen Stockin, director of Massey University's Coastal-Marine Research Group, said recently-published research and a further study under review from Oregon State University researchers, "without doubt" showed the significance of the Taranaki Basin for New Zealand's blue whale population.

The world's largest seismic oilfields company, Schlumberger, is waiting for the Government to approve an application to seismic blast over 19,000 sq km of the Taranaki Basin this summer. Photo / File
The world's largest seismic oilfields company, Schlumberger, is waiting for the Government to approve an application to seismic blast over 19,000 sq km of the Taranaki Basin this summer. Photo / File

"I am not surprised by the blog released by Dr Torres and her team and concur without reservation, that the progress of such exploration within this region is of utmost concern for the whales which are shown to use this region for feeding."

Department of Conservation director aquatic Ian Angus told the Herald that DoC had supported the new study with funding and expertise.

"We want to understand more about blue whales. This includes the potential for any impact from human activities and where we might look to strengthen existing mitigation, including the seismic survey code of practice."

Angus said the new findings were "useful" and would be carefully considered in future decisions about activity undertaken in whale habitats.

"We will be providing advice on any review of the code of conduct to the minister."

Conservation Minister and Green MP Eugenie Sage said a commitment to establishing a blue whale sanctuary in Taranaki was one of the points in her party's confidence and supply agreement with Labour.

Sage also planned to review whether DoC's code was adequate to protect marine mammals - particularly given the significance of the Taranaki area for blue whales.

Petroleum Exploration & Production New Zealand (PEPANZ) chief executive Cameron Madgwick said the industry took the issue "very seriously" and all seismic operators followed DoC's existing code.

All vessels also used Passive Acoustic Monitoring (PAM) systems, which operated 24 hours a day to detect and track mammals.

Madgwick stated the sound generated by seismic acoustic work was about 230 to 255dB, which he said was a similar level to some natural sounds.

Petroleum Exploration & Production New Zealand (PEPANZ) chief executive Cameron Madgwick says the industry takes the issue
Petroleum Exploration & Production New Zealand (PEPANZ) chief executive Cameron Madgwick says the industry takes the issue "very seriously". Photo / File

"This sound also dissipates rapidly in the water - at 1km from the source the sound levels have generally dropped below 171dB, which is lower than the noise from large commercial shipping vessels.

"We strongly support evidence-based science, but in this case it's difficult to tell the distance from the recording device to either the blue whale or the seismic source.

"The two sounds are similar in sound intensity and frequency range, and the much lower recorded intensity of the blue whale's call indicates that it was at a considerably further distance from the seismic acoustic source."

But Torres pointed out 171dB was still "very loud" - and while commercial shipping vessels also contributed much noise pollution to oceans, they didn't produce a constant noise in one area for months.

She also contended the distance between the recording device and the airguns or blue whale were "not very relevant to the point that seismic airguns impact whale communication".

"Even at a far distance the airgun noise drowns out the blue whale call.

"We have multiple examples of seismic airguns and blue whale calls co-occurring at variable distances from the hydrophone."

Madgwick said the industry was conducting its own research into marine mammal distribution, and all observer reports were being submitted to DoC.