The Great Australian Bight is one of the most pristine marine ecosystems on the planet.

Home to orcas, seals, dolphins and southern right whales, much of the biodiversity found here exists nowhere else on earth.

The Great Southern Reef is estimated to generate $10 billion every year from fishing and tourism for the Australian economy.

But the lure of riches buried deep beneath the seabed — oil and gas — has some of the biggest players in the fossil fuel industry eyeing off its potential.

Equinor, formerly Statoil, a joint venture partner of BP, was planning to start drilling for oil this year but has delayed until 2020/21.

And while BP and Chevron have abandoned immediate plans to drill in the Bight, Petroleum Geo-Services (PGS) was granted an exploratory drilling license in January this year after being knocked back several times.

Between September and November, PGS will begin seismic testing. This involves setting off a series of underwater blasts that send soundwaves through the ocean floor, reflecting off different substrates to locate fossil fuel deposits.

The effects of seismic testing is unknown for a lot of marine life. ( Supplied: Richard Robinson/Greenpeace )

Advocates of drilling in the Bight say it could be developed into one of the biggest offshore oil fields on earth.

In 2013, BP said it could be as productive as the Mississippi Delta oil region.

But while there are strict environmental controls around exploration and drilling, critics say drilling rigs like BP's disastrous Deepwater Horizon in the Gulf of Mexico have failed in far less challenging conditions than the Bight's often towering seas.

And community and environmental groups like Greenpeace are calling for a total ban on oil and gas exploitation.

A lot of noise about nothing?

Not much is known about how southern right whales react to seismic testing. ( Supplied: Andrew Halsall/WA Museum )

Sound travels about five times faster through water than air, and whales in particular use sound as a means of long-distance communication.

Blue whales call at around 180 decibels, and can hear each other from hundreds of kilometres away.

Seismic testing uses airguns to pump out a series of blasts up to 240 decibels, and can cause major disruptions to marine life, according to Nathaniel Pelle from Greenpeace.

"Seismic testing is listed as a threat to marine species all over the world," he said.



"Seismic testing, in terms of noise in the ocean, there's nothing louder at all. It's life-threatening if you disrupt a whale's ability to navigate — if it can't find its pod, if a calf can't find its mother, it's at risk."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 34 seconds 34 s Seismic surveys worry fishermen over marine life impacts

Research on scallops has shown a significant increase in mortality, disrupted behavioural patterns and impaired reflex responses during and following exposure to seismic blasts.

But research funded in part by the International Association of Oil and Gas Producers (IOGP) on migrating humpback whales on Australia's east coast found they did not show any dramatic response to seismic activity.

And a statement from the Australian Petroleum Production and Exploration Association (APPEA) claimed some whale populations have been increasing, including in areas "with long-standing oil and gas operations".

"There is a rigorous regulatory system in place that requires both robust environmental plans and effective consultation with other industries and the community," the statement said.

"There is absolutely no reason that South Australia can't enjoy the benefits of offshore exploration and development in harmony with its marine environment."

Approval for PGS to carry out seismic testing was granted by the National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA), but is conditional.

Testing must stop temporarily if southern right whales come within 1 kilometre of an operational area, and must be abandoned altogether if a pygmy blue whale is spotted or a bluefin tuna aggregation is found within 20 kilometres.

A spokesperson for PGS said they will have marine mammal observers on board, and will also be conducting acoustic monitoring for whales.

"All measures have been assessed and verified to be acceptable," they said.

'We're just making stuff up, basically'

The boundaries of PGS's planned seismic testing area take in a Commonwealth Marine Reserve. ( Supplied: NOPSEMA )

Rebecca Dunlop, who was involved in the IOGP-backed research on humpback whales, said there was not enough data to know how southern right whales would respond to seismic testing.

"The oil industry gave themselves a pat on the back for funding our study, but that's one study," said Dr Dunlop, from the University of Queensland's Cetacean Ecology and Acoustics Laboratory.

"You can't extrapolate between species and even between feeding and migrating — their behaviours might be different.

"The southern right whale may hate seismic [noise] and avoid it completely, we just don't know. Until you have the research, we're just making stuff up, basically."

But PGS said they are confident they can conduct the tests without disturbing southern right whales.

"We have appropriate measures in place and we have moved the timing of the survey to minimise any potential impacts," they said.

"There isn't any scientific evidence that seismic acquisition impacts the behaviour of whales away from the immediate vicinity of the source."

But focusing on the immediate response of whales to seismic blasting does not show the whole picture, according to Rob McCauley from Curtin University.

Larger animals show some resilience to testing, but as body size shrinks, seismic blasts can become more lethal.

Associate Professor McCauley used a seismic source to test mortality on krill — a key food source for southern right whales.

"There was about a threefold increase in death after the seismic had gone through," he said.

"There was one group — Nyctiphanes — a type of krill, they were all dead. They're an important food source for quite a few animals all along the southern coast."

But krill mortality from that experiment only extended to around a kilometre from the seismic source. Although actual seismic testing involves a much greater number of blasts than in Dr McCauley's experiment, more research is needed to determine the extent of potential krill mortality.

Wiping out adult krill means there will be less recruitment to the population in following years, according to Dr McCauley, and subsequently less food for whales.

Oil spill clean-up theatre

Crews conducted controlled burns of oil in the Gulf of Mexico after the Deepwater Horizon incident. ( Reuters: John Kepsimelis )

PGS is a seismic exploration company that "oil companies rely on to find oil and gas reserves worldwide".

It is not clear at this stage who its clients in the Bight might be, but if it maps large fossil fuel reserves, drilling companies will not be far behind.

Documents leaked last year of Equinor's spill modelling showed that in the event of a "worst credible case discharge", an oil spill in the Bight would reach Bondi.

Company spokesperson Jone Stangeland told the ABC at the time that the modelling showed a worst-case scenario "without any response taken".

Leaked documents show a worst-case scenario oil spill in the Bight could reach Bondi. ( Supplied )

"The images don't represent an actual scenario, but the combination of 100 different, extremely unlikely worst-case scenarios," he said.

In response to questions from the ABC, a spokesperson for Equinor said they were confident in their ability to prevent incidents from happening in the first place.

"The chance of a well leak is very low," they said. "Managing risk is the most important priority in our business."

But Mr Pelle believes the wild seas and remoteness of the Great Australian Bight mean in the case of a well blowout, a worst-case scenario could be possible.

"[To cap a blowout] they have a thing called a capping stack that weighs more than 50 tonnes, and there's only a few of those in the world. The closest one is in Singapore," he said.

An environmental assessment from 2016 showed it would take BP five weeks to get a capping stack from Singapore to the site of an offshore well in the Bight.

And that is only the first hurdle to stopping a leak, according to Mr Pelle.

"Then if the waves are above 3.5 metres high, they can't use it anyway," he said.

Greenpeace obtained BP's Well Operations Management Plan under FOI, which stated that their capping stack could not be deployed in seas above 3.5-4 metres, according to Mr Pelle.

Greenpeace's analysis of the Stromlo-1 well site, which Equinor proposes drilling, showed seas there were higher than 3.5 metres for more than a third of the year — 122.8 days on average.

Developers of OSPRAG, a UK-based capping stack, claimed they could deploy in seas up to 5 metres.

Equinor said they have been operating in "stronger winds, higher waves, and colder waters" in the Norwegian sea for 45 years.

"We have completed extensive research on the conditions and geology of the area, and determined this project sits well within our range of safe operating parameter," Equinor said.

But the problem, according to Mr Pelle, is that BP gave similar assurances before the Deepwater Horizon disaster. And once a spill happens, there is no going back.

"Companies engage in this oil-spill clean-up theatre," he said.

"But they only ever recover a tiny fraction, the rest stays in the environment."