CLOSE EYE: New Zealanders keep a close eye on the activities of oil companies, concerned about spills and well ruptures which could destroy our oceans.

New Zealanders keep a close eye on the activities of oil companies, concerned about spills and well ruptures which could destroy our oceans. However, some scientists are concerned that greater and more continuous damage is being done below the ocean surface. Abbie Napier reports

Imagine the neighbour's car alarm going off every few minutes, all day, every day, for months. Infuriating? This is what it's like to be a whale in New Zealand waters when oil companies carry out seismic surveys.

New Zealand is one of the few remaining oil and gas frontiers in the world. Oil companies vie for exploration permits, and much of our sea floor is yet to be mapped for oil deposits. New Zealand's largest off-shore well, Maari, has pumped out millions of barrels of oil since 2009. Success stories like this have kept oil and gas companies hunting for the next sweet spot. As they race to mine the depths of our ocean floors, seismic surveys used in exploration are being carried out year-round.

Seismic surveying bounces sound waves off the ocean floor, mapping the underground terrain and revealing gas pockets and oil deposits. The result is a 3-D image showing the best places to drill.

Marine expert and zoologist Dr Liz Slooten says this seismic surveying can cause serious damage to marine mammals using sonar for communication and guidance. The sound waves used in surveying can conflict with the sonar frequencies used by whales, in particular, the endangered blue whale. At worst, the noise could force erratic behaviour as whales try to escape it quickly, and, at best, it blocks communication between whales, causing dislocation within pods and reducing the already slim chances of breeding.

According to the International Association of Geophysical Contractors, the average seismic survey takes many months to complete, using airguns firing pulses up to 220 decibels - twice as loud as a live rock concert. Airguns are fired every 10 seconds for as long as 12 hours at a time, creating serious underwater noise pollution. The effect is similar to a church bell ringing in a neighbourhood day after day for months.

Slooten says the acoustic blasts used by surveyors can travel at least 80 kilometres underwater. The noise could be enough to drive whales and dolphins away.

Whale feeding grounds around the world often overlap with oil fields and Slooten says the surveying puts the marine mammals in physical danger. Because sound reduces in shallow water, whales fleeing the air guns may strand themselves by swimming too close to shore; however, no conclusive research has proved this.

A more immediate danger is rapid surfacing. When trying to escape a loud noise, Slooten says there is evidence to show whales may surface from a dive too rapidly, effectively giving themselves decompression sickness, similar to the bends suffered by deep sea divers. Over time the effects can be serious and even life threatening.

THERE IS conjecture in the scientific community around auditory damage from seismic air guns and conclusive research is yet to be done. As a result, oil companies have taken what they consider to be a cautious approach and what Slooten labels a cop-out. All abide by a voluntary code of conduct developed in conjunction with industry and finalised last year. Under the code, survey ships keep marine mammal observers on board to scan the ocean for whales and dolphins. If a whale is spotted within a kilometre of the ship, the operation is suspended until it moves away. Slooten says the 1km limit is perfunctory and largely useless. "This distance has nothing to do with the whales or how far sound travels. That's just how far the human eye can see."

Oil and gas company OMV also uses passive-acoustic monitoring to listen for whale calls in the area. Further measures include the use of soft starts, in the hope that the quieter starting pulses will drive mammals from the area. However, there is concern that the softer pulses could attract curious whales rather than drive them away.

Despite all these problems, Slooten doesn't lay the blame squarely on the shoulders of oil companies saying New Zealand's laws are woefully inadequate when it comes to offshore exploration - and the oil companies agree.

OMV exploration manager Timothy Allan says oil companies insisted that the code of conduct be developed in the absence of legislation. He says all companies exploring in New Zealand are following - and often exceeding - the code, which he says is limited by a lack of concrete research.

"Everything we do errs on the side of caution. Before the code, the list of what we had to do in New Zealand was pretty much nothing. . . This criticism comes from a very vocal sector which wants us to be the bad guys."

Green MP Gareth Hughes says the Government's legislative efforts around oil exploration aren't good enough.

"If the Government concedes there's not enough information in this area, then they shouldn't be going ahead."

Allan says if credible research shows concrete evidence of damage to whales, the processes may undergo some change. Right now, however, the oil industry does not believe existing research proves any harm.

Allan is keen to see research funded to clarify which species are in our waters and when, perhaps allowing oil companies to time their surveying for when it will have minimal impact.

This is an approach adopted by some companies internationally, but such research would take years.

In the meantime, Slooten predicts inaction and ignorance mean there is every chance we will lose significant populations of endangered species visiting our waters. "They'll just keep blasting the hell out of those whales and dolphins. They just do whatever they want. It's ridiculous."