With sick and dead dolphins turning up along Louisiana's coast, federal regulators are curbing an oil and natural gas exploration company from using seismic equipment that sends out underwater pulses known to disturb marine mammals.
The Bureau of Ocean Energy Management has told Global Geophysical Services Inc. to not conduct deep-penetration seismic surveys until May, when the bottlenose dolphin calving season ends. The agency says the surveys are done with air-guns that the emit sounds that could disrupt mother and calf bonding and mask "important acoustic cues."
The company said it laid off about 30 workers because of the restriction, which it called unnecessary.
But environmental groups suing BOEM over the use of underwater seismic equipment say restrictions should be extended to surveyors across the Gulf of Mexico.
The new limit on exploration highlights the friction over oil drilling in the Gulf since the April 20, 2010 blowout of a BP PLC well that resulted in the death of 11 workers and the nation's largest offshore oil spill in the nation's history.
After the 2010 spill, the Natural Resources Defense Council and the Center for Biological Diversity sued to get curbs placed on underwater seismic surveys. The environmental groups argued they harm marine mammals and that the federal government violated animal protection laws after it declared in 2004 that the surveys were safe.
The government is in settlement talks with those environmental groups, according to court documents.
"Imagine dynamite going off in your neighborhood for days, months on end," said Michael Jasny, a senior policy analyst at the NRDC. "That's the situation these animals are facing."
Jasny said the restriction placed on Global Geophysical was a good sign, but far from enough.
In its ruling, the federal agency said it was concerned that seismic surveys could affect marine mammals, and even cause them to lose their hearing.
Amy Scholik, a fisheries biologist with NOAA, said it was unknown what kind of effects air-guns have on bottlenose dolphins, but she said there was concern about possible effects on dolphin calves because they are vulnerable to stresses. She added that whales in Alaska have been shown to change migration routes because of seismic surveys.
George Ioup, a physics professor at the University of New Orleans studying the effects of air-guns on marine mammals, said the verdict was out on the effects of air-guns on mammals. He said BOEM seemed to be ruling "on the side of caution."
"Proving there is an effect, I don't know if that has been done," he said. "I don't think the answer is overwhelmingly simple."
The air-guns are towed at low speeds behind a survey ship and emit high-intensity, low-frequency sound waves to find geological layers. Seismic surveying is essential to drillers because they tell them where to drill and not drill.
The government also relies on the seismic data to know where it's safe to drill and to determine how much it should charge for leasing offshore blocks to oil and gas companies.
Marc Lawrence, Global Geophysical's vice president in the Gulf region, said the seismic surveys do not pose a danger to marine mammals.