When the air blast goes off, it sends a deafening 250 decibels of low frequency sound through the ocean. Most people feel pain at 140 decibels. A jet engine is intolerable at 150 decibels.

The air explodes downward at 2,000 psi. The pressure in a car tire is about 32 psi.

How would you expect a whale or dolphin to respond to one such blast every 10 seconds, day after day?

Now imagine how the minor creatures of the sea, krill, microscopic plankton, and pelagic drifters handle this enormous, repeat rush of energy through the environment.

Oil and gas companies use the massive air guns to survey the ocean floor for oil. The air gun is towed behind a powerful boat that soon may cruise up and down the eastern coastline of the US. The gun shoots a blast of compressed air so powerful it can penetrate deep into the ocean floor. The returning echo from the blast is received and processed to give geologists some idea of the likelihood of geological structures indicating valuable deposits. It works well for this purpose and might locate valuable new oil fields.

Conversely, the US government has calculated that this activity could harm up to 138,500 whales, turtles, and dolphins, destroying their hearing or killing them outright.

NOAA and its National Marine Fisheries Service will hold a public hearing on July 6 with five companies that need permits to conduct air-blast surveys. The Marine Mammal Protection Act allows incidental harassment of whales, dolphins, and manatees, and the interpretation of this is part of the ongoing debate between finding new oil reserves and protecting fragile marine environments.

The debate deepened this week when a report from Australia's Curtin University conducted in the sea of Storm Bay, Tasmania revealed that not only are whales hurt by the blasts, but so are jellyfish, fish larvae, and the tiniest of zooplankton.  

Robert McCauley and his team found that a low frequency air gun blast like that used by oil seekers decreased zooplankton incidence by 64% and caused huge organism die-offs up to three quarters of a mile away .

The blast blew a hole right through the entire survey area. What was a rich zooplankton area just vanished. Every krill larva died.

The current political debate on the need for oil and gas exploration in underwater sites should be separated from the overwhelming evidence that air guns, however effective in mapping the sea floor, cause massive damage to marine life, from the largest whales to the smallest plankton.

There must be a better way to find oil.