ChevronTexaco won a permit for an offshore terminal in 2003, before concerns over "open loop" gas warming systems became widespread. Despite protests, Shell won a Coast Guard permit for a similar facility in February.

Conservationists have pushed for more expensive "closed loop" systems, which burn some cargo for heating fuel and are less dangerous to fish.

"They're going to be pumping anywhere from 100 million to 150 million gallons of water per day, and over the course of a year you're talking about billions of gallons of water that's essentially being sterilized," said Jeff Rester, habitat coordinator at the Gulf States Marine Fisheries Commission.

Opponents mobilized after Excelerate and ChevronTexaco's plans won approval, prompting more scrutiny of Shell Gas & Power's application for its Gulf Landing terminal 38 miles off southwestern Louisiana. But the US Maritime Administration signed off in February after Shell promised to limit fishery impacts and monitor effects.

"Shell believes the regulatory review has resulted in a balance between protecting the environment and helping the US meet a critical need for reliable, clean-burning natural gas," Catherine Tanna, Shell Gas & Power's director for the Americas and Africa, said after the application was approved.

Open loop terminals take in seawater to warm LNG from 260 degrees below Fahrenheit until it returns to gaseous state, then return the water to the Gulf.

"The temperature changes 10 to 20 degrees Fahrenheit, which is very shocking (to sea life)," Rester said.

Several onshore and offshore LNG terminals have been proposed for the US Gulf Coast. Four other offshore terminals also would use "open loop" systems. The public comment period for ConocoPhillips' proposed terminal off the Alabama coast, ended this week.

The National Marine Fisheries Service, as it has for the other three projects approved by the Coast Guard, said the threat to wildlife demands a closed system that reheats and recirculates water, as in an automobile radiator.

"We're continuing to express concern about impacts to commercially important marine species," said Rick Ruebsamen, the agency's Gulf Branch supervisor.

ConocoPhillips, which has enlisted a lab to identify species in the area, believes using intake screens for the seawater will protect fisheries, spokeswoman Linsi Crain said.

"This system creates less air emissions than other systems and allows us to send nearly all the energy to shore to be used by consumers, industry and utilities," Crain said.

Rester said a closed loop system is worth the extra expense to protect fish. "Red drum is the species that will be impacted the most," he said, referring to a popular species that is recovering because of overfishing.

Their vulnerable eggs and larvae, and the zooplankton they eat upon hatching, are unlikely to survive a trip through an LNG terminal, he said.