Oil gushing from a ruptured well in the Gulf of Mexico has seeped into the precious wetland of the U.S. state of Louisiana, threatening the Gulf ecosystem and the U.S. seafood industry, the state's governor said Wednesday.

Greenpeace staff member Lindsey Allen takes a sample of water in a heavily oiled marsh near South Pass, Louisiana May 19, 2010. For nearly a month, roughly 5,000 barrels (210,000 gallons/795,000 liters) of oil per day have been gushing from BP's broken Deepwater oil well situated in the Gulf of Mexico, in what could be named the worst oil spill in U.S. history. [Xinhua/Reuters]

"This is the first time we've seen this much heavy oil this far into our wetland," Louisiana Governor Bobby Jindal said during a news conference. "We know there's a lot more heavy oil behind it that hasn't made it to shore yet."

He called for the U.S. Army Corps of Engineers to grant an emergency permit for the state to dredge sand from barrier islands to create sand booms as another line of defense against the oil spill.

Video from Pass a Loutre in Plaquemines Parish, Louisiana, showed thick, brown oil lapping against reeds in a small area of marshes after creeping past booms and barriers.

"If I had been standing up, I would have fell to my knees," Billy Nungesser, president of Plaquemines Parish, told The Washington Post about learning of the news. "It's our greatest fear."

The oil's landfall puts Gulf wildlife in danger, and brown pelican, Louisiana's state bird which was removed from the U.S. federal endangered species list only in November, is at particular risk because it dives beneath the water's surface to forage.

Also in harm's way are at least 12 Gulf species listed by the U.S. government as endangered or threatened, including birds, sea turtles and the sperm whale.

So far, no brown pelicans are known to have died from the spill. But officials warned that things will change if oil invades brown pelicans' nesting and feeding grounds along coastal and barrier islands.