WASHINGTON — President Bush today will create three new marine monuments in the Pacific Ocean to protect the deepest place on Earth, some of the last pristine corals and sanctuaries for vanishing marine species.

The three monuments — in the Mariana Islands in the western Pacific, the Rose Atoll off American Samoa and remote islands in the central Pacific — cover 195,280 square miles, the largest protected area of ocean.

Conservationists and the White House declared a new era for protection of unique and endangered places in the ocean, opportunities of scientific discovery and an important effort to protect some of the last places where the ocean still looks like the abundant world of centuries or even thousands of years past.

The Marianas Marine National Monument will protect the Mariana Trench, the deepest place on Earth — deeper than Mount Everest is high and explored for the first time only in 1960. The three monuments also protect corals and the ecosystems that include large migratory, resting and feeding sea birds, and endangered animals such as sea turtles.

"To me and the president and first lady, one of the things that really affected us in learning from the scientists is these locations are truly among the last pristine areas in marine environments on Earth," White House Council on Environmental Quality chairman James Connaughton told reporters yesterday. "This is a huge day for marine conservation."

"The president has given the world a Texas-sized gift," said Diane Regas, manager of the ocean program at the Environmental Defense Fund.

Joshua S. Reichert of the Pew Environment Group said it had taken more than a century to start to protect unique places in the ocean in the way that America has protected its treasured places as natural parks on land.

In 2006, Bush also protected 139,793 square miles in the Papahanaumokuakea Marine National Monument in the Northwestern Hawaiian Islands. In all, Bush has protected more of the oceans than anyone else in the world, Reichert said.

Commercial and recreational fishing will be forbidden within 50 miles of the islands. Recreational fishing permits will be considered on a limited basis.