The move, together with President Bush's 2006 decision to create a 140,000 square mile marine sanctuary near the Northern Hawaiian Islands, won him rare praise from environmentalists.
"With the designation of the world's largest marine reserve in the Northwestern Hawaiian Islands in 2006 and now these three other sites, George W. Bush has done more to protect unique areas of the world's oceans than any other person in history," said Pew Environmental Group Managing Director Joshua Reichert, according to the New York Times.
But other environmentalists were more cautious with their praise.
"On balance, when you compare this to little to no action on climate change and the lifting of the moratorium [on offshore oil drilling] that's been in place for 27 years, that begins to paint a different picture," Vikki Spruill, president and chief executive of the Ocean Conservatory, told the Washington Post. "This move, by itself, is a really positive move. The net gain is a question we will have to address years from now."
Mr. Bush used executive powers established under the Antiquities Act of 1906 to create the three Marine National Monuments, and the decision does not need congressional or any other approval.
The three areas encompass the 1500-mile-long Mariana Trench, which includes underwater active volcanoes and thermal vents; the Rose Atoll in American Samoa; and a string of largely uninhabited islands and reefs in the Central Pacific.
Together the areas host many rare and endangered species and habitats, including sharks, terns, albatrosses, the Micronesian megapode -- a bird that incubates its eggs in volcano-heated water -- and a sulfur pool so unusual that its closest cousin is found on one of Jupiter's moons.
The National Monument designation will protect the areas from commercial fishing, seafloor mining, oil exploration and other uses, and will limit indigenous and recreational fishing.
James Connaughton, chairman of the White House Council on Environmental Quality, and First Lady Laura Bush worked to persuade the president to create both the 2006 and Tuesday's protected marine areas, according to the Los Angeles Times.
On Monday, Connaughton said that federal officials were able to overcome the resistance of commercial fisherman and mining companies by showing that the areas contained few lucrative fish or minerals.
"Having done the science, we were able to actually take an issue off the table because it wasn't relevant," Connaughton said, according to the Los Angeles Times.
President Bush used the announcement of the marine conservation areas to broadly defend his environmental record.
"The new steps I've announced today are the capstone of an eight-year commitment to strong environmental protection and conservation. I know that sounds contrary to the conventional wisdom of many," Mr. Bush said.
"For sea birds and marine life, they will be sanctuaries to grow and thrive. For scientists, they will be places to extend the frontiers of discovery. And for the American people, they will be places that honor our duty to be good stewards of the Almighty's creation," the president added.