WASHINGTON » President Barack Obama said today that creating the Atlantic Ocean’s first marine national monument was a needed response to dangerous climate changes, ocean dead zones and unsustainable fishing practices.

The new Northeast Canyons and Seamounts Marine National Monument consists of nearly 5,000 square miles of underwater canyons and mountains off the New England coast. It’s the 27th time that Obama has created or enlarged a national monument.

“If we’re going to leave our children with oceans like the ones that were left to us, then we’re going to have to act and we’re going to have to act boldly,” Obama said at a State Department conference. More than 20 countries represented at the meeting were also announcing the creation of their own marine protected areas.

Monument designations come with restrictions on certain activities. The White House said the designation will lead to a ban on commercial fishing, mining and drilling, though a seven-year exception will occur for the lobster and red crab industries. Recreational fishing will be allowed within the monument.

Supporters of the new monument say protecting large swaths of ocean from human stresses can sustain important species and reduce the toll of climate change. Fishermen worry it will become harder for them to earn a living as a result of Obama’s move.

“We’ve been fishing out there for 35 years. It’s a big blow to us,” said Jon Williams, president of the Atlantic Red Crab Company in New Bedford, Massachusetts.

White House officials said the administration listened to industry’s concerns, and noted the monument is smaller than originally proposed and contains a transition period for companies like Williams’.

Williams said his company will survive, but the changes designed to address some of his concerns don’t sway him about the merits of the monument.

“I think the entire New England fishery is upside down over this,” Williams said.

Obama said the world was asking too much of its oceans. He said the investments the U.S. and other nations were taking with new marine protected areas were vital for their economy and national security, but “also vital to our spirit.”

“We cannot truly protect our planet without protecting our oceans,” Obama said.

In all, the Atlantic Ocean monument will include three underwater canyons deeper than the Grand Canyon and four underwater mountains. It is home to such protected species as the sperm, fin and sei whales, and Kemp’s ridley turtles. Expeditions also have found species of coral found nowhere else on earth.

Environmental groups pushed the effort to designate the new monument and sought to make the case it was as important to be good stewards of the ocean as it was the land and air.

“Just as wild lands around the globe are beleaguered by human development and climate change, our oceans are under duress today more than ever before,” said Jamie Williams, president of The Wilderness Society.