Local environmentalists, scientists and lawmakers banded together Thursday to announce that the Obama administration has responded to their proposal to expand Papahanaumokuakea Marine National Monument and make it, once again, the largest marine sanctuary in the world.

Representatives from the White House Council on Environmental Quality have met with stakeholders this week in Hawaii after Native Hawaiian leaders sent a letter to the administration in January asking President Barack Obama to vastly increase the size of Papa­hanaumokuakea to 200 from 50 nautical miles from shore.

“We urge people providing advice to the president to be bold,” said William Aila Jr., former head of the state Department of Land and Natural Resources, during a press conference Thursday at the University of Hawaii at Manoa’s Kewalo Marine Laboratory.

Aila, Office of Hawaiian Affairs CEO Kamanaopono Crabbe and Polynesian Voyaging Society President Nainoa Thompson were among the leaders who sent the letter to the White House. The Native Hawaiian leaders also asked the president to designate the state Office of Hawaiian Affairs as a co-trustee on the management committee.

The name Papahanau­mokuakea pays homage to the union of two Hawaiian ancestors — Papahanaumoku and Wakea — who are credited with creating the Hawaiian Archipelago, the taro plant and the Hawaiian people.

The coalition of groups seeking the expansion maintain that the monument’s marine species, such as sea turtles, whales, dolphins, seabirds, sharks and tuna, are threatened by longline fishing vessels when they range outside the current protected area.

Since President George W. Bush made the original monument designation 10 years ago, scientific expeditions within the proposed expansion area have discovered high-density communities in which most of the animals are unknown to science, including black corals estimated to be 4,500 years old. Black corals are described as the old-growth redwood forests of the ocean.

Marti Townsend, executive director of the Sierra Club Hawaii Chapter, said, “This is an opportunity for Hawaii to protect its ocean resources and the health of its ocean, not only for the people of Hawaii who are directly relying on this as their own refrigerator, but also for the world because the oceans are dying.”

Within the region there are more than 7,000 marine species. The area is one of the few remaining predator-dominated ecosystems in the world. Large predatory fish such as sharks, giant trevally and groupers are abundant in Papa­hanaumokuakea waters. Elsewhere, these populations have been heavily depleted by fishing.

The commercial fishing industry opposes the proposed expansion. The Hawaii Seafood Council, Pacific Islands Fisheries Group and Hawaii Fishermen’s Alliance for Conservation and Tradition Inc. sent letters to the president asserting that widening Papahanau­mokuakea’s boundaries would hurt the domestic fishing industry due to the loss of access for U.S. fishermen to fish in U.S. waters.

“The expansion of current boundaries will further disadvantage our domestic longline fishery that competes on the global market with cheap foreign imports that are harvested at higher environmental costs,” the Hawaii Fishermen’s Alliance said in a letter.

“This fishery anchors the local production of seafood consumed 40 percent here in the islands. In contrast, only 10 percent of the seafood consumed on the mainland is domestically produced,” said Neil Kanemoto, Pacific Islands Fisheries Group president, in a letter.

Not all fishermen oppose the bid for expansion. Jay Carpio, a fisherman from Maui, said tuna populations have declined due to longline fishing in Hawaii.

“We have seen the decline in tuna populations that longline fishing in Hawaii has caused, subjecting Hawaiians and Hawaii residents to import ahi poke from other countries,” Carpio said in a press release.

“What breaks my heart is you have so many local fishermen and fisher people who have a real sense of aloha aina who will refrain from fishing to help restore ocean resources, then you have these commercial takers who have no sense of that and are taking far more than their fair share,” Townsend said.

Proponents of the expansion celebrated the administration’s presence on the islands this week, saying it makes them hopeful Obama would broaden the zone.

“The very fact they are out here right now means they are listening,” said Narrissa Spies, a biologist at Kewalo Marine Laboratory. She called Papahanau­mokuakea’s expansion the “easiest and most important thing the administration can do for the ocean.”

Backers hope Obama will support the proposal and make the announcement about it at the International Union for Conservation of Nature Council World Conservation Congress, which will be held at the the Hawai‘i Convention Center in September.

“It is perfectly lined up with the largest conservation conference in the world, because it would be the largest marine protected area in the world if President Obama expands it,” Spies said.