The world's biggest marine reserve, almost as large as Alaska, will be established in the Ross Sea in Antarctica under an agreement reached by representatives of 24 nations and the European Union. The policy makers and scientists agreed unanimously to create a zone that will encompass 600,000 square miles of ocean. Commercial fishing will be banned from the entire area, but 28 percent of it will be designated as research zones, where scientists can catch limited amounts of fish and krill, tiny invertebrates that provide food for whales, penguins, seals and other animals. The area, which is mostly contiguous and hugs the coast off the Ross Sea ice shelf, will come under protection on Dec. 1, 2017, and remain a reserve for 35 years. The agreement was reached in Hobart, Tasmania, at the Commission for the Conservation of Antarctic Marine Living Resources. Protecting the Ross Sea, in the Southern Ocean, had been on the commission's agenda for around six years, and conservationists had been arguing for a no-fishing zone there for a decade, said Andrea Kavanagh, a director of the Southern Oceans Sanctuaries Campaign at the Pew Charitable Trusts in Washington. This is a great result for quiet diplomacy and honest toil," New Zealand's foreign minister, Murray McCully, said from Auckland. "The fact that an agreement like this can be reached ... when there are so many difficulties, so many other political differences happening elsewhere ... is pleasing."