The guardians of Antarctica's marine wealth gather in Germany on Sunday for a fresh round of talks on creating the world's largest ocean sanctuary.
Two plans of unprecedented scope are on the table, aimed at protecting vast, pristine waters and 16,000 species from human predation.
But whether one scheme, both -- or none -- gets approval is unclear, given Russian and Chinese concerns that the restrictions are too draconian.
One proposal, floated by the United States and New Zealand, would cover 1.6 million square kilometers (640,000 square miles) of the Ross Sea, the deep bay on Antarctica's Pacific side.
The other, backed by Australia, France and the European Union (EU), would protect 1.9 million sq. km (733,000 sq. miles) of coastal seas off East Antarctica, on the frozen continent's Indian Ocean side.
The three-day meeting in Bremerhaven, Germany, gathers 24 nations plus an EU delegation in the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).
The CCAMLR is a treaty tasked with overseeing conservation and sustainable exploitation of the resources of the Southern Ocean.
It aims to fill a gap left by the Antarctic Treaty that came into force in 1961, which addressed the land of the continent but not its surrounding waters.
For nearly all of its 32 years, the CCAMLR -- pronounced "cam-lar" -- has barely flickered on the world's political radar.
But that is now changing as the world's fish stocks reel from decades of plundering and industrial trawlers venture ever farther to feed the planet's surging population.
High-profile campaigns about overfishing have also pushed the issue of the Antarctic's oceans higher up the agenda.
"Fishing has so accelerated on many parts of the globe that 85 percent of fish stocks are over-exploited," said Andrea Kavanagh, in charge of the Southern Ocean Sanctuaries campaign at the US green research group Pew Environment.
"Creating those protecting areas would more than double the amount of protected oceans in the world."
Robert Calcagno, director of the Monaco Oceanographic Institute, said the waters around Antarctica were a vital link in the ecological web.
"The Southern Ocean is of major importance, given its wealth of biodiversity, including fish that can live in waters below zero degrees (Celsius, 32 degrees Fahrenheit)," he said.
"It is also connected to the world's ocean current system, and has massive stocks of krill," he said, referring to the tiny shrimp that is a vital protein source for whales, penguins and seals.
Even as they welcome the initiatives, some conservationists argue the proposals do not go far enough to protect marine life.
They are particularly worried for the toothfish, a predator species that grows slowly and reproduces late in life, which makes it vulnerable to overfishing of juveniles.
The US and New Zealand proposal, while creating a reserve to protect Adelie and emperor penguins, killer whales and Weddell seals, would still allow some 3,000 tonnes of toothfish to be commercially caught each year.
Some heavy hitters are giving the Bremerhaven meeting their support, including US Secretary of State John Kerry.
The outcome, though, will not be known until Tuesday. CCAMLR meetings are held behind closed doors, and any decision has to be reached by consensus.
Parties met in Hobart, Australia, last October, but failed to reach a deal because of opposition by China and Russia, supported by Ukraine, which said restrictions on fishing were too onerous.
As a result, parties agreed to an exceptional meeting this July. It is only the second time that the CCAMLR has met outside its annual gathering, and a sign of the difficulties of getting international agreement over protection of a dwindling resource.
"It's really a Wild West when it comes to doing things like nations getting together to declare some protected areas," said Tony Haymet of the Scripps Institution of Oceanography in California.