On an August morning aboard the Nathaniel B. Palmer research vessel floating at the bottom of the world, Christian Reiss was listening for acoustic signals bouncing off krill, a pinkish, feathery-limbed crustacean that is the lifeblood of the Antarctic ecosystem.
It was the last month of the Southern Hemisphere winter, and conditions were good: There was no thud from sea ice pancakes bumping together to distort his tests in the clear waters of the South Shetland Islands, about 500 miles south of Cape Horn.
Dr. Reiss, an oceanographer with the National Oceanic and Atmospheric Administration, and his team were studying where krill live in winter.
Low levels of sea ice gave them access to bays that in previous winters were closed. They wanted to know if a lack of sea ice, where krill gather to feed off the algae that live on the underside, was threatening the ocean’s largest biomass. Krill form schools that can be miles long and miles deep.
Whales, sea birds, penguins, squid and seals all feed off krill. And they compete with commercial fisheries in the same waters, who sell the tiny creatures to be used as fish food or to make omega-3 fish oil for human use.
Dr. Reiss’s findings are crucial. Two hundred and fifty scientists and policy makers are now gathered in Hobart, Tasmania, for an annual conference on managing Antarctica’s marine life, including how to preserve the krill population. Dr. Reiss’s five winter expeditions to the Antarctic showed that large numbers of krill remain in the open sea, in areas where fishing companies trawl for them.
At issue for scientists and policy makers is a measure that limits how much krill large commercial trawlers can vacuum from each of four designated zones of the South Atlantic. The rule, known as Conservation Measure 51-07, expires in November. It forces fishing companies to spread their fishing activity across larger areas to reduce the impact in any one zone.