National Science Foundation News
November 4, 1994
Lynn Simarski

Algae locked up inside the ice covering the southwestern corner of Antarctica's Weddell Sea undergo an unexpected autumn bloom, announces an article in the November 4 issue of Science. The perennially iced-over region lay beyond the reach of researchers until 1992, when the joint U.S.-Russian Ice Station Weddell I set up shop afloat an ice floe to conduct five months of investigations funded by the National Science Foundation. Labyrinthine sea ice, riddled with channels like Swiss cheese, is a nursery ground for krill, the shrimp-like mainstay of the Southern Ocean food web. The unexpected second algal bloom -- the first is in spring -- furnishes winter food for the krill.

"Virtually no 'biologically active' light reaches the water beneath the ice, so the algae living within the ice may be the only producers of food in that permanently ice-covered area," says Cornelius Sullivan, director of NSF's Office of Polar Programs and coauthor of the paper. "It was a surprise that there was enough light in the Antarctic autumn to allow a second bloom." As porous areas of the ice freeze, the process kicks off an exchange between nutrient-depleted brine in the ice and seawater, replenishing the nutrients in the ice. The results suggest that autumnal blooms are an important food source in some areas of sea ice. The paper's lead author is C.H. Fritsen, of the University of Southern California, and other authors are V.I. Lytle, University of Tasmania, and S.F. Ackley, U.S. Army Cold Regions Research and Engineering Laboratory.