Microbiota under Antarctic ice shelves

Abstract

WHETHER or not life can exist far from the open sea beneath the permanent ice shelves of Antarctica is not known, but there are three opinions. (1) A biota cannot exist at all because of the absence of surface primary and secondary productivity¹. (2) A biota exists but with specialisations unique to life in the absence of surface productivity and in isolation under an ice shelf¹. (3) A typical Antarctic biota exists under any Antarctic ice shelf because currents are surely present that could carry food to it². Evidence supporting any of these views is unreliable. On the Ross Ice Shelf, samples taken through cracks 22 and 28 km from the open sea and in a newly calved area 8 km from the former ice front yielded rich benthic faunas but no floras^3,4. Plant life was presumably restricted by the lack of light coming through the ice. Some of the more common species of animals at nearby McMurdo Sound were not found in the samples, indicating that there was a possibility that conditions under the ice precluded them. Such differences, however, are common in Antarctic shallow-water areas, and can be due to local substrate differences, recent grounding of ice, or sampling bias dependent on the size and penetration depth of the sampler⁵. The Ross Ice Shelf locations are so close to the open ocean that typical benthic communities might live there. At George VI Sound, marine fish whose stomachs contained several species of invertebrates were caught through a proglacial lake adjacent to the ice shelf 100km from the nearest open water⁶. These animals were interpreted as evidence that a marine biome occurs under the entire shelf⁶. However, we describe here a microbiota from the George VI Sound occurrence that indicates that the fauna there may also be unique because it resides in a situation not typical of the entire ice shelf. Available evidence thus does not support any opinion.