Occurrence and Metabolic Activity of Organisms Under the Ross Ice Shelf, Antarctica, at Station J9

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Abstract
Seawater samples below the Ross Ice Shelf were collected through an access hole at J9, approximately 400 kilometers from the Ross Sea, Antarctica. The 237-meter water column had sparse populations of bacteria (8.7 × 10 6 to 1.2 × 10 7 per liter), microplankters (10 2 to 10 3 per cubic meter), and zooplankters (10 to 20 per cubic meter) at the depths studied. Microbial biomass estimates from cellular adenosine 5′-triphosphate measurements were very low (10 to 150 nanograms of carbon per liter), comparable with values for the abyssal ocean. Microbial populations assimilated tritiated D-glucose, thymidine, uridine, and adenosine triphosphate at extremely low rates, comparable with deep-sea heterotrophic populations. Sediment samples had 10 7 to 10 8 bacteria per gram (dry weight), which were metabolically active as shown by respiration of uniformly labeled D-[ 14 C]glucose. From this study it cannot be determined whether these organisms in the water column and sediments constitute a functioning food web.