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

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 x 10⁶ to 1.2 x 10⁷ per liter), microplankters (10² to 10³ 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 10⁷ to 10⁸ bacteria per gram (dry weight), which were metabolically active as shown by respiration of uniformly labeled D-[¹⁴C]glucose. From this study it cannot be determined whether these organisms in the water column and sediments constitute a functioning food web.