Vertical Distribution of Bacterial Population in Lake Fryxell, an Antarctic Lake.

Abstract

Vertical distributions of bacterial numbers, cell sizes, and biomass in the water of Lake Fryxell in the McMurdo Dry Valleys of the Antarctic were examined by the acridine orange direct count (AODC) method. Total bacterial numbers increased with increasing depth from 5.4×105 cells⋅ml-1 in the surface water (5.0 m depth) to 1.7×107 cells⋅ml-1 in the bottom water (19.0 m depth). Bacteria from waters at all sampling depths were dominated by rod-shaped cells having the average values in the ranges of 0.37-0.64 μm width and 1.04-1.85 μm length. However, those from waters with depth of between 10.0 and 12.5 m had relatively large mean cell sizes. Bacterial biomass estimated from cell volumes ranged from 0.017 to 0.29 mgC⋅-1, corresponding to from 0.75 to 5.9% of total organic carbon. A total of 80 isolates from the stored water samples were identified as Pseudomonas, Acinetobacter-Moraxella and Caulobacter. Sulfate-reducing bacteria were recovered from the anaerobic bottom water.