McMurdo Dry Valleys: Water Sample Analysis

Created by George Rice, Montana State University

The niskin bottle, shown below on the left, is attached to a winch and collects water at specific depths for biogeochemical analysis of the lake. Water samples are then moved to lakeside laboratories and filtered.

Water sample collection and Lakeside laboratory

Selected biogechemical parameters for three of the dry valley lakes:

Biogechemical parameters for three of the dry valley lakes.

The vials in the bottom row show a dissolved oxygen profile from Lake Fryxell, based on the Winkler method. Samples from left to right show water taken from shallower to deeper depths. Moving from left to right, you can see that the upper waters of the lake are super-saturated with oxygen but become increasingly anoxic with depth. Through a series of chemical reactions, the oxygen combines with iodine to form a golden yellow chemical, which is evident in the vials on the left from the shallower depths.

Example of the Winkler method to determin disolve oxygen content in lake water samples.