Dissolved oxygen concentrations in discrete water column samples collected from lakes in the McMurdo Dry Valleys, Antarctica (2010-2025, ongoing)

As part of the McMurdo Dry Valleys Long Term Ecological Research (LTER) project, dissolved oxygen (DO) concentrations are monitored in several perennially ice-covered lakes in the McMurdo Dry Valleys of Antarctica. Dissolved oxygen concentrations in these lakes ranges from anoxic to 350% of air saturation. DO concentrations are an important driver for bacterial diversity in the water column. Dissolved oxygen is routinely measured twice every austral summer (in November and December) at discrete sampling depths in Lakes Fryxell, East Lobe Bonney, and West Lobe Bonney. Less frequent measurements are available from Lakes Hoare and Miers. Water samples are collected from the lakes during “limno runs”, routine sampling of a broad suite of physical, chemical, and biological parameters performed by the MCM LTER limno team. Lake water is collected at depth specific intervals with a five-liter Niskin bottle. Sub-samples for dissolved oxygen are immediately fixed with a manganous solution and alkali-iodide-azide solution. Mini-Winkler titrations (adapted from Carpenter (1965)) are performed in the Dry Valley field labs on the same day.