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.作为麦克默多干谷长期生态研究（Long Term Ecological Research, LTER）项目的组成部分，研究人员针对南极洲麦克默多干谷内数座终年封冻的湖泊，对其溶解氧（dissolved oxygen, DO）浓度开展监测。此类湖泊的溶解氧浓度范围从无氧状态至空气饱和值的350%，而溶解氧浓度是驱动水体细菌多样性变化的关键因素。在每年南半球夏季（11月与12月），研究人员会对弗莱克塞尔湖（Fryxell Lake）、邦尼湖东支（East Lobe Bonney）与邦尼湖西支（West Lobe Bonney）的离散采样深度处的溶解氧进行两次常规测定。霍尔湖（Hoare Lake）与迈尔斯湖（Miers Lake）的采样频次则相对更低。水样采集工作于“湖沼学采样航次（limno runs）”期间开展，该航次由MCM LTER湖沼学团队执行，旨在对一系列物理、化学与生物学参数实施常规采样。研究人员采用5升容量的尼斯金采水器（Niskin bottle），按特定深度间隔采集湖水。溶解氧检测所需的子样本会立即以锰溶液与碱性碘化物叠氮溶液进行固定，当日即在干谷野外实验室中完成微量温克勒滴定（Mini-Winkler titrations，改编自Carpenter 1965年的方法）操作。