Reconnaissance Of The Chemical And Biological Limnology In Four Large Lakes Of The Yukon River Basin

Author : Ellorie McKnight
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (134 download)

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Download or read book Limnology of a Large Northern Lake (Lhù'ààn Mânʼ [Kluane Lake], Yukon) in an Era of Reconciliation and Rapid Climate Change written by Ellorie McKnight and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Almost 60% of Canada's freshwater drains North, where air temperatures are increasing at twice the global rate. Despite the exposure of northern lakes to higher rates of change and their ecological, hydrological, and cultural importance, baseline knowledge and monitoring of their water properties and dynamics remains limited. However, impacts to physical, biological, and chemical lake water properties have been documented and are likely to continue, with consequences for ecological and human communities. As such, understanding how northern lakes are changing is critical for implementing adaptation, mitigation, and protection measures to help ensure their long-term health. Lhù'ààn Mânʼ (Kluane Lake) is Yukon's largest lake, is important to local communities, and provides habitat to keystone species. In 2016, Lhù'ààn Mânʼ lost its primary inflow -- comprised mostly of glacial meltwater -- to glacier recession, offering a unique opportunity to investigate how glacier recession (and eventual disappearance) can impact downstream lakes. For these reasons, Lhù'ààn Mânʼ is a good case study to better understand how large northern lakes are impacted by climate change. In 2015, a baseline study to characterize physical, biological, and chemical lake water properties was conducted with Kluane First Nation, Dän Keyi Renewable Resources Council, academic and community colleagues (Chapter 2). This baseline revealed that Lhù'ààn Mânʼ was comprised of four distinct regions influenced by depth and proximity to glacial inflow: a cold, turbid, and poorly stratified southern basin, a mid basin and northeastern arm with relatively clear and consistently stratified waters, and a warm, nutrient-rich, productive northwestern arm. Spatial variability between lake regions and seasonal variability within sites was significant, emphasizing the need for sufficient spatial and temporal resolution in limnological studies. The baseline study led to the design and implementation of a long-term monitoring program for Lhù'ààn Mânʼ (Chapter 3). While the initial research interest focused on how gradual climate change was impacting the lake, after 2016 it evolved to include how more abrupt climatic changes (i.e., sudden loss of glacial inflow) could impact lake thermal dynamics. Four moorings equipped with continuously recording temperature data loggers were deployed in spring 2017 across the lake's different regions. Water temperature was selected because it is a key indicator of general freshwater conditions, and is reliable and cost-effective to measure. The first three years of Lhù'ààn Mânʼ thermal monitoring confirmed that each region of the lake has distinct thermal dynamics, but also different temporal patterns in thermal dynamics: warming occurred in the south end of the lake between 2017 and 2019 (but not in other regions of the lake), possibly impacted by the loss of significant glacial inflow in 2016. Continued monitoring will be critical to determine whether the south-end warming pattern continues, if warming will occur elsewhere in the lake, and how fish habitat will be impacted. Since thermal monitoring of large northern lakes is scarce, other available data was explored to investigate how these systems are changing. MODIS satellite imagery between 2000 and 2019 was used to examine whether lake ice break-up was occurring earlier at Lhù'ààn Mânʼ and nine other large lakes in southwest Yukon/northeast British Columbia (Chapter 4). All lakes revealed negative slopes indicating trends towards earlier spring ice break-up (and possibly longer ice-free periods), with mean start/end of break-up of all lakes occurring 0.72/0.46 days per year earlier. Three lakes exhibited significant trends (p