Alkalinity,pH, and pCO2 in the Laurentian Great Lakes: An initial view of seasonal and inter-annual trends |
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| Affiliation: | 1. Large Lakes Observatory and Department of Chemistry and Biochemistry, University of Minnesota, Duluth, 2205 East 5th St, Duluth, MN 55812, USA;2. Department of Chemistry and Biochemistry, University of Minnesota Duluth, 1038 University Drive, Duluth, MN 55812, USA;1. Natural Resources Department, Sault Ste. Marie Tribe of Chippewa Indians, 2428 Shunk Rd, Sault Ste. Marie, MI Resources 49783, USA;2. Michigan Department of Natural Resources, Charlevoix Fisheries Research Station, 96 Grant Street, Charlevoix, MI 49720, USA;3. Michigan State University, 480 Wilson Rd, East Lansing, MI 48824, USA;4. Little Traverse Bay Bands of Odawa Indians, 7500 Odawa Circle, Harbor Springs, MI 49740, USA;1. Department of Civil and Environmental Engineering, University of Windsor, Windsor, ON, Canada;2. Environment and Climate Change Canada, Water Science and Technology, Canada Centre for Inland Waters, Burlington, ON L7S 1A1, Canada;3. UWA School of Agriculture and Environment, The University of Western Australia, 35 Stirling Hwy, M004, Crawley, WA 6009, Australia;1. US Environmental Protection Agency, Office of Research and Development, 2000 Traverwood Drive #C59, Ann Arbor, MI 48105, USA;2. General Dynamics Information Technology, Falls Church, VA 22042, USA;3. US Environmental Protection Agency, Office of Research and Development, Duluth, MN, USA;4. US Environmental Protection Agency, National Student Services Contract, Office of Research and Development, Duluth, MN, USA;1. Department of Biology, Clarkson University, Potsdam, NY 13699, United States;2. Institute for a Sustainable Environment, Clarkson University, Potsdam, NY 13699, United States;3. Département des Sciences de l’Environnement, Université du Québec à Trois-Rivières, CP 500, Trois-Rivières, QC G9A 5H7, Canada;1. Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA;2. Illinois-Indiana Sea Grant, Purdue University, West Lafayette, IN 47907, USA;3. U.S. Geological Survey, Great Lakes Science Center, Ann Arbor, MI 48105, USA;4. Michigan Department of Natural Resources, Alpena Fisheries Research Station, Alpena, MI 49707, USA |
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| Abstract: | Ongoing human perturbations to the global inorganic carbon cycle can cause various changes in the pH and alkalinity of aquatic systems. Here seasonal and inter-annual trends in these variables were investigated in the five Laurentian Great Lakes using data from the U.S. EPA GLENDA database. These observations, along with temperature, were also used to predict the partial pressure of carbon dioxide in surface water (pCO2). There are strong seasonal differences in pH in all five lakes, with higher pH levels in summer than in spring. All lakes show significantly higher pCO2 values in spring than in summer. Michigan and Ontario show higher alkalinity values in spring; Huron shows lower spring values. Inter-annually, open-lake pH shows the highest values in all lakes around 2010, the time frame of lowest lake water levels, though only lakes Superior and Erie show statistically significant inflection points at that time. Inter-annual alkalinity trends differ considerably from those of pH. Superior’s alkalinity increases until ～2008 and then begins dropping; Ontario’s alkalinity decreases until ～2004 and then begins increasing, with the decrease coinciding with the introduction and establishment of Dreissenid mussels. The other lakes show much less clear inter-annual alkalinity trends. For pCO2, inter-annual trends in each lake show either increases from 1992 to 2019 (for Superior, Michigan, and Huron) or shifts from slightly decreasing values to increasing values for the other lakes. The timing of this shift is from 2008 to 2010. |
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| Keywords: | Laurentian Great Lakes Alkalinity pH |
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