%ALambrecht, Nicholas [Department of Geological and Atmospheric Sciences Iowa State University Ames IA USA]%ALambrecht, Nicholas [Department of Geological and Atmospheric Sciences, Iowa State University, Ames IA USA]%AWittkop, Chad [Department of Chemistry and Geology Minnesota State University Mankato MN USA]%AWittkop, Chad [Department of Chemistry and Geology, Minnesota State University, Mankato MN USA]%AKatsev, Sergei [Department of Physics University of Minnesota, Duluth Duluth MN USA, Large Lakes Observatory University of Minnesota, Duluth Duluth MN USA]%AKatsev, Sergei [Department of Physics, University of Minnesota, Duluth, Duluth MN USA, Large Lakes Observatory, University of Minnesota, Duluth, Duluth MN USA]%AFakhraee, Mojtaba [Large Lakes Observatory, University of Minnesota, Duluth, Duluth MN USA]%AFakhraee, Mojtaba [Large Lakes Observatory University of Minnesota, Duluth Duluth MN USA]%ASwanner, Elizabeth [Department of Geological and Atmospheric Sciences Iowa State University Ames IA USA]%ASwanner, Elizabeth [Department of Geological and Atmospheric Sciences, Iowa State University, Ames IA USA]%BJournal Name: Journal of Geophysical Research: Biogeosciences; Journal Volume: 123; Journal Issue: 10; Related Information: CHORUS Timestamp: 2023-09-09 23:05:32 %D2018%IDOI PREFIX: 10.1029 %JJournal Name: Journal of Geophysical Research: Biogeosciences; Journal Volume: 123; Journal Issue: 10; Related Information: CHORUS Timestamp: 2023-09-09 23:05:32 %K %MOSTI ID: 10077900 %PMedium: X %TGeochemical Characterization of Two Ferruginous Meromictic Lakes in the Upper Midwest, USA %XAbstract

To elucidate the role of (bio)geochemical processes that fueled iron and carbon cycling in early Earth oceans, modern environments with similar geochemical conditions are needed. As the range of chemical, physical, and biological attributes of the Precambrian oceans must have varied in time and space, lakes of different compositions are useful to ask and answer different questions. Tropical Lake Matano (Indonesia), the largest known ferruginous lake, and Lake Pavin (France), a meromictic crater lake, are the two best studied Precambrian ocean analogs. Here we present seasonal geochemical data from two glacially formed temperate ferruginous lakes: Brownie Lake (MN) and Canyon Lake (MI) in the Upper Midwest, USA. The results of seasonal monitoring over multiple years indicate that (1) each lake is meromictic with a dense, anoxic monimolimnion, which is separated from the less dense, oxic mixolimnion by a sharp chemocline; (2) below this chemocline are ferruginous waters, with maximum dissolved iron concentrations >1 mM; (3) meromixis in Brownie Lake is largely anthropogenic, whereas in Canyon Lake it is natural; (4) the shallow chemocline of Brownie Lake and high phosphorus reservoir make it an ideal analog to study anoxygenic photosynthesis, elemental ratios, and mineralogy; and (5) a deep penetrating suboxic zone in Canyon Lake may support future studies of suboxic microbial activity or mineral transformation.

%0Journal Article