Sergei Katsev


Associate Professor • Large Lakes Observatory & Department of Physics • University of Minnesota Duluth


      

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NSF
Lake Superior:

Geochemical dynamics in sediments with deep oxygen penetration
Publications:
Li et al. (2012) Carbon mineralization and oxygen dynamics in sediments with deep oxygen penetration, Lake Superior. Limnology&Oceanography 75: 1634-1650 (PDF).
Li (2011) Diagenesis and sediment-water exchanges in organic-poor sediments of Lake Superior. M.Sc. Thesis. (PDF).
Kistner (2013) Reactivity of organic carbon in Lake Superior. M.Sc. project (PDF).

Funding:
NSF OCE: Transient diagenesis in organic-poor sediments: Lake Superior, $416,961, 2010-2013.

The sediments of Lake Superior are characterized by extremely deep oxygen penetration. Whereas in most lakes and coastal ocean oxygen penetrates into sediments only by several mm, in Lake Superior we typically measure oxygen penetrations of 3-12 cm, and at one location even 27 cm! This is unusual for lakes, but actually typical for the deep ocean. We can therefore use Lake Superior as an easily accesible laboratory in which to investigate processes that are important globally: rates of organic carbon mineralization, fluctuations in the depth of the sediment oxic/anoxic boundary, and dynamics of nutrient fluxes across the sediment-water interface.

Our past work has shown that sediments with deep penetration of oxygen are particularly sensitive to changes in external conditions. We have now recorded seasonal changes in oxygen penetration of up to 2 cm in Lake Superior, a process that affects the rates of nitrate removal and metals solubilization.
Lake Superior sediment oxygen penetration

Our results allow us to compare the rates at which microbial communities process organic material in freshwater vs. marine environments, which links to the fundamental questions about the controls on reaction rates in aquatic environments in the modern world, as well as in the Earth's early oceans.




Fe layer in Lake Superior Below: The sediments of Lake Superior are characterized by extreme lateral variability, with sediment properties varying strongly over as little as hundreds of meters. The highly dynamic lake-bottom environment leads to frequent migrations in the sediment oxic-anoxic boundary and is recorded in priminent Fe-rich layers that are ubiquitous in Lake Superior.

  

Lake Superior sediment oxygen penetration
Lake Superior in comparison to the Ocean

Lake Superior sediment images