Drivers of microbial food web structure and function: Bottom-up and topdown controls across Lake Michigan

Major Goals and Objectives

The researchers used molecular tools to characterize microbial communities in the changing biogeochemistry of Lake Michigan (2012-2015) and across the Laurentian Great Lakes.

Story: IISG researchers identify microbes throughout the Great Lakes


ecology, food web, microbes

Lay Summary

Microorganisms consume, recycle, and transform essential nutrients and form the base of the food web in lakes. Understanding how the composition of microbial assemblages (i.e., which microorganisms are present and their relative abundance) and the functions they are able to carry out (e.g., photosynthesis) change over space and time can help us predict how ecosystems like Lake Michigan will respond to changes in the environment. We surveyed microorganisms across all five Laurentian Great Lakes over four years. The main factor that affected the composition of microbial assemblages was depth. For example, during summer stratification, the microbial community at the bottom of Lake Michigan more strongly resembled the microbial community at the bottom of Lake Ontario than the microbial community collected at the surface of Lake Michigan. Depth differences are not observed in the spring when the lakes are mixing; spring surface communities resemble deep communities. We also observed differences in the abundance and composition of microorganisms at the surface of the five Great Lakes, with the largest differences observed between the upper lakes (Superior, Michigan, and Huron) and lower lakes (Erie, Ontario). Despite these differences, many microbial species were observed in all of the lakes. Some of these species appear to have different adaptations depending on which lake they inhabit, such as the ability to acquire and transform various forms of nitrogen. Together, our results reveal a complex microbial biogeography that is shaped by, and likely contributes to, biogeochemical variability across the Great Lakes.


US EPA Great Lakes National Program Office; University of Notre Dame; University of Wisconsin – Milwaukee

Undergraduates / Graduates

  • Justin Podowski (Ph.D. student, Geophysical Sciences)
  • Gabriel Vargas (Ph.D. student, Geophysical Sciences)
  • Mark Anderson (Ph.D. student, Geophysical Sciences)
  • Daniel Muratore (post-postbaccalaureate, Biological Sciences)
  • Kyra Grantz (undergraduate, Geophysical Sciences)
  • Diana Bojanova (undergraduate, Geophysical Sciences)
  • Michael Wasney (undergraduate, Geophysical Sciences)
  • Shane Coffield (undergraduate, Geophysical Sciences)
  • Petra Byl (undergraduate, Geophysical Sciences)
  • Anastasia Bernat (undergraduate, Geophysical Sciences)

Research Information

Principal Investigator:
Maureen Coleman
Initiation Date:
Completion Date:
University of Chicago


Maureen Coleman
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