Microbial Community Analyses of the Saginaw Bay Watershed
Dr. James L. McEvoy, Assistant Professor of Biology, SVSU
Quality of the water in the Saginaw Bay Watershed is a matter of concern for residents of much of mid-
Michigan. Most of the research to date involved monitoring chemical constituents, algal blooms, or
coliform/E. coli counts of various parts of the Saginaw Bay Watershed. Our research group is interested
in learning more about the microbial communities present in these waterways and what role they may
play in nutrient turnover. To do this we are examining the metabolic fingerprints (carbohydrate
utilization profiles) of the microbial communities as well as determining the Escherichia coli and total
coliform concentrations in samples of water, sand, silt and muck obtained from the Saginaw Bay and
associated river ways. The Biolog EcoPlate TM system, containing 31 carbon sources in triplicate in a 96
well micro-plate format and developed specifically for microbial community analysis, is being utilized to
determine the microbial metabolic fingerprints of the samples. Microbial communities can and often do
shift in response to environmental changes. These shifts in microbial community function can be useful
in associating one or more environmental factors with this phenomenon (Felicia A. Krelwitz, 2014,
Masters Thesis, Governors State University, University Park, IL). The Biolog EcoPlate TM system has proven
to be quite sensitive (J.L. Garland, A.L. Mills, Applied and Environmental Microbiology, 1991, v.57, p.
2351-2359) and may prove useful to detect microbial changes that precede such phenomena as toxic
algal blooms or the presence of high levels of coliform bacteria. We hypothesize those environmental
factors such as rain and/or wind events, air and water temperature, and E. coli/coliform counts will
correlate with changes in the metabolic fingerprints of the microbial communities.
A part of this study involves examining E. coli and total coliform numbers in the water, sand, silt and
muck at Bay City State Park and the Saginaw, Cass, Shiawassee and Tittabawassee rivers. 3M Petrifilms TM
are being utilized for these analyses. Not only are we interested in correlating these microbial numbers
with changes in microbial metabolic fingerprints, we are interested in determining whether E. coli and
total coliforms are associated with sand, silt or muck. If we find significant numbers of these bacteria,
we hypothesize that they may be released from these media during wind or rain events causing an
increase in E. coli and total coliforms counts in the surrounding waters.
Results of metabolic fingerprinting of microbial communities in all media examined (water, sand, silt and
muck) indicated that weather events such as rain or high wind changed the makeup of the communities.
In most cases the diversity of the communities increased after such an event. This finding was also
supported by the fact that coliform and E. coli numbers as well as total microbial loads were also
influenced by the more extreme weather events. Interestingly, more E. coli was associated with the sand
than water, muck or silt. We hypothesize that increases in E. coli numbers in water at beaches (such as
Bay City State Park) may be, at least in part, due to a release of these microorganisms from sand during
wave action generated from a wind event.