The University Bay Marsh is located along the western margin of University Bay, forming the wetland that walkers and bicyclists skirt as they travel along the Lakeshore Path in this stretch of the Preserve.
There has been a marsh in this corner of Lake Mendota for thousands of years, but not always precisely at this location. In fact, the playing fields west of the Class of 1918 Marsh were once part of a much more extensive wetland between the Village of Shorewood Hills and the lake, but this large area was drained to create an experimental farm for the College of Agriculture in the early decades of the 20th century. In the late 1960s, part of that drained wetland was restored to create the Class of 1918 Marsh.
In a sense, the Class of 1918 Marsh and the University Bay Marsh are part of the same system, but the presence of an artificial barrier between the two—University Bay Drive and the Lakeshore Path, and complex pumping and drainage systems—make the two wetlands quite different from each other. You can read more about the University Bay Pump House also.
Lake Mendota has a history of generating marsh vegetation in this vicinity because natural currents tend to accumulate silt along an offshore ridge paralleling the main shoreline, and also because Willow Creek deposits a large amount of silt at the southwestern corner of the bay. The current route of the Lakeshore Path follows one of these old offshore sediment ridges, and the same kind of feature may eventually form offshore of the current marsh as well.
You can read more about these sedimentation mechanisms at other locations in the Preserve, including Willow Creek, and University Bay.
The area between University Bay Marsh and the mouth of Willow Creek is a wonderful place to watch migrating and nesting waterfowl.