Detroit River-Western Lake Erie Basin Indicator Project
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American wildcelery (Figure 1) is a submersed aquatic plant that is a very important food for diving ducks in the Detroit River. Extensive wildcelery beds in the lower Detroit River attract canvasbacks and other diving ducks that feed on the tubers of wildcelery for energy during migration (Miller 1943, Jones 1982).
Wildcelery is also an important ecological indicator in the Detroit River because it is very sensitive to pollution and will not grow where pollutants, such as oil, contaminate bottom sediment (Schloesser and Manny 1990).
Before the beginning of the 20th century, contiguous coastal wetlands up to a mile wide, existed along both shores of the Detroit River (Manny 2003). By 1950, wildcelery beds in the river had decreased, owing to oil pollution and loss of wetlands due to development (Hunt 1963). Despite pollution abatement programs implemented in the 1960s and 1970s, wildcelery in the lower Detroit River decreased even further between 1950 and 1984-1985 (Schloesser and Manny 1990). In 1986, the non-native zebra mussel (Dreissena polymorpha) began to colonize Lake St. Clair located immediately up stream of the Detroit River. These filter-feeders are responsible for increasing water clarity by filtering large quantities of suspended particulate matter from the water. It is believed that increased water clarity allowed more light penetration, which permitted increased wildcelery abundance (Schloesser and Manny In Prep.).
|Sugar Island Bar||23||5||19|
|Swan Island Bar||2||5||10|
Including 1950-1951, wildcelery abundance has been measured three times at five historically important duck feeding locations in the lower Detroit River. Wildcelery tubers or winter buds in river bottom sediments were collected and counted at Ballard Bar, Sugar Island Bar, Swan Island Bar, North Bar, and Humbug Bar in May of 1950-1951, 1984-1985, and 1996-1997. Sampling locations were located in areas of shallow water where waterfowl were seen feeding (Schloesser and Manny 1990).
Wildcelery tuber abundance declined 72% between 1950-51 and 1984-1985, and then increased 200% between 1984-1985 and 1996-1997. (Figure 2). In 1985, wildcelery beds had decreased, resulting in a net loss of 36,720,000 tubers at the five locations (Schloesser and Manny 1990).
From 1950-1951 to 1984-1985 there were small increases in wildcelery abundances at Swan Island Bar and North Bar, however, the increases were not significant enough to compensate for the large losses of wildcelery at other locations sampled. Between the 1984-1985 and 1996-1997 counts the mean density of wildcelery tubers increased significantly at all five sites. The Humbug Bar site increased the least amount, from zero to one, most likely because bottom sediments were contaminated with oil. The Swan Island Bar and North Bar had a higher mean number of tubers in 1994-1995 than in 1950-1951. However, the total estimated number of tubers at all locations was not significantly different between the 1950-1951 and 1994-1995 counts (Schlosser and Manny In Prep).In general, less wildcelery means less food for ducks. For example, an average daily meal (feeding twice a day) of a canvasback duck feeding on wildcelery buds in the Detroit River is 78.47 mL. The decrease in the mean number of tubers from the 1950s to the 1980s was equivalent to a net loss of 11,540,000 mL of food. This net loss corresponds to a potential loss of 147,000 waterfowl feeding days in the spring for canvasbacks, assuming that they did not consume other food (Schloesser and Manny 1990). It should be noted that these feeding day figures are likely an underestimate because more wildcelery tubers were consumed by the higher numbers of diving ducks that migrated through Michigan in 1950 than in 1984-1985 (Hunt 1957, Martz et al. 1976). Further, there was an increase in duck feeding days between 1984-1985 and 1996-1997 because of the slight increase in the migrating waterfowl population.
It is recommended that management agencies continue to place priority on pollution abatement programs that aid in improving water quality and clarity to encourage recovery of wildcelery beds. Priority should also be placed on preserving remaining coastal wetland habitats and rehabilitating degraded ones to support wildlife populations.
Scientists should continue to monitor wildcelery abundance at the five historical sampling locations. The next logical period of sampling is 2006-2007, 10 years since the last survey was done. Future wildcelery monitoring should be performed in conjunction with waterfowl surveys and parallel feeding habit studies. Research should also be undertaken to fully understand the factors affecting wildcelery abundance, such as the proliferation of zebra mussels, water clarity, and oil pollution.
Hunt, G.S. 1957. Causes of mortality among ducks wintering on the lower Detroit River Ph. D. Thesis, University of Michigan, Ann Arbor. pp. 269.
Hunt, G.S. 1963. Wildcelery in the lower Detroit River. Ecology 44:360-370.
Jones, J.J. 1982. Potential effects of winter shipping on diving ducks wintering in the Detroit River. M.S. Thesis, University of Michigan, Ann Arbor. pp. 91.
Manny, B.A. 2003. Setting priorities for conserving and rehabilitating Detroit River habitats.. pp. 121-139 In: J.H.Hartig ed., Honoring Our Detroit River Caring for Our Home. Cranbrook Institute of Science, Bloomfield Hills, Michigan. pp. 233.
Martz, G.F, J.W. Aldrich, and D. Ostyn. 1976. History and future of canvasback populations in Michigan's Great Lakes habitat during fall migration and early winter. Michigan Department of Natural Resources, Wildlife Development Report 2759. Lansing, Michigan. pp. 22.
Miller, H.J. 1943. Waterfowl survey of Saginaw Bay, Lake St. Clair, Detroit River, Lake Erie and marshes adjacent to these waters. Project No. 13-R Wildlife Division, Michigan Department of Natural Resources. Lansing, Michigan. pp. 132.
Schloesser, D.W. and B.A. Manny. 1990. Decline of wildcelery buds in the lower Detroit River, 1950-1985. Journal of Wildlife Management. 54(1):72-76.
Schloesser, D.W., and B.A. Manny. In Prep. Recovery of wildcelery, Vallisneria americana, in the lower Detroit River of the Great Lakes. U.S. Geological Survey, Great Lakes Science Center, Ann Arbor, Michigan.
U.S. Geological Survey, Great Lakes Science Center
Bruce A. Manny
U.S. Geological Survey, Great Lakes Science Center
Southwest Michigan Land Conservancy