(h(r Liviiifi Kc\ci((nf\ — Aquatic Ecosystems 



247 



Reftrences 



Cornelius. F.C.. K.M. Muth, and R. Kenyon. 1995. Lake 



trout rehabilitation in Lake Erie: a case history. Journal of 



Great Lakes Res. In press. 

 Elrod. J.H.. R. O'Gomian. C.R Schneider, T.H. Eckert. T. 



Schaner, J.N. Bowlby. and L.R Schleen. 199.5. Lake trout 



rehabilitation in Lake Ontario. Journal of Great Lakes 



Res. In press. 

 Eschmeyer. RH. 1968. The lake trout [Sal\eliniis iiaimiy- 



ciish). U.S. Fish and Wildlife Service. Fishery LeaOet 



5.5.5. 8 pp. 

 Eshenroder. R.L.. N.R. Payne. J.E. Johnson. C.A. Bowen II. 



and M.R Ebener 1995. Lake trout rehabilitation in Lake 



Huron. Journal of Great Lakes Res. In press. 

 Hansen. M.J.. J.W. Peck. R.G. Schortliaar, J.H. Selgeby. 



D.R. Schreiner. S.T. Schram, B.L. Swanson, W.R. 



MacCallum, M.K. Burnham-Curtis. G.L. Curtis, J.W. 



Heinrich. and R.J. Young. 1995. Lake trout LSalveliiuts 



i}ainii\ci{sh) restoration in Lake Superior Journal of 

 Great Lakes Res. In press. 



Hile, R., P.H. Eschmeyer, and G.F. Lunger. 1951. Status of 

 the lake trout fishery in Lake Superior Transactions of 

 the American Fisheries Society 80:278-.^ 1 2. 



Holey. M.E.. R.W. Rybicki, G.W. Eck, E.H. Brown, Jr. J.E. 

 Marsden, D.S. Lavis, M.L. Toneys, T.N. Trudeau, and 

 R.M. Horrall. 1995. Progress toward lake trout restora- 

 tion in Lake Michigan. Journal of Great Lakes Res. In 

 press, 



Pycha. R.L.. and G.R. King. 1975. Changes in the lake trout 

 population of southern Lake Superior in relation to the 

 Fishery, the sea lamprey, and stocking, 1950-70. Great 

 Lakes Fishery Commission Tech. Rep. 2S. Ann Arbor. 

 MI. 34 pp. 



Smith, B.R. 1971. Sea lampreys in the Great Lakes of North 

 America. Pages 207-247 in M.W. Hardisty and I.C. 

 Potter, eds. The biology of lampreys. Vol. 1. Academic 

 Press. New York. 



For further information: 



Michael J. Han.sen 



National Biological Service 



Great Lakes Center 



1451 Green Rd. 



Ann Arbor, MI 48105 



Water levels in the Great Lakes are affected 

 by variations in precipitation, evapora- 

 tion, ice build up, internal waves (seiches), and 

 human alterations that include modifying the 

 connecting channels between lakes and regulat- 

 ing the water levels of Lake Superior and Lake 

 Ontario, Fluctuations in water level promote the 

 interaction of aquatic and terrestrial systems, 

 thereby resulting in higher quality habitat and 

 increased productivity. When the fluctuations in 

 water levels are reduced through stabilization, 

 shifting of vegetation types decreases, more sta- 

 ble plant communities develop, and species 

 diversity and habitat value decrease (Wilcox 

 and Meeker 1991, 1992). Although water levels 

 in Lake Superior are regulated by structures at 

 the outlet, water-level cycles and patterns 

 remain fairly similar to natural conditions. Lake 

 Ontario water levels are also regulated, but high 

 and low water extremes have been eliminated 

 since the mid-1970"s. The effects of water-level 

 history on wetland plant communities under the 

 two regulation regimes were investigated by 

 studying wetlands on each lake. 



Seventeen sites on Lake Ontario and 18 on 

 Lake Superior were sampled. Vegetation was 

 mapped and then sampled along transects thai 

 followed elevation contours with specific watei 

 level histories (number of years since last flood- 

 ed or last dry). The histories and elevations dif- 

 fered between lakes. Correlations between spe- 

 cific elevations and accompanying plant com- 

 munities were assessed across all wetlands sam- 

 pled in each lake to determine the range of ele- 

 vations in which the most diverse plant commu- 

 nities occur; these data were u.sed to create 

 schematic cross-sections depicting the structur- 

 al habitat provided by the plant communities 

 characteristic of each lake. 



Vegetation and Water Level 



At study sites on both Lakes Ontario and 

 Superior, wetland plant communities differed at 

 different elevations; these plant communities 

 developed as a result of the water-level history 

 of each elevation that was sampled. In general, 

 plant communities at elevations that had not 

 been flooded for many years were dominated by 

 shrubs, grasses, and old-field plants. If flooding 

 was more recent, small shrubs that became 

 established after flooding were present, as were 

 grasses, sedges, and other nonwoody plants. 



The plant communities at elevations that 

 were flooded periodically at 10- to 20-year 

 intervals and dewatered for successive years 

 between floods had the greatest diversity of 



Wetlands in 

 Regulated 

 Great Lakes 



by 



Douglas A. Wilcox 



National Biological Service 



James E. Meeker 

 Northland College. WI 



Small unnamed bay near Bete Grise. Lake Superior. August 1991. Scattered lilies [Niipluir ninc- 

 gala) with submersed plants adjacent to a fioating bog mat. 



