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Disturbance effects on aquatic vegetation in regulated and unregulated lakes in northern Minnesota

Canadian Journal of Botany

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Abstract

The effects of water-level regulation on aquatic macrophyte communities were investigated by comparing two regulated lakes in northern Minnesota with a nearby unregulated lake (Lac La Croix). Natural annual fluctuations of about 1.8 m were replaced with fluctuations of 1.1 m and 2.7 m in the regulated lakes, and the timing of water-level changes was also altered. Quadrats were sampled along transects that followed depth contours representing different plant habitats in the unregulated lake. Ordinations showed that the macrophyte communities at all sampled depths of the regulated lakes differed from those in the unregulated lake. The unregulated lake supported structurally diverse plant communities at all depths. In the lake with reduced fluctuations, only four taxa were present along transects that were never dewatered; all were erect aquatics that extended through the entire water column. In the lake with increased fluctuations, rosette and mat-forming species dominated transects where drawdown occurred in early winter and disturbance resulted from ice formation in the sediments. The natural hydrologic regime at the unregulated lake resulted in intermediate disturbance and high diversity. There was either too little or too much disturbance from water-level fluctuations in the regulated lakes, both resulting in reduced structural diversity.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Disturbance effects on aquatic vegetation in regulated and unregulated lakes in northern Minnesota
Series title:
Canadian Journal of Botany
Volume
69
Issue:
7
Year Published:
1991
Language:
English
Contributing office(s):
Great Lakes Science Center
Description:
p. 1542-1551
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1542
Last page:
1551
Number of Pages:
9