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Interacting Watershed Size and Landcover Influences on Habitat and Biota of Lake Superior Coastal Wetlands
Citation:
TREBITZ, A. S., J. C. BRAZNER, D. K. TANNER, AND R. MEYER. Interacting Watershed Size and Landcover Influences on Habitat and Biota of Lake Superior Coastal Wetlands. Aquatic Ecosystem Health and Management. Taylor & Francis, Inc., Philadelphia, PA, 14(4):443-455, (2011).
Impact/Purpose:
This study explores how strength of connection to the watershed (represented by watershed size and wetland morphological type) influence background wetland conditions and the nature of the response to anthropogenic disturbance.
Description:
Coastal wetlands are important contributors to the productivity and biodiversity of large lakes and important mediators of the lake - watershed connection. This study explores how strength of connection to the watershed (represented by watershed size and wetland morphological type) influence background wetland conditions and the nature of the response to anthropogenic disturbance. We draw on data from 33 Lake Superior coastal wetlands spanning a substantial geographic and watershed size range. Habitat and biotic endpoints analyzed include water quality, submerged vegetation structure, zoobenthos composition (funnel traps), and turtle and crayfish catch and fish composition (fyke nets). Compared to coastal wetlands elsewhere in the Laurentian Great Lakes, these Lake Superior coastal wetlands had relatively unimpacted landcover and good water clarity, vegetation structure, and fish composition. As a consequence of having only a short disturbance gradient, land-use effects on habitat and biota in the Lake Superior wetlands were somewhat difficult to resolve, but when present, were consistently stronger for wetlands embedded in large rather than in small watersheds. Wetland water clarity, vegetation structural complexity, and zoobenthos richness all declined more rapidly in the large-watershed size group. Watershed size alone influenced wetland morphology and turtle abundance but had no detectable effect on other habitat and biotic endpoints in minimally-disturbed wetlands. Apparently, receiving inflows from larger watersheds influences coastal wetlands primarily by delivering cumulatively larger stressor loads under watershed disturbance rather than through the physical impacts of the flow itself, at least in wetlands where substantial off-channel habitat is available. Classification of wetlands by watershed size and exposure to river-flow influences can help resolve responses to anthropogenic stress. Management of coastal wetlands in Lake Superior should focus on protecting healthy wetlands and watersheds as well as restoring degraded ones.