Tuesday, May 19, 2009
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Determining the effects of urbanization on stream metabolism of Duluth streams

Jeremy M. Erickson1, LaRae Lehto2, Lucinda B. Johnson3, Richard Axler1, and Brian Hill2. (1) Center for Water and the Environment, Natural Resources Research Institute, University of Minnesota-Duluth, 5013 Miller Trunk Highway, Duluth, MN 55811, (2) Mid-Continent Ecology Division, Environmental Protection Agency, 6201 Congdon Boulevard, Duluth, MN 55804, (3) Natural Resources Research Institute, University of Minnesota Duluth, 5013 Miller Trunk Highway, Duluth, MN 55811

The North Shore streams of Lake Superior are known for their clear cool waters that flow through expanses of undeveloped land. However, many North Shore watersheds are experiencing rapid urbanization, resulting in increased impervious surface development. Previous research on the impact of ecological disturbances to stream health has primarily relied on biotic community, physical habitat, or water chemistry studies, with few  focusing on ecosystem processes such as stream metabolism. This study assesses the effect of increasing urbanization on summer whole stream community respiration (CR) and gross primary production (GPP) rates on nine low productivity, heterotrophic streams spanning an impervious surface gradient (0.8 % to 20.1 %). Stream metabolism rates were determined using single station diel dissolved oxygen changes.  We used propane evasion to estimate stream reaeration rates. We also measured total nitrogen and total phosphorus levels, canopy shading, and epilithon chlorophyll-a.  GPP estimates ranged from 0.07 g O2 m-2d-1 to 2.03 g O2 m-2d-1 and CR  from 0.18 g O2 m-2d-1 to 6.58 g O2 m-2d-1.  Preliminary results for July and August indicate a positive relationship between increasing impervious surface and CR and a very weak positive or no relationship with GPP. 


Web Page: stream, metabolism, urbanization

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