Tuesday, June 5, 2007 - 8:15 AM
101

The influence of a substrate-based restoration strategy on nutrient uptake and metabolism in three northern Michigan streams

Timothy J. Hoellein1, Jennifer L. Tank1, Sally A. Entrekin1, Gary A. Lamberti1, and Emma J. Rosi-Marshall2. (1) Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, (2) Biology, Loyola University Chicago, Chicago, IL 60626

Three forested headwater streams (50-70m reaches) in northern Michigan were manipulated to increase trout habitat by adding solid substrate (e.g. logs, boulders and gravel) and creating sediment traps.  Five years post manipulation, we examined how the manipulation influenced nutrient uptake (via short-term nutrient enrichment), and whole-stream metabolism (as diel change in oxygen) in multiple seasons.  We predicted that increased hard substrate in these typically sandy-bottomed streams would increase primary production and nutrient uptake by increasing algal biofilms. For metabolism, primary production was significantly higher in restored reaches in spring and fall, relative to upstream reference reaches (ANOVA, p=0.05), but there were no significant differences in community respiration.  For nutrient uptake, one stream showed higher ammonium uptake in the manipulated reach compared to the reference (t-test, p=0.005), possibly associated with lower standing stocks of large wood and coarse particulate organic matter, and more rock habitat in the restored reach (t-test, p<0.05 for all). Although the other two streams showed similar trends, differences in nutrient uptake were not significant. Our analyses showed this substrate-based restoration focused on trout habitat also had the potential to influence metrics of ecosystem function, but these effects varied by season and by stream.   

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