Tuesday, May 27, 2008 - 9:30 AM
142

Inter- and intra-system variation in whole-stream metabolism within an agricultural landscape

Natalie A. Griffiths1, Jennifer L. Tank1, Emma J. Rosi-Marshall2, Todd V. Royer3, Matt R. Whiles4, Jake J. Beaulieu5, Laura T. Johnson1, Sarah S. Roley1, and Mia L. Stephen1. (1) Department of Biological Sciences, University of Notre Dame, Galvin Life Sciences, Notre Dame, IN 46556, (2) Biology, Loyola University Chicago, 1050 W. Sheridan Rd, Quinlan 319-Dept of Biology, Chicago, IL 60626, (3) School of Public and Environmental Affairs, Indiana University, 1315 E 10th St, Bloomington, IN 47405, (4) Department of Zoology and Center for Ecology, Southern Illinois University, Life Science II, Room #307, Carbondale, IL 62901, (5) US EPA, 26 W. Martin Luther King Drive, Cincinnati, OH 45268

Whole-stream metabolism is commonly used to assess trophic status of headwater streams; however, few studies have examined temporal variation in metabolism within and among systems.  We measured whole-stream metabolism in 6 agricultural streams six times, and daily metabolism within one agricultural stream for one year.  Gross primary production (GPP) and community respiration (CR) varied >10-fold among streams on a single day in summer (GPP=1.0-14.4 gO2/m2/day, CR=1.0-16.2 gO2/m2/day) and one day in fall (GPP=0.1-3.6 gO2/m2/day, CR=0.4-8.0 gO2/m2/day).  GPP and CR were similarly variable within one agricultural stream during one month in summer (GPP=2.2-13.0 gO2/m2/day and CR=5.4-15.4 gO2/m2/day) and one month in the fall (GPP=1.4-4.0 gO2/m2/day and CR=4.8-7.3 gO2/m2/day).  Further, the 6 agricultural streams varied in their trophic status, with half of the streams in the summer exhibiting P/R>1, and all streams exhibiting P/R<1 in the fall.  Continuous measurements showed that trophic status switched repeatedly within one agricultural stream.  For example, during April through June, the stream switched between heterotrophy and autotrophy three times. Overall, metabolism and trophic status in agricultural streams was highly variable temporally and spatially despite similar channel alterations and nutrient enrichment.  Further analyses will examine environmental drivers of observed variation in stream metabolism.


Web Page: whole-stream metabolism, agriculture

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