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How Disturbance to the Streambed Affects Stream Metabolism Carl Cappelletti Conceptual Model Control Variable Structure Function Discharge Streambed Metabolism Metabolism Photosynthesis Metabol ism GEP GPP Respirati on CR Metabolism = GEP - CR How do you measure it? Reaeration k DO DO In DO Out CR GEP Figure 3. WSM ≡ NEP = GEP - CR Streambed & Subsurface Sediments Sunlight Flow Hyporheic Zone Disturbance Light Attenuation Surface Abrasion Possible bed load transport Possible damage to hyporheic zone Nutrient dilution (in urban areas the nutrients can increase initially then dilute) Disturbance Sunlight [N] Turbidity & Depth Surface Abrasion Bedload Hyporheic Damage Transport Disturbance effects on Metabolism Decreased Photosynthesis-sometimes it totally shuts down Photosynthetic organisms on the top of rocks- epilithon, mosses Respiration is different Lots of heterotrophic bacteria in the hyporheic zone Can make up 85% of respiration (Fellows et al. 2001) Disturbance effects on Metabolism Uehlinger & Naegeli 1998, found that primary production was less resistant to disturbance than respiration That means photosynthetic organisms are more prone to damage In contrast, respiration is less resilient to disturbance than primary production That means the heterotrophic organisms have slower recovery rates Why is this important? What if the control variables change Increased discharge volume and peak with urbanization Many more bed moving spates-more damage to the hyporheic zone Increased sedimentation with urbanization Sediments cover pore spaces in the upper substrate and blocks access to hyporheic zone Sedimentation Effects Sunlight Flow Hyporheic Zone References Edwardson K., W. Bowden, C. Dahm, and J. Morrice, 2003. The Hydraulic Characteristics and Geochemistry of Hyporheic and Parafluvial Zones in Artic Tundra Streams, North Slope, Alaska. Advances in Water Resources 26: 907-923. Fellows C., H. Valett, and C. Dahm, 2001. Whole-Stream Metabolism in Two Montane Streams: Contributions of the Hyporheic Zone. Limnol. Oceanogr. 46: 523-531. Gooseff M.N., S.M. Wondzell, R. Haggerty, and J. Anderson 2003. Comparing Transient Storage Modeling and Residence Time Distribution (RTD) Analysis in Geomorphically Varied Reaches in the Lookout Creek Basin, Oregon, USA. Advances in Water Resources 26: 925-937. Mulholland P.J., C.S. Fellows, J.L. Tank, N.B. Grimm, J.R. Webster, S.K. Hamilton, E. Marti, L. Askenas, W.B. Bowden, W.K. Dodds, W.H. McDowell, M.J. Paul, and B.J. Peterson, 2001. Inter-Biome Comparison of Factors Controlling Stream Metabolism. Freshwater Biology 46: 1503-1517. Uehlinger U., and M. Naegeli, 1998. Ecosystem Metabolism, Disturbance, and Stability in a Prealpine Gravel Bed River. J. N. Am. Benthol. Soc. 17: 165-178. Young R., and A. Huryn, 1996. Interannual Variation in Discharge Controls Ecosystem Metabolism Along a Grassland River Continuum. Can. J. Fish. Aquat. Sci. 53: 2199-2211.
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