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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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