Article

Whole-Stream Metabolism in Two Montane Streams: Contribution of the Hyporheic Zone

Department of Biology, University of New Mexico, Albuquerque, New Mexico, United States
Limnology and Oceanography (Impact Factor: 3.79). 05/2001; 46(3). DOI: 10.4319/lo.2001.46.3.0523
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ABSTRACT

We used whole-stream and benthic chamber methods to measure rates of metabolism and determine the contribution of the hyporheic zone to ecosystem respiration (R) in two streams with differing surface–subsurface exchange characteristics, Rio Calaveras and Gallina Creek, New Mexico. We used the difference between whole-stream and benthic R to calculate the rate of hyporheic zone R and coupled this estimate to an independent measure of hyporheic sediment R to estimate the cross-sectional area of the hyporheic zone (AH) for two reaches from each stream. Conservative tracer injections and solute transport modeling were used to characterize surface–subsurface hydrologic exchange by determining values of the cross-sectional area of the transient storage zone (As). The hyporheic zone contributed a substantial proportion of whole-stream R in all four study reaches, ranging from 40 to 93%. Wholestream R, hyporheic R, and percent contribution of hyporheic R all increased as transient storage increased, with whole-stream and hyporheic R exhibiting significant relationships with As. All three measures of respiration and values of AH were much greater for both reaches of the stream with greater surface–subsurface exchange. AH is valuable for cross-site comparisons because it accounts for differences in rates of both benthic and hyporheic sediment R and can be used to predict the importance of the hyporheic zone to other stream ecosystem processes. Yes Yes

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    • "The region where the water in the aquifer and the river mix is known as the hyporheos and is important in that in its sediments there are diverse, metabolically active microbial communities, which retain and transform essential biological elements. There are few studies on the influence of the hyporheos on fluvial ecosystem metabolism, but some conceptual models propose that this depends on the type and metabolic rate of the microbial communities, the proportion of the river volume that flows through them and their influence on hydrological residence times (Triska et al. 1989a; Fellows et al. 2001). The hyporheic zone can have a very dynamic flow regimen. "

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    • "The exchange of water between ground water, hyporheic and surface layers is controlled in time by changes in discharge and in space by geomorphology (Fellows, Valett & Dahm, 2001; Kasahara & Wondzell, 2003). The exchange is complex but generally depends on the flow rate of the surface water (Hancock & Boulton, 2005). "
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    • "Although often defined on the basis of bidirectional mixing between exfiltrating ground water and infiltrating surface water (Triska et al. 1989, Bencala 2000), the HZ can be more broadly distinguished as a region ecologically, chemically, and hydrologically distinct from either adjacent system and characterized by steep chemical and redox gradients (Triska et al. 1993a, Brunke and Gonser 1997) and high biogeochemical activity (Boulton et al. 1998). The HZ is important for stream solute dynamics (Triska et al. 1989, 1993a, Valett et al. 1996, Brunke and Gonser 1997, Gandy et al. 2007) and, thus, for stream ecosystem function and structure (Grimm and Fisher 1984, Boulton et al. 1998, Fellows et al. 2001, Krause et al. 2011). "
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