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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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. "

    Full-text · Article · Dec 2015
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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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    ABSTRACT: River regulation and altered land use are two common anthropogenic disturbances in rivers worldwide. Alteration of the stream bed, through processes such as siltation, or of hydrology through river regulation, are likely to modify hyporheic processes or clog interstitial space and thereby affect both hyporheic invertebrates and nutrient dynamics.We tested the separate and combined effects of increased flow and increased fine sediment on hyporheic water quality and invertebrates in flume mesocosms. Each mesocosm contained two bed sediment types: clean sediment in the upstream section and experimentally colmated (EC) sediment (10% by weight of fine sediment) in the downstream section. Two flow rates were established, a higher flow rate to create turbulent flow in six mesocosms and a lower flow rate to create a transitional flow between turbulent and laminar flows in the remaining six mesocosms. Invertebrates and physicochemistry were sampled after 30 days at three depths (5, 11 and 18 cm), and the flows in six of twelve mesocosms were switched. The experiment was concluded after sampling invertebrates and physicochemistry on day 70.The addition of fine sediment to the mesocosm bed generally increased ammonium and decreased nitrate and soluble reactive phosphorus concentrations, decreased oxygen penetration and altered invertebrate assemblage structure. Increased flow rates generally lowered ammonium concentrations, increased soluble reactive phosphorus concentrations, increased oxygen penetration and altered invertebrate assemblage structure. Our hypothesis that higher flows would ameliorate any effects of added fine sediment was generally supported for oxygen penetration and nitrate concentration. However, we observed no differences in interaction effects of flow regime and sediment type either on other nutrient concentrations or invertebrate assemblage structure.The rates of flow used in our mesocosms did not appear to reach the threshold required to remove fine sediment. It is generally recognised that river hyporheic restoration requires a set of objectives against which the outcomes can be measured yet this is often overlooked. Our research provides preliminary guidelines that small amounts of fine sediment can have deleterious ecological effects. However, further research is required to evaluate whether lower percentages of bed fine sediment result in ecological impairment and to determine what flow rates are required to ameliorate colmation impacts.
    Full-text · Article · Apr 2015 · Freshwater Biology
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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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    ABSTRACT: The hyporheic zone (HZ) can be an important source of solutes to streams. Hyporheic solute fluxes are commonly dominated by advective exchange. However, fluxes from the HZ also may include diffusion and upward advection of ground water from underlying aquifers. We compared the relative importance of these transport mechanisms on solute budgets of a large, spring-fed river in north-central Florida using measurements of spring, river, and porewater chemistry, hydraulic gradients, and sediment hydraulic conductivity, and dilution of an injected dye (Rhodamine WT). Downstream increases in Fe, soluble reactive P (SRP), Ca2+, and Cl− concentrations of the river water suggest solute sources in addition to the major source springs. Shallow porewater concentrations of Fe, Mn, Ca2+, SRP, and Cl− were elevated relative to the river. Calculations of Fickian diffusion based on concentration gradients of these solutes indicate diffusion could account for the downstream increase in Fe concentration but only 5% of the downstream increase in SRP and <0.1% of the increases in Ca2+ and Cl−. Downstream decreases in Mn concentrations reflect in-stream retention despite predicted diffusion. Dye-trace results indicate that ∼13% of the river discharge originates from sources other than the major springs. Measured head gradients and low sediment hydraulic conductivity suggest vertical groundwater flow through the HZ is small. We used the SRP budget to partition the additional groundwater inputs between seepage through the HZ (∼3% of river discharge) and flow paths that bypass the HZ (∼10% of total river discharge). Flow paths that bypass the HZ dominated additional water delivery to the river, but diffusion, resulting from steep chemical gradients and low-permeability sediments, is an important mechanism for transporting solutes from the HZ to the river.
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