Organic detritus particles: Initiation of motion criteria on sand and gravel beds

Fisher, John S.; Sill, Ben L.; Clark, D. F.

doi:10.1029/wr019i006p01627

Cited by 18 publications

(10 citation statements)

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“…Additionally, Cushing et al (1993) noted that FPOM might be resuspended and exported after initial deposition in the streambed. Potentially, this may occur more frequently under more turbulent, higher flows (Fisher et al 1983). Table 3 Parameter estimates for the fixed and random effects of the AIC favoured model for SM.…”

Section: Discussionmentioning

confidence: 99%

Distance, flow and PCR inhibition: eDNA dynamics in two headwater streams

Jane

Wilcox

McKelvey

et al. 2014

Molecular Ecology Resources

439

556

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Environmental DNA (eDNA) detection has emerged as a powerful tool for monitoring aquatic organisms, but much remains unknown about the dynamics of aquatic eDNA over a range of environmental conditions. DNA concentrations in streams and rivers will depend not only on the equilibrium between DNA entering the water and DNA leaving the system through degradation, but also on downstream transport. To improve understanding of the dynamics of eDNA concentration in lotic systems, we introduced caged trout into two fishless headwater streams and took eDNA samples at evenly spaced downstream intervals. This was repeated 18 times from mid-summer through autumn, over flows ranging from approximately 1-96 L/s. We used quantitative PCR to relate DNA copy number to distance from source. We found that regardless of flow, there were detectable levels of DNA at 239.5 m. The main effect of flow on eDNA counts was in opposite directions in the two streams. At the lowest flows, eDNA counts were highest close to the source and quickly trailed off over distance. At the highest flows, DNA counts were relatively low both near and far from the source. Biomass was positively related to eDNA copy number in both streams. A combination of cell settling, turbulence and dilution effects is probably responsible for our observations. Additionally, during high leaf deposition periods, the presence of inhibitors resulted in no amplification for high copy number samples in the absence of an inhibition-releasing strategy, demonstrating the necessity to carefully consider inhibition in eDNA analysis.

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Section: Discussionmentioning

confidence: 99%

Distance, flow and PCR inhibition: eDNA dynamics in two headwater streams

Jane

Wilcox

McKelvey

et al. 2014

Molecular Ecology Resources

439

556

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“…For example, large grains on a bed composed primarily of fines are more exposed and hence more susceptible to transport. Data from Fenton and Abbot [1977] and Fisher et al [1983], together with the analysis of Wiberg and Smith [1987] indicate that a “perched” grain with diameter 5 times larger than the diameter of the grains which comprise the bed has a critical shear velocity that is reduced by a factor of √6 compared to the necessary shear velocity for the case where the same grain rests on a bed of particles of the same size. Further, even sparse coverage of coarse sediment inhibits the transport of finer grains, because the larger grains extract momentum from the flow [ Gillette and Stockton , 1989; Nickling and McKenna Neuman , 1995].…”

Section: Theory and Methodsmentioning

confidence: 99%

Spatial grain size sorting in eolian ripples and estimation of wind conditions on planetary surfaces: Application to Meridiani Planum, Mars

et al. 2006

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[1] The landscape seen by the Mars Exploration Rover (MER) Opportunity at Meridiani Planum is dominated by eolian (wind-blown) ripples with concentrated surface lags of hematitic spherules and fragments. These ripples exhibit profound spatial grain size sorting, with well-sorted coarse-grained crests and poorly sorted, generally finer-grained troughs. These ripples were the most common bed form encountered by Opportunity in its traverse from Eagle Crater to Endurance Crater. Field measurements from White Sands National Monument, New Mexico, show that such coarse-grained ripples form by the different transport modes of coarse-and fine-grain fractions. On the basis of our field study, and simple theoretical and experimental considerations, we show how surface deposits of coarse-grained ripples can be used to place tight constraints on formative wind conditions on planetary surfaces. Activation of Meridiani Planum coarse-grained ripples requires a wind velocity of 70 m/s (at a reference elevation of 1 m above the bed). From images by the Mars Orbiter Camera (MOC) of reversing dust streaks, we estimate that modern surface winds reach a velocity of at least 40 m/s and hence may occasionally activate these ripples. The presence of hematite at Meridiani Planum is ultimately related to formation of concretions during aqueous diagenesis in groundwater environments; however, the eolian concentration of these durable particles may have led to the recognition from orbit of this environmentally significant landing site.

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“…Many previous and later studies have shown that Shields values are affected by whether bed particles are loose and easily mobilized or restrained by bed structures and by particle interlock. Particle entrainment has been reported to be affected by particle imbrication Gordon et al, 1992], by different particle shapes , the presence of particle clusters [Brayshaw et al, 1983], by particle hiding and protrusion, bed sorting, pocket, and pivot angles [Isbash, 1936;White, 1940;Fenton and Abbott, 1977;Parker et al, 1982;Andrews, 1983;Fisher et al, 1983;Wiberg and Smith, 1987;Kirchner et al, 1990;Andrews and Smith, 1992;Carling et al, 1992;Andrews, 1994;Ferguson, 2012]; by packing density [Gordon et al, 1992], stone structures [Church et al, 1998;Hassan and Church, 2000], as well as by antecedent flow and bed conditions [e.g., Gomez, 1983;Reid et al, 1985;Beschta, 1987;Turowski et al, 2011]. An increasingly wider range of Shields values from <0.03 to >0.5 has been reported for steep channels [Bathurst et al, 1983[Bathurst et al, , 1987Lepp et al, 1993;Rosgen, 1994Rosgen, , 1996Shvidchenko and Pender, 2000;Buffington and Montgomery, 2001;Buffington et al, 2004Buffington et al, , 2006Zimmermann et al, 2010;Bunte et al, 2010a;Comiti and Mao, 2012].…”

Section: Introductionmentioning

confidence: 99%

Critical Shields values in coarse‐bedded steep streams

Bunte

Abt

Swingle³

et al. 2013

Water Resources Research

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Critical Shields values ( τc*) suitable for specific applications are back‐calculated from representative bed load samples in mountain streams and a flow competence/critical flow approach. The general increase of τc50* (for the bed D50 size) as well as τc16* and τc84* (for the bed D16 and D84 sizes) with stream gradient Sx and also the stratification of τc50* by relative flow depth and relative roughness are confirmed. Critical Shields values τc16* are shown to exceed τc50* by about threefold, while those for τc84* are nearly half of τc50*. However, it remains unclear to what extent physical processes or numerical artifacts contribute to determining critical Shields values. Critical bankfull Shields values ( τcbf*) back‐computed from the average largest particles mobile at bankfull flow DBmax,bf approach τc16* at steep gradients and τc84* at low gradients and therefore increase very steeply with Sx. The relation τcbf*=f(Sx) is stratified by bed stability (D50/DBmax,bf) and predictable if bed stability can be field categorized. Noncritical Shields values ( τbf50*) computed from bankfull flow depth and the D50 size differ from τc50* and τcbf*. Only in bankfull mobile streams where D50/DBmax = 1 can τ*cbf, τc50*, and τbf50* be used interchangeably. In highly mobile streams, substituting τcbf* by τbf50* overpredicts the DBmax,bf size by up to fivefold and underpredicts DBmax,bf by the same amount in highly stable streams. A value of 0.03 is appropriate for τcbf* only on low stability beds with Sx ≅ 0.01, but overpredicts DBmax,bf by 30‐fold on highly stable beds with Sx ≅ 0.1. Differences in field and computational methods also affect critical Shields values.

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Organic detritus particles: Initiation of motion criteria on sand and gravel beds

Cited by 18 publications

References 1 publication

Distance, flow and PCR inhibition: eDNA dynamics in two headwater streams

Distance, flow and PCR inhibition: eDNA dynamics in two headwater streams

Spatial grain size sorting in eolian ripples and estimation of wind conditions on planetary surfaces: Application to Meridiani Planum, Mars

Critical Shields values in coarse‐bedded steep streams

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