The movement of organisms and resources within ecosystems are essential elements in the productivity, stability, and distribution of communities. This thesis examines how water velocity, a defining factor of lotic systems, influences the dispersion of benthic organisms and particulate organic matter in small stream ecosystems. Variation in movement-related behaviours in two rheophilous (‘flow-loving’) mayflies (Epeorus and Baetis) and two rheophobic (‘flow-avoiding’) mayflies (Ameletus and Paraleptophlebia) were compared to determine how benthic organisms disperse between and within habitat patches in hydrodynamically complex landscapes. The degree to which water velocity and particle shape influence the retention of organic matter (including deciduous leaves, conifer needles, red-cedar fronds, and branch fragments) was examined to determine how physical factors determine detrital resource availability in streams. Although water velocity did not influence the crawling rates of Baetis and Ameletus in daylight conditions, both mayflies dispersed rapidly upstream in low-velocity flows in dark conditions. Drift rates of both mayflies were lower in daylight than dark conditions, and were generally inversely related to their habitat preferences. Escape responses in grazing Epeorus, Baetis, and Ameletus larvae in a range of flow conditions showed that retreat distance was more sensitive than flight initiation distance to variation in water velocity, suggesting that hydrodynamics mediate the risks of predation and the costs of flight in stream systems. Comparisons of the transport distances of live larvae, dead larvae, and passive tracer particles in low and high water velocities showed that drift distance varied substantially among taxa, and that behavioural control over drift distance generally declined as water velocity increased. While organic matter particles generally travelled further in high-velocity reaches, leaves were retained in riffles when they impacted on protruding clasts, while ‘stiff’ particles were retained when they settled into streambed interstices. Leaves placed in high-velocity microhabitats were broken down more slowly than leaves in low-flow areas, likely due to the exclusion of large-bodied detritivores. In conclusion, this thesis supports the view that hydrodynamic forces control trophic interactions and local population dynamics in stream ecosystems by directly altering the physical – and sometimes behavioural – processes of particle entrainment, transport, and deposition.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references.

Master of Science / Division of Biology / Walter K. Dodds / Contrary to the previous notion that a stream acts primarily as the transporter of materials from land to oceans, research has shown that in-stream processing of organic matter and nutrients is significant and relevant at a global scale. Dissolved organic carbon (DOC) is the most abundant form of organic carbon in streams and has been demonstrated as an important source of energy supporting stream food webs. Understanding the dynamics of DOC in streams is, therefore, important in determining the contribution of flowing waters to global carbon storage and release. However, DOC exists as many different compounds, varying in source, composition, and quality. The composition of DOC that ends up in streams is partly controlled by the surrounding watershed, and landscape effects on DOC quality and quantity in streams have been observed. In the North American Tallgrass prairie, woody encroachment has led to changes in riparian vegetation, potentially altering the DOC received by the stream, and making it important to understand rates of DOC transformation as landscape alterations continue. The heterogeneity of the DOC pool makes it difficult to fully describe its components and to measure transformation rates. DOC uptake, or biological use, has been estimated through several methods including in-stream additions of various DOC sources and bottle incubations of stream water and sediments. One problem with addition methods for calculating uptake is that the DOC pool is difficult to replicate and additions of simple compounds or organic leachates do not represent total dissolved organic carbon (TDOC) dynamics. Another potential issue is that additions of a labile compound could potentially alter microbial activity through a priming effect and therefore distort ambient DOC uptake estimates. Finally, uptake parameters are mostly calculated assuming benthic uptake while recent studies have shown that planktonic uptake of DOC can also be significant. We conducted this study with these three considerations in mind. In the first chapter, we describe our use of in situ additions of glucose and bur oak leaf leachate in prairie stream reaches and concentrations of specific components to determine uptake dynamics of various specific DOC components, from a simple sugar to more complex plant compounds. We calculated uptake parameters of glucose and two different oak leaf components. We found that using glucose concentrations rather than TDOC concentrations, as has been done in previous studies, to measure uptake parameters resulted in higher uptake rates, indicating the importance of measuring the specific component added. Through leaf leachate additions, we found that an amino acid like component was consistently taken up faster than a humic-like component. The second chapter addresses the questions of uptake location and priming through a series of recirculating chamber incubations. We found that benthic uptake of leaf leachate was more important than that in the water column. Finally, elevated uptake of one leaf leachate component in the presence of glucose indicated a priming effect on microbial DOC uptake.

The movement of organisms and resources within ecosystems are essential elements in the productivity, stability, and distribution of communities. This thesis examines how water velocity, a defining factor of lotic systems, influences the dispersion of benthic organisms and particulate organic matter in small stream ecosystems. Variation in movement-related behaviours in two rheophilous (‘flow-loving’) mayflies (Epeorus and Baetis) and two rheophobic (‘flow-avoiding’) mayflies (Ameletus and Paraleptophlebia) were compared to determine how benthic organisms disperse between and within habitat patches in hydrodynamically complex landscapes. The degree to which water velocity and particle shape influence the retention of organic matter (including deciduous leaves, conifer needles, red-cedar fronds, and branch fragments) was examined to determine how physical factors determine detrital resource availability in streams. Although water velocity did not influence the crawling rates of Baetis and Ameletus in daylight conditions, both mayflies dispersed rapidly upstream in low-velocity flows in dark conditions. Drift rates of both mayflies were lower in daylight than dark conditions, and were generally inversely related to their habitat preferences. Escape responses in grazing Epeorus, Baetis, and Ameletus larvae in a range of flow conditions showed that retreat distance was more sensitive than flight initiation distance to variation in water velocity, suggesting that hydrodynamics mediate the risks of predation and the costs of flight in stream systems. Comparisons of the transport distances of live larvae, dead larvae, and passive tracer particles in low and high water velocities showed that drift distance varied substantially among taxa, and that behavioural control over drift distance generally declined as water velocity increased. While organic matter particles generally travelled further in high-velocity reaches, leaves were retained in riffles when they impacted on protruding clasts, while ‘stiff’ particles were retained when they settled into streambed interstices. Leaves placed in high-velocity microhabitats were broken down more slowly than leaves in low-flow areas, likely due to the exclusion of large-bodied detritivores. In conclusion, this thesis supports the view that hydrodynamic forces control trophic interactions and local population dynamics in stream ecosystems by directly altering the physical – and sometimes behavioural – processes of particle entrainment, transport, and deposition. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

<p> A method of modelling the mixing phenomenon in natural streams is presented. A wide range of mixing situations can be characterized using a lumped parameter model consisting of a network of ideally mixed components. The components represent two ideal states of mixing: complete mixing of the total component volume, and the other extreme where no mixing occurs in the direction of flow through the component volume. The use of frequency response techniques to match the mathematical model to the real situation is also discussed.</p> <p> Experimental work was carried out on a small natural stream to illustrate how the method is to be applied. The frequency response was obtained using sinusoidal, pulse, and impulse inputs and fluorometric dye tracing techniques. The non-linear model parameters were evaluated using the principles of least squares. The mathematical model chosen for this particular stream illustrates how the phenomenon of stagnant or slow moving regions can be included. The necessary data was collected on several days under different flow conditions to show how the model can be made a function of stream flow.</p> / Thesis / Master of Engineering (MEngr)

No description available.

To quantify sediment contributions due to urban channel enlargement, 50 study sites were selected on 1st- through 3rd-order streams, in watersheds with varying levels of urbanization, in two Physiographic Regions (Coastal Plain and Piedmont), and in the Coastal Zone Management Area of Virginia. At each site, riffle cross-sectional and longitudinal surveys were conducted to measure the channel morphology. Enlargement ratios for bankfull cross-sectional parameters were calculated to quantify channel change relative to stable streams (from regional curves). Relationships between dependent, channel characteristics and watershed-scale, independent variables were assessed. The main objectives were to: 1) test for differences in the morphological features between Coastal Plain and Piedmont streams; 2) develop relationships between watershed-level, urbanization characteristics and stream morphological features; and, 3) determine if relationships exist between watershed urbanization and channel enlargement ratios to estimate sediment loading from urban streams for use in statewide nonpoint source pollution assessment activities. It was determined that: 1) for a given watershed area, streams in the Piedmont tended to be larger than those in the Coastal Plain Region (for regional curve streams and for project streams); 2) among all project sites and sites in the Piedmont, watershed area was the best indicator of channel morphology, but among the Coastal Plain sites, the number of road crossings over streams was the best indicator of channel morphology; and, 3) few significant relationships between enlargement ratios and watershed urbanization variables existed; however, one commonality observed across all sites was an inverse relationship between watershed area and channel enlargement ratios. / Master of Science

Doctor of Philosophy / Department of Biology / Walter K. Dodds / Much of the North American tallgrass prairie ecosystem has been converted to cropland or urbanized. One threat to the remaining prairie ecosystems, and the streams within, is woody vegetation encroachment. Stream productivity, measured as metabolism, is a fundamental process comprised of gross primary production (GPP) and (CR) community respiration. Understanding GPP and CR is important because these processes are vital to ecosystem function and can be impacted by a change in canopy cover. First, I investigated improvements in existing methods for estimating whole-stream metabolism as estimated from diel patterns of oxygen (O2). I compared measured and modeled O2 and aeration (a physical parameter required for measurement of metabolism) rates to determine if direct measurement of aeration is necessary and the importance of temperature correction of metabolism. Modeling was moderately successful in determining aeration rates, and temperature correction of GPP and CR substantially improved model fits. Second, effects of woody vegetation encroachment on prairie stream function were investigated. Stream metabolism was measured for four years in duplicate reaches with varying canopy cover (closed canopy, naturally open canopy, and vegetation removal reaches). The removal reaches had closed canopy for the first two years and open canopy for the last two years. Canopy cover increased CR rates and had minimal effects on GPP. Third, the same experiment was used to determine the effects of woody vegetation encroachment on prairie stream ecosystem structure and food web interactions. Chlorophyll a and filamentous algal biomass were greater in naturally open and vegetation removal reaches, although the effects were stronger on filamentous algal biomass. As canopy cover decreased, the filamentous algal biomass to chlorophyll ratio increased, indicating a shift in algal community structure. Stable isotope analysis indicated some shift in pathways of nitrogen and carbon flux into the food web related to degree of canopy cover, but overlap in the signature of food sources made distinct food sources difficult to identify. The data indicate that riparian encroachment can influence ecosystem structure and function in prairie streams and restoration to remove woody riparian cover may restore some ecosystem features of naturally open canopy streams.

Although bicycling has been the subject of increasing academic attention, particularly in the areas of mode choice, benefit analyses, and discussions of policies/treatments, much less attention has been devoted to actually studying how communities have made decisions about whether and what they’ll implement in regards to bicycle infrastructure. “Policy entrepreneurs” are theorized as actors centrally responsible for either creating an opportunity or capitalizing on an opportunity to pair a public problem with a policy solution. A survey instrument solicited directly the participation of the 200 most populous municipalities within the United States. Using a variety of analytical tools (and merged data sources) as well as a novel matching methodology for the selection of case studies, it was possible to identify interesting and broadly informative relationships, which were explored further via the case study comparison. 20 case interviews were conducted across 6 case study cities as a complement to the survey project. Individual policy entrepreneurs and their role or qualities were not significant quantitatively or qualitatively, despite being regularly present. However, having a network of supportive actors (including strong champions/policy entrepreneurs) played a critical role in making projects happen and at larger scales. Advocates and planners may be more successful by being attuned to these networks and political contexts and taking advantage of open “windows” of engagement. Alternatively, these windows can be opened ‘manually’ through grant applications, developing relationships, hosting trainings or speakers, and more. Lastly, city population was also associated with implementation, suggesting underlying factors to be explored in the future.

No description available.