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Study Streams (study + stream)
Selected AbstractsDiscontinuity in fish assemblages across an elevation gradient in a southern Appalachian watershed, USAECOLOGY OF FRESHWATER FISH, Issue 1 2005J. L. Robinson This region is noted for extreme topographical relief, high cumulative annual rainfall and many rare and endemic plants and animals. The study area encompasses a portion of the Blue Ridge Escarpment and the associated Brevard Fault Zone. We hypothesise that major waterfalls and cascade complexes have acted to limit invasion and colonisation by fishes from downstream. This hypothesis is supported by longitudinal fish assemblage patterns in our study streams. Fish species richness in Toxaway River increased from 4 to 23 between Lake Toxaway and Lake Jocassee, a distance of 10 river km. We found similar discontinuities in neighbouring Horsepasture River and Bearwallow Creek. We found no instances of species replacement along this elevation gradient, and the trend in increased diversity downstream showed discontinuities coincident with sharp elevation breaks. With regard to theories posited to explain community formation in headwater stream fish communities (especially in those characterised by high topographical relief), we suggest coloniser ,access' may be more important than other factors including competitive interactions. Resumen 1. En este estudio examinamos patrones en los ensamblajes de peces de los ríos Toxaway y Horsepasture, dos ríos de elevada altitud de Carolina del Norte (USA). Esta región se caracteriza por rupturas topografías extremas, gran cantidad de lluvia anual y numerosos endemismos animales y vegetales. El estudio incluye una porción de la región del Blue Ridge Escarpment y la zona asociada de Brevard Fault. 2. Nuestra hipótesis es que los complejos sistemas de cataratas han limitado la invasión y la colonización de los peces desde las localidades aguas abajo. Los patrones longitudinales de los ensamblajes de peces fueron consistentes con esta hipótesis. La riqueza de las especies de peces en el río Toxaway incrementó desde 4 a 23 especies en una distancia de 10 Km de río, entre los lagos Taxoway y Jocasee. Encontramos discontinuidades similares en los vecinos ríos Horsepasture y Bearwallow. No encontramos ningún caso de re-emplazamiento de especies a lo largo del gradiente de altitud y la tendencia a incrementar la diversidad aguas abajo mostró discontinuidades que coincidieron con rupturas de altitudes. 3. Al considerar teorías que explican la formación de comunidades en zonas altas de ríos (especialmente en regiones caracterizadas por rupturas topografías), sugerimos que el acceso para los colonizadores puede ser más importante que otros factores incluyendo interacciones competitivas. [source] Effects of upstream lakes and nutrient limitation on periphytic biomass and nitrogen fixation in oligotrophic, subalpine streamsFRESHWATER BIOLOGY, Issue 11 2007AMY M. MARCARELLI Summary 1. We conducted bioassays of nutrient limitation to understand how macronutrients and the position of streams relative to lakes control nitrogen (N2) fixation and periphytic biomass in three oligotrophic Rocky Mountain catchments. We measured periphytic chlorophyll- a (chl- a) and nitrogen-fixation responses to nitrogen (N) and phosphorus (P) additions using nutrient-diffusing substrata at 19 stream study sites, located above and below lakes within the study catchments. 2. We found that periphytic chl- a was significantly co-limited by N and P at 13 of the 19 sites, with sole limitation by P observed at another four sites, and no nutrient response at the final two sites. On average, the addition of N, P and N + P stimulated chl- a 35%, 114% and 700% above control values respectively. The addition of P alone stimulated nitrogen fixation by 2500% at five of the 19 sites. The addition of N, either with or without simultaneous P addition, suppressed nitrogen fixation by 73% at nine of the 19 sites. 3. Lake outlet streams were warmer and had higher dissolved organic carbon concentrations than inlet streams and those further upstream, but position relative to lakes did not affect chl- a and nitrogen fixation in the absence of nutrient additions. Chl- a response to nutrient additions did not change along the length of the study streams, but nitrogen fixation was suppressed more strongly by N, and stimulated more strongly by P, at lower altitude sites. The responses of chl- a and nitrogen fixation to nutrients were not affected by location relative to lakes. Some variation in responses to nutrients could be explained by nitrate and/or total N concentration. 4. Periphytic chl- a and nitrogen fixation were affected by nutrient supply, but responses to nutrients were independent of stream position in the landscape relative to lakes. Understanding interactions between nutrient supply, nitrogen fixation and chl- a may help predict periphytic responses to future perturbations of oligotrophic streams, such as the deposition of atmospheric N. [source] The effect of riparian land use on transport hydraulics in agricultural headwater streams located in northeast Ohio, USAHYDROLOGICAL PROCESSES, Issue 1 2010Kyle S. Herrman Abstract This study examined if riparian land use (forested vs agricultural) affects hydraulic transport in headwater streams located in an agriculturally fragmented watershed. We identified paired 50-m reaches (one reach in agricultural land use and the other in forested land use) along three headwater streams in the Upper Sugar Creek Watershed in northeast Ohio, USA (40° 51,42,N, 81° 50,29,W). Using breakthrough curves obtained by Rhodamine WT slug injections and the one-dimensional transport with inflow and storage model (OTIS), hydraulic transport parameters were obtained for each reach on six different occasions (n = 36). Relative transient storage (AS:A) was similar between both reach types (As: A = 0·3 ± 0·1 for both agricultural and forested reaches). Comparing values of Fmed200 to those in the literature indicates that the effect of transient storage was moderately high in the study streams in the Upper Sugar Creek Watershed. Examining travel times revealed that overall residence time (HRT) and residence time in transient storage (TSTO) were both longer in forested reaches (forested HRT = 19·1 ± 11·5 min and TSTO = 4·0 ± 3·8 min; agricultural HRT = 9·3 ± 5·3 min and TSTO = 1·7 ± 1·4 min). We concluded that the effect of transient storage on solute transport was similar between the forested and agricultural reaches but the forested reaches had a greater potential to retain solutes as a result of longer travel times. Copyright © 2009 John Wiley & Sons, Ltd. [source] Comparison of Three Pebble Count Protocols (EMAP, PIBO, and SFT) in Two Mountain Gravel-Bed Streams,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2009Kristin Bunte Abstract:, Although the term "pebble count" is in widespread use, there is no standardized methodology used for the field application of this procedure. Each pebble count analysis is the product of several methodological choices, any of which are capable of influencing the final result. Because there are virtually countless variations on pebble count protocols, the question of how their results differ when applied to the same study reach is becoming increasingly important. This study compared three pebble count protocols: the reach-averaged Environmental Monitoring and Assessment Program (EMAP) protocol named after the EMAP developed by the Environmental Protection Agency, the habitat-unit specific U.S. Forest Service's PACFISH/INFISH Biological Opinion (PIBO) Effectiveness Monitoring Program protocol, and a data-intensive method developed by the authors named Sampling Frame and Template (SFT). When applied to the same study reaches, particle-size distributions varied among the three pebble count protocols because of differences in sample locations within a stream reach and along a transect, in particle selection, and particle-size determination. The EMAP protocol yielded considerably finer, and the PIBO protocol considerably coarser distributions than the SFT protocol in the pool-riffle study streams, suggesting that the data cannot be used interchangeably. Approximately half of the difference was due to sampling at different areas within the study reach (i.e., wetted width, riffles, and bankfull width) and at different locations within a transect. The other half was attributed to using different methods for particle selection from the bed, particle-size determination, and the use of wide, nonstandard size classes. Most of the differences in sampling outcomes could be eliminated by using simple field tools, by collecting a larger sample size, and by systematically sampling the entire bankfull channel and all geomorphic units within the reach. [source] Surface water balance to evaluate the hydrological impacts of small instream diversions and application to the Russian River basin, California, USAAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2009Matthew J. Deitch 1.Small streams are increasingly under pressure to meet water needs associated with expanding human development, but the hydrologic and ecological effects are not commonly described in scientific literature. 2.To evaluate the potential effects that surface water abstraction can have on flow regime, scientists and resource managers require tools that compare abstraction to stream flow at ecologically relevant time scales. 3.The classic water balance model was adapted to evaluate how small instream diversions can affect catchment stream-flow; the adapted model maintains the basic mass balance concept, but limits the parameters and considers surface water data at an appropriate timescale. 4.This surface water balance was applied to 20 Russian River tributaries in north-central California to evaluate how recognized diversions can affect stream flow throughout the region. 5.The model indicates that existing diversions have little capacity to influence peak or base flows during the rainy winter season, but may reduce stream flow during spring by 20% in one-third of all the study streams; and have the potential to accelerate summer intermittence in 80% of the streams included in this study. 6.The surface water balance model may be especially useful for guiding river restoration from a hydrologic perspective: it can distinguish among streams with high diversion regimes that may require more than just physical channel restoration to provide ecological benefits, and can illustrate the extent to which changing the diversion parameters of particular water users can affect the persistence of a natural flow regime. 7.As applied to Russian River tributaries, the surface water balances suggest that reducing demand for stream flow in summer may be as important as physical channel restoration to restoring anadromous salmonids in this region. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||