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In this study, we modelled idealized stream reaches using empirical hydrodynamic and bioenergetic parameters to predict how rainbow trout production depends on physical and biological variations across a downstream gradient, and we compared these downstream effects in a low and high‐gradient stream reach. We found that longitudinal production potential (i.e. net rate of energetic intake per 100 m of stream length) generally increased with increasing stream size when stream gradient was low. This was not the case, however, for high‐gradient streams, wherein maximum longitudinal production potential was associated with middle or low stream size (QMAD = 2.5 to 25 m3 s?1). Areal production potential (net rate of energetic intake per m2 of wetted stream bed) reached a maximum at low stream size (QMAD = 2.5 m3 s?1) with both high and low gradients. We also showed that high stream temperature and low drift density could potentially cause adult rainbow trout to be excluded from stream reaches with high flow. The models presented here have a stronger mechanistic basis for predicting fish production across heterogeneous stream environments and provide more nuanced predictions in response to variation in environmental features than their physical habitat‐based predecessors. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Understanding how much water must remain in a stream to maintain a healthy functioning ecosystem has become an important focus in stream ecology research. The drift of stream invertebrates is important as a mechanism of dispersal, recolonization and as a food source for fish in flowing water. Drift behaviour of stream invertebrates in response to flow reduction was examined in natural and streamside channels in two countries (Canada and New Zealand). We hypothesised that the drift of some taxa would increase following flow reduction as they attempted to avoid unfavourable conditions. Taxa such as Baetis sp. (Ephemeroptera) in Canadian streamside channels and Coloburiscus humeralis (Ephemeroptera) and Austrosimulium sp. (Simulidae) in streams in New Zealand exhibited a short‐term increase in drift following flow reduction. This appears to be in response to decreased velocities and available habitat in flow reduced areas. The majority of taxa displaying this response were filter feeders, suggesting a decline in food delivery with reduced flow contributed to increased drift. Some taxa (e.g. the amphipod Paracalliope fluviatilis) had a sustained increase in drift throughout the reduced flow period, probably because a preference for reduced flows increased their abundance or levels of activity. Water allocation decisions should consider potential impacts on the drift behaviour of the more commonly drifting taxa in a stream. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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东江河流生态评价及其修复方略 总被引：13，自引：0，他引：13
本文通过对大型无脊椎底栖动物状况的调查对东江河流水生态状况进行了分析,并在此基础上提出了生态修复方略。从上游到河口选12个点采集底栖动物样本,发现东江流域底栖动物生物多样性在上游和中游保持在较高水平,而到下游则迅速降低到零。对增江湾、西枝江牛轭湖等处的取样进行分析并探讨改善东江生态的方法。针对不同生态应力提出了3种生态修复方略:1.创造多样性的生物栖息地,开发和形成一系列类似增江湾那样的缓流滞流区,把已经隔离的牛轭湖和江边湖泊湿地重新与江水连通;2.调整大坝运用方式,采取大坝泄放的流量逐渐增加和减少的方式,给生物发出流速增大和降低的信号,使其得以准备和躲避;3.稳定岸坡、控制侵蚀、保护和发育河边植被。 相似文献
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J. A. Simmons M. Anderson W. Dress C. Hanna D. J. Hornbach A. Janmaat F. Kuserk J. G. March T. Murray J. Niedzwiecki D. Panvini B. Pohlad C. Thomas L. Vasseur 《河流研究与利用》2015,31(8):964-974
When forested riparian zones are cleared for agriculture or development, major changes can occur in the stream temperature regime and consequently in ecosystem structure and function. Our main objective was to compare the summer temperature regimes of streams with and without forest canopy cover at multiple sites. The secondary objective was to identify the components of the stream heat budget that had the greatest influence on the stream temperature regime. Paired stream reaches (one forested and one non‐forested or ‘open’) were identified at 11 sites distributed across the USA and Canada. Stream temperature was monitored at the upstream and downstream ends of 80 to 130‐m‐long reaches during summer, and five variables were calculated to describe the stream temperature regime. Overall, compared with forested reaches, open reaches tended to have significantly higher daily mean (mean difference = 0.33 ± 1.1°C) and daily maximum (mean difference = 1.0 ± 1.7°C) temperatures and wider daily ranges (mean difference = 1.1 ± 1.7°C). Mean and maximum daily net heat fluxes in open reaches tended to be greater (or less negative) than those in forested reaches. However, certain sites showed the opposite trends in some variables because of the following: (i) Daily mean and maximum temperatures were biased by differences in inflow temperature between paired reaches and (ii) inputs of cold groundwater exerted a strong influence on temperature. Modelling and regression results suggested that within sites, differences in direct solar radiation were mainly responsible for the observed differences in stream temperature variables at the daily scale. © 2014 The Authors. River Research and Applications published by John Wiley & Sons, Ltd. 相似文献
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Grant M. Graves Jason R. Vogel 《Journal of Contemporary Water Research & Education》2023,177(1):94-102
Fecal indicator bacteria, Escherichia coli, for primary body contact recreation (PBCR) in Oklahoma waterbodies, is defined as the geometric mean of 10 samples from the recreation season, May 1 to September 30, with an impairment threshold of 126 colony forming units (cfu) per 100 mL. However, the water quality standards provide limited guidance on spatiotemporal and environmental factors that could influence samples collected and analyzed. In this study, two stream cross sections under baseflow conditions in a central Oklahoma urban perennial stream, Spring Creek, were densely sampled to investigate temporal and spatial variability of E. coli concentrations and water quality parameters across the stream channel. Water quality parameters (specific conductivity, temperature, dissolved oxygen, pH, turbidity, and total suspended solids (TSS)), stream discharge, and bacteria samples were collected simultaneously at equal intervals across the two cross sections in the morning and afternoon during one summer day with sunny, dry, and hot weather conditions. Results indicate a significant difference between time-of-day samples and water quality parameters and E. coli concentrations. Strong correlations between temperature, dissolved oxygen, and time versus E. coli concentrations were observed, while location, turbidity, and TSS were not significant or correlated to measured values. Furthermore, E. coli concentrations were highly variable spatially across each stream cross section, regardless of time of day or location. Results from this study provide an initial indication that stream water quality, spatial cross section sample location, and diurnal variations may be influencing factors on bacteria concentrations. 相似文献
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为研究麦田暗管排水地段氮肥运移转化及淋失规律,在地下水位以上的土壤非饱和带建立了氮素运移与转化的一维模型,在地下水位以下的饱和带采用流网与一维模型相结合近似模拟暗管排水地段的二维溶质运移问题,这样田间饱和非饱和流动区域即可作为一个整体进行研究,方法简单、实用。对方法及模型的正确性进行了田间试验验证。 相似文献
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在数字化变电站的应用中,对同步采样时钟要求高稳定和高精度,其实现关键在于消除同步采样时钟的误差。文中从分析同步采样时钟误差产生的原因出发,利用全球定位系统（GPS）接收机输出GPS时钟误差分布的特点和晶振频率在短时间内的相对稳定性及现场可编程门阵列（FPGA）的高速数字信号处理的特性,采用相应处理措施消除了晶振频率偏差对同步采样时钟的影响,实现了GPS时钟在短时间内出现较大偏移或扰动时对其进行人为补偿,从而保证了采样时钟的精确同步,为数字化变电站的设计应用提供了一种高稳定、高精度的同步采样时钟设计方法。 相似文献
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An analytical solution of drawdown caused by pumping was developed for an aquifer partially penetrated by two streams.The proposed analytical solution modifies Hunt's analytical solution and considers the effects of stream width and the interaction of two streams on drawdown.Advantages of the solution include its simple structure,consisting of the Theis well function and parameters of aquifer and streambed semipervious material.The calculated results show that the proposed analytical solution agrees with a previously developed acceptable solution and the errors between the two solutions are equal to zero without consideration of the effect of stream width.Also,deviations between the two analytical solutions incrcase with stream width.Four cases were studied to examine the effect of two streams on drawdown,assuming that some parameters were changeable,and other parameters were constant,such as the stream width,the distance between the stream and the pumping well,the stream recharge rate,and the leakage coefficient of streambed semipervious material. 相似文献
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The distinction between a “stream” and “river” is imprecise and vague despite the popular usage of the terms across disciplines for describing flowing waterbodies. Based on an analysis of named flowing waterbodies in the continental United States, we suggest a bank-to-bank channel width of 15 m as a working threshold in defining smaller “streams” from larger “rivers.” 相似文献
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Large river systems create challenges when sampling zooplankton. The dynamics of large rivers, spatial heterogeneity of biota, and behaviours of zooplankton can all contribute to large variation in estimation. The gear utilized for zooplankton collections may also be a factor, and there is not a well‐studied gear, nor industry standard, for collection in riverine systems. The lack of consistent sampling methods makes it difficult to compare zooplankton within and across systems. A standard method for zooplankton collection would be valuable for comparison among studies. To optimize zooplankton assessment in large river habitats, we tested how community estimations varied between four common zooplankton sampling devices across three river habitat types. We tested four gears: the Schindler–Patalas trap, integrated tube sampler, powered water pump, and horizontal tow net. Each device was used to collect samples in thalweg, channel border, and backwater river habitats within Pool 8 of the Upper Mississippi River in June, July, and August of 2017. Our results support that there are qualitative and quantitative differences in zooplankton estimates among gear in different habitats. The powered pump most often yielded highest abundances of total and individual zooplankton taxa allowing for more reliable community comparisons. With some modification, the pump is recommended as the most appropriate sampling gear when performing quantitative studies of zooplankton composition and abundance in large river habitats. 相似文献
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Morten Stickler Knut T. Alfredsen Tommi Linnansaari Hans‐Petter Fjeldstad 《河流研究与利用》2010,26(9):1187-1197
During winter, different types of ice formation are commonly observed in northern boreal stream systems. Although largely overlooked today, river ice has profound effects on in‐stream hydraulics and therefore ice processes should be considered in freshwater stream management and assessment. In particular, limited knowledge exists about the impacts of dynamic ice formation on stream environments. Results presented from the changes of in‐stream heterogeneity in three steep stream environments caused by dynamic ice formation demonstrate that the formation of anchor ice and anchor ice dams may induce significant backwater effects by increasing wetted areas (maximum 43%) and water depths (maximum 241%) and reducing water velocities (maximum 70%); independent of minimal changes in discharge. Consequently, stream environments are transformed from fast‐flow to slow‐flow areas, even on a short temporal scale (<12 h). Furthermore, the anchor ice build‐up initiated static (surface) ice formation due to reduced local water velocities upstream ice dams. Thus, dynamic ice formation plays a key role in the balanced ice regime in steep stream environments and contributes largely to stable static ice cover in these environments. Observations from the present study suggest that the current paradigm emphasizing the role of discharge as the main controller of in‐stream heterogeneity may call for a modification in steep streams that experience seasonal ice formation. This is particularly important if future hydraulic‐/habitat models and assessment tools are to be implemented in freshwater management to realistically characterize steep stream environments in cold climate regions on a seasonal scale. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Many anthropogenic inputs, such as municipal wastewater effluents (MWWEs), affect stable isotope signatures (δ13C and δ15N) at the base of exposed food webs creating spatial patterns reflecting their incorporation into aquatic food webs. The Grand River in southern Ontario, Canada, is a heavily modified, rapidly urbanizing river that assimilates wastewater from 30 municipal wastewater treatment plants. Stable isotope analysis was applied to resident aquatic invertebrates and fish influenced by three different wastewater outfalls in early, middle, and late summer to determine how values shifted seasonally and with differing effluent quality. There was a slight increase in δ13C in both invertebrates and fish in late summer downstream from the three outfalls, but it is difficult to separate effects of the effluents from downstream gradients. Downstream of two of the three outfalls, the δ15N tended to increase relative to upstream, while the remaining effluent, of the poorest quality, decreased δ15N values of both invertebrates and fish. Spatial trends in stable isotopes became more pronounced as the summer progressed with the greatest between‐site differences occurring in late summer. This study reflects the complex nutrient dynamics associated with MWWE inputs to rivers and contributes to our understanding and application of stable isotope analysis in impacted lotic ecosystems. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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This preliminary study (March–October, 1994) describes the effects of an inter-basin water transfer (IBT) on discharge and benthic macro-invertebrate community structure. The IBT from Theewaterskloof, an impoundment on the Riviersonderend system, to the Berg River in the Western Cape, South Africa is part of the water supply system for Greater Cape Town. Transfers occur during summer for irrigation and rainbow trout (Oncorhyncus mykiss) farming in the Berg catchment and lead to greatly elevated summer discharges in the recipient river: 4500% in late summer (March) and 830% in autumn (May). During winter and spring, when the transfer ceases, discharges revert to normal winter volumes below the outlet. A decrease in taxon richness of the invertebrate communities was observed below the transfer outlet, compared to the river above the transfer. Sensitive families such as the heptageniid Ephemeroptera and leptocerid Trichoptera were not recorded below the outlet during transfer months (March and May). On the other hand, collector-predators such as the hydropsychid trichopterans showed large increases in numbers during the same transfer months, when compared against above-outlet samples: 240 and 80 individuals m−2, in March and May, from above the IBT, versus 46 994 and 5600 individuals m−2 below the IBT. This change was probably due to the introduction of live zooplankton to the receiving river from the source reservoir. Dendrograms and MDS-ordination diagrams showed that, in summer, invertebrate communities sampled at the two sites above and below the IBT were between 52 and 56% similar, while in winter and spring, in the absence of water releases similarities were higher (>70%) in July and October. There were also seasonal differences between invertebrate communities sampled in different months, but, during water release months, MDS-ordination diagrams showed clear grouping of communities according to position above or below the IBT, rather than month. Results to hand indicate a ‘reset’ of the entire benthic invertebrate community during winter and spring when no transfers occur. Of concern is the potential for the transfer of cyanophyte blooms (commonly of the genus Anabaena) from the source reservoir to the Berg River: transfers of non-toxic, malodorous geosmin, a cyanophyte exudate which has affected the flesh of rainbow trout farmed in the Berg catchment, have already been reported. © 1998 John Wiley & Sons, Ltd. 相似文献
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《Journal of Great Lakes research》2020,46(1):48-52
Macrohectopus branickii is the only amphipod with an exclusively pelagic lifestyle. Although this species plays an important role in the diet of pelagic fish of Lake Baikal, there is no regular monitoring of its abundance. We present data on the status of the population from a lake-wide 2015 survey and compare these data with available historical information. The survey was conducted with a modified Juday net and simultaneous hydroacoustics profiling from up to 700 m depth to the surface. The abundance of M. branickii in the pelagic zone over depths >300 m in 2015 averaged 1700 ind/m2 (range 320–4090 ind/m2) and the biomass averaged 3.7 g/m2 (range 1.1–14.4 g/m2). Sites with the greatest abundance of M. branickii were located in the South and Middle Basins off the eastern shore. These values are comparable to the published data from 1950s to 1980s. The characteristics of nearshore aggregations of larger mature females were more variable and need further study. 相似文献
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采用长系列数据,分析了影响泰晤士河潮汐河段生态状况的主要因素。1915～2006年的监测数据表明其生态状况经历了污染、恢复和稳定3个阶段,20世纪40-60年代是污染最重的时期,伴随着较高的水温、氨氮和生化需氧量以及较低的溶解氧含量,该时期少有底栖无脊椎动物的记录。自60年代以来,随着水质的恢复,无脊椎动物也逐渐增多,其数量的波动与水化学指标,尤其是溶解氧具有相关性。尽管1960年以前的无脊椎动物和水质资料缺失比较严重,但仍需彻底整理和分析所有数据,以便在以后的研究中建立水质指标与无脊椎动物群落间的定量关系。 相似文献
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Holly J. Coe Peter M. Kiffney George R. Pess Kris K. Kloehn Michael L. McHenry 《河流研究与利用》2009,25(8):1025-1035
Wood abundance in aquatic systems has been dramatically reduced compared to historical levels due to anthropogenic activities that led to wood removal and stream simplification. As a result, reintroduction of wood to aquatic systems is now a widely used and relatively well‐studied restoration technique for increasing habitat complexity. Although stream periphyton (biofilm) and invertebrates serve as food sources for a variety of predators including fish, birds and bats, data on how lower trophic levels respond to wood placement are relatively scarce. The purpose of this study was to test the hypothesis that periphyton biomass and aquatic invertebrate density were higher on Engineered Log Jams (ELJs) than on inorganic substrates in two large Pacific Northwest river systems. Among years and rivers, periphyton biomass and invertebrate densities were significantly higher on ELJs than on cobbles within the same reach. Invertebrate communities on ELJs were dominated by meiofauna (<500 µm), whereas cobbles were dominated by larger chironomids. We attribute these trophic level differences to substrate type, as we did not detect taxonomic differences between cobbles in reaches with and without ELJs. We show that adding wood to reaches with little or no naturally occurring wood increased overall habitat surface area and thereby the potential for increased productivity relative to reaches with low levels of wood. Finally, wood supports a unique community of invertebrates that are often overlooked in lotic system studies but may be contributing substantially to overall biological diversity. Published in 2009 by John Wiley & Sons, Ltd. 相似文献
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Stream rehabilitation and enhancement projects in the Norwalk River (urban‐forest watershed) and Merrick Brook (agriculture‐forest watershed) were evaluated. Instream structure installation, streambank stabilization and meander re‐creation were performed 2–5 years before monitoring. Physical, chemical and biological variables were monitored at control, enhanced (treatment sites originally controls), impaired and rehabilitated (treatment sites originally impaired) sites for three field seasons to evaluate the projects and formulate monitoring strategies. Small improvements in local habitat and macroinvertebrate assemblages were observed at rehabilitated sites on the Norwalk River however control conditions were not attained. Changes to stream health were less evident at the reach scale suggesting that watershed processes that form and maintain habitat were too altered for more widespread recovery. A localized sediment source from a failing streambank was eliminated from Merrick Brook protecting the abundant nearby quality habitat, yet fining occurred at the rehabilitation site due to hydraulic changes leading to localized shifts in macroinvertebrate assemblages. Single‐season sampling created a useful snapshot to compare enhanced and rehabilitated sites to control and impaired sites. We recommend a tiered sampling strategy where effectiveness monitoring may include a detailed effort at many sites over a short time (as performed here), a relatively low level of detail (e.g. a rapid assessment) at an intermediate number of sites over a short time, and a detailed long‐term monitoring at few sites (e.g. before‐after‐control‐impact, BACI). More research is needed to continue the trend of increased project evaluation to advance the science and application of stream restoration. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献