- LINKING STREAM SEDIMENT DEPOSITION AND AQUATIC HABITAT QUALITY IN PEARL
MUSSEL STREAMS: IMPLICATIONS FOR CONSERVATION
- Authors: M. Denic; J. Geist
Abstract: The introduction of fine sediments into streams is considered to have a major effect on habitat quality affecting the reproduction of sensitive species such as unionid mussels and salmonid fishes. To date, there is a lack of information on the magnitude and spatio-temporal resolution of sediment introduction.This study aimed to quantify the spatio-temporal deposition of fine sediments in headwater streams in relation to the status of Margaritifera margaritifera and Salmo trutta. Fine sediment deposition was linked to physicochemical conditions of the adjacent streambed.The mean observed deposition of fine sediments over the study period was 3.4 kg m−2 month−1 with a high spatio-temporal variation ranging from
- CAN THE REGENERATION OF VEGETATION FROM RIPARIAN SEED BANKS SUPPORT
BIOGEOMORPHIC SUCCESSION AND THE GEOMORPHIC RECOVERY OF DEGRADED RIVER
- Authors: J. O'Donnell; K. Fryirs, M. R. Leishman
Abstract: For rivers degraded by erosion and channel widening, the re-establishment of riparian vegetation is essential. We assess the potential for riparian seed banks to facilitate natural channel contraction through the regeneration of plants involved in the biogeomorphic succession of three discrete geomorphic units of increasing age and height above the channel bed: bars, benches and floodplain. Standing vegetation upon each unit type was surveyed for four river reaches in the Hunter catchment of eastern Australia. Seed bank composition was determined using seedling emergence techniques on sediment sampled from the units. We compared species richness and composition, and longevity, growth form and seed dispersal mechanisms between the standing vegetation and seed bank species. The seed bank was similar across bars, benches and floodplain, containing mostly perennial pioneer herbs, sedges and rushes, dispersed by wind and hydrochory (water transport). While bar vegetation was similar to the seed bank, bench and floodplain vegetation included later successional species such as shrubs and trees, significantly more grasses and vines (benches: χ25, N = 402 = 102.033, p
- DOWNSTREAM ECOLOGICAL IMPACTS OF CONTROLLED SEDIMENT FLUSHING IN AN ALPINE
VALLEY RIVER: A CASE STUDY
- Authors: P. Espa; G. Crosa, G. Gentili, S. Quadroni, G. Petts
Abstract: Sediment flushing may be effective to tackle the loss of reservoir storage as a result of siltation. When operationally possible, the impact of this practice on the downstream aquatic environment can be mitigated by limiting the sediment concentration of the discharged waters (controlled sediment flushing). However, this topic is poorly documented, and concerns arise when limits are discussed. We present the results of a 3-year field investigation concerning the controlled sediment flushing of a small reservoir on the Adda River, the main tributary of Lake Como—Italy. Two limits for suspended solid concentration (SSC) were adopted: 1.5 g L−1, as average value throughout the whole working day, and 3.0 g L−1, as alert threshold to adjust the ongoing activity. These constraints were essentially fulfilled in the course of the documented operations. The first year sediment flushing was more significant than the following year: 25 000 tons of fines below 2 mm in diameter were flushed in six non-consecutive days in summer 2010, while, one year earlier, 75 000 tons were flushed in 16 non-consecutive days. In the third year of investigation (2011), no sediment evacuation took place. The benthic macroinvertebrate and the fish communities were surveyed a short distance below the reservoir, that is, in the potentially more affected river reach. Clear pieces of evidence of environmental quality degradation were not detected; the adopted strategies can therefore be considered to be appropriate when planning sediment flushing management in comparable contexts. Copyright © 2014 John Wiley & Sons, Ltd.
- THE INFLUENCE OF LOGJAMS ON LARGEMOUTH BASS (MICROPTERUS SALMOIDES)
CONCENTRATIONS ON THE LOWER ROANOKE RIVER, A LARGE SAND-BED RIVER
- Authors: E. R. Schenk; J. W. McCargo, B. Moulin, C. R. Hupp, J. M. Richter
Abstract: This study examines the relation between logjams and largemouth bass (Micropterus salmoides) on the alluvial sand-bed lower Roanoke River. Disparate data sets from previous bank erosion, fisheries, and large wood studies were used to compare the distribution of largemouth bass with logjam frequency. Logjams are related to the frequency of bank mass wasting increasing from near an upstream dam to the middle reach of the study segment and then decreasing as the river approaches sea level. The highest concentration of largemouth bass and logjams was in the middle reach (110 fish per hour and 21 jams per km). Another measure of largemouth bass distribution, fish biomass density (g h−1), had a similar trend with logjams and was a better predictor of fish distribution versus logjams (R2 = 0.6 and 0.8 and p = 0.08 and 0.02 for fish per hour and g h−1 versus logjam, respectively). We theorize that the preference for adult bass to congregate near logjams indicates the use of the jams as feeding areas. The results of a principal component analysis indicate that fish biomass concentration is much more related to logjam frequency than channel geometry (width, depth, and bank height), bed grain size, bank erosion, or turbidity. The results of this research support recent studies on in-channel wood and fisheries: Logjams appear to be important for maintaining, or increasing, both largemouth bass numbers and total biomass of fish in large eastern North American rivers. Persistent logjams, important as habitat, exist where relatively undisturbed river reaches allow for bank erosion inputs of wood and available anchoring locations. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- COMPARISON OF CARBON SEQUESTRATION ABILITY AND EFFECT OF ELEVATION IN
FENCED WETLAND PLANT COMMUNITIES OF THE XILIN RIVER FLOODPLAINS: A MODEL
- Authors: Y. Liu; L. Wang, H. Liu, W. Wang, C. Liang, J. Yang, J. T. A. Verhoeven
Abstract: Floodplain habitats of the Xilin River in Inner Mongolia, China, were overgrazed by sheep and cattle until fencing of the floodplains was implemented in 2000. Carbon cycling of three plant communities of differing floodplain elevation after fencing showed that biomass in low-elevation wetlands increased fastest until reaching its maximum at 20 years in the future, while a slower increase in biomass existed in high-elevation and ‘hummock’ wetlands. Modelling and field experiments revealed differences between the three plant communities that were primarily attributed to different elevation levels and inundation periods. This study also determined the carbon sequestration capacity of the three floodplain wetland types (0.18 kg C m−2 year−1 in low-elevation wetlands, 0.09 kg C m−2 year−1 in high-elevation wetlands, and 0.05 kg C m−2 year−1 in hummock wetlands). Copyright © 2014 John Wiley & Sons, Ltd.
- THE EFFECTS OF DAM REMOVAL ON RIVER COLONIZATION BY SEA LAMPREY PETROMYZON
- Authors: E. Lasne; M.-R. Sabatié, N. Jeannot, J. Cucherousset
Abstract: Habitat fragmentation is an important cause of biodiversity loss in freshwater systems, as worldwide rivers have been fragmented by dams and other hydraulic structures. To restore freshwater fish populations, some barriers have been removed, but the long-term ecological effects of this removal have been rarely quantified. In the present study, we quantified the effects of barrier removal on river colonization by anadromous sea lamprey (Petromyzon marinus) by analyzing the spatial distribution and nest density in a small coastal river (France) from 1994 to 2011. Our results demonstrated the benefit of dam removal within few years after restoration. Indeed, the spatial distribution of nests shifted significantly upstream and was more uniform throughout the river after removal. Our results also suggest that the spatial patterns of habitat colonization were affected by the density of nests, river flow and connectivity. Finally, although the number of nests was significantly higher after removal, it was not possible to clearly identify the contribution of intrinsic versus external factors involved in this pattern. Further investigations are therefore needed to quantify the potential subsequent effects on juvenile recruitment and the overall population dynamics. Copyright © 2014 John Wiley & Sons, Ltd.
- A COMPARISON OF ELECTROFISHING AND VISUAL SURVEYING METHODS FOR ESTIMATING
FISH COMMUNITY STRUCTURE IN TEMPERATE RIVERS
- Authors: C. J. Macnaughton; S. Harvey-Lavoie, C. Senay, G. Lanthier, G. Bourque, P. Legendre, D. Boisclair
Abstract: Studies attempting to describe fish community structure in shallow riverine environments typically rely on electrofishing and/or visual (snorkelling) surveys, but few have addressed the relative efficiencies of these two methods at estimating fish density and biomass across wide ranges of geography, taxonomy and life history stages. Multiple paired electrofishing and visual surveys were conducted in 18 temperate Canadian rivers in order to obtain community-wide density and biomass estimates from both methods. Partial canonical multivariate analyses were applied to the paired fish community matrices comparing the results of both surveying methods at the taxonomic levels of family, genus and species, as well as size classes within families and species, to assess the particular effectiveness of each sampling method. Although electrofishing estimates of family and species richness were generally greater, snorkelling surveys tended to generate higher density and biomass estimates for different size classes of many salmonid and cyprinid species. Moreover, mean river biomass estimates derived from visual surveying matched those obtained from our best mean river biomass estimates arising from the two methods combined. This study provides empirical evidence that electrofishing and visual survey methods generate different types of information when assessing fish community structure at the family level or by size classes. Our results provide ample background information for determining the most accurate sampling method for a particular fish community assemblage, which is fundamental to fisheries management and research. Copyright © 2014 John Wiley & Sons, Ltd.
- EFFECTS OF IMPOUNDMENT ON MACROINVERTEBRATE COMMUNITY ASSEMBLAGES IN
- Authors: B. R. Gillespie; L. E. Brown, P. Kay
Abstract: Approximately 15% of the world's river flow is regulated, but evidence for the impacts of regulation on macroinvertebrate communities remains contradictory. Sound understanding of this topic is now required to meet legislative targets (e.g. EU Water Framework Directive good ecological potential). In the UK, research has either been undertaken at large (national) or small (reach) scales, and typically, researchers have made comparisons between sites classed simply as either regulated or unregulated. We present an alternative, medium (regional) scale study and contrast three methods of defining the extent to which a site is regulated (ER): (i) regulated or unregulated (ERLOW); (ii) fully-regulated, semi-regulated or unregulated (ERMED); and (iii) a continuous score reflecting the relative regulated and unregulated river influence on a site (ERHIGH). The potential for highlighting the impacts of regulation of two recently developed pressure-specific biotic indices [Lotic Invertebrate index for Flow Evaluation (LIFE) and Proportion of Sediment-sensitive Invertebrates] is also assessed. We found that (i) regulation was associated with reduced relative abundance of Coleoptera and Ephemeroptera and enhanced relative abundance of Trichoptera, Chironomidae and Oligochaeta; (ii) Potamopyrgus antipodarum and Amphinemura sulcicollis were both positively associated with regulation; this observation is novel for the UK; (iii) ERHIGH was superior to both ERLOW and MED as a means of detecting an impact; and (iv) of all indices tested, only LIFE was significantly associated with regulation. The use of LIFE and ERHIGH should be tested further to understand the extent to which they can provide clearer insights into the effects of river regulation on macroinvertebrate communities. Copyright © 2014 John Wiley & Sons, Ltd.
- FISH RESPONSE TO ANTHROPOGENIC PRESSURES IN TEMPORARY STREAMS: THE
IMPORTANCE OF ENVIRONMENTAL DRIVERS
- Authors: P. Matono; J. M. Bernardo, A. M. Costa, M. Ilhéu
Abstract: Mediterranean temporary streams show high spatial and temporal heterogeneity. Native fish species are adapted to this natural variability, but the cumulative effect of natural and anthropogenic disturbances may compromise the stability and persistence of fish assemblages. This study aimed to determine if environmental drivers affect the response of fish assemblages to anthropogenic pressures in temporary streams and identify what type of fish assemblages are particularly vulnerable to anthropogenic disturbance. Data were collected from 22 sites located in southern Portuguese temporary streams between 1996 and 2012. The temporal pattern of fish assemblages in each site was used to examine fish assemblage stability, that is, the relative constancy of species abundance over time, quantified using the Bray–Curtis similarity coefficient. Native fish assemblage stability was positively associated with altitude, annual rainfall, percentage of riffles and habitat diversity and highly negatively related to anthropogenic pressure, particularly land use intensification, riparian degradation, sediment load and organic contamination/nutrient enrichment. Results highlighted an interaction between natural environmental and anthropogenic pressure gradients; anthropogenic disturbance tends to be lower in high-elevation headwater streams and increases in lowland streams, particularly in downstream reaches. In upstream reaches, especially in lowland streams, fish assemblage stability showed a steep decline with the increase in anthropogenic pressure. Lowland downstream reaches displayed a less steep decline of fish assemblage stability in response to degradation, despite having greater anthropogenic disturbance. The results highlight the particular vulnerability of headwater streams in lowland sectors to anthropogenic disturbance. Copyright © 2014 John Wiley & Sons, Ltd.
- THE HYDROLOGICAL STATUS CONCEPT: APPLICATION AT A TEMPORARY RIVER
- Authors: A. M. De Girolamo; A. Lo Porto, G. Pappagallo, O. Tzoraki, F. Gallart
Abstract: In achieving the final objective of the European Water Framework Directive, the evaluation of the ‘hydrological status’ of a water body in a catchment is of the utmost importance. It represents the divergence of the actual hydrological regime from its ‘natural’ condition and may thus provide crucial information about the ecological status of a river. In this paper, a new approach in evaluating the hydrological status of a temporary river was tested. The flow regime of a river has been classified through the analysis of two metrics: the permanence of flow and the predictability of no-flow conditions that were evaluated on monthly streamflow data. This method was applied to the Candelaro river basin (Puglia, Italy) where we had to face the problem of limited data availability. The Soil and Water Assessment Tool model was used when streamflow data were not available, and a geographic information system procedure was applied to estimate potential water abstractions from the river. Four types of rivers were identified whose regimes may exert a control on aquatic life. By using the two metrics as coordinates in a plot, a graphic representation of the regime can be visualized in a point. Hydrological perturbations associated with water abstractions, point discharges and the presence of a reservoir were assessed by comparing the position of the two points representing the regime before and after the impacts. The method is intended to be used with biological metrics in order to define the ecological status of a stream, and it could also be used in planning the ‘measures’ aimed at fulfilling the Water Framework Directive goals. Copyright © 2014 John Wiley & Sons, Ltd.
- ESTIMATION OF SEDIMENT HYDRAULIC CONDUCTIVITY IN RIVER REACHES AND ITS
POTENTIAL USE TO EVALUATE STREAMBED CLOGGING
- Authors: T. Datry; N. Lamouroux, G. Thivin, S. Descloux, J. M. Baudoin
Abstract: Streambed substrates have pervasive effects on stream biodiversity and biogeochemistry. The excessive input of fine sediments in streams and the subsequent alteration of the physical characteristics of streambed substrates are considered today as a major environmental issue. The estimation of streambed hydraulic conductivity (K) may be simpler than other estimations of reach-scale physical characteristics and could serve to quantify the alterations of streambeds across stream networks. In this study, we examined between-reach and within-reach variability and temporal changes of streambed K across 101 stream reaches in France, including nine reaches previously judged as clogged and nine as references (unclogged). We also examined the relationships between K and some environmental variables such as vertical hydraulic gradient, streambed grain size, flow velocity or distance to the bank. We demonstrated that 15 measurements of streambed K per reach could be used to compare streams among each other and over time. Clogged reaches displayed much lower K than reference reaches, and more generally, reach-averaged K and the number of non-null K values per reach allowed discriminating reaches among each other without observer bias. K was higher in upwelling compared with downwelling areas, probably because of fine sediment uplifting. With the low cost in terms of equipment (
- OUT OF POOLS: MOVEMENT PATTERNS OF MEDITERRANEAN STREAM FISH IN RELATION
TO DRY SEASON REFUGIA
- Authors: D. F. Pires; P. Beja, M. F. Magalhães
Abstract: Movement may critically influence population persistence in the face of disturbance. However, data on individual movements into and out of refugia in response to disturbance remain limited, leading to an incomplete understanding of the ecological significance of mobility. Using individually marked chubs Squalius torgalensis in a seasonally drying Mediterranean stream, we quantified the rate, direction and magnitude of movements out of dry season pools, and of movements displayed across the stream over the period of hydrological connection. Recapture rate was lower in individuals marked in dry season pools (3.3%; n = 894) than in individuals marked during hydrological connection (13.0%; n = 522). Nearly half the recaptures (46.7%; n = 30) of chubs marked in dry season pools corresponded to movements that were generally longer than 100 m, overpassing the average distance among isolated pools. The frequency and distances travelled out of dry season pools were similar in upstream and downstream directions. Only 20.6% of recaptures of individuals marked during hydrological connection corresponded to movements, with more frequent and larger movements in the upstream direction. Body size was related to movement probability only for chubs marked during hydrological connection. Our results highlight considerable individual variability in movement and underscore the importance of understanding the consequences of this variation and how it may be maintained in fish populations facing increasing fragmentation and intermittency of riverscapes. Copyright © 2014 John Wiley & Sons, Ltd.
- HABITAT RESTORATION IN THE CONTEXT OF WATERSHED PRIORITIZATION: THE
ECOLOGICAL PERFORMANCE OF URBAN STREAM RESTORATION PROJECTS IN PORTLAND,
- Authors: B. Rios-Touma; C. Prescott, S. Axtell, G. M. Kondolf
Abstract: In Portland (Oregon, USA), restoration actions have been undertaken at the watershed scale (e.g. revegetation and stormwater management) to improve water quality and, where water quality and quantity are adequate at the reach scale, to increase habitat heterogeneity. Habitat enhancement in urban streams can be important for threatened species, but challenging, because of altered catchment hydrology and urban encroachment on floodplains and channel banks. To evaluate reach-scale restoration projects in the Tryon Creek watershed, we sampled benthic macroinvertebrates and conducted habitat quality surveys pre-project and over 4 years post-project. Species sensitive to pollution and diversity of trophic groups increased after restoration. Taxonomic diversity increased after restoration but was still low compared with reference streams. We found no significant changes in trait proportions and functional diversity. Functional diversity, proportion of shredders and semivoltine invertebrates were significantly higher in reference streams than in the restored stream reaches. We hypothesized that inputs of coarse particulate organic matter and land use at watershed scale may explain the differences in biodiversity between restored and reference stream reaches. Habitat variables did not change from pre-project to post-project, so they could not explain community changes. This may have been partly attributable to insensitivity of the visual estimate methods used but likely also reflects the importance of watershed variables on aquatic biota—suggesting watershed actions may be more effective for the ecological recovery of streams. For future projects, we recommend multihabitat benthic sampling supported by studies of channel geomorphology to better understand stream response to restoration actions. Copyright © 2014 John Wiley & Sons, Ltd.
- HERBACEOUS VERSUS FORESTED RIPARIAN VEGETATION: NARROW AND SIMPLE VERSUS
WIDE, WOODY AND DIVERSE STREAM HABITAT
- Authors: C. R. Jackson; D. S. Leigh, S. L. Scarbrough, J. F. Chamblee
Abstract: We investigated interactions of riparian vegetative conditions upon a suite of channel morphological variables: active channel width, variability of width within a reach, large wood frequency, mesoscale habitat distributions, mesoscale habitat diversity, median particle size and per cent fines. We surveyed 49 wadeable streams, 45 with low levels of development, throughout the Upper Little Tennessee River Basin in the Southern Appalachians. Conversion of riparian forest to grass has reduced aquatic habitat area (quantified by active channel width), channel width variability, wood frequency, mesoscale habitat diversity and obstruction habitat (wood and rock jams), and such conversion has increased the fraction of run and glide habitat. Channels with grassy riparian zones were only one-third to three-fifths of the width of channels with forested riparian zones, and channels with grassy or narrow forested riparian zones were nearly devoid of wood. Particle size metrics were strongly affected by stream power and agricultural cover in the basin, but the data suggest that elimination of riparian forest reduces median bed particle size. Results indicate that even modest increases in the extent and width of forested riparian buffers would improve stream habitat conditions. Copyright © 2014 John Wiley & Sons, Ltd.
- CHARACTERIZING SUB-DAILY FLOW REGIMES: IMPLICATIONS OF HYDROLOGIC
RESOLUTION ON ECOHYDROLOGY STUDIES
- Authors: M. S. Bevelhimer; R. A. McManamay, B. O'Connor
Abstract: Natural variability in flow is a primary factor controlling geomorphic and ecological processes in riverine ecosystems. Within the hydropower industry, there is growing pressure from environmental groups and natural resource managers to change reservoir releases from daily peaking to run-of-river operations on the basis of the assumption that downstream biological communities will improve under a more natural flow regime. In this paper, we discuss the importance of assessing sub-daily flows for understanding the physical and ecological dynamics within river systems. We present a variety of metrics for characterizing sub-daily flow variation and use these metrics to evaluate general trends among streams affected by peaking hydroelectric projects, run-of-river projects and streams that are largely unaffected by flow altering activities. Univariate and multivariate techniques were used to assess similarity among different stream types on the basis of these sub-daily metrics. For comparison, similar analyses were performed using analogous metrics calculated with mean daily flow values. Our results confirm that sub-daily flow metrics reveal variation among and within streams that are not captured by daily flow statistics. Using sub-daily flow statistics, we were able to quantify the degree of difference between unaltered and peaking streams and the amount of similarity between unaltered and run-of-river streams. The sub-daily statistics were largely uncorrelated with daily statistics of similar scope. On short temporal scales, sub-daily statistics reveal the relatively constant nature of unaltered stream reaches and the highly variable nature of hydropower-affected streams, whereas daily statistics show just the opposite over longer temporal scales. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- THERMAL INFLUENCES ON LIFE-HISTORY TRAITS AND REPRODUCTIVE EFFORT OF
INTRODUCED PUMPKINSEED SUNFISH LEPOMIS GIBBOSUS IN THE RIVER MOSELLE BASIN
- Authors: G. Masson; E. Valente, M. G. Fox, G. H. Copp
Abstract: The influence of local thermal regimes on juvenile growth rates, life-history traits, and reproductive effort of introduced populations of pumpkinseed Lepomis gibbosus was examined in 11 water bodies in the River Moselle basin (northeastern France). Female pumpkinseed were collected during their reproductive period in mid-June in 2009 and 2010, and water temperature was assessed over a 12-month period in 2010. Annual thermal degree-days above 10 °C varied from 1529 in a headwater site to 2722 in the Mirgenbach Reservoir, heated by cooling water from a nuclear power plant. Mean age at maturity varied from 1.3 to 2.2 and was inversely related to annual thermal degree-days. The proportion of mature age-1 females also increased with temperature, but neither mean total length at maturity nor gonadosomatic index was related to waterbody thermal regime. Body size at the end of the first year of life was unrelated to thermal regime, but the growth rate of immature age-1 females in their second growing season was positively related to thermal degree-days in the spring. Warmer water bodies showed elevated reproductive effort in age-1 females when either early season gain in mass or mass at the beginning of the second growing season was controlled for; however, reproductive effort was unrelated to thermal regime in age-2 and age-3 females. Mean age at maturity was related to mean length at age 1 but not to mean length at age 2, in contrast to native North American and introduced European populations. We conclude that the life-history response of pumpkinseed to warmer temperatures occurs primarily in age-1 individuals and predict that climate warming will produce changes in pumpkinseed life-history traits that will make the species more invasive in parts of Europe where the species is present but not actively spreading. Copyright © 2014 John Wiley & Sons, Ltd.
- EFFICACY OF MECHANICALLY REMOVING NONNATIVE PREDATORS FROM A DESERT STREAM
- Authors: D. L. Propst; K. B. Gido, J. E. Whitney, E. I. Gilbert, T. J. Pilger, A. M. Monié, Y. M. Paroz, J. M. Wick, J. A. Monzingo, D. M. Myers
Abstract: Native fish faunas throughout the American Southwest have declined dramatically in the past century, mainly a consequence of habitat alteration and alien species introductions. We initiated this 6-year study to evaluate the efficacy of mechanical removal of nonnative predaceous rainbow trout Oncorhynchus mykiss, brown trout Salmo trutta, yellow bullhead Ameiurus natalis and smallmouth bass Micropterus dolomieu from an open 4.6-km reach of West Fork Gila River in southwest New Mexico, USA. Removal efforts involved intensive sampling with a 10- to 12-person crew using backpack electrofishers and seines to capture fish over a 4- to 5-day period each year. Additionally, two reference sites were sampled with similar methods to compare temporal changes in species mass in the absence of a removal effort. Results were mixed. Mass of yellow bullhead, rainbow trout and brown trout declined in the removal reach from 2007 through 2012, but there was no change in smallmouth bass. Concurrently, mass of Rainbow trout, yellow bullhead and smallmouth bass did not change at reference sites, but brown trout mass declined, indicating factors other than removal were driving abundance of brown trout. Occurrence of several large flathead catfish Pylodictis olivaris in the removal reach in 2012 changed what would have been a decline in overall nonnative mass to no change over the course of the study. Spikedace Meda fulgida was the only native species positively responding to predator removal. Results of this study suggest that with moderate effort and resources applied systematically, mechanical removal can benefit some native fish species, but movement of problem species from surrounding areas into removal reaches necessitates continued control efforts. Copyright © 2014 John Wiley & Sons, Ltd.
- OBSERVATIONS OF RIPARIAN TREE GEOMETRY AND BANK CHARACTERISTICS ALONG A
BANK STABILITY GRADIENT AT THE SOUTH RIVER, VA
- Authors: S. Stotts; M. A. O'Neal, J. E. Pizzuto
Abstract: In this study, we evaluate the use of riparian tree-geometry and bank-characteristic data in developing riverbank stability forecasts at four study sites along a mercury-contaminated reach of the South River, Virginia. Our forecast data set includes measurements of tree diameter, lean angle and percent root-plate undercut, coupled with bank characteristics included in the Pfankuch Index. Stepwise comparisons and statistical analyses of our tree-geometry data reveal that lean angle and percent root-plate undercut are effective measures for discriminating between riparian tree populations at eroding and stable banks, with the strongest discriminant power from the percent root-plate undercut. Our stability forecasts, using both tree and bank characteristics, agree with long-term observations, underscoring the value of rarely used tree-geometry data in such evaluations. The application of these results is important in long study reaches where forecasts of erosion potential from contaminated banks are required to develop mitigation strategies, but direct measurements of bank stability are not feasible. Copyright © 2014 John Wiley & Sons, Ltd.
- RISK-BASED APPROACH TO DESIGNING AND REVIEWING PIPELINE STREAM CROSSINGS
TO MINIMIZE IMPACTS TO AQUATIC HABITATS AND SPECIES
- Authors: J. M. Castro; A. MacDonald, E. Lynch, C. R. Thorne
Abstract: Extensive new pipeline systems proposed to transport natural gas and oil throughout North America will potentially result in thousands of new stream crossings. The watercourses encountered at these crossings will range from small, ephemeral headwater streams to large, perennial mainstem rivers; from dynamic gravel-bed streams to stable bedrock channels; and from steep, source reaches to low gradient, response reaches. Based on past experience at pipeline crossings, the potential for both short and long-term negative impacts on aquatic habitat and species is substantial. In assessing potential hazards to aquatic habitat and species, the diverse physiography and ecology of the stream affected, combined with the number and range of new pipelines proposed, pose significant challenges for project developers charged with collecting, stratifying, evaluating, analysing, interpreting, and presenting stream crossing data in formats that are accessible, usable and useful. It is equally challenging for project reviewers to detect, distill and summarize potential project impacts and then identify reasonable options for their avoidance, minimization, and mitigation. To address these concerns, the US Fish and Wildlife Service, in conjunction with Ruby Pipeline, LLC, developed a pipeline crossing framework and risk analysis approach to stratify potential aquatic impacts, based on both stream characteristics and project types. In this approach, pipeline crossings are ranked in terms of relative short and long-term risk to aquatic habitat and are then analysed, designed, and monitored in ways appropriate to their risk. This approach allows project developers and reviewers to focus resources and monitoring on the crossings that present the highest risks to aquatic habitat and species, while expediting design and construction, and minimizing the monitoring of low-risk crossings. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- HYDROLOGICALLY BASED ENVIRONMENTAL FLOW METHODS APPLIED TO RIVERS IN THE
MARITIME PROVINCES (CANADA)
- Authors: J. Caissie; D. Caissie, N. El-Jabi
Abstract: The demand for water withdrawal continues to increase worldwide. These water withdrawals from rivers can affect fish habitat and aquatic life. As such, environmental flow assessment methods are used in order to protect rivers against excessive water withdrawals. The concept of environmental flow relates to the quantity of water required in rivers to sustain an acceptable level of living conditions for aquatic biota at various phases of their development. For many agencies, environmental flow methods are essential in environmental impact assessments and in the protection of important fisheries resources. The present study deals with the evaluation of hydrologically based environmental flow methods within the Maritime Province of Canada. In total, six hydrologically based environmental flow methods were compared using data from 52 hydrometric stations across the region. Some methods provided adequate environmental flow protection (e.g. 25% mean annual flow and Q50 flow duration method); however, other methods did not provide adequate flow protection (e.g. Q90 flow duration method and 7Q10 and 7Q2 low-flow frequency). The 70% Q50 method provided adequate flow protection only under good baseflow conditions and should be applied with extreme caution. The present study shows the importance of the hydrologic flow regime, particularly as it pertains to the baseflow component, as a significant determinant in the level of instream flow protection. © 2014 Her Majesty the Queen in Right of Canada. River Research and Applications © 2014 John Wiley & Sons, Ltd.
- THE RETURN OF ATLANTIC SALMON (SALMO SALAR L.) AND IMPROVED WATER QUALITY
IN URBAN RIVERS IN OSLO, NORWAY
- Authors: S. J. Saltveit; J. E. Brittain, T. Bremnes, Å. Brabrand, T. Bækken
First page: 571
Abstract: Most rivers and streams in the city of Oslo, Norway, rise in the surrounding forests, and all run through industrial and urban areas before they reach the sea. Most of these rivers have a long history of poor water quality in the middle and lower reaches until the early 1980s. This was reflected in low benthic diversity and the absence of fish. However, at the end of the 1970s, considerable efforts were made to limit industrial discharges, pollution episodes, and urban runoff, resulting in a substantial improvement in water quality. This improvement in water quality resulted in major changes in the benthos and fish populations of the rivers, especially the river Akerselva, which runs through the city centre. Here Atlantic salmon (Salmo salar) became extinct in the mid-1800s and did not return until 1983. Atlantic salmon and sea trout (Salmo trutta) now spawn in the lower reaches, and the river supports juvenile populations of these salmonids. In line with the improvement in water quality, benthic biodiversity has also increased. These improvements have been documented based on long-term monitoring of benthos and fish. Increased benthic diversity and presence of fish also enabled the authorities to trace the source of several pollution episodes that led to fish kills. The European Union Water Framework Directive will bring further pressure to maintain a stable and good ecological status for the Oslo rivers, although it may be difficult to attain this goal in an urban environment. Copyright © 2013 John Wiley & Sons, Ltd.
- IMPLEMENTING ENVIRONMENTAL FLOWS IN SEMI-REGULATED AND UNREGULATED RIVERS
USING A FLEXIBLE FRAMEWORK: CASE STUDIES FROM TASMANIA, AUSTRALIA
- Authors: C. J. Bobbi; D. M. Warfe, S. A. Hardie
First page: 578
Abstract: Despite the many methodologies available for undertaking environmental flow assessments, there are few published examples of environmental flow recommendations that arise from those assessments, and even fewer that evaluate their implementation. This is somewhat surprising considering environmental flow recommendations are effectively testable hypotheses of flow-ecology responses. We describe a framework to guide the assessment and recommendation of environmental flow regimes in Tasmania, Australia, where environmental values are highly catchment specific and rivers are largely semi-regulated or unregulated. This means that environmental flows must be focussed on setting water use thresholds to prevent degradation in condition, rather than delivering water to restore condition. The framework retains the philosophy and elements of many other methodologies but differs by having the flexibility to support application across different catchments while catering for catchment-specific issues. We present two case studies that demonstrate the application of our Framework, its use in the development of scientifically defensible environmental flow recommendations, and their implementation in catchment water management plans. The strengths of the Framework are: (i) using specific ecosystem values to define and communicate the objectives of environmental flows; (ii) using a non-prescriptive and flexible approach to incorporate catchment-specific issues; and (iii) framing recommendations in a manner that clearly illustrates flow linkages with ecosystem values so that stakeholders and managers understand the risks associated with water abstraction. Our experience demonstrates the imperative that scientists are not only involved in water planning but also in the implementation, monitoring, and evaluation of plans so that the benefits of adaptive management can be realized. Copyright © 2013 John Wiley & Sons, Ltd.
- HYDRAULIC GEOMETRY AND LONGITUDINAL PATTERNS OF HABITAT QUANTITY AND
QUALITY FOR RAINBOW TROUT (Oncorhynchus mykiss)
- Authors: J. J. Laliberte; J. R. Post, J. S. Rosenfeld
First page: 593
Abstract: We developed predictions of habitat quantity and quality for three life stages of rainbow trout, Oncorhynchus mykiss, across a range of stream sizes characterized by mean annual discharge of 1 to 50 m3 s−1. The physical habitat template was created by nesting a reach-scale two-dimensional hydrodynamic model (River2D) within a downstream hydraulic geometry system using published coefficients for low-gradient and high-gradient watersheds. This provided both longitudinal and transverse estimates of depth and velocity profiles that, when combined with habitat suitability curves for the life stages, resulted in predictions of habitat quantity (weighted usable area) and habitat quality (the proportion of the stream profile that provided useable habitat) for rainbow trout along the stream continuum. Habitat quantity increased asymptotically for all life history stages but increased more rapidly in the low-gradient watershed. Habitat quality decreased non-linearly for young-of-the-year and peaked at intermediate stream sizes for juveniles in both low-gradient and high-gradient watersheds. Adult habitat quality peaked in the high-gradient watershed but increased asymptotically in the low-gradient watershed, presumably due to lower mean velocities at larger stream sizes. Incorporation of transverse variation in depth and velocity in our physical habitat template provides a more realistic representation of habitat quantity and quality than do earlier assessments based on simple modal estimates of depth and velocity. Copyright © 2013 John Wiley & Sons, Ltd.
- MASS OCCURRENCE OF BLOODSUCKING BLACKFLIES IN A REGULATED RIVER REACH:
LOCALIZATION OF OVIPOSITION HABITAT OF SIMULIUM TRUNCATUM USING DNA
- Authors: Å. Brabrand; T. Bremnes, A. G. Koestler, G. Marthinsen, H. Pavels, E. Rindal, J. E. Raastad, S. J. Saltveit, A. Johnsen
First page: 602
Abstract: In order to understand the factors giving rise to a stable and annual outbreak of the pest blackfly species Simulium truncatum (Lundström, 1911) (Simuliidae), the oviposition habitat has been localized and the egg density quantified at different contour levels in the studied regulated river channel bank. Larvae and adults of 12 blackfly species were identified to species based on morphology. As reference library for subsequent species identification of eggs and small larvae, these specimens were subsequently DNA sequenced for the barcode gene cytochrome c oxidase subunit I. Interspecific distance was large between species or species complexes (average nearest neighbour distance: 0.14; range: 0.09–0.20), while intraspecific distance was comparatively low except for the Simulium ornatum and Simulium tuberosum species complexes. S. truncatum was the only species located high up in the channel bank. The core oviposition habitat was a steep moist erosion edge with moss and dead roots and with a continuous supply of groundwater. Egg densities were estimated to 42 773–50 274 eggs cm–2. Humid oviposition areas high up on the riverbank, but within the annual spring flood levels, seem to be the basis for annual outbreaks of S. truncatum. The mass occurrence of S. truncatum is a phenomenon probably created by man, directly related to the river regulation regime and the construction of a dam in 1936, which gave rise to the formation of the channel and the erosion edge. Copyright © 2013 John Wiley & Sons, Ltd.
- EFFECT OF A MAJOR FLOOD ON BREEDING AND HABITAT OF THE CRIMSON FINCH
(NEOCHMIA PHAETON): A RIPARIAN SPECIALIST
- Authors: W. A. Houston; R. L. Black
First page: 609
Abstract: Riparian specialists, such as the Crimson Finch (Estrildidae: Neochmia phaeton), are vulnerable to declines in habitat quality, including alterations of flow regime associated with dam construction. Crimson Finches persisted and bred in substantial numbers following two large floods in the Isaac–Connors catchment in early 2008. Major flooding was not detrimental to nesting and breeding success, although the immediate post-flood period was identified as a bottleneck in the availability of riparian grass seed. Crimson Finches nested at 16 m or more above the normal river level (compared with an average of 2–3 m elsewhere in Northern Australia); indicating that they have adapted to the extreme flood peaks in the Fitzroy River basin. The tall river-associated grass Chionachne cyathopoda was a key habitat plant, retaining seed well into the dry season when most other grasses are expended. It also provided abundant seeds following floods, coinciding with peaks in abundance of dependent young finches. The adaptations of both Crimson Finches and Chionachne suggest that increased flooding, predicted by climate change, is unlikely to be a problem. In contrast, a proposed dam on the Connors River may be a threat. River regulation that reduces peaks of major floods may favour introduced riparian grasses over flood adapted native grasses such as Chionachne. Any change in the quantity of this species could be detrimental to persistence of Crimson Finches. Environmental managers should carefully consider the ecology of Chionachne when making decisions about river flows. Copyright © 2013 John Wiley & Sons, Ltd.
- EFFECTS OF GEOMORPHIC PROCESS DOMAINS ON RIVER ECOSYSTEMS: A COMPARISON OF
FLOODPLAIN AND CONFINED VALLEY SEGMENTS
- Authors: J. R. Bellmore; C. V. Baxter
First page: 617
Abstract: The geomorphic template of streams and rivers exerts strong controls on the structure and function of aquatic ecosystems. However, relationships between stream geomorphology and ecosystem structure and function are not always clear and have not been investigated equally across spatial scales. In montane regions, rivers often alternate between canyon-confined segments and unconfined floodplain segments. Yet, few studies have evaluated how this pattern influences aquatic ecosystems. Here, we compared five confined river segments to five paired floodplain segments in terms of allochthonous inputs, aquatic primary producer and invertebrate production, stream retentive capacity, and aquatic invertebrate community composition. We found that floodplains had a higher (up to 4×) retentive capacity, a greater richness (58%) of aquatic invertebrates, and a distinctly different invertebrate community, relative to confined segments. Contrary to our expectations, allochthonous inputs were approximately 2× greater for confined segments, and aquatic primary and invertebrate production exhibited no consistent differences between segment types. However, results did indicate that floodplains had greater overall community respiration than confined segments. Together, these findings suggest that floodplain and confined segments do indeed differ in terms of aquatic ecosystem structure and function but not entirely as expected. Confined segments had greater allochthonous inputs but a lower capacity to retain those inputs, whereas floodplains had a high capacity to retain transported organic matter and also a more diverse community of invertebrates and higher overall community respiration to ‘digest’ retained organic matter. If these findings are generalizable, then they would indicate that confined segments are sources for organic matter within river networks, whereas floodplains act as filters, removing and processing organic matter transported from upstream confined segments. Copyright © 2013 John Wiley & Sons, Ltd.
- PATTERNS OF ICHTHYOFAUNAL DISTRIBUTION AND CONNECTIVITY IN NAVIGABLE AND
FREE-FLOWING REACHES OF A MAJOR RIVER SYSTEM: THE ALLEGHENY RIVER IN
- Authors: D. G. Argent; W. G. Kimmel
First page: 631
Abstract: Connectivity throughout large riverine networks is often compromised by lock and dam (L/D) structures designed to facilitate year-round navigation. The resultant interruption of flow inhibits free passage of aquatic biota potentially isolating mainstem and tributary communities. Our objectives were (i) to evaluate the impact of a series of navigational L/D structures on two targeted fish assemblages (TFAs): large-bodied (>250 mm total length) pelagic and benthic (darter) communities and (ii) to examine patterns of tributary and mainstem connectivity. We systematically captured fishes utilizing gillnets, benthic trawls and backpack electrofishers from an impounded and a free-flowing reach extending over 203 km of the Allegheny River in Pennsylvania. Species richness among the large-bodied targeted fish assemblage was distributed somewhat evenly throughout each pool, peaking near dams and in an undredged pool. Depauperate darter assemblages of low species richness characterized most of the navigable reach with diversity and abundance concentrated in L/D tailrace areas. By contrast, darter communities inhabiting the free-flowing reach were more diverse, abundant and evenly distributed, indicating the influence of uninterrupted connectivity. Community similarity at mainstem/tributary junctions increased with increasing tributary size with 50% of the mainstem species complement also inhabiting the largest tributary. This study underscores the importance of dams as barriers to ichthyofaunal connectivity, particularly to those benthic fishes which are relatively immobile and habitat specific, and the importance of mainstem/tributary junctions as avenues of riverine connectivity. Copyright © 2013 John Wiley & Sons, Ltd.
- THE ECONOMIC VALUE OF MISSOURI RIVER RECREATION: ESTIMATES FROM THE
MISSOURI RIVER PUBLIC USE ASSESSMENT
- Authors: T. B. Treiman; S. L. Sheriff, R. B. Renken, J. Loomis
First page: 639
Abstract: Exit interviews with visitors were used to estimate public use on and along 811 miles of the Missouri River from Gavins Point Dam near Yankton, South Dakota, to the river's mouth near St. Louis, Missouri, during a 13-month period in 2004 and 2005. We estimated both types and amount of public use and the economic value of the river to the users. Economic values of recreation to the public were estimated using both the Travel Cost Method (TCM) and the Contingent Valuation Method (CVM). For these public access and areas, an estimated 2 042 980 individual visits were made to the river, with total economic benefits of the river to users estimated at $12.79 per individual visit (TCM) and $23.65 per individual visit (CVM).We discuss methodological differences between the two methods and the potential utility of this information to river management. Copyright © 2013 John Wiley & Sons, Ltd.
- SPATIAL AND TEMPORAL PATTERNS OF NITRIFICATION RATES IN FORESTED
FLOODPLAIN WETLAND SOILS OF UPPER MISSISSIPPI RIVER POOL 8
- Authors: T. M. Jicha; L. B. Johnson, B. H. Hill, R. R. Regal, C. M. Elonen, M. S. Pearson
First page: 650
Abstract: Overbank flooding is thought to be a critical process controlling nitrogen retention and cycling. Yet, studies aimed at quantifying these effects, specifically nitrification, are relatively few. In this study, we investigated the effects of season and flood frequency on soil nitrification rates in forested floodplains of Upper Mississippi River, Pool 8. Samples were collected from three plots within each site in April, August and November 2006. Plots were equally divided among three flood frequency categories as follows: rare, moderate and frequent based on elevation and flood probability model. We found a significant difference in nitrification rates among flood frequency categories as follows: rare > moderate > frequent (F = 4.49, p summer > autumn (F = 8.88, p
- A ROADMAP FOR RIPARIAN INVASION RESEARCH
- Authors: Samantha L. Greene
First page: 663
Abstract: Riparian habitats provide numerous ecosystem services and support a diversity of ecological processes, yet they are environmentally sensitive landscapes susceptible to species invasion. As the global population grows, urban, exurban, suburban and rural development of riparian landscapes and dependence on the associated ecosystem services will increase. To preserve riparian systems, research should assess causes and consequences of riparian invasion and effective restoration measures across a diversity of biomes. This paper categorizes the types of riparian invasion research studies and investigates research trends in the riparian invasion literature. The analysis shows that research focuses on drivers and patterns of invasion is primarily focused on North America and Europe and is scant in high biodiversity biomes, such as the tropics and humid subtropics. Future population growth is predicted to occur in poorly researched regions. Future riparian invasion research should focus on regions of high biodiversity and identify consequences of invasion and restoration measures. Copyright © 2013 John Wiley & Sons, Ltd.
- MORPHOLOGICALLY RELATED INTEGRATIVE MANAGEMENT CONCEPT FOR RECONNECTING
ABANDONED CHANNELS BASED ON AIRBORNE LiDAR DATA AND HABITAT MODELLING
- Authors: Christoph Hauer; Gottfried Mandlburger, Bernhard Schober, Helmut Habersack
First page: 537
Abstract: Most of the large rivers are heavily degraded and lack near-natural conditions due to high human pressure (agricultural use and settlements) especially on former inundation areas. Hence, it is rarely possible to ‘restore’ predisturbance conditions of rivers and their floodplains. Further, river or floodplain restoration programs are often based on type-specific reference conditions. Those reference conditions are mainly determined on the basis of historical maps not giving any information of, for example, sediment supply, flood frequency and vegetation cover (density). Especially for improving the ecological status of rivers with abandoned channel features, key habitats for target fish species have to be restored by reconnecting floodplains and their secondary channel system. In addition, because of the necessity of improving the ecological status, there is growing interest in interdisciplinary river restoration techniques. Within the presented article, an integrative concept is derived based on Light Detection and Ranging measurements and numerical modelling with respect to river dynamics (hydrologic and morphological). Further habitat modelling, based on unsteady depth-averaged two-dimensional hydrodynamics, is applied with a focus on the mesounit scale. For testing the conceptual model, various river reaches at the Morava River were selected, featuring different morphological characteristics. It was found that the applied management concept allows considering the important issues of river dynamics (morphological/hydrologic) using a flow- and flood-pulse approach for identifying bottlenecks of target species at the Morava River. The reconnection of abandoned channels will result in an increase of hydromorphological heterogeneity and/or woody debris within the study reach. This might be of high relevance for habitat features (e.g. backwater habitats) especially for flow pulses between low flow and mean flow and/or in reaches without abandoned channels between low-flow and the bankfull stage. Copyright © 2012 John Wiley & Sons, Ltd.
- SHORT-TERM IMPACTS OF LATERAL HYDROLOGICAL CONNECTIVITY RESTORATION ON
- Authors: A.-L. Besacier-Monbertrand; A. Paillex, E. Castella
First page: 557
Abstract: In floodplain ecosystems, the lateral hydrological connectivity between the main river channel and the secondary channels plays a major role in shaping both the habitat conditions and the macroinvertebrate diversity. Among other threats, human activities tend to reduce the lateral connectivity, which increases floodplain terrestrialization and induces a loss of aquatic biodiversity. Consequently, the restoration of lateral connectivity is of growing concern. We studied four secondary channels of the Rhône floodplain that were subjected either to no restoration or to three different restoration measures (river flow increase only, flow increase plus dredging and flow increase plus reconnection to the river). Macroinvertebrate and environmental data were analysed one year before and during a period of five years after restoration. We expected a progressive increase of lateral connectivity according to the type of restoration. Changes in macroinvertebrate assemblages were predicted to be towards more rheophilic communities and proportionally related to the changes in lateral connectivity.In the reconnected channel, lateral connectivity increased and remained high five years after restoration. In the dredged channel, the immediate increase of the lateral connectivity metric induced by sediment removal was followed by a rapid decrease. In the unrestored channel and the channel only influenced by flow increase, the metric remained constant in time. The macroinvertebrate composition and the rarefied EPT richness changes were proportionally related to the changes in lateral connectivity. Alien species richness and densities increased progressively in all channels after restoration. Our results showed that modifications of the lateral connectivity lead to predictable changes in macroinvertebrate diversity. Synergistic interactions between restoration and longer-term changes (e.g. climatic change, invasion of alien species) encourage long-term monitoring to assess the durability and trends of restoration measures. Copyright © 2012 John Wiley & Sons, Ltd.