bluuebunny/crossref_metadata_2025 huggingface dataset:
Typology of aquatic habitats in the great ouse, a small regulated lowland river
Authors: Copp Gordon H.
Published: February 2007

A study of aquatic habitat types was undertaken in August 1989 on the River Great Ouse. Habitat character at 44 sites was evaluated via twelve qualitative and quantitative environmental variables. Discriminant Analysis of the environmental data revealed a weak discrimination of sites corresponding with longitudinal changes in channel width. Distinction between the habitat types in the analysis was relatively weak. Compared with unregulated European lowland rivers of similar geomorphological origin, the Great Ouse possesses little transversal habitat diversity (abandoned channels, oxbows, etc.) and the ponding effect of water retention structures in downstream sections appears to have created a slight longitudinal gradient in channel width and depth. This comparatively low habitat heterogeneity corroborates a previous report of limited recruitment in the Great Ouse by 0 + fishes of both limnophilous and rheophilous reproductive guilds, with a predominance of generalist spawners.
Macroinvertebrate assemblages in floodplain habitats of the lower river murray, South Australia
Authors: Boulton A. J. , Lloyd L. N.
Published: February 2007

Macroinvertebrates were sampled in seven microhabitats (submerged woody debris, reeds, sedges, inundated grass, floating aquatic vegetation, lignum, and the unvegetated littoral) at thirteen sites representing six macrohabitats (single temporary and permanent ox‐bow lakes (billabongs), fast and slow‐flowing anabranches, backwaters, and the main channel) of the River Murray, and Australian lowland river. Sites were sampled in spring 1988, shortly after floodwaters had receded.

Most of the 95 taxa collected were aquatic insects. Detritivores were most abundant in all macrohabitats except the temporary billabong where predators predominated. Scrapers were only abundant in the permanent billabong. The temporary billabong harboured the most species and individuals whereas slowly‐flowing anabranches contained the fewest species and individuals. At the microhabitat level, most taxa and individuals occurred in stands of aquatic vegetation. The unvegetated littoral zone was the most depauperate microhabitat.

Multivariate analyses illustrated the distinctiveness of the faunal assemblage found in the temporary billabong. Subsequent analyses of the permanently inundated macrohabitats indicated gradients related to current velocity and the extent to which the sites were continuous with the main river. Current velocity apparently determined assemblage composition at the macrohabitat scale whereas the structural complexity of submerged vegetation operated at the microhabitat scale.

The relatively large number of taxa collected from this area emphasizes the importance of a range of macrohabitats and microhabitats to faunal diversity in a floodplain ecosystem. Although there was little faunal overlap between billabongs and the main river, billabongs probably serve as refuges for many lentic taxa that rely upon regular inundation to survive. Surveys of floodplain rivers for management purposes must include samples from aquatic habitats adjacent to the main channel because the fauna of the floodplain is potentially most threatened by regulation and alteration of the flooding regime.
Grasshoppers (Orthoptera, Saltatoria) on alpine and dealpine riverbanks and their use as indicators for natural floodplain dynamics
Authors: Reich Michael
Published: February 2007

Gravel banks with sparse vegetation are typical habitats of braided alpine and dealpine floodplains. They are not only habitats for semiaquatic or hygrophilous organisms, but include also xerophilous elements: 17 species of grasshoppers were recorded in the floodplain of the Upper Isar (Bavaria, FRG). In the alpine region, two species (Bryodema tuberculata, Chorthippus pullus) occur only in floodplains, colonizing young gravel banks with sparse vegetation. Population dynamics and habitat selection of Bryodema tuberculata, studied on the Upper Isar for several years, are characterized by small scale movements of marked individuals between neighbouring gravel banks and fluctuations of the abundance on different sections of the gravel banks. Furthermore, the periodic desiccation of small watercourses is important for the dispersal of the females by walking. Historically widespread, today its distribution corresponds to the few remaining inundation areas. The main causes of decrease and extinction in most localities are man‐made changes in floodplain dynamics. The building of retention reservoirs and the diverting of streams for hydropower influenced succession in the downstream floodplains. Most of the gravel banks with sparse vegetation changed into willow thickets or pine forests. All remaining inundation areas should be protected. Bryodema tuberculata is a good indicator for the balance between progressing succession and the reorganization of gravel banks by floods.
A floodplain forest mosquito community after man‐made moisture changes (Culicidae, Diptera)
Authors: Vaňhara Jaromír
Published: February 2007

This paper summarizes data on the response of mosquitoes to changed water regime following extensive water management alterations on the southern Moravian Dyje and Morava rivers. Maximum groundwater level dropped by an average of 90 cm, previous regular floods were prevented, and the area covered by floodplain forests was significantly decreased due to the construction of three reservoirs.

The original mosquito community of temporary water bodies (Aedes) is in retreat both quantitatively and, in places, qualitatively. Of the initial number of six species causing plagues, only Ae. vexans has remained (63.3 per cent), the rest occurring at percentages of only 0.1–4.1 per cent. After flood regulation, the breeding grounds of the species developing in temporary water bodies has filled only during periods of sufficiently high groundwater levels and sufficient saturation of soil with rainfall.

A prospective group in this area includes mosquito species developing in permanent water bodies (Culex, Anopheles, Culiseta, etc.). This group is increasing in numbers and species richness. After the completion of three reservoirs, Anopheles spp. spread throughout the study area. They develop in the waters accompanying the reservoirs, especially in channels rich in vegetation, in which they attain densities of up to 39.9 larvae per 100 cm2 water surface. The drier environment, and drier and warmer climate prevailing in recent years have probably influenced the occurrence of southern species in the area, notably Culex martinii and Uranotaenia unguiculata.

Long‐term quantitative collections of mosquitoes enable first note to be made on the possible fluctuation mechanisms, previously obscured by the essential influence of floods on community development.
Variations of the hyporheic zone through a riffle in the r. morava, Czechoslovakia
Authors: Štěrba Otakar , Uvíra Vladimír , Mathur Praveen , Rulík Martin
Published: February 2007

We observed the dynamic changes in the hyporheic zone, both in the vertical (0‐80 cm) and horizontal directions. Two stations with different hydrological conditions were compared, and subsequently related to two basic processes: infiltration of surface water into the sediments of the river bottom and repeated entry back to the surface stream. By comparing these two locations we attempted to show the existence of a continuous exchange of water between the surface of the river and the hyporheic zone in a process which we call ‘small bottom circulation’. At the same time, we also attempted to demonstrate that this process involves the self‐purification of the infiltrated water. We presume that self‐purification is realized both by means of physical processes (filtration, sedimentation and deposition) and by the biological decomposition of organic matter. Self‐purification of the infiltrated water between the stations which were compared are proved, above all, by the values of O2, BOD, COD, FPOM + CPOM, pH and conductivity. There are also remarkable differences in the qualitative composition in the macroinvertebrate community.
Vertical distribution of fauna in the bed sediment of three running water sites: Influence of physical and trophic factors
Authors: Maridet Laurence , Wasson Jean‐Gabriel , Philippe Michel
Published: February 2007

Relationships between invertebrates, substrate characteristics and trophic factors were investigated, with special emphasis on the hyporheic habitat, in order to characterize the functioning of different running waters ecosystems.

Three contrasting study sites were chosen in catchments exhibiting different features: (1) a meandering reach of the Loire River in its alluvial floodplain, upstream of the ‘Bec d'Allier’; (2) a reach of the Galaure with a fairly developed riparian corridor, a small sinuous foothill river; and (3) a braided reach of the Drac, an alpine torrential stream.

Each site was sampled once using the freezing‐core technique with previous electro‐positioning of the invertebrates. In each site, four 60 cm cores were extracted, each one from different morphodynamic units.

In the Loire and Galaure rivers, most invertebrates are found in the first 15 cm of the sediment, with the exception of some particular taxa or morphodynamic units (riffle head). Conversely, in the Drac lotic units, maximum density of invertebrates occurs between 15 and 30 cm and more than 75 per cent of all organisms are found at a depth > 15 cm. The vertical distribution of organisms does not follow a uniform pattern in different streams.

In the substrate, the vertical distribution of macroinvertebrates is very closely related to porosity in contrast with trophic parameters that always decrease with depth. The porosity is negatively correlated with the percentage of sand in the sediment and seems to be important in determining the vertical distribution of fauna, and should be integrated in a functional typology of running waters.

The trophic parameters and the structure of invertebrate community with its dominant feeding groups allow discrimination of the different sites.
Spatial distribution of interstitial assemblages in the floodplain of the rhǒne river
Authors: Marmonier P. , Dole‐Olivier M. J. , Creuz Chǎtelliers M. É Des
Published: February 2007

Interstitial invertebrate assemblages of the Rhǒne River were studied at the scale of the entire alluvial plain. Ten stations, located in five former channels, were sampled with a Bou‐Rouch pump at 50 and 100 cm depth. The chemical characteristics of the interstitial water allowed the differentiation of stations without hydrological connections with the subterranean habitats, stations fed by surface water coming through the bank sediments and stations fed by true groundwater. The faunal assemblages reflect the difference between connected and isolated stations but did not demonstrate any differences related to the origin of the water. In fact the interstitial assemblages are distributed along a gradient from the margin of the floodplain (stations with a high physical stability associated with the absence of flood periods) to the area close to the main channel regularly influenced by floods. These results demonstrate that both groundwater characteristics and the position of the station in the floodplain influence the spatial distribution of interstitial fauna in the alluvial valley of the Rhǒne River.
Spring ecotone and gradient study of interstitial fauna along two floodplain tributaries of the river rhǒne, France
Authors: Chafiq Mohamed , Gibert Janine , Marmonier Pierre , Dole‐Olivier Marie‐José , Juget Jacques
Published: February 2007

The hyporheic zone of two small tributaries of the upper Rhǒne River where they cross the floodplain (approximately 2 km wide) was studied. The streams originate in karstic areas which directly border the floodplain. The surveys were conducted at 11 sites along the course of the two tributaries at a depth of 50 cm in bed sediments. Ten litre samples were collected six times a year with a Bou‐Rouch sampler. The paper examines the distribution of interstitial communities along two transverse (floodplain) profiles, defines the spring ecotone, analyses the heterogeneity, and underlines the importance of the tributaries in the functioning of the floodplain.

A comparison between the spatial distributions of fauna and organic matter content along the two profiles underlines the important relationships between the groundwater and surface environment, and makes it possible to differentiate parts of the floodplain where the exchanges are most intense (interstitial spring, karst/floodplain interface). Along the longitudinal course of these streams, we observe the influence of groundwater circulation on community structure/i.e. the interactions between stream channel, alluvial aquifer and adjacent karstic aquifer.
Colonization of periodically inundated interstitial habitats of an alluvial pond by invertebrates
Authors: Tabacchi Eric
Published: February 2007

The interstitial fauna of an alluvial pond on the floodplain of the Adour River, South‐west France was sampled over a period of 13 months. The pond was connected to the adjacent river through phreatic flow and its water level varied in an annual cycle related to the level of the river. Monthly samples were taken from fixed points along five transects across the pond. The littoral zone was sampled between +20 and −80 cm from the substrate surface. From the seasonal variations in the distribution and abundance of invertebrates, the dynamics of their colonization and decolonization cycles could be elucidated and related to the variations in the groundwater level. Eight different colonization/decolonization cycles were determined, each one being characterized by a ‘typical’ common species. These included both passive and active movements in response to the changes in water level. Many taxa were shown to have behavioural strategies which altered according to the stages of their life cycles. Most aquatic invertebrates were adapted to move into the most stable conditions at a given time of the year. Certain terrestial species were also shown to tolerate short periods of immersion.
The effect of discharge and predation on habitat use by wild and hatchery brown trout (Salmo Trutta)
Authors: Greenberg Larry A.
Published: February 2007

The effects of trout stock, discharge and predation risk on habitat use by brown trout, Salmo trutta, were studied in four artificial streams. Trout stock had no effect on habitat use as both wild and hatchery fish used similar habitats. The presence of pike (Esox lucius) caused trout to decrease their use of pools, the habitat in which pike occurred, and increase their use of other habitats. Decreasing discharge reduced available area of the stream and resulted in fewer fish in the shallow margins. Both decreased flow and increased predation risk caused more overlap in habitat use, and thus increased the potential for intraspecific competition, predation and the use of poorer habitats. The results illustrate the danger of applying habitat use relationships obtained from one stream to all other streams where habitat availability and biotic interactions may differ.
Model study of the negara river basin to assess the regulating role of its wetlands
Authors: Klepper Olivier
Published: February 2007

The Sungai Negara basin covers about 4000 km2 of the Barito river floodplain in south‐east Borneo (Kalimantan). In view of plans to regulate the swamps in this area by impoldering or drainage a model study was initiated to describe the present state of the system and to assess potential impacts of these developments. In this paper a summary of the climatological, hydrological and topographical database is given, and model equations formulated. A comparison between calculated and observed river levels shows good agreement. The model is then used to estimate the increase in peak flows in the hypothetical absence of wetlands in the system. The results show that impoldering large areas of the wetlands would considerably increase the risk of flooding in the area. In another application, the model is used to calculate residence times in the lakes and swamps. This makes it possible to indicate the areas most sensitive for pollution. The results are also useful to assist in a soil mapping study, as only areas with very long residence times (only rain fed) coincide with peat areas.
Water quality changes and effects on fish populations in the hanjiang river, china, following hydroelectric dam construction
Authors: Liu J. K. , Yu Z. T.
Published: February 2007

Since its completion in 1973 the Danjiangkou Dam has markedly changed downstream flows, water levels, temperatures, sediment loads and other water quality characteristics in downstream reaches of the Hanjiang River. There have been changes in the growth, spawning behaviour and overwintering condition of local fish populations, in the composition and abundance of food organisms and in the composition of the commercial fish catch. Despite the changed environment and the absence of a fish pass, fish populations are still able to grow and spawn under the new regime. Where conditions are like those of the Hanjiang River, dams may not necessarily have calamitous consequences for fishery production.
Quantification of daily peak hydropower effects on aquatic fauna and management to minimize environmental impacts
Authors: Moog Otto
Published: February 2007

The effects of intermittent power generation on the fish fauna and benthic invertebrates of several Austrian rivers have been investigated quantitatively. In contrast to the more or less local adverse effects of impoundments or stream channelization, artificial flow fluctuations generally disturb a long section of a given river. Within all the river sections investigated, a breakdown of the benthic invertebrate biomass of between 75 and 95% was observed within the first few kilometres of river length. A reduction of between 40 and 60% of biomass compared with undisturbed areas could be detected within the following 20–40 km. The reduction of the fish fauna is within the same order of magnitude and correlates well with the amplitude of the flow fluctuations. Several reasons for the breakdown are summarized and proposals for the minimization of these detrimental effects of artificial short‐term fluctuations are given.
Conceptual model for quantifying pre‐smolt production from flow‐dependent physical habitat and water temperature
Authors: Williamson S. C. , Bartholow J. M. , Stalnaker C. B.
Published: February 2007

A conceptual model has been developed to test river regulation concepts by linking physical habitat and water temperature with salmonid population and production in cold water streams. Work is in progress to examine numerous questions as part of flow evaluation and habitat restoration programmes in the Trinity River of California and elsewhere. For instance, how much change in pre‐smolt chinook salmon (Oncorhynchus tshawytscha) production in the Trinity River would result from a different annual instream allocation (i.e. up or down from 271 × 106 m3 released in the late 1980s) and how much change in pre‐smolt production would result from a different release pattern (i.e. different from the 8.5 m3 s−1 year‐round release). The conceptual model is being used to: design, integrate and improve young‐of‐year population data collection efforts; test hypotheses that physical habitat significantly influences movement, growth and mortality of salmonid fishes; and analyse the relative severity of limiting factors during each life stage. The conceptual model, in conjunction with previously developed tools in the Instream Flow Incremental Methodology, should provide the means to more effectively manage a fishery resource below a regulated reservoir and to provide positive feedback to planning of annual reservoir operations.
Juvenile competitive bottleneck in the production of brown trout in hydroelectric reservoirs due to intraspecific habitat segregation
Authors: Hegge Ola , Hesthagen Trygve , Skurdal Jostein
Published: February 2007

Resource utilization and growth of brown trout were studied in four deep (mean depths 16.2–37.5 m) Norwegian hydroelectric reservoirs by benthic and pelagic gillnet sampling. In all the reservoirs supplementary stockings are carried out. The brown trout were spatially segregated according to size as the habitat use of small individuals (< 180–220 mm) was completely restricted to benthic habitats, whereas larger individuals mainly utilized the upper strata of pelagic waters. It is argued that the pelagic habitat is the more rewarding, and that small‐sized brown trout are forced into the less favourable benthic habitat through social interactions with larger specimens. This is supported by an increase in growth of brown trout from their third to fifth year of life, which seems to be related to the shift from benthic to pelagic behaviour. It is also argued that the conditions for small‐sized brown trout may be a bottleneck in the capacity to produce brown trout in hydroelectric reservoirs with limited benthic feeding conditions, despite ample access to food in pelagic habitats.

When evaluating the possibility of increasing the yield of brown trout through supplementary stockings, it is therefore important to consider food and growth conditions for all age and size groups of brown trout. In reservoirs with poor benthic feeding conditions it may be necessary to stock with brown trout of sizes that are large enough to utilize pelagic habitat, to avoid the limiting benthic living stage.
Use of the abundance/biomass method for comparison of fish communities in regulated and unregulated lowland rivers in Belgium
Authors: Coeck J. , Vandelannoote A. , Yseboodt R. , Verheyen R. F.
Published: February 2007

The abundance/biomass comparison (ABC) method, proposed by Warwick (1986) for detecting pollution effects on marine macrobenthic communities, was tested on distribution patterns of numbers and biomass among fish species in regulated and non‐regulated lowland rivers in Belgium. The biomass and abundance of the fish populations were determined by electrofishing. The sample sites represent a range of physically disturbed watercourses, from natural meandering to heavily channelized reaches. Sites upstream and downstream from a polluting discharge were also evaluated. The physical habitat and water quality were measured on each site. Our data show a significant correlation between the qualitatively measured physical habitat and an ABC index, calculated from the ABC graph data. A significant correlation was also found between the pollution level and the ABC index. It is concluded that the ABC method is applicable to the assessment of disturbance in fish communities in rivers, and that the method gives information about both pollution and physical disturbance. The ABC method is a useful instrument to assess the status of a fish community before and after river channel works or natural and human induced river restorations.
Effect of habitat improvement on atlantic salmon in the regulated river suldalslågen
Authors: Raastad Jan E. , Lillehammer Albert , Lillehammer Leif , Kaasa Halvard , Eie Jon A.
Published: February 2007

The River Suldalslågen, which holds a population of large Atlantic salmon, has been regulated twice for hydropower production. The first regulation occurred in 1968 and the second in 1980. Present problems include the reduced density of benthic fauna, the reduced growth rate of young salmon, the low survival of 0+ fish and the increased time required for smoltification. A programme of habitat restoration includes building a rearing channel system where water flow and the substrate can be controlled. The salmon fry are stocked in the rearing channel and in an adjacent tributary stream. The effects on macrobenthos of introduced dead organic material were also studied. Improvement of physical habitat increased the density of benthic animals, and the survival of 1+ salmon was about 30%. Experiments that included adding of 115g wheat/m2 resulted in a threefold increase in benthic fauna compared with a control area. The largest increase in numbers was in Chironomidae in August‐September, when benthic Crustacea also showed a significant increase. An increase in macrobenthos is expected to increase the growth and survival of young salmon fry.
Efficiency of fishways and impact of dams on the migration of grayling and brown trout in the Glomma river system, south‐eastern Norway
Authors: Linløkken Arne
Published: February 2007

This study was carried out to assess the efficiency of eight fishways constructed in connection with hydroelectric dams in the Glomma river system in south‐eastern Norway. The fishways were of the pool and weir type, except for one which was of the counter current (Denil) type, and had a discharge of 0.5–1.0 m3/s. During 1985–8 3077 grayling and 2995 brown trout were captured in traps in the fishways, measured and floy‐tagged before being released in the river upstream of the fishways. The number of fish captured in two of the fishways were compared with estimated fish stocks in the areas around the fishways. Migrations began in May or June when the water temperature was > 5–6°C. Spawning migration of grayling occurred in May. During May more than 200 grayling may enter a single fishway within a week. In other fishways grayling occur only sporadically before late June or early July, when they migrate upstream to feed. Brown trout migrate during late spring, summer and autumn. The spawning migration takes place more or less during the whole summer, but mostly in late July and August. Immature brown trout also pass through the fishways, with a peak in October in three fishways. This migration is probably an ascending emigration from recruitment areas located downstream of these fishways. The efficiency of these fishways appears low, as the number of fish ascending was less than 2% of the estimated stock within the stretches where 90% of the recaptures occurred. The discharge in the fishway relative to the total discharge seemed to be of great importance, and to achieve efficient fishways they should be constructed for higher discharges, compared with river discharge, than the fishways in this area. The longest migration of grayling was 100 km, whereas the longest migration of brown trout was 122 km. The fish seemed to exploit shorter river stretches in areas influenced by several dams/fishways than fish in an area influenced by only one dam.
Flow regulation and restoration of Florida's Kissimmee river
Authors: Toth Louis A. , Obeysekera Jayantha T. B. , Perkins William A. , Loftin M. Kent
Published: February 2007

Channelization of the Kissimmee River in central Florida destroyed or degraded most of the fish and wildlife habitat once provided by the river and its floodplain wetlands. Between 1984 and 1989 a demonstration project was conducted to evaluate the feasibility of restoring the river's biological resources. Reintroduction of flow through remnant river channels improved river channel habitat diversity and led to favourable responses by fish and invertebrate communities. However, results indicated that more complete restoration of biological attributes will require the re‐establishment of historical inflow characteristics. Owing to the flood control regulation schedule of its headwater lakes, current river discharge regimes are pulse‐like, include extended periods of low or no flow, and have high and low flow periods which are out of phase compared with typical seasonal patterns that occurred before channelization. These flow characteristics will preclude effective river restoration by contributing to chronic low dissolved oxygen regimes and repetitive fish kills, interfering with fish reproduction and limiting floodplain inundation. Simulation modelling was used to develop a modified headwater lakes regulation schedule which re‐establishes season flow patterns, smooths discharge peaks and maintains base flows for a greater portion of the year. Implementation of the new schedule, combined with extensive canal backfilling, will lead to discharge and stage characteristics that meet established criteria for achieving ecosystem restoration goals.
Physical habitat changes and macroinvertebrate response to river regulation: The river Rede, UK
Authors: Petts Geoff , Armitage Patrick , Castella Emmanuel
Published: February 2007

Downstream variations of benthic macroinvertebrate communities on the River Rede below Catcleugh Reservoir, impounded in 1905, are related to a simple index of regulation magnitude, related to hydrological, water quality and trophic changes, and variations of channel morphology. The river is divided into five sectors on the basis of network morphometry and channel form. Channel change to flow regulation is confined to a short (1.6 km) reach immediately below the dam within which channel width and conveyance have been reduced by 53 and 75%, respectively. Downstream, siltation has occurred, but it is patchy and average levels of sediment finer than 2 mm are less than 10%. The main faunal responses — increased abundance and number of taxa — are also confined to the first sector below the dam. Ephemeroptera are shown to be the best describers of the downstream pattern. Variations of the fauna between riffles within sectors are shown to relate to site‐specific hydraulic conditions, especially bed shear stress.
Improvement of fish habitat in a Norwegian river channelization scheme
Authors: Brittain John E. , Eie Jon Arne , Brabrand Age , Saltveit Svein Jakob , Heggenes Jan
Published: February 2007

Techniques for reducing adverse effects of river and lake regulation are being developed and tested within the framework of the Norwegian Biotope Adjustment Programme. The programme is illustrated by studies of a river flowing through the wetland area, Lesjaleirene, which has been drained and channelized to provide additional agricultural land. The channelized river has a homogeneous sand substrate. Experimental placement of rocks and stones increased brown trout densities, especially in areas in contact with the river banks. The new areas of rocks and stones provide cover for fish as well as a greater variation in depth and flow conditions.
Zooplankton population in the river tigris: Effects of samarra impoundment
Authors: Sabri Anmar W. , Ali Zainab H. , Shawkat Serwan F. , Thejar Lamia A. , Kassim Thaer I. , Rasheed Khalid A.
Published: February 2007

The influences of the Samarra impoundment on the ecology of the downstream sector of the river Tigris are investigated. Zooplankton were collected monthly from July 1987 to July 1988. It was found that zooplankton were most abundant during high river discharges in March. During the month of low river discharge, September, the zooplankton population was greatly reduced immediately below the barrage and remained so to the last downstream station. Several factors seem to explain such differences. The high discharge from the impoundment was found to be the dominating factor and may flush the small backwaters in which zooplankton were abundant, thus increasing the population in the river. Zooplankton species vary in their ability to sustain populations in the river, variations which are due mainly to species‐specific characteristics.
Stable carbon and nitrogen isotope analysis of seston in a regulated Rocky Mountain river, USA
Authors: Angradi Ted R.
Published: February 2007

The δ13C and δ15N of seston, organic matter sources (riparian vegetation, algae, macrophytes, plankton) and an invertebrate detritivore were examined in a regulated Rocky Mountain river (fourth order). The isotopic composition of seston varied among sites and seasons for all size fractions; among‐site variation was weakest for ultra‐fine particulate organic matter (< 53 μm). Comminution of seston to ultra‐fine size partially obscured isotopic differences among sites. Multiple isotope signatures of seston were distinct among sites at different distances from a dam (0.5, 5.3, 8.7 km) and between the river and a third order tributary. Seston (> 53 μm) from 0.5 km below the dam was relatively 13C‐depleted (−30 to −28°), reflecting the contribution of reservoir‐derived plankton; seston from the site 8.7 km downstream was relatively 13C‐enriched (−18 to −23°), reflecting autochthonous inputs. Tributary seston had an intermediate δ13C value (−22 to −26°), reflecting allochthonous inputs (conifer litter) and macrophyte (Elodea) detrital inputs. δ15N values of seston were generally similar among sites (4–8°) but were more depleted for the tributary (1–4°). Depleted δ15N values (0–2.5°) for seston from below the dam in late summer corresponded to a blue‐green algae bloom in the reservoir. Isotopic shifts of organic matter incubated for 60–90 days in situ were small (< 2°) and varied in direction depending on isotope and litter type. The isotopic composition of stonefly larvae, Pteronarcys californica, varied among sites, and closely matched that of the local seston (especially FPOM), suggesting that with respect to detritus origin, larvae were opportunistic foragers. The origin of organic matter is influenced by flow regulation, resulting in compressed isotopic gradients.
Application and testing of a procedure to evaluate transferability of habitat suitability criteria
Authors: Thomas Jeff A. , Bovee Ken D.
Published: February 2007

A procedure designed to test the transferability of habitat suitability criteria was evaluated in the Cache la Poudre River, Colorado. Habitat suitability criteria were developed for active adult and juvenile rainbow trout in the South Platte River, Colorado. These criteria were tested by comparing microhabitat use predicted from the criteria with observed microhabitat use by adult rainbow trout in the Cache la Poudre River. A one‐sided X2 test, using counts of occupied and unoccupied cells in each suitability classification, was used to test for non‐random selection for optimum habitat use over usable habitat and for suitable over unsuitable habitat. Criteria for adult rainbow trout were judged to be transferable to the Cache la Poudre River, but juvenile criteria (applied to adults) were not transferable. Random subsampling of occupied and unoccupied cells was conducted to determine the effect of sample size on the reliability of the test procedure. The incidence of type I and type II errors increased rapidly as the sample size was reduced below 55 occupied and 200 unoccupied cells. Recommended modifications to the procedure included the adoption of a systematic or randomized sampling design and direct measurement of microhabitat variables. With these modifications, the procedure is economical, simple and reliable. Use of the procedure as a quality assurance device in routine applications of the instream flow incremental methodology was encouraged.
Particulate organic matter transport in the lower Colorado river, South‐Western USA
Authors: Lieberman Davine M. , Burke Thomas A.
Published: February 2007

The lower Colorado River from Laughlin, Nevada, to the border with Mexico is one of the most regulated rivers in North America. An analysis of particulate organic matter (POM) transport through the system was made to determine POM concentrations, composition and point of origin, as well as to determine the effect dams had on this transport. Particulate organic matter concentrations generally increased from upstream to downstream, and were dominated by very fine organic detritus (< 25μm size fraction). Reservoirs released more POM than they received during spring and summer, but less during autumn and winter. Reservoirs recycled POM, taking in organic detritus and discharging small limnoplankton. Backwater complexes functioned as filters during storm events, trapping coarse material and releasing fine material. Agricultural drains made only minor contributions of POM, but provided important nutrients for in‐channel production of POM. Water diversions forced POM off‐channel, whereas sluicing operations reduced inorganic loads in the canals. Despite the presence of six mainstem dams, the lower reaches support a diverse assemblage of detritivorous fishes, similar to that found in the lowermost reaches of natural, unregulated rivers. The food base for this fishery stems from autochthonous production of POM.
Dissolved organic carbon dynamics in the upper rhone: The influence of side‐arms?
Authors: Cellot B. , Rostan J. C.
Published: February 2007

Dissolved organic carbon (DOC) dynamics were investigated over a two year period in the Upper Rhǒne River to examine the role of side‐arms in providing DOC to the main channel in relation to discharge fluctuations, especially floods. Concentrations of DOC are shown to remain low in space and in time (average 1.5 mg −1) and to be more related to global hydrological events (precipitation) than to any local flushing for backwaters during floods. The results do not support the general assumption that side‐arms are the providers of DOC to the main channel.
Vertical distribution of coarse particulate organic matter in river bed sediments (Morava river, Czech Republic)
Authors: Rulík Martin
Published: February 2007

The vertical and temporal distribution of coarse particulate organic matter (CPOM) larger than 1 mm from 0 to 70 cm depth within the substrate was observed at two different sites along a riffle in the River Morava. Samples of hyporheal sediments were taken by inserting a steel cylinder and a special grab. The amount of CPOM was determined by combustion. The maximum amount of CPOM was found at a depth of 30‐40 cm; lower levels of CPOM were observed in deeper horizons. The average amount of CPOM in 10cm layers (volume 1582.9 cm3) was 232.2 gm−3 at station A and 691.3 gm−3 at station B. The content of CPOM showed a maximum during the summer.
Alteration of patch boundaries on the floodplain of the regulated river trent, UK
Authors: Large A. R. G. , Prach K. , Bickerton M. A. , Wade P. M.
Published: February 2007

Investigations were carried out into the contemporary distribution and structure of the vegetation communities at Gunthorpe, Nottinghamshire on the floodplain of the River Trent. A 60 km reach of the river was examined to determine the overall distribution and structure of vegetation communities; the Gunthorpe site was chosen as a representative example. Three hundred and thirty‐nine separate plots were examined and the site contained 132 species. It is clear that the extent of zones of discontinuity or transition (ecotones) between different vegetation patches has decreased due to long‐term land‐use management. The overall number of vegetation patches has also been reduced. A hierarchy relating boundaries to external influences is proposed and the relationship of ecotones to more clearly differentiated patch habitats identified. Highest species diversity is seen to be associated with the transition zones or ecotonal habitats, particularly under conditions of moderate disturbance intensity. It is concluded that the ecotones remaining still provide a habitat for a wide range of species with differing autecological requirements, but all typical of less disturbed alluvial meadows and marshes. These zones of transition potentially provide a pool for species expansion given improved ecological conditions following river restoration measures.
Application of mobile acoustic techniques fish surveys in shallow water: The river seine
Authors: Guillard Jean , Boet Philippe , Gerdeaux Daniel , Roux Philippe
Published: February 2007

Mobile acoustic techniques (echo‐sounding and echo‐integration) for fish surveys were used in shallow waters of depths less than 5 m. These techniques show the importance of fish biomass in the side‐channels and the detection of echoes in the main channel. Diurnal spatial migrations are seen. The advantages and limitations of the method as a complement to traditional sampling methods in the river are examined.
Determination of ecologically acceptable flows in rivers with seasonal changes in the density of macrophyte
Authors: Hearne John , Johnson Ian , Armitage Patrick
Published: February 2007

The Instream Flow Incremental Methodology (IFIM) is a procedure that has been applied to the rivers of many countries to determine the relationship between discharge and a measure of the physical habitat area available to aquatic species. PHABSIM is a software package that is used to perform the calculations required for the IFIM procedure. Published data on instream macrophyte growth in chalk streams are used here to test the seasonal effects of plant growth in a hypothetical channel. The results show how these effects can significantly distort PHABSIM results. The predicted weighted useable area can differ by as much as 34% depending on the season used for the principal calibration of the Water Surface Profile module (WSP) of PHABSIM. An algorithm is proposed for use with PHABSIM which allows the effects of changes in macrophyte biomass to be included.
Hydraulic study of a two‐stage river channel
Authors: Myers W. Robert , Lyness John F.
Published: February 2007

Many regulated rivers have compound or two‐stage cross‐sections consisting of a deep main channel flanked by one or two floodplains. Existing methods of assessing discharge capacity in such channels can lead to serious errors, and hence there is a need for the acquisition of flow data to validate models suggested as improvements to existing methods. Stage and discharge data, under both steady and unsteady conditions, were collected from a reach of the River Main in Northern Ireland, which has been reconstructed for flood defence purposes to form a two‐stage channel. The data were analysed using a steady flow computational model to yield water surface profiles and values of Manning's resistance coefficient at various flow depths. The complex nature of flow resistance in two‐stage channels is demonstrated. Unsteady stage hydrographs were linked to a computational model which illustrates the magnitude of errors incurred in applying conventional methods of discharge estimation in compound rivers.
Effects of draining and desilting a small weir on downstream fish and macroinvertebrates
Authors: Doeg T. J. , Koehn J. D.
Published: February 2007

Draining a small off‐take weir in February 1991 before desilting introduced large amounts of sediment (at least 100m3) into the downstream creek. Increased suspended solids concentrations up to 4610 mg/l were recorded downstream during the release. Large volumes of sand were deposited close to the weir, with finer fractions (silt) deposited up to 2 km further downstream. Very fine silt was washed through the system to a major river 4.5 km below the weir. Over the first day of the release, at a site 2.1 km below the weir, there was a reduction of 19.4% in the total number of benthic macroinvertebrate taxa, and average reductions of 63.9% in the abundance of and 39.7% in the number of taxa per sample. Over the following 45 days the fauna recovered towards pre‐release diversity and density. This recovery was not sustained and further reductions in diversity and abundance were recorded over the following five months, probably due to fresh disturbance from desilting works and further mobilization of sediment during high flows. A major storm and flood in September 1991 apparently flushed all additional silt from the creek and the macroinvertebrate fauna subsequently recovered to higher diversity and density levels than before the release.

Compared with densities recorded in 1985 and 1988, the population of river blackfish (Gadopsis marmoratus) was reduced by 93% after the release at a site 250m downstream of the weir, with reductions of 81 and 59% at distances from the weir of 2.1 and 2.7 km, respectively. An additional reduction in this fish population occurred at the lower site in late 1991, probably due to further flushing of sediments during the September flood. Although reductions in fish numbers occurred across the whole population, greater reductions were recorded for the younger age classes. Small subsequent increases in fish numbers at upper sites during 1992‐1993 indicated that a recovery of the blackfish population may be occurring through recruitment, but such a recovery will only be confirmed over the long term.
Addressing nonscientific presuppositions in genetics using a conceptual change strategy
Authors: Mbajiorgu N. M. , Ezechi N. G. , Idoko E. C.
Published: February 2007

Researchers are becoming aware of the influence of students' presuppositions in directing their construction of science concepts. When these are entrenched and drastically nonscientific, they predispose the children to alternative explanatory frameworks that are inhibiting, especially in a knowledge domain such as genetics. In this study, we identified such nonscientific presuppositions among 17‐ to 18‐year‐old secondary school students from the Igbo community of Southeastern Nigeria. We designed a research‐based instructional model to address these presuppositions. The relationship between the levels of nonscientific presuppositions held by students and their achievement in genetics was assessed. Finally, the effect of the instructional model on students' relinquishing these nonscientific presuppositions and on their achievement was determined relative to a comparison group. It was found that this group of students had nonscientific presuppositions that they used in explaining genetic phenomena, and that the present instructional model aided the students in relinquishing these nonscientific presuppositions to a great extent. We conclude that a conceptual change model that addresses explicitly nonscientific presuppositions will lead to an increased understanding of science concepts. © 2007 Wiley Periodicals, Inc. Sci Ed 91:419–438, 2007
Positron backscattering from an Al target: analytical calculation and Monte Carlo simulation
Authors: Bentabet A. , Bouarissa N.
Published: February 2007

Positron backscattering coefficients are analytically calculated and numerically simulated for an Al target in the positron energy range 0.50–4 keV and for incident angles between 0° and 80° . The differential elastic scattering cross section has been obtained using the Bentabet and Bouarissa approximation (Phys. Lett. 2006; A 355: 390). Both the analytical and simulated results show good agreement with the experiment and previous theoretical work. Copyright © 2007 John Wiley & Sons, Ltd.
Rice Starch Molecular Size and its Relationship with Amylose Content
Authors: Park In Myoung , Ibáñez Ana Maria , Shoemaker Charles F.
Published: February 2007

The composition and starch molecular structure of eight rice varieties were studied. Waxy and non‐waxy (long‐, medium‐, and short‐grain) rice varieties from California and Texas were used. The amylose contents were measured using the Concanavalin A method and were found to be related to the type of rice: waxy ≈ 1.0%, short and medium grain 8.7–15.4%, and long grain 17.1–19.9%. The weight‐average molar masses (Mw) of the starches varied from 0.52 to 1.96×108 g/mol. As would be expected, a higher Mw of rice starch correlated to lower amylose content. The range of Mw of amylopectin was 0.82 to 2.50 ×108 g/mol, and there was also a negative correlation of amylopectin Mw with amylose content. Amylose Mw ranged from 2.20 to 8.31×105 g/mol. After debranching the amylopectin with isoamylase, the weight‐average degree of polymerization (DPw) for the long‐chain fraction correlated positively with a higher amylose content. California and Texas varieties were significantly different in their amylose content, starch Mw (short‐ and medium‐grain only), and amylopectin Mw (p < 0.05).