bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of shell strength in selective foraging by crayfish for gastropod prey
Authors: Brown K. M. 
Published: March 2003

Summary1. Four gastropods common in Wisconsin lakes, Amnicola limosa, Gyraulus parvus, Physella gyrina and Helisoma anceps, were exposed to predation by three crayfish congeners, Orconectes rusticus, O. propinquus and O. virilis in the laboratory to determine prey preference.2. There were no differences in prey choice among the crayfish congeners, but there were clear differences in electivity for the different snail prey.3. Crayfish had higher electivities for the thin‐shelled, plano‐spiral pulmonate Gyraulus parvus, despite its lower abundance in samples, than the thicker‐shelled prosobranch Amnicola limosa. Electivity for another plano‐spiral pulmonate, Helisoma anceps, was low, evidently because of its relatively thick shell and larger size. Amnicola limosa and the thin‐shelled pulmonate Physella gyrina (present at roughly the same relative abundance as Gyraulus parvus) were neither selected nor avoided.4. Crayfish electivity appears to be a function of the resistance of shells to chipping by crayfish mandibles. Although different species are preferred, this is similar to the previously described selection of thin‐shelled species by sunfish.
Influence of hypolimnetic hydropeaking on the distribution and population dynamics of Ephemeroptera in a mountain stream
Authors: Céréghino R. , Lavandier P. 
Published: March 2003

Summary1. The Ephemeroptera assemblage of the River Oriège (Pyrenees, France) was studied up‐ and downstream of a hydroelectric power plant with hypolimnetic releases from a nearby high altitude reservoir. The life histories and larval growth of the six dominant species (Rhithrogena semicolorata, R. sp. gr. hercynia, R. kimminsi, Baetis alpinus, B. rhodani, Ephemerella ignita) were studied 700 m upstream (site A) and 700 and 3500 m downstream (sites B and C, respectively) of the power plant. Their drift patterns were studied at sites A and B.2. The natural flow of the river was preserved when the plant was inoperative. During power generation, flow and temperature were the two main environmental factors modified. The natural flow in the river below the outlet may be enhanced several times a day from 1 to 11 m3 s–1 in summer and winter, and from 5 to 15 m3 s–1 during spring spates. During hydropeaking, the water was cooled in summer and slightly warmed in winter, but this was attenuated 3500 m downstream from the plant.3. The density and biomass of the species studied at the three sites reflected both the impact of hydropeaking and the natural longitudinal zonation of the fauna. The lowest density and biomass was estimated at 700 m downstream from the plant (site B), consistent with a prominent role for hydropeaking. Site A showed constant mayfly drift caused by accidental dislodgement plus behavioural drift that was mainly nocturnal. Below the plant, the flushing action of peaking flows added to this a catastrophic drift, which was highest in autumn when the difference between natural and peak flows was greatest.4. Environmental change caused only slight modifications in the life history patterns, affecting the hatching and/or emergence period and growth of several species. For instance, R. semicolorata grew through the winter below the outlet, when growth was slight upstream from the power plant. Under this kind of river regulation (natural discharge and temperature except during periods of power generation, and intermittent hydropeaking from a separate reservoir) modifications of the thermal regime had a minor effect on the population dynamics of mayflies, unlike hydraulic disturbances which strongly influenced the abundance and structure of the benthic community. Frequent (at least daily) high flow disturbances caused depletion of mayfly populations, despite daily renewal and colonization (drift) from undisturbed upstream locations.
Effect of primary producers on the heterotrophic metabolism of a stream biofilm
Authors: Roman Anna M. , Sabater Sergi 
Published: March 2003

1. ,The influence of benthic algae on heterotrophic metabolism in a forested Mediterranean stream was investigated. Bacterial density and ectoenzymatic activities, as well as algal biomass (chlorophyll‐a) and metabolism (the rate of 14C incorporation), were measured during colonization over 60 days of artificial substrata (clay tiles) under light and dark conditions.2. ,Chlorophyll‐a and the rate of 14C incorporation were significantly higher in light‐grown than in dark‐grown biofilms. Bacterial density and ectoenzymatic activity (especially β‐glucosidase) were also significantly higher in light‐grown biofilms.3. ,Regressions of chlorophyll‐a and 14C incorporation values on the ectoenzymatic activities were significant. The slopes of regression lines obtained for dark‐grown biofilms were significantly higher than those obtained for light ‐grown biofilms.4. ,The differences in the slope (of the regression lines) between dark and light‐grown biofilms suggest that the response of the heterotrophs is faster in biofilms with low algal biomass accrual and slows down when algal biomass is increased.5. ,It is concluded that algal accumulation in the epilithic biofilm influences the use of organic matter by the heterotrophic community by increasing the amount of organic substrate available for bacteria.
Effects of physical refuges on fish–plankton interactions
Authors: Bertolo A. , Lacroix G. , Lescher‐Moutouš F. , Sala S. 
Published: March 2003

1.Refuges that reduce fish‐induced mortality of zooplankton are considered to be key factors in controlling phytoplankton growth in lake ecosystems. In order to better understand the role of physical refuges for zooplankton on zooplanktivorous fish‐plankton relationships, an enclosure experiment was run in a mesotrophic lake. Even‐link systems (zooplankton and phytoplankton) and odd‐link systems (zooplanktivorous fish, zooplankton and phytoplankton) were established. We also established an odd‐link system with a physical refuge for zooplankton where fish predation was limited in the upper half of the enclosure.2.Fish negatively affected density and mean body length of herbivorous zooplankton and total zooplankton, filtering rates with some intermediate effects in the presence of the refuge. A clear refuge effect was observed for the dominant herbivore, Ceriodaphnia. On the other hand, the refuge seemed to increase the vulnerability of those taxa that aggregated in upper layers of the water column. Grazing was thus reduced in both odd‐link systems.3.The lack of significant correlation between nutrient availability and phytoplankton biomass in enclosures suggested a top‐down control of algal growth in our experimental systems. In both odd‐link systems (‘fish’ and ‘refuge’) phytoplankton biomass was significantly enhanced, and transparency was reduced in comparison with the even‐link system.
Patterns of distribution of macroinvertebrate families in rivers of north‐western Australia
Authors: Kay W. R. , Smith M. J. , Pinder A. M. , Mcrae J. M. , Davis J. A. , Halse S. A. 
Published: March 2003

Summary1. The northern half of Western Australia is a large, sparsely populated area with a climate that ranges from monsoonal in the Kimberley to arid in the Gascoyne and Pilbara regions. The aquatic invertebrate fauna is poorly known.2. Fifty‐one sites located on 14 river systems were sampled three times between August 1994 and October 1995. A total of 90 taxa, most identified to family level, were collected. The fauna was dominated by insects, which constituted 74% of the total number of taxa collected.3. Major habitats at each site were sampled separately and sites with more habitats tended to have a richer fauna. All habitats showed significant differences in taxonomic richness between regions. Family richness decreased with increasing latitude, being highest in the Kimberley region and lowest in the Gascoyne.4. Despite the differences in taxon richness between regions, community composition of the aquatic invertebrate fauna at the family level did not differ greatly. Four major groups of sites were identified by cluster analysis, based on the invertebrate families present at each site, but differences between groups were small.5. Significant temporal variation in taxon richness was found in channel habitat but not the three other habitats sampled (riffle, macrophyte, pool‐rocks). Community composition in channel habitat varied temporally among groups of sites identified by cluster analysis but the pattern was not consistent.
Habitat structure along channel‐unit sequences for juvenile salmon: a subunit‐based analysis of in‐stream landscapes
Authors: Inoue Mikio , Nakano S. H. Igeru 
Published: March 2003

1. Habitat structure and habitat use by juvenile masu salmon, Oncorhynchus masou Brevoort, in small streams in northern Hokkaido, Japan, were examined by considering ‘subunits’ (patches within channel units) as structural elements of stream reaches.2. Whole wetted channel surfaces of three study reaches were divided into 0.5 × 0.5 m quadrats, which were grouped into eight subunit types according to water depth and velocity, and substratum conditions by a cluster analysis. The subunit distribution showed a regular mosaic pattern corresponding to the channel‐unit sequence in each of the three reaches.3. Juvenile masu salmon exhibited a strong preference for a subunit type characterized by greater depth and moderate current velocity (deep–moderate subunit; mean depth = 0.29 m; mean velocity = 0.19 m s−1). This subunit type usually occurred downstream of stretches with fast current. The preference of masu salmon for the deep–moderate subunit could be because of its usual spatial position in relation to other subunit types as well as to the characteristics of the subunit itself.4. The results suggest that the value of a habitat is determined not only by the characteristics of the habitat itself, but also by those of adjacent habitats. Therefore, habitat use by stream fish should be studied in the context of the whole ‘in‐stream landscapes’.
Fish habitat preferences in large streams of southern France
Authors: Lamouroux Nicolas , Capra Hervé , Pouilly Marc , Souchon Yves 
Published: March 2003

1. Relationships between fish and their habitat over whole geographic regions, which are evident from studies of many streams and species, can improve understanding of lotic communities and provide reliable management tools. Nevertheless, most habitat preference studies have been based on single sites, and confined to small streams and to game species.2. Regional habitat preference models, based on local velocity, depth and roughness, were developed for twenty‐four species and their size classes commonly found in large European streams. Fish surveys were conducted in six large streams in southern France over an 8‐year period. To limit the influences of habitat variables other than those studied, we estimated fish preferences within each survey and averaged this information across surveys. Preferences were fitted with confidence intervals and their sensitivity to field uncertainty was evaluated.3. Most species and size classes had significant preferences for local habitat conditions which were consistent across the region. Habitat preferences predominant in the region overall were not always observed at any one site, but habitat conditions preferred on average in the region were never actually avoided locally. These results support the use of regional preference models for fish and the development of similar models for other lotic groups whose sensitivity to local habitat conditions has been reported elsewhere.
Lake districts of north‐western Russia: identification of subregions based on analyses of hydrologic data
Authors: Gronskaya T. P. 
Published: March 2003

1. There are more than 400 000 lakes in the north‐western part of European Russia. Data from 50 gauging stations (located on lakes with water surface area ≤ 400 km2), within the region, was used to identify regions that exhibit common hydrologic patterns.2. Analyses of common hydrologic patterns permitted the division of the overall area into four regions within which lakes exhibit common hydrologic and limnologic features.
Spatial and temporal impacts of a diesel fuel spill on stream invertebrates
Authors: Lytle David A. , Peckarsky Barbara L. 
Published: March 2003

1. We assessed the effects of a 26 500 L diesel fuel spill on the macroinvertebrate fauna of a small trout stream in central New York, U.S.A. To determine the spatial extent of the spill we sampled three locations (0.7, 5.0 and 11.8 km downstream of the spill), each containing a reference site (unaffected tributary) and an impact site (downstream of spill). Sampling was repeated four times over a 15‐month period to assess temporal recovery.2. Immediately after the spill, invertebrate density at all three locations below the spill was significantly lower than reference density. Three months after the spill, density up to 5 km below the spill was still far lower (<100 individuals per sample) than reference density (800–1200 individuals per sample). A year after the spill, density was similar between reference and impact sites, suggesting that invertebrates had recovered numerically.3. Taxonomic richness up to 5.0 km below the spill was less than half the reference taxonomic richness and this difference persisted for at least 3 months. Some significant differences between reference and impact sites were observed after 15 months, but these differences could not be attributed to the oil spill.4. For at least 3 months following the spill, the site immediately downstream of the spill was dominated by Optioservus, a petrochemical‐tolerant riffle beetle. Twelve to 15 months after the spill, both the reference and impact sites near the spill were dominated numerically by the mayfly Ephemerella, but the degree of dominance was twice as large at the impact site.5. We concluded that the diesel fuel spill significantly reduced the density of invertebrates (by 90%) and taxonomic richness (by 50%) at least 5.0 km downstream, but density recovered within a year. Throughout the study, however, the fauna immediately below the spill was species poor and significantly over‐represented by a single dominant taxon, suggesting that 15 months was not sufficient for full community recovery from the oil spill.
Biodiversity: towards a unifying theme for river ecology
Authors: Ward  , Tockner  
Published: March 2003

1. A broadened concept of biodiversity, encompassing spatio‐temporal heterogeneity, functional processes and species diversity, could provide a unifying theme for river ecology.2. The theoretical foundations of stream ecology often do not reflect fully the crucial roles of spatial complexity and fluvial dynamics in natural river ecosystems, which has hindered conceptual advances and the effectiveness of efforts at conservation and restoration.3. Inclusion of surface waters (lotic and lentic), subsurface waters (hyporheic and phreatic), riparian systems (in both constrained and floodplain reaches), and the ecotones between them (e.g. springs) as interacting components contributing to total biodiversity, is crucial for developing a holistic framework of rivers as ecosystems.4. Measures of species diversity, including alpha, beta and gamma diversity, are a result of disturbance history, resource partitioning, habitat fragmentation and successional phenomena across the riverine landscape. A hierarchical approach to diversity in natural and altered river‐floodplain ecosystems will enhance understanding of ecological phenomena operating at different scales along multidimensional environmental gradients.5. Re‐establishing functional diversity (e.g. hydrologic and successional processes) across the active corridor could serve as the focus of river conservation initiatives. Once functional processes have been reconstituted, habitat heterogeneity will increase, followed by corresponding increases in species diversity of aquatic and riparian biota.
Taxonomic composition and biomass of heterotrophic flagellates in relation to lake trophy and season
Authors: Auer Brigitte , Arndt Hartmut 
Published: March 2003

1. Taxonomic composition and abundance of heterotrophic flagellates (HF) were studied in 55 lakes with different trophy in northern Germany using a live‐counting technique.2. Mean abundances and biomasses of HF ranged from 169 cells L−1and 22 μg L−1in mesotrophic lakes to 2439 cells mL–1and 475 μg L−1in hypertrophic lakes, respectively. Highest values were generally observed in spring, but mesotrophic lakes showed maximum values in early summer.3. The taxonomic composition of HF was not significantly influenced by lake trophy and season. The major fraction of HF consisted of chrysomonads and Protista incertae sedis; other important groups were choanoflagellates and bicosoecids. The size distribution of HF changed with lake trophy and season, with a higher proportion of large HF (> 10 μm) in hypertrophic lakes and in spring, respectively.4. Correlation analyses revealed a strong negative impact of cladocerans on total HF biomass and especially on large HF. Ciliates and large bacteria (> 10 μm) were strongly positively correlated with HF biomass; small bacteria (< 2 μm) showed a weak positive correlation.5. Analyses at the level of species and genera revealed distinct distribution patterns of some taxa.Paraphysomonas,AulacomonasandQuadriciliaas large‐bodied HF showed highest abundance in hypertrophic lakes and in spring. Attached taxa (e.g.Monosiga,Salpingoeca amphoridium) were highly abundant in late summer and autumn, whereasSpumellaandKathablepharisoccurred frequently in most samples.
Adaptive significance of facultative paedomorphosis in Triturus alpestris (Amphibia, Caudata): resource partitioning in an alpine lake
Authors: Denoël Mathieu , Joly Pierre 
Published: March 2003

1. Facultative paedomorphosis is a polymorphism that has important evolutionary implications in promoting morphological differentiation and variation in habitat use. It occurs in several urodele species throughout the world. Several hypotheses based on life‐history theory have been proposed to explain the wide range of habitats in which facultative paedomorphosis occurs, suggesting multifactorial causes.2. In harsh habitats, such as mountain lakes, paedomorphosis might promote niche partitioning between morphs. This hypothesis was tested by comparing micro‐habitat use and diet of two coexisting morphs in an alpine lake.3. Paedomorphs occupied all microhabitats in the lake while metamorphs occurred only along the shoreline or at the water surface. Paedomorphic newts were frequent in deep water, where they foraged mainly on plankton. Plankton was poorly exploited by metamorphic newts, which fed mainly on terrestrial insects. Difference between morphs in microhabitat use, and consequently in the diet, were consistent in both sexes and in juveniles.4. In adults, the mass and energy value of stomach contents did not differ between morphs, suggesting a similar food availability in the habitats occupied.5. This study indicates habitat partitioning between morphs involving dietary differences. Specific benefits and costs of each ontogenetic pathway may allow their coexistence in this deep and fishless lake. Paedomorphosis benefits individual newts by making new food resources available and presumably reducing competition at the shore of the lake. However, the proximate causes of such an ontogenetic switch remain unclear.
The influence of glacial runoff on stream macroinvertebrate communities in the Taillon catchment, French Pyrénées
Authors: Snook Deborah L. , Milner Alexander M. 
Published: March 2003

1. Benthic communities were sampled from five sites within a glacial catchment in the Cirque du Gavaranie, French Pyrénées, over two consecutive years (i) to investigate whether longitudinal patterns in zoobenthic communities exist downstream of a glacial margin and (ii) to identify the principal environmental variables influencing such patterns.2. There was a distinct zonation of communities with increasing distance from the glacial margin. Ordination of the zoobenthic distribution indicated sites were separated by the relative contributions of taxa rather than their presence or absence. A shift in community composition and diversity separated a kryal type community dominated by Diamesa spp., Prosimulium spp., Eriopterini and Empididae at ≥2200 m a.s.l., from a more rhithral community of Orthocladiinae, Ephemeroptera, Plecoptera and Trichoptera at 1900 m a.s.l.3. Chironomidae showed a defined gradient in distribution from Pseudokiefferiella parva and Diamesa latitarsis groups close to the glacier, through D. zernyi and D. cinerella groups, Orthocladius, Parametriocnemus and Micropsectra further downstream with Rheocricotopus, Corynoneura and Nilotanypus furthest from the glacial margin. Diamesa cinerella/zernyi group was the most euryzonal taxon.4. Gradients in channel and hydraulic stability, groundwater input and mean water temperature were identified as the principal environmental variables associated with the downstream distribution gradient of zoobenthos. Diamesa, Empididae, Eriopterini and Nematoda were most tolerant of channel and hydraulically unstable and cold water habitats. Simuliidae (Prosimulium), Crenobia alpina, Rhyacophila, Chaetopterygini, Drusus rectus, Capnioneura, Orthocladius and Parametriocnemus were associated with intermediate conditions. Corynoneura, Tanypodinae, Perlidae, Chloroperlidae, Agapetus fuscipes and Coleoptera were least tolerant of channel and hydraulic instability and low water temperature.
Chironomid (Diptera: Chironomidae) communities in six European glacier‐fed streams
Authors: Lods‐Crozet B. , Lencioni V. , Ólafsson J. S. , Snook D. L. , Velle G. , Brittain J. E. , Castella E. , Rossaro B. 
Published: March 2003

1. A study on glacial stream ecosystems was carried out in six regions across Europe, from Svalbard to the French Pyrenees. The main aim was to test the validity of the conceptual model of Milner & Petts (1994) with regard to the zonation of chironomids of glacier‐fed rivers along altitudinal and latitudinal gradient.2. Channel stability varied considerably, both on the latitudinal and altitudinal scale, being lowest in the northern regions (Svalbard, Iceland and Norway) and the Swiss Alps. Water temperature at the upstream sites was always <2 °C.3. There was a prominent difference in taxonomic richness between the Alpine and the northern European regions, with a higher number of taxa in the south. In all regions, the chironomid community was characterized by the genus Diamesa and the subfamily Orthocladiinae. Of a total of 63 taxa recorded, two (Diamesa bertrami and Orthocladius frigidus) were common in all the regions except Svalbard.4. On the basis of cluster analysis, seven distinct groups of sites were evident amongst glacial‐fed systems of the five regions (Pyrenees excluded). This classification separated the glacier‐fed streams on geographical, latitudinal and downstream gradients.5. Canonical Correspondence Analysis (CCA) of environmental variables was carried out using 41 taxa at 105 sites. Slope, water depth, distance from source, water temperature and the Pfankuch channel stability index were found to be the major explanatory environmental variables. The analysis separated Diamesinae and typical upstream orthoclads from the other chironomids by low temperature and high channel instability.6. In all six regions, Diamesa was present closest to the glacier. Within 200 m of the glacier snout, other genera of Diamesinae were found together with Orthocladiinae. Pioneer taxa like Diamesa species coexisted with later colonizers like Eukiefferiella minor/fittkaui in relatively unstable channels.7. The longitudinal succession of chironomid assemblages across altitudinal and latitudinal gradients in glacial streams followed the same pattern, with similar genera and groups of species. The general aspects of the conceptual model of Milner & Petts (1994) were supported. However, Diamesa species have wider temperature limits than predicted and other Diamesinae as well as Orthocladiinae colonize metakryal habitats.