bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carry‐over effects of embryonic acid conditions on development and growth ofRana temporariatadpoles
Authors: RÄsänen K. , Laurila A. , Merilä J. 
Published: March 2003

1. Conditions experienced during the early stages of development may have carry‐over effects on performance during later life. The egg laying period and embryonic development of temperate and boreal zone amphibians often coincides with peak acidity resulting from spring snow‐melt, but the effects of acid conditions during embryonic stage on subsequent performance are unknown.2. We investigated the potential carry‐over effects of acidity during the embryonic stage on performance up to metamorphosis in the common frog (Rana temporaria) tadpoles. There were four combinations of acid (4.5) and neutral (7.5) pH treatments applied to the egg and larval stages in a factorial laboratory experiment. In addition, we studied the difference in embryonic and larval tolerance of acidity between two populations originating from circumneutral (pH 6.6) and acidic conditions (pH 4.8).3. The effects of acid conditions during the embryonic stage were sublethal, as indicated by delayed development and reduced size. Under acid conditions, tadpoles that had been raised in neutral water as embryos at first grew more slowly than tadpoles raised under acid conditions as embryos. At metamorphosis, no effects of embryonic acidity were detectable indicating that tadpoles were able to compensate fully for the initial reduction in growth.4. Acid conditions during the larval period had a strongly negative effect on survival, size and age at metamorphosis. The amount of food consumed was lower under acid conditions, suggesting that reduced food consumption was at least partly responsible for the negative effects.5. Although the two populations differed in the length of larval period, there was no indication of a differential response to the treatments in any of the metamorphic traits studied.6. These results suggest that, although moderate acid conditions during embryonic development affect growth and development negatively, this influence does not persist after conditions have returned to normal. However, even moderately acid conditions during the larval period may have a strong negative influence on survival and performance of the tadpoles.
Population genetic structure of two water strider species in the Ecuadorian Amazon
Authors: GALACATOS KATERINA , COGNATO ANTHONY I. , SPERLING FELIX A. H. 
Published: March 2003

1. We used mtDNA sequence variation to estimate population genetic structure between and among water strider populations ofPotamobates williamsiandP.sumacoin the Ecuadorian Amazon.2. Sequencing of the COI mitochondrial gene revealed 16 haplotypes, which were summarised into four haplotype groups.P.williamsiandP.sumacoshared two common and widespread haplotypes.3. Population structure was moderate and gene flow was low. Both air and river distances were significantly correlated with gene flow and, thus, indicative of isolation by distance.4. The genetic structure within and among populations ofP. williamsiandP. sumacowas probably not influenced by the dynamic tropical lotic system.
Dispersal of aquatic organisms by waterbirds: a review of past research and priorities for future studies
Authors: FIGUEROLA JORDI , GREEN ANDY J. 
Published: March 2003

1. Inland wetlands constitute ecological islands of aquatic habitat often isolated by huge areas of non‐suitable terrestrial habitats. Although most aquatic organisms lack the capacity to disperse by themselves to neighbouring catchments, many species present widespread distributions consistent with frequent dispersal by migratory waterbirds.2. A literature review indicates that bird‐mediated passive transport of propagules of aquatic invertebrates and plants is a frequent process in the field, at least at a local scale. Both endozoochory (internal transport) and ectozoochory (external transport) are important processes.3. The characteristics of the dispersed and the disperser species that facilitate such transport remain largely uninvestigated, but a small propagule size tends to favour dispersal by both internal and external transport.4. We review the information currently available on the processes of waterbird‐mediated dispersal, establishing the limits of current knowledge and highlighting problems with research methods used in previous studies. We also identify studies required in the future to further our understanding of the role of such dispersal in aquatic ecology.
Biodiversity and resource use of larval chironomids in relation to environmental factors in a large river
Authors: FESL CHRISTIAN 
Published: March 2003

1. Larval chironomids were examined at four sites on a cross‐section of the River Danube in Austria between September 1995 and August 1996. The sites differed in hydraulics, sediment composition and habitat stability.2. Species–accumulation curves, showing the increase in number of species with increasing sampling effort, from three main channel sites were best described by a logarithmic model, suggesting that most of the species occurring at these sites were found. Data from a site connected to a backwater fitted best to a power model, indicating a random assemblage with additional species immigrating from the backwater area.3. Properties of the community were estimated using Jackknife techniques: species richness (range of mean values at the four sites: 32–91), H′ diversity (1.5–2.3), evenness (0.23–0.28), spatial resource width (0.01–0.06), spatial resource overlap (0.13–0.20), spatial species aggregation (0.60–0.77), temporal community persistence (Kendal's correlation coefficient: 0.47–0.60) and beta‐diversity (6.2–9.7).4. Redundancy analysis (RDA) was used to relate the community properties and species abundance to environmental factors. Habitat stability was the major factor associated with community structure. Higher sediment turnover led to higher spatial aggregation and, consequently, a decrease in spatial resource width and overlap, and to a decline in larval density and species richness.5. Species‐abundance patterns agreed well with the log‐normal model. Moderate community persistence and stability of the streambed sediments suggest that the log‐normal model may be a good descriptor for communities of intermediately disturbed habitats, like large rivers, rather than stable habitats.
Terrestrial invertebrates inhabiting lowland river floodplains of Central Amazonia and Central Europe: a review
Authors: ADIS JOACHIM , JUNK WOLFGANG J. 
Published: March 2003

1. Amazonian terrestrial invertebrates produce high population densities during favourable periods and may suffer a drastic decrease during occasional floods and droughts. However, the monomodal, predictable flood pulse of the larger Amazonian rivers favours the development of morphological (respiratory organs, wing‐dimorphism), phenological (synchronization of life cycles, univoltine mode of life), physiological (flooding ability, gonad dormancy, alternating number of developmental stages), and behavioural adaptations (migration, temporal diving) with numerous interactions.2. In lowlands of Central Europe, the flood pulse of large rivers is less predictable than in Central Amazonia and is superimposed by the seasonal light/temperature pulse (summer/winter regime). Some terrestrial invertebrates show physiological resistance against inundation or drought, phenologies fitting the normal annual rhythm of water level fluctuation (quiescence or diapause of eggs or adult invertebrates), high dispersal ability and migration. However, most species survive simply using a `risk strategy', combining high reproduction rates, dispersal and reimmigration following catastrophic events.3. The diversity of species in terrestrial invertebrates is lower in lowland riverine ecosystems of Central Amazonia and Central Europe compared with the respective uplands because of flood stress in these systems. However, floodplains in Central Amazonia possess a greater number of endemic species in comparison with Central European floodplains because of long periods of fairly stable climatic conditions in comparison with large palaeoclimatic changes in Central Europe.
A landscape perspective of surface–subsurface hydrological exchanges in river corridors
Authors: MALARD FLORIAN , TOCKNER KLEMENT , DOLE‐OLIVIER MARIE‐JOSÉ , WARD J. V. 
Published: March 2003

1.  River corridors can be visualised as a three‐dimensional mosaic of surface–subsurface exchange patches over multiple spatial scales. Along major flow paths, surface water downwells into the sediment, travels for some distance beneath or along the stream, eventually mixes with ground water, and then returns to the stream.2.  Spatial variations in bed topography and sediment permeability result in a mosaic of patch types (e.g. gravel versus sandy patches) that differ in their hydrological exchange rate with the surface stream. Biogeochemical processes and invertebrate assemblages vary among patch types as a function of the flux of advected channel water that determines the supply of organic matter and terminal electron acceptors.3.  The overall effect of surface–subsurface hydrological exchanges on nutrient cycling and biodiversity in streams not only depends on the proportion of the different patch types, but also on the frequency distribution of patch size and shape.4.  Because nutrients are essentially produced or depleted at the downwelling end of hyporheic flow paths, reach‐scale processing rates of nutrients should be greater in stretches with many small patches (e.g. short compact gravel bars) than in stretches with only a few large patches (e.g. large gravel bars).5.  Based on data from the Rhône River, we predict that a reach with many small bars should offer more hyporheic refugia for epigean fauna than a reach containing only a few large gravel bars because benthic organisms accumulate preferentially in sediments located at the upstream and downwelling edge of bars during floods. However, large bars are more stable and may provide the only refugia during severe flood events.6.  In river floodplain systems exhibiting pronounced expansion/contraction cycles, hyporheic assemblages within newly created patches not only depend on the intrinsic characteristics of these patches but also on their life span, hydrological connection with neighbouring patches, and movement patterns of organisms.7.  Empirical and theoretical evidence illustrate how the spatial arrangement of surface–subsurface exchange patches affects heterogeneity in stream nutrient concentration, surface water temperature, and colonisation of dry reaches by invertebrates.8.  Interactions between fluvial action and geomorphic features, resulting from seasonal and episodic flow pulses, alter surface–subsurface exchange pathways and repeatedly modify the configuration of the mosaic, thereby altering the contribution of the hyporheic zone to nutrient transformation and biodiversity in river corridors.
Large wood and fluvial processes
Authors: GURNELL A. M. , PIÉGAY H. , SWANSON F. J. , GREGORY S. V. 
Published: March 2003

1. Large wood forms an important component of woodland river ecosystems. The relationship between large wood and the physical characteristics of river systems varies greatly with changes in the tree species of the marginal woodland, the climatic and hydrological regime, the fluvial geomorphological setting and the river and woodland management context.2. Research on large wood and fluvial processes over the last 25 years has focussed on three main themes: the effects of wood on flow hydraulics; on the transfer of mineral and organic sediment; and on the geomorphology of river channels.3. Analogies between wood and mineral sediment transfer processes (supply, mobility and river characteristics that affect retention) are found useful as a framework for synthesising current knowledge on large wood in rivers.4. An important property of wood is its size when scaled to the size of the river channel. ′Small′ channels are defined as those whose width is less than the majority of wood pieces (e.g. width < median wood piece length). `Medium' channels have widths greater than the size of most wood pieces (e.g. width < upper quartile wood piece length), and `Large' channels are wider than the length of all of the wood pieces delivered to them.5. A conceptual framework defined here for evaluating the storage and dynamics of wood in rivers ranks the relative importance of hydrological characteristics (flow regime, sediment transport regime), wood characteristics (piece size, buoyancy, morphological complexity) and geomorphological characteristics (channel width, geomorphological style) in `Small', `Medium' and `Large' rivers.6. Wood pieces are large in comparison with river size in `small' rivers, therefore they tend to remain close to where they are delivered to the river and provide important structures in the stream, controlling rather than responding to the hydrological and sediment transfer characteristics of the river.7. For `Medium' rivers, the combination of wood length and form becomes critical to the stability of wood within the channel. Wood accumulations form as a result of smaller or more mobile wood pieces accumulating behind key pieces. Wood transport is governed mainly by the flow regime and the buoyancy of the wood. Even quite large wood pieces may require partial burial to give them stability, so enhancing the importance of the sediment transport regime.8. Wood dynamics in `Large' rivers vary with the geometry of the channel (slope and channel pattern), which controls the delivery, mobility and breakage of wood, and also the characteristics of the riparian zone, from where the greatest volume of wood is introduced. Wood retention depends on the channel pattern and the distribution of flow velocity. A large amount is stored at the channel margins. The greater the contact between the active channel and the forested floodplain and islands, the greater the quantity of wood that is stored.
Life history of Daphnia galeata in a hypertrophic reservoir and consequences of non‐consumptive mortality for the initiation of a midsummer decline
Authors: Hülsmann S. , Voigt H. 
Published: March 2003

SUMMARY 1. Field and laboratory investigations were combined in a 2‐year study on the initiation of a midsummer decline of Daphnia galeata Sars in a hypertrophic reservoir. Quantitative field samples were taken twice a week, and, adult and juvenile mortality rates were calculated. Patterns of reproduction and survival of daphnids born during spring and early summer under fluctuating food conditions were determined in life‐table experiments.2. The abundance of Daphnia increased strongly in early May and declined in June 1998 (midsummer decline). In 1999, Daphnia density increased only slowly in spring and remained constantly high throughout the summer.3. Food conditions (concentrations of POC<30 μm) for daphnids deteriorated in both years in response to increasing Daphnia densities, resulting in a clear‐water phase of about 4 weeks. When Daphnia abundance declined in 1998, POC<30 μm concentrations increased greatly, whereas in 1999 food conditions improved only slightly and Secchi depth remained high.4. Survival of daphnids in life‐table experiments decreased greatly after food became rare and was strongly reduced in those animals born during the clear‐water phase compared with those born later. In addition, age at first reproduction was retarded during the clear‐water phase, resulting in very low population growth rates. Survivorship patterns in life‐table experiments suggest a strong impact of non‐consumptive mortality on Daphnia population dynamics.5. Field data of mortality point to differences in mortality patterns between years, probably resulting from different predation impacts of juvenile fish. In both years, however, adult mortality contributed substantially to overall mortality at the end of the clear‐water phase. As bottom‐up effects on D. galeata were very similar in both years, the significance of non‐consumptive mortality on the initiation of midsummer declines appears to depend largely on recruitment patterns before the clear‐water phase. A high impact can be expected when Daphnia populations are dominated by a peak cohort of nearly identical age during the clear‐water phase.
Migratory Atlantic salmon as vectors for the transfer of energy and nutrients between freshwater and marine environments
Authors: Jonsson Bror , Jonsson Nina 
Published: March 2003

SUMMARY 1. Annual energy, carbon, nitrogen and phosphorus fluxes across the river mouth by Atlantic salmon were estimated for 18 years (1976–94) in the Norwegian River Imsa. The total energy content of the emigrating smolts in each year varied considerably with a mean value of 237 × 103 kJ. That of returning adults also varied between years with a mean value of 141 × 104 kJ. One‐sea‐winter salmon (grilse) made up 65% of the total energy content of the spawners in the river. Dead carcasses remaining in the river after spawning were estimated to have a mean annual energy content of 175 × 103 kJ.2. The net annual energy flux from the sea to the river varied between 48 × 103 kJ (1987) and 152 × 104 kJ (1989) with a mean of 616 × 103 kJ, and a coefficient of variation of 67%. Average net marine import of the returning adults was 83 × 104 kJ year−1 with a coefficient of variation of 52%. Mean annual export of C, N and P to sea by the smolts was 595, 131 and 22 kg, and by kelts 1535, 352 and 70 kg, respectively, whereas gross import via the adults was 3176 kg C, 735 kg N and 132 kg P. The annual flux across the river mouth was 1046 kg C, 253 kg N and 39 kg P. The net marine import were 1585 kg C, 371 kg N and 60 kg P. The net flux was estimated at 0.2% for nitrogen and 5% for phosphorus of the total river load.3. The energy flux caused by Atlantic salmon spawning in the River Imsa was relatively high because the general nutrient load in the river is low. Thus, even though most Atlantic salmon survive spawning, their contribution to the nutrient flux in the river is significant.
Effects of stream phosphorus levels on microbial respiration
Authors: Ramírez Alonso , Pringle Catherine M. , Molina Luisenrique 
Published: March 2003

SUMMARY 1. We examined microbial respiration among streams in lowland Costa Rica comprising a natural phosphorus gradient (5–350 μg SRP L−1) resulting from variable inputs of solute‐rich (e.g. P, SO4 and Cl) groundwater.2. Microbial respiration rates were determined by measuring oxygen change in situ in nine low‐order streams on three substrate types: mixed leaves collected from the stream bottom, conditioned Ficus leaves and sediments.3. Respiration rates on both leaf types were positively related to phosphorus and negatively related to N : P ratios. Microbial respiration rates on sediments were not related to any of the variables [i.e. soluble reactive phosphorus (SRP), N‐NO3 and N : P] measured.4. Respiration rates on newly colonised Ficus leaves formed an asymptotic curve increasing to a plateau, suggesting that saturation with phosphorus occurred at concentrations <15 μg SRP L−1.5. To test the hypothesis that phosphorus was the main solute in solute‐rich water that was driving observed differences in microbial respiration rates, we artificially enriched a small stream with phosphorus and measured changes in respiration before and after enrichment.6. Experimental phosphorus enrichment produced increases in respiration rates similar in magnitude to those observed in the nine streams forming the natural phosphorus gradient, supporting our hypothesis that phosphorus was the major variable driving interstream differences in microbial respiration rates. Respiration rates were higher in this study than those reported for most other tropical streams and rivers with the exception of those reported for tropical Asian streams.7. Results indicate that variations in phosphorus concentrations can potentially affect patterns of microbial respiration rates at a landscape level via differential inputs of solute‐rich groundwater into streams.
Sex and outcrossing in a sessile freshwater invertebrate
Authors: Freeland Joanna R. , Lodge Rebecca J. , Okamura Beth 
Published: March 2003

SUMMARY 1. The freshwater bryozoan Cristatella mucedo, in common with other sessile, benthic freshwater taxa, has an unusual life history: sex occurs during a relatively brief period near the start of the growing season, and overwintering occurs in the form of asexually produced dormant propagules (statoblasts). Consistent observed heterozygosity (Ho) deficits in C. mucedo populations have previously suggested that inbreeding is common, although a possible contribution of a Wahlund effect to low Ho could not be discounted.2. We have used microsatellite data in the first study based on codominant markers to genetically characterise maternal colonies and larval offspring of C. mucedo. The ‘population’ represented by the larvae was in Hardy–Weinberg equilibrium, which has previously been found in only one of 39 populations of C. mucedo. At least 64% of larvae were the products of outcrossing. We suggest that the unusual early timing of sex may be a strategy to maximise rates of outcrossing within populations of sessile freshwater invertebrates.
Vulnerability of cladoceran species to predation by the copepod Mesocyclops leuckarti: laboratory observations on the behavioural interactions between predator and prey
Authors: Chang Kwang‐Hyeon , Hanazato Takayuki 
Published: March 2003

SUMMARY 1. We analysed the vulnerability of a number of cladoceran species (Bosmina longirostris, B. fatalis, Diaphanosoma brachyurum, Ceriodaphnia reticulata, Daphnia ambigua and D. pulex) to predation by Mesocyclops leuckarti in the laboratory.2. The prey species represented a wide range of body size, morphology, and swimming behaviour. To compare vulnerability, we measured the efficiency of capture and ingestion of each prey species by Mesocyclops. We also measured the rate at which prey were damaged in attacks by Mesocyclops.3. Mesocyclops preyed effectively on Diaphanosoma and small juvenile Ceriodaphnia but not on Bosmina or Daphnia. Observations suggested that various defence mechanisms, including protruding structures and swimming behaviour and speed, are important in determining prey vulnerability.4. The body size of Daphnia and Ceriodaphnia seems to be important, because larger animals were better able to escape Mesocyclops attacks. Attacks by Mesocyclops often caused fatal damage, however, even to large Daphnia.