bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of water temperature on the mass emergence of the mayfly, Ephoron shigae, in a Japanese river (Ephemeroptera: Polymitarcyidae)
Authors: Watanabe N. C. , Mori I. , Yoshitaka I. 
Published: March 2003

Summary1. Winged stages of Ephoron shigae were collected every day during their emergence period during a 6‐year period from 1989 to 1994, by net sweeps or a light trap along the Asahi‐gawa River in western Japan. Emergence occurred mainly in September.2. Coefficients of determination (r2) were calculated for the regression of the mean date of emergence against cumulative degree‐days during various periods from late March to early September.3. In both sexes the highest values of r2 were obtained for regression with degree‐days from late June to late August. This indicates that thermal conditions during the late instars affected the emergence timing most strongly. The timing of emergence can be well predicted from the cumulative degree‐days during summer.
Hydrological connectivity, and the exchange of organic matter and nutrients in a dynamic river–floodplain system (Danube, Austria)
Authors: Tockner Klement , Pennetzdorfer Doris , Reiner Niko , Schiemer Fritz , Ward J. V. 
Published: March 2003

Summary1. The relationship between hydrological connectivity, and the exchange processes of suspended sediments, organic matter and nutrients (NO3‐N) was investigated in a dynamically connected river–floodplain segment of the Danube over a 15‐month period in 1995 and 1996 in the Alluvial Zone National Park, Austria.2. Based on water level dynamics and water retention times, three phases of river–floodplain connectivity were identified: disconnection (phase I), seepage inflow (phase II) and upstream surface connection (phase III). The frequency of occurrence of these phases was 67.5%, 29.3% and 3.2%, respectively, during the study period.3. A conceptual model is presented linking hydrological connectivity with ecological processes. Generally, the floodplain shifts from a closed and mainly biologically controlled ecosystem during phase I to an increasingly open and more hydrologically controlled system during phases II and III. Phase I, with internal processes dominating, is designated the ‘biotic interaction phase’.4. Phase II, with massive nutrient inputs to the floodplain yet relatively high residence times, and therefore, high algal biomass, is classified as the ‘primary production phase’. This demonstrates that water level fluctuations well below bankfull may considerably enhance floodplain productivity.5. Finally, since transport of particulate matter is mainly restricted to short flood pulses above bankfull level, phase III has been defined as the ‘transport phase’.6. The floodplain served as a major sink for suspended sediments (250 mt ha−−1 year−−1), FPOM (96 mt ha−−1 year−−1), particulate organic carbon (POC; 2.9 mt ha−−1 year−−1) and nitrate‐nitrogen (0.96 mt ha−−1 year−−1), but was a source for dissolved organic carbon (DOC; 240 kg ha−−1 year−−1), algal biomass (chlorophyll‐a; 0.5 kg ha−−1 year−−1) and CPOM (21 kgha−−1 year−−1). Considerable quantities of DOC and algal biomass were exported to the river channel during phase II, whereas particulate matter transport was largely restricted to the short floods of phase III.7. The Danube Restoration Project will create a more gradual change between the individual phases by increasing hydrological connectivity between the river channel and the floodplain, and is predicted to enhance productivity by maintaining a balance between retention and export of nutrients and organic matter.
What happens to allochthonous material that falls into streams? A synthesis of new and published information from Coweeta
Authors: Webster J. R. , Benfield E. F. , Ehrman T. P. , Schaeffer M. A. , Tank J. L. , Hutchens J. J. , D’Angelo D. J. 
Published: March 2003

1. ,One of two things can happen to allochthonous material once it enters a stream: it can be broken down or it can be transported downstream. The efficiency with which allochthonous material is used is the result of these two opposing factors: breakdown and transport.2. ,The present synthesis of new and published studies at Coweeta Hydrologic Laboratory compares biological use versus transport for four categories of particulate organic material: (1) large wood (logs); (2) small wood (sticks); (3) leaves; and (4) fine particulate organic matter (FPOM).3. ,Over 8_years, logs showed no breakdown or movement.4. ,The breakdown rate of sticks (≤3_cm diameter) ranged from 0.00017 to 0.00103_day−1, while their rate of transport, although varying considerably with discharge, ranged from 0 to 0.1_m_day−1.5. ,Based on 40 published measurements, the average rate of leaf breakdown was 0.0098_day−1. The leaf transport rate depended on stream size and discharge.6. ,The average respiration rate of FPOM was 1.4_mg_O2_g_AFDM−1_day−1 over a temperature range of 6–22_°C, which implies a decomposition rate of 0.00104_day−1. Transport distances of both corn pollen and glass beads, surrogates of natural FPOM, were short (<_10_m) except during high discharge.7. , Estimates of transport rate were substantially larger than the breakdown rates for sticks, leaves and FPOM. Thus, an organic particle on the stream bottom is more likely to be transported than broken down by biological processes, although estimates of turnover length suggest that sticks and leaves do not travel far. However, once these larger particles are converted to refractory FPOM, either by physical or biological processes, they may be transported long distances before being metabolized.
Small‐scale movements of lotic macroinvertebrates with variations in flow
Authors: Lancaster Jill 
Published: March 2003

Summary1. The small‐scale movements and distribution patterns of invertebrates were observed in an attempt to identify the various mechanisms by which organisms may use flow refugia during flow disturbances. The microdistribution of lotic macroinvertebrates was examined in two replicate, non‐circulating laboratory flumes with variations in flow among microhabitat patches (≈ 0.015–0.035 m2). The discharge in one experimental flume was manipulated to mimic spates and alter near‐bed flow patterns; the other flume acted as a control. After an initial settling period, the position and behaviour of animals within the flumes was recorded before, during and after a simulated spate. Three species with contrasting flow microhabitat preferences and movement behaviour were examined.2. At low discharge, the microdistribution of all three study species in flumes was broadly consistent with field observations. In the field, the optimum current speed was lowest for adults of the dytiscid beetle, Oreodytes sanmarkii, and highest for mayfly nymphs, Ephemerella ignita, with nymphs of the stonefly, Leuctra inermis, most abundant at intermediate velocities. In the flumes, O. sanmarkii occurred only in very low velocity areas, L. inermis occurred widely throughout the flumes with highest density in low velocity areas and E. ignita also occurred throughout the flumes, but maximum density was in moderately high velocity areas.3. Increased discharge did not reduce the total number of individuals in experimental versus control flumes for any of the three species studied, although total numbers did decrease over the observation period in both treatments. Simulated spates resulted in a change in the microdistribution of O. sanmarkii and E. ignita, but not L. inermis, such that numbers were reduced in very high velocity microhabitats and animals accumulated in lower flow areas, analogous to flow refugia. These distributional shifts were attributed to movements of individuals among microhabitats.4. Both active and passive modes of movement contributed to the accumulation of E. ignita and O. sanmarkii in low flow microhabitats (i.e. flow refugia). Some nymphs of E. ignita actively crawled from high to low flow microhabitats. Both species drifted between microhabitats. Drift entry could be active or passive, whereas regaining the substratum was active: O. sanmarkii swam down and E. ignita altered its body posture to promote sinking.
Effects of ice duration on plankton succession during spring in a shallow polymictic lake
Authors: Adrian Rita , Walz Norbert , Hintze Thomas , Hoeg Sigrid , Rusche Renate 
Published: March 2003

Summary1. Long‐term records of air temperature and ice phenology (ice duration), and phyto‐ and zooplankton time series (1979–1997) were used to study the effects of ice duration on the successional pattern within plankton communities during spring in a shallow polymictic lake.2. Water temperature in March was significantly lower after cold winters when compared to average or mild winters. Mean water temperature in April was not significantly different after mild, average or cold winters, but showed an overall significant negative correlation with ice duration.3. Ice duration affected the timing and the magnitude of the peak abundance of diatoms, rotifers and daphnids during spring, but had no direct effects on the timing and maximum of chlorophytes, cryptophytes, cyanobacteria, bosminids and cyclopoid copepods.4. Plankton groups which appeared first in the seasonal succession (i.e. diatoms, rotifers and daphnids) reached maximum abundance earlier after mild and average winters. The peak abundance of diatoms was negatively correlated with ice duration, whereas that of rotifers and daphnids was independent of the conditions during the preceding winter.5. Temperature alone was generally a poor predictor of the timing and magnitude of both phyto‐ and zooplankton maxima. Turbulence may be important in the timing and the magnitude of peaks in diatoms, while total algal biomass was the most important determinant for the timing of the rotifer maximum. The magnitude of the daphnid maxima were significantly influenced by water temperature in March and April, and by rotifer abundance. The magnitude of the bosminid maximum was correlated with food availability and predation, whereas the timing of the maximum was more closely related to water temperature in May.6. We conclude that, as a result of the low heat storage capacity of shallow lakes, the effects of winter on planktonic communities are short lived, and soon overtaken by the prevailing weather and by biotic interactions.
What is river health?
Authors: Norris Richard H. , Thoms Martin C. 
Published: March 2003

Summary1. Traditionally the assessment of river water quality has been based solely on the measurement of physical, chemical and some biological characteristics. While these measurements may be efficient for regulating effluent discharges and protecting humans, they are not very useful for large‐scale management of catchments or for assessing whether river ecosystems are being protected.2. Measurements of aquatic biota, to identify structural or functional integrity of ecosystems, have recently gained acceptance for river assessment. Empirical evidence from studies of river ecosystems under stress suggests that a small group of biological ecosystem‐level indicators can assess river condition. However, physical and chemical features of the environment affect these indicators, the structure and function of which may be changed by human activities.3. The term ‘river health’, applied to the assessment of river condition, is often seen as being analogous with human health, giving many a sense of understanding. Unfortunately, the meaning of ‘river health’ remains obscure. It is not clear what aspects of river health sets of ecosystem‐level indicators actually identify, nor how physical, chemical and biological characteristics may be integrated into measures rather than just observations of cause and effect.4. Increased examination of relationships between environmental variables that affect aquatic biota, such as habitat structure, flow regime, energy sources, water quality and biotic interactions and biological condition, are required in the study of river health.
Predicting diatom communities at the genus level for the rapid biological assessment of rivers
Authors: Chessman Bruce , Growns IvoR. , Currey Julie , Plunkett‐Cole Nicola 
Published: March 2003

Summary1. Diatoms were sampled in the spring of 1994 and the autumn of 1995 at 137 pristine or near‐pristine reference sites on large and small streams at various altitudes in eastern New South Wales and Victoria. Scrapings were taken from five firm substrata across a range of microhabitat conditions at each site on each occasion. For each substratum, 100 valves were identified to genus level.2. Multivariate statistical models were constructed to predict the probability of occurrence of each genus at a given site under near‐pristine conditions on the basis of physical features of the site that are not affected by human activity. Model predictions were compared with the flora observed at the reference sites and at 55 test sites affected by varying degrees of human disturbance.3. Test sites were characterized more by the presence of genera not predicted by the model than by the absence of predicted genera. The degree of departure from model predictions was related mainly to increasing alkalinity, electrical conductivity, hardness and pH of river water. We therefore conclude that the main effect of human activity on the composition of diatom communities in the rivers of coastal south‐eastern Australia has been to increase genus richness through enrichment with alkaline salts.4. The models did not perform as well as similar models applied to river macroinvertebrates at the family level, perhaps because of greater temporal variability in diatom communities and differences in the environmental variables to which diatoms and macroinvertebrates respond. Means of improving the current models are discussed.
Assessment of river health: accounting for perturbation pathways in physical and ecological space
Authors: Townsend Colin R. , Riley Ralph H. 
Published: March 2003

Summary1. A full understanding of changes to river ecosystem structure and functioning along the continuum from relatively pristine to profoundly perturbed requires knowledge of physical, chemical and ecological properties at many spatial and temporal scales. Perturbations may span broad spatio‐temporal scales or be spatially and temporally discrete.2. The relevant scale for study depends on the manner in which perturbations move through two kinds of pathways – through the physical space of the catchment hierarchy and through the ecological space of river food webs. Different kinds of perturbation (e.g. inputs of sediment, nitrogen or phosphorus, changes to shading or discharge) vary in the degree and manner in which they are propagated downstream and through food webs.3. The fundamental importance of disturbance regimes and refugia to river health is now clear and managers need to take this into account when devising river management schemes.4. A comparison of the physics, chemistry and ecology of streams in catchments of native tussock and exotic pasture grassland in New Zealand serves to emphasize (i) the extreme complexity of interacting factors resulting from land use change, (ii) the importance of disturbance regime (not encapsulated in biotic indices) and biogeographic patterns (usually unmeasured) in determining ecosystem structure and functioning, and (iii) the lack of concordance between any single index of health and various fundamental features of ecosystem functioning.5. Practical considerations limit most evaluations of river health to a small suite of indices, though it is important that researchers continue to evaluate the spatial, temporal and biological limitations of these indices. The vagaries of history and geography (extinction and colonization trajectories in relation to natural disturbance regimes) and the complexity of interacting physical, chemical and ecological responses to perturbation suggest that multi‐scale, multi‐temporal studies of river function offer the best opportunity to evaluate river health.
An overview of river health assessment: philosophies, practice, problems and prognosis
Authors: Boulton Andrew J. 
Published: March 2003

Summary1. Philosophically, the term ‘river health’ is useful because it is readily interpreted by the general public and evokes societal concern about human impacts on rivers. The common goal of achieving healthy rivers unites ecologists and the general public because the value of the ecologists’ contributions is clear (and, hence, funded). The difficulty arises in the choice of relevant symptoms because there is a wide variety that can be measured with varying accuracy at a broad range of spatial scales. These indicators may respond to impacts at different time scales, and no single indicator is a ‘silver bullet’ that reveals river health unequivocally.2. In practice, choice of indicator often shows personal bias, technical considerations, and constraints of knowledge. Selection of appropriate spatial and temporal scales for these measures is crucial. Although most measurements are spot samples (e.g. concentration, abundance, species richness), assessment of river health based on changes in ecological processes such as post‐disturbance recovery rate or nutrient spiralling lengths may be more suitable in some cases.3. Problems include validation of the indicator, its response time at a range of scales, and the reliability of its measurement. Assessment of river health should be accurate, timely (warning of deterioration instead of waiting until the patient is terminal), rapid (so that the response is swift), and inexpensive. The connectedness of running waters with their floodplains and catchments must be explicitly recognized. Hydrological and geomorphological modifications of rivers usually affect their health by severing or impairing the linkages, and the ‘cure’ may lie in addressing these causes. Often, we need landscape‐level data for management because this is the scale where cumulative effects of impacts are evident.4. The prognosis is uncertain. We need to explore further the use of integrative measures of river health, and focus on establishing a link between the measure and impaired ecological integrity. Ecosystem‐level variables (e.g. estimates of production or respiration) show promise and recent technological advances make these more accessible. Data analytical approaches (e.g. multimetric vs. predictive models) need further debate but must not overlook the importance of high quality and relevant input data. Appropriate choice of indicators, rigorous sampling and analysis, and careful data interpretation must be matched with effective communication to policy‐makers and the public. When this occurs, the concept of ‘river health’ becomes more than just a rhetorical tool.‘
Bioenergetics and phenology of reproduction of the introduced red swamp crayfish, Procambarus clarkii, in Do·ana National Park, Spain, and implications for species management
Authors: Gutiérrez‐Yurrita Pedro J. , Montes Carlos 
Published: March 2003

1. The red swamp crayfish, Procambarus clarkii (Girard), is a North American species which was introduced into the Lower Guadalquivir, Spain, in 1974. Procambarus clarkii has become a key species since it has greatly altered the functioning and structure of the ecosystems it has invaded.2. Since P. clarkii spawn spontaneously throughout the year, it is to be expected that their ecological impact on the ecosystem may vary depending of the timing of habitat flooding (e.g. temporary freshwater marsh, and temporary or permanent pond). The objective of the present study was to understand the reproductive phenology and bioenergetics of P. clarkii in Do·ana National Park, Spain, freshwater ecosystems, and consequently, propose some management plans for their populations.3. Five stages of ovarian development were detected. Final ovarian maturation occurred a few days before spawning and spawning was synchronized among mature females of all populations. Egg numbers hatched in pleopods ranged from 450 to 550. Timing of juvenile release from pleopods varied greatly (10–35 days).4. Gravid females support most of their metabolic needs by catabolizing carbohydrates (overall mean of O:N = 30.39), and to a lesser extent, lipids. The aerobic and excretory metabolisms of gravid females were lower than those of immature animals of similar weight.5. Analysis suggested that several factors influence the spawning of crayfish at the monitored sites. The major factors are water regime and temperature. Red swamp crayfish appear to be a spontaneous spawning species which may adjust their reproductive cycle to the timing of flooding, enhancing the utilization of available resources.6. Populations of P. clarkii in Do·ana National Park could be controlled by the management of the water regime and by devising a fishing scheme which would maintain an appropriate population structure.
Species traits for future biomonitoring across ecoregions: patterns along a human‐impacted river
Authors: Dolédec Sylvain , Statzner Bernhard , Bournard Michel 
Published: March 2003

1. Current budgets for environmental management are high, tend to increase, and are used to support policy and legislation which is standardized for large geographic units. Therefore, the search for tools to monitor the effects of this investment is a major issue in applied ecology. Ideally, such a biomonitoring tool should: (1) be as general as possible with respect to its geographic application; (2) be as specific as possible by separating different types of human impact on a given ecosystem; (3) reliably indicate changes in human impact of a particular type; and (4) be derived from a sound theoretical concept in ecology.2. We developed an approach to biomonitoring which matches these ‘ideal’ characteristics by focusing on numerous, general biological species traits (e.g. size, number of descendants per reproductive cycle, parental care, mobility) and on the habitat templet concept, which relates trends in these general species traits to disturbance patterns. Using the French Rhône River and benthic macroinvertebrates as an example, we have used the data to demonstrate a general framework and the potential of our approach rather than to produce a ready‐made tool. Our data covered a large river and its major tributaries, which has a catchment that crosses ecoregions, and known gradients and discontinuities in human impact.3. We applied multivariate analyses to evaluate how the distribution of species traits in invertebrate communities could discriminate environmental differences along the Rhône in comparison to traditionally used approaches (e.g. community structure, based on species abundances, or ecological species traits, such as velocity preferences and pollution tolerance). Invertebrate community structure expressed in terms either of the abundance or the traits of species reliably indicated differences in overall human impact. The community structure based on biological traits was less confounded by natural spatial gradients and reliably indicated human impact, while community structure based on ecological traits was the most confounded by natural spatial gradients and was the poorest indicator of human impact. Community structure based on species abundances was an intermediate indicator of human impact.4. These results indicate that a revision of biomonitoring approaches which have been based on a single aspect of the biological responses may be warranted. The biological traits of species could separate the different types of human impact. Therefore, the use of these traits in biomonitoring could improve existing multi‐metric approaches. Future research has to show if the general applicability of species traits allows the development of a unique biomonitoring tool for running waters of the European Union, for running waters in temperate climates on several continents, for freshwater, marine and terrestrial systems, and/or for global biodiversity assessment.