bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patch selection by mottled sculpin (Pisces: Cottidae) in a southern Appalachian stream
Authors: PETTY TODD , GROSSMAN GARY 
Published: November 2003

1. We examined the effects of prey abundance on patch selection by a benthic fish, the mottled sculpin (Cottus bairdi), in a fourth order, southern Appalachian stream (North Carolina, U.S.A.). This habitat is a mosaic of small (i.e. < 0.5 m2), relatively discrete patches.2. Patches were characterized in terms of physical habitat variables, detritus (coarse particulate organic matter, CPOM) and macroinvertebrate abundance (number and biomass). We quantified patch selection by comparing the characteristics of patches utilized by sculpin with those of locally available patches. Locally available patches were selected using a constrained random sampling design (i.e. randomly selected within a 2 m radius from each fish). We also examined the relationship between macroinvertebrate abundance, CPOM and the physical characteristics of available patches.3. Patches selected by sculpin contained significantly higher macroinvertebrate abundances (both number and biomass) than locally available patches in five out of six seasonal samples. Sculpin also occupied patches with significantly higher amounts of CPOM in three out of five seasonal samples. Patches utilized by sculpin, however, could not be consistently differentiated from locally available patches on the basis of physical variables. In addition, macroinvertebrate abundance was not consistently related to physical habitat variables or CPOM during the course of the study.4. Our results suggest that sculpin are able to assess patch quality on the basis of prey abundance and select patches that potentially maximize energy gain. This behaviour may produce an increase in individual fitness, especially when prey distributions are not consistently related to habitat variables. Quantifying patch use in relation to prey abundance may help elucidate the causal factors determining habitat use by benthic fishes in other lotic systems.
The role of parthenogenesis in the biology of two species of mayfly (Ephemeroptera)
Authors: HARKER JANET 
Published: November 2003

1. From a single founder virgin female of each species, nine and seven successive parthenogenetic generations of Cloeon dipterum and Cloeon simile, respectively, were reared: all offspring were female. Eggs were removed from final instar nymphs, subimagos and virgin imagos of each generation and their development assessed. The life cycles of 487 individual C. dipterum and 315 C. simile were recorded, together with details of growth rate, egg production and adult size of these and other representatives of each generation. In order to distinguish between the effects of parthenogenesis and the effects of culture conditions, fertilized eggs of both species were reared under the same laboratory conditions.2. Fewer unfertilized than fertilized eggs hatched. There was no consistent trend in the percentage hatch in successive parthenogenetic generations. In both species the time taken for parthenogenetic individuals to complete a generation varied considerably, and no relationship was found between generation length and the number of parthenogenetic generations that had passed, the developmental stage of the donor, or the time taken for the eggs to hatch. After 50 weeks there was, in both species, an overlap of up to six generations. The number of eggs produced by both species was significantly greater in the first parthenogenetic generation than in later generations but the numbers for later generations lie within the recorded range of egg number in imagos captured in the field.3. To find if parthenogenetic individuals occur in the field, the sex ratios of last instar nymphs and subimagos of C. simile were measured in samples collected over 13 successive years from a set of small isolated pools. There was a female bias both in winter and at the start of the emergence season. It is possible that, when mature nymphs and emerging subimagos are damaged by predators, the eggs which are released from them survive and develop.4. Mature, egg‐containing nymphs of both species were present in the field throughout the year, although their numbers were small at the beginning of winter.5. Oviposition by imagos captured from mating swarms and by virgin imagos, of both species, was recorded for the first time, showing that C. dipterum is not always ovoviviparous. It is suggested that early instar nymphs occurring in mid‐winter come not only from unfertilized eggs released from injured nymphs and subimagos, but also from fertilized eggs laid in autumn.
Effects of neonate size and food concentration on the life history responses of a clone of the hybrid Daphnia hyalina × galeata to fish kairomones
Authors: REEDE TINEKE 
Published: November 2003

1. The influence of fish kairomones on the life history parameters of a clone of the hybrid Daphnia galeata × hyalina was measured in laboratory experiments with small and large neonates at one food concentration. The influence of fish kairomones on neonates of the same size at two food concentrations was also investigated.2. Neonate size (maternal investment per egg) changed the influence of fish kairomones on life history parameters. Daphnids that were small at birth showed greater differences between fish (kairomones present) and no‐fish (kairomones absent) treatments for age at maturity and number of eggs in the first clutch than animals that were large at birth. On the other hand, animals that were large at birth differed more in size at maturity between fish and no‐fish treatments than small neonates.3. The food concentrations used in the experiments (0.25–0.75 mg C l–1) hardly affected the influence of fish kairomones on the life history characteristics studied.4. The effect of fish kairomones on the size of neonates from the first clutch was similar for large and small daphnids. In the no‐fish treatment significant differences were found between small and large neonates for age at maturity and number of eggs in the first clutch. In the fish treatment size at maturity differed significantly between small and large neonates.5. In life history experiments, neonate size has to be taken into account when measuring the effects of fish kairomones because size at birth influences the results.
The functional trophic role of lotic primary consumers: generalist versus specialist strategies
Authors: MIHUC TIMOTHY BRIAN 
Published: November 2003

1. The relative extent of generalist or specialist resource use strategies is an important question in ecology. A community dominated by specialist strategies suggests a high level of interspecific competition for resources, resulting in the evolutionary development of isolating mechanisms between species (e.g. resource specialization to avoid and/or outcompete other species). A community dominated by generalist strategies suggests less interspecific competition for resources, allowing many taxa to utilize the same resources. In stream systems, generalist food habits are a common strategy among primary consumers, but little is known about resource assimilation strategies (resources incorporated into tissue growth). Published data indicate that generalist resource assimilation strategies may prevail in lotic systems as well.2. Functional feeding groups (FFGs) are often used to infer resource assimilation among lotic macroinvertebrates (e.g. shredder‐detritivore, scraper‐herbivore). While these groupings are aptly used to describe invertebrate feeding modes and community structure, the use of FFGs to describe resource assimilation among lotic consumers is not appropriate. Sufficient data now exist to seriously question how accurately FFG assignments describe the processes of energy flow and material transfer between trophic levels in stream ecosystems.3. Because FFGs may not accurately describe functional attributes in lotic systems, an alternative approach is needed. One approach is to determine the amount of secondary production that is derived from autochthonous (e.g. periphyton and algae) and allochthonous (e.g. detritus) resources directly. A simple model of community function based on this approach is presented. The model incorporates trophic generalists into measurement of consumer–resource energetics in lotic systems.
Geographical variation of mitochondrial DNA between populations of the white‐clawed crayfish Austropotamobius pallipes
Authors: GRANDJEAN FRÉDÉRIC , SOUTY‐GROSSET CATHERINE , RAIMOND ROLAND , HOLDICH DAVID 
Published: November 2003

1. The white‐clawed crayfish Austropotamobius pallipes has a widespread distribution in Europe, but since the last century its distribution has been severely affected by a combination of factors, particularly the disease crayfish plague, introduced by foreign crayfish species. At present A. pallipes is considered as vulnerable and endangered and measures are being taken in a number of countries to conserve it.2. The application of genetics to conservation is of practical value particularly where restocking is being considered. This study assesses levels of genetic differentiation from an analysis of mitochondrial DNA (mtDNA) variation by restriction fragment length polymorphism of four populations sampled on a European scale. Six different composite haplotypes were detected among sixty‐four crayfish representing the four populations. mtDNA nucleon diversity values within species ranged from 0.63% to 12.35%. A close genetic similarity was found between British and French populations of A. pallipes.3. Results show that mtDNA can be as a suitable diagnostic marker for measuring genetic diversity between crayfish populations and that such information is of use in planning crayfish conservation strategies.
Using predictive models to estimate effects of flow regulation on net‐spinning caddis larvae in North Swedish rivers
Authors: ENGLUND GÖRAN , MALMQVIST BJÖRN , ZHANG YIXIN 
Published: November 2003

1. Effects of flow regulation on abundance and richness of net‐spinning caddis larvae (Hydropsychoidea; Trichoptera) were examined in fifty‐two North Swedish rivers. Models based on conditions at unregulated sites were used to predict densities at impacted sites and the residuals, i.e. the differences between observed and predicted numbers, were used as measures of the effects.2. Two broad categories of impacted sites were identified. Sites with regulated but unreduced flow often have reduced seasonal flow variation and slightly enhanced short‐term variation, while those with reduced flow usually have long periods of low and stable flow occasionally interrupted by short periods of violently fluctuating flow.3. The abundance of net‐spinning caddis larvae was significantly lower than predicted at both types of sites (reduction 30%), while richness was significantly reduced only at sites with reduced flow (reduction 20%).4. A subsequent analysis of the relationship between the effects and variables altered by flow regulations, e.g. flow magnitude and flow variation, indicated that species richness was primarily affected by the occurrence of periods with zero flow, while negative effects of abundance were associated with high flow variability.5. Significant negative effects on the abundance of individual taxa were observed for Cheumatopsyche lepida and Hydropsyche pellucidula at sites with regulated but unreduced flow.6. Analyses of the relationships between the effects and regulation‐related variables suggest that H. siltalai was significantly negatively affected by the occurrence of zero flow and that negative effects on Arctopsyche ladogensis were associated with flow reduction and high flow variability.
The influence of upstream predation on the expression of fish effects in downstream patches
Authors: ROSENFELD JORDAN 
Published: November 2003

1. Enclosures were installed in a fishless stream and divided transversely into upstream and downstream sections. Downstream sections were further divided longitudinally, and one of the downstream sections in each enclosure was stocked with juvenile coho salmon (Oncorhynchus kisutch), and the other side was left as a fishless control. Densities of juvenile coho were then manipulated in upper sections of enclosures to determine the effect of upstream predation intensity on fish predation effects in downstream sections.2. Significantly fewer mayflies (primarily Ameletus sp.) were observed grazing on unglazed ceramic tiles in lower enclosure sections with fish present. There was no detectable effect of fish density in upstream enclosure sections on the number of mayflies observed grazing on ceramic tiles in lower sections of the enclosures.3. There was a significant positive effect of both fish presence and upstream density on chlorophyll a concentrations on ceramic tiles in lower enclosure sections, but not on chlorophyll a on natural gravel substratum.4. Behavioural experiments with mayflies and coho in streamside troughs suggest that Ameletus sp. responds primarily to mechanical rather than chemical cues from coho parr.
Seasonal pattern in nutrient limitation and grazing control of the phytoplankton community in a non‐stratified lake
Authors: HANSEN ANNE‐METTE , ØSTERGAARD ANDERSEN FREDE , SKOVGAARD JENSEN HENNING 
Published: November 2003

1. The relative importance of zooplankton grazing and nutrient limitation in regulating the phytoplankton community in the non‐stratified Lake Kvie, Denmark, were measured nine times during the growing season.2. Natural phytoplankton assemblage bioassays showed increasing importance of nutrient limitation during summer. Growth rates at ambient nutrient concentrations were continually below 0.12 per day, while co‐enrichment with nitrogen (N) and phosphorus (P) to above concentration‐saturated conditions enhanced growth rates from May to the end of July.3. Stoichiometric ratios of important elements in seston (C : N, C : P, N : P), in lake water (TN : TP), in external loading (TN : TP) and in internal loading (DIN : DIP) were measured to determine whether N or P could be the limiting nutrient. TN : TP molar ratio of both lake water, benthic fluxes and external loading suggested P limitation throughout the growing season. However, seston molar ratios suggested moderate P‐deficiency only during mid‐summer.4. Abundance and community structure of the zooplankton varied considerably through the season and proved to be important in determining the responses of algal assemblages to grazing. High abundance of cladocerans and rotifers resulted in significant grazing impact, while cyclopoid copepods had no significant effect on the phytoplankton biomass.5. Regeneration of ammonium and phosphate by zooplankton were periodically important for phytoplankton growth. A comparison of nutrient regeneration by zooplankton with nutrient inputs from sediment and external sources indicated that zooplankton may contribute significantly in supplying N and P for the growth of phytoplankton.
Prediction of benthic macroinvertebrate composition using microhabitat characteristics derived from stereo photography
Authors: EVANS LISA , NORRIS RICHARD 
Published: November 2003

1. Benthic macroinvertebrate community and habitat features varying at the microscale ( 0.09 m2) were measured on one sampling occasion in the Thredbo River, Kosciusko National Park, NSW, Australia.2. Most of the substratum habitat variables were measured in three dimensions using stereo photography. This is the first time that this method has been used so extensively for this purpose in freshwater ecology.3. Microhabitat variables most related to benthic macroinvertebrate distribution and abundance were selected with multivariate analyses included rock length, height, area and water velocity. Individual variables alone could not account for macroinvertebrate variation, indicating the importance of interactions among variables.4. Nine selected habitat variables were used to predict macroinvertebrate taxonomic content of additional sites. Predictions were 87% accurate for taxa with a > 50% chance of occurrence and 93% accuracy for taxa with a > 70% chance of occurrence. Variability observed in macroinvertebrate assemblages at the time of sampling was largely physically controlled and highly deterministic.
The use of artificial neural networks to predict the presence of small‐bodied fish in a river
Authors: MASTRORILLO SYLVAIN , LEK SOVAN , DAUBA FRANCIS , BELAUD ALAIN 
Published: November 2003

1. Discriminant factorial analysis (DFA) and artificial neural networks (ANN) were used to develop models of presence/absence for three species of small‐bodied fish (minnow, Phoxinus phoxinus, gudgeon, Gobio gobio, and stone loach, Barbatula barbatula).2. Fish and ten environmental variables were sampled using point abundance sampling by electrofishing in the Ariège River (France) at 464 sampling points.3. Using DFA, the percentage of correct assignments, expressed as the percentage of individuals correctly classified over the total number of examined individuals, was 62.5% for stone loach, 66.6% for gudgeon and 78% for minnow. With back‐propagation of ANN, the recognition performance obtained after 500 iterations was: 82.1% for stone loach, 87.7% for gudgeon and 90.1% for minnow.4. The better predictive performance of the artificial neural networks holds promise for other situations with non‐linearly related variables.
Historical changes in epilimnetic phosphorus concentrations in six rural lakes in Northern Ireland
Authors: ANDERSON N. 
Published: November 2003

1. Sediment cores were taken from six lakes in Northern Ireland: Loughs Heron, Ballywillin, Corbet, Patrick, Brantry and Creeve. The present‐day total phosphorus (TP) concentrations of these lakes range from around 30 to 400 μg TP l–1. None of the lakes have sewage point‐sources disposing into them, and all have primarily agricultural catchments.2. Sediment cores were dated using 210Pb. The cores cover time periods ranging from about 100 years at Lough Corbet to periods considerably greater than the range of 210Pb (more than 150 years), Lough Patrick.3. Diatom stratigraphies indicate considerable ecological change at all the lakes, regardless of their current nutrient status. Epilimnetic phosphorus concentrations were inferred using weighted averaging regression and calibration. Diatom‐inferred TP values for the core surface samples agreed reasonably well with the contemporary values. Pre‐1900 TP concentrations range from about 10 μg TP l–1 at Lough Patrick to 80 μg TP l–1 at Lough Corbet. The higher values prior to 1900 are assumed to relate to land‐clearance activities and the expansion of agriculture associated with the Plantation period.4. Although there are increasing diatom‐inferred TP concentrations between 1850 and 1900 at some sites, there is a final and more marked increase at all lakes after 1950. Phosphorus concentrations have increased at all lakes, by between a factor of three to five, over an average 50‐year period. At four of the lakes, TP concentrations have been increasing linearly from around 1950 to the present day, suggesting that, in general, there is little sign of amelioration of the eutrophication problem.5. The post‐1950 increases are assumed to relate to changes in agricultural activity within their catchments, notably the continued improvement in field drainage, which has facilitated transfer of nutrients to water courses and lakes and increasing soil‐P concentration due to a positive annual‐P balance. Another factor, probably associated with increased animal grazing densities and improvement of grassland, is the application of animal slurries, which appears to be a largely unquantified factor.
Catchment and reach‐scale properties as indicators of macroinvertebrate species traits
Authors: RICHARDS CARL , HARO ROGER , JOHNSON LUCINDA , HOST GEORGE 
Published: November 2003

1. We used catchment and reach‐scale physical properties to predict the occurrence of specific species life history and behaviour traits of aquatic insects across fifty‐eight catchments in a mixed land use basin. Catchment‐scale attributes were derived using a geographical information system (GIS). Logistic regression techniques were used to model the relationships.2. The reach‐scale properties were highly predictive of species traits. Fourteen of the fifteen traits had significant models with concordance values greater than 68%. Cross‐sectional area at bank full discharge, % shallow, slow‐water habitats, and % fines were the most important variables.3. Life history and behavioural attributes were best related to reach‐scale physical features. This suggests that species traits exhibit strong relationships to local environmental conditions.4. Catchment‐scale variables had fewer significant models with species traits (four of fifteen), however these variables may have direct or indirect influence on reach‐scale properties.5. Catchment features, in particular surficial geology, influence macroinvertebrate assemblages through their control over channel morphology and hydrologic patterns.6. The effects of land use were masked by geology (i.e. lacustrine clay geology and rowcrop agriculture were correlated), lack of detail in land use data and the aggregation of the species data.7. These models reflect the coupling of local environmental conditions and the set of adaptations among the local taxa. These observations underscore the idea that habitat plays a major role in organizing stream assemblages.8. Using these approaches, predictions can be made about the ability of various taxonomic groupings to track environmental change through time, or for projecting the impact of alternative land management scenarios. Identifying fundamental life history and other traits can improve the selection and evaluation of such indicators.
Effects of drought and phenology on GPP in Pinus sylvestris: a simulation study along a geographical gradient
Authors: BERNINGER F. 
Published: November 2003

1. A simple canopy model was developed for Scots Pine (Pinus sylvestris L.) and applied to a transect of six meteorological stations in Europe. The model accounts for possible genetic adaptation of phenology of photosynthesis to the local climate and to decreases of gas exchange owing to drought. 2. Simulations accounting for adaptation of phenology to the local climate differed up to 20% from simulations using the same phenology parameter values for all locations. 3. A temperature increase of 3°C and a doubling of the CO2 concentration, while adjusting the photosynthesis parameters to give approximately the observed changed photosynthesis of +30%, also increased the length of the growing season by 23–42%. Combination of increases in the rate of photosynthesis and the length of the growing season resulted in increases of yearly Gross Primary Productivity (GPP) from 72 to 101%. Increases in transpiration were smaller. 4. A decrease of the precipitation by 25% reduced this increase to 54–64%. 5. The relative magnitude of the simulated increases in GPP was similar for locations representing boreal, temperate and mediterranean climates.