bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring acid waters in the U.K.: an overview of the U.K. Acid Waters Monitoring Network and summary of the first interpretative exercise
Authors: PATRICK S. , BATTARBEE R.W. , JENKINS A.
Published: November 2003

1. The U.K. Acid Waters Monitoring Network (AWMN) was established in 1988. It comprises eleven lake and eleven stream sites located throughout the U.K. in areas sensitive to acidification. The principal objective of the AWMN is to provide a long‐term, high‐quality chemical, biological and palaeolimnological record which, in conjunction with the U.K. precipitation monitoring networks, will facilitate the assessment of trends within U.K. surface waters.

2. The first interpretation of results generated by the AWMN (April 1988–March 1993) has recently been completed and is summarized. During this period there have been no sustained changes in atmospheric deposition in the U.K. Trends are recognized in certain chemical and/or biological parameters at individual AWMN sites, but despite some (regional) patterns no regional trends toward increasing or decreasing acidification are apparent. The data comprise an excellent baseline with which future changes may be compared.

3. The methodology of the AWMN is reviewed and some amendments are suggested in the light of the first 5 years experience. These include: additional determinations for nitrogen species and total phosphorus; changes to the frequency of macrophyte and palaeolimnological sampling; new emphasis on data generated by sediment traps at lake sites; and the addition of extra sites to address better the full extent of acid‐sensitive surface waters revealed by the national critical loads mapping programme, and to pay particular attention to the acidifying role of nitrogen.

4. The contribution of AWMN data to other national and international environmental monitoring programmes is highlighted. In addition, AWMN sites provide data to develop and validate critical loads models and dynamic models of acidification, and could also be used to monitor the impact of other air pollutants such as trace metals and persistent organic compounds on the freshwater environment.
The determination of total nitrogen and total phosphorus concentrations in freshwaters from land use, stock headage and population data: testing of a model for use in conservation and water quality management
Authors: JOHNES PENNY , MOSS BRIAN , PHILLIPS GEOFFREY
Published: November 2003

1. Nutrient concentrations (particularly N and P) determine the extent to which water bodies are or may become eutrophic. Direct determination of nutrient content on a wide scale is labour intensive but the main sources of N and P are well known. This paper describes and tests an export coefficient model for prediction of total N and total P from: (i) land use, stock headage and human population; (ii) the export rates of N and P from these sources; and (iii) the river discharge. Such a model might be used to forecast the effects of changes in land use in the future and to hindcast past water quality to establish comparative or baseline states for the monitoring of change.

2. The model has been calibrated against observed data for 1988 and validated against sets of observed data for a sequence of earlier years in ten British catchments varying from uplands through rolling, fertile lowlands to the flat topography of East Anglia.

3. The model predicted total N and total P concentrations with high precision (> 95% of the variance in observed data explained). It has been used in two forms: the first on a specific catchment basis; the second for a larger natural region which contains the catchment with the assumption that all catchments within that region will be similar. Both models gave similar results with little loss of precision in the latter case. This implies that it will be possible to describe the overall pattern of nutrient export in the UK with only a fraction of the effort needed to carry out the calculations for each individual water body.

4. Comparison between land use, stock headage, population numbers and nutrient export for the ten catchments in the pre‐war year of 1931, and for 1970 and 1988 show that there has been a substantial loss of rough grazing to fertilized temporary and permanent grasslands, an increase in the hectarage devoted to arable, consistent increases in the stocking of cattle and sheep and a marked movement of humans to these rural catchments.

5. All of these trends have increased the flows of nutrients with more than a doubling of both total N and total P loads during the period. On average in these rural catchments, stock wastes have been the greatest contributors to both N and P exports, with cultivation the next most important source of N and people of P. Ratios of N to P were high in 1931 and remain little changed so that, in these catchments, phosphorus continues to be the nutrient most likely to control algal crops in standing waters supplied by the rivers studied.
Diatoms as indicators of river quality in the Nepalese Middle Hills with consideration of the effects of habitat‐specific sampling
Authors: JÜTTNER INGRID , ROTHFRITZ HEIKE , ORMEROD S.J.
Published: November 2003

1. Using a replicated survey design at the catchment scale, we compared the composition and diversity of diatom communities in three stream groups in the Middle Hills of Nepal: semi‐natural reference (Arun Valley), enriched by agricultural runoff (Likhu Khola) and grossly polluted by sewage (Kathmandu Valley). We sampled riffles at all sites; in the Kathmandu Valley and Likhu Khola we also sampled diatoms in pools and on vegetation.

2. Species richness and diversity H′ were significantly higher in agricultural streams than in either organically polluted streams or references. Community composition, as shown by principal components analysis, varied significantly between all three stream types due to differences in the abundances of species characteristic of organic enrichment (Kathmandu Valley), moderate enrichment (Likhu Khola) or undisturbed hillstreams (Arun Valley).

3. Few species varied in relative abundance between pools, riffles and vegetation so that variations in community composition and diversity were stronger between stream groups than between habitats. Samples from any one habitat produced only 75.7% (± 8.6 SD) of the species from three habitats, so that surveys aimed at recording biodiversity may need more comprehensive habitat coverage than surveys for biomonitoring.

4. We conclude that diatom communities can indicate different sources of pollution in Nepalese streams, and advocate further studies to develop this indicator potential over a wider area of the Himalaya. Comparisons between replicate groups of streams selected a priori helped to clarify effects which were sometimes obscured by other survey designs.
A functional model for maximum growth of immature stone loach, Barbatula barbatula, from three populations in north‐west England
Authors: ELLIOT J.M. , HURLEY M.A. , ALLONBY J.D.
Published: November 2003

1. The chief objective was to develop a functional model for growth of stone loach, Barbatula barbatula, using immature fish from three populations. The growth model had been developed previously for brown trout, Salmo trutta, but new estimates of the five parameters for the stone loach had to be obtained from laboratory experiments.

2. Fish from four size groups (initial arithmetic mean live weights 0.053 g, 0.231 g, 0.840 g, 1.612 g, with five fish per group) from Great Oaks Wood Beck were acclimatized to constant temperatures of either 3, 5, 10, 15, 20 or 25 °C. Each fish was kept in a separate tank and fed to satiation on freshwater shrimps. Weights and lengths of each fish were recorded at the start and finish of a growth period of 35 days. For each of the other populations (Black and Ford Wood Becks), there were only three temperatures

(5, 10, 20 °C) with ten fish per temperature.

3. The growth model was an excellent fit (P < 0.001, R2 > 0.99) for the 120 fish from Great Oaks Wood Beck. Growth rates were negative at 3 °C, close to zero at 5 and 25 °C, and positive at 10, 15 and 20 °C, with an optimum value of 19 °C. When growth rates were positive, they decreased markedly with increasing fish weight for small fish but decreased more slowly for larger fish. At the start of the experiments, weight–length relationships were similar for fish from all three populations and were well described by a power function. There was excellent agreement between growth rates estimated from the fitted growth model for fish from Great Oaks Wood Beck and values obtained for fish from Black and Ford Wood Becks. Data from all three populations were therefore pooled (n = 180) to obtain new estimates of the five parameters in the model.

4. Comparisons between parameter estimates for trout and stone loach showed that the latter grew better in warmer waters (e.g. optimum value for growth was 19.0 °C for stone loach and 13.1 °C for trout, with ranges for growth of 5.0–25.0 °C and 3.6–19.5 °C, respectively).
Functional differences in epiphytic microbial communities in nutrient‐rich freshwater ecosystems: an assay of denitrifying capacity
Authors: ERIKSSON PEDER , WEISNER STEFAN
Published: November 2003

1. The denitrifying capacity of epiphyton was used to evaluate differences in the function of epiphytic microbial communities on submersed macrophytes in nutrient‐rich freshwater ecosystems. The denitrifying capacity of epiphyton on Potamogeton perfoliatus shoots of different age and with different epiphytic abundances from a eutrophic lake was investigated in laboratory microcosms in the light and dark. Additionally, differences between epiphyton on shoots of Potamogeton pectinatus grown under different in situ nutrient and hydraulic conditions were investigated by examining their denitrifying capacity.

2. Denitrification was registered in well‐developed epiphytic layers on both mature and senescent shoots in the dark, with activities 3‐ to 10‐fold higher in the epiphytic communities of senescent shoots. No activity was detected on young shoots with sparse epiphyton or on shoots from which loosely attached epiphyton had been removed. Denitrification never occurred during illumination.

3. Even though the epiphytic abundance was similar in magnitude, the denitrifying capacity of epiphyton adapted to high nutrient loadings was about a hundred times higher than that of epiphyton adapted to lower nutrient levels. Additionally, epiphytic abundance and denitrifying capacity were higher at sites less exposed to wave turbulence or water currents, than at sites with more water turbulence.

4. The results illustrate how the hydraulic and nutrient conditions of the surrounding water affect both the quantity and function of epiphytic microbial communities in nutrient‐rich freshwater ecosystems.
Oral deformities in tadpoles (Ranacatesbeiana) associated with coal ash deposition: effects on grazing ability and growth
Authors: CHRISTOPHER ROWE , KINNEY OWEN , FIORI ALISON , CONGDON JUSTIN
Published: November 2003

1. Tadpoles of the bullfrog (Ranacatesbeiana) collected in a coal ash deposition basin (contaminated with As, Cd, Cr, Cu, Se and other elements) and a downstream drainage swamp had a reduced number of labial teeth and deformations of labial papillae when compared with tadpoles from reference areas. Tadpoles from the coal ash‐affected areas had 90% fewer teeth in anterior tooth row number 2 and 40% fewer teeth in posterior row number 1 than reference animals. In the deposition basins, drainage swamp and reference ponds, respectively, 96.2, 85.1 and 2.9% of tadpoles had oral deformities.

2. Tadpoles with deformities were less able to graze periphyton than were normal tadpoles, when tested in the laboratory. When presented with periphyton as a sole food source, tadpoles with deformed teeth had lower (negative) growth rates than those with normal teeth, which had slightly positive growth rates. When particulate food was also available, tadpoles grew well regardless of deformities.

3. It appears that the morphological deformities associated with this coal ash‐polluted environment can have ecological ramifications for the affected organisms by limiting the type of food that can be consumed and the ability to grow when multiple food types are unavailable.
Multi‐scale approach to species–habitat relationships: juvenile fish in a large river section
Authors: POIZAT GILLES , PONT DIDIER
Published: November 2003

1. Juvenile fish were sampled by electrofishing using the point abundance sampling method from August to November 1991 in the Lower Rhône River. Variations in fish abundance between point samples were partitioned according to three spatial scales of habitat heterogeneity.

2. The compartment scale, differentiating channel and ‘dike fields’ (an area marginal to the main channel partially enclosed by an artificial embankment), was associated with variation in water current, temperature and biological productivity. Every juvenile fish species studied was more abundant in the dike fields, using them as a nursery.

3. Within both compartments (i.e. main channel and dike fields), the same five bank types were represented, defining the intermediate scale of habitat heterogeneity. In the dike fields, beaches were selected by most of the species, whereas steep silt banks were more often selected in the main channel.

4. After having removed the variation explained at the two larger habitat scales, only depth and shelter were found to have a significant effect on fish abundance at the microhabitat scale.

5. When compared with a classical single‐scale approach, the multi‐scale approach was found to explain a greater amount of fish abundance variations and to facilitate the interpretation of observed patterns by scaling the species’ responses to habitat heterogeneity. The difference between the amounts of variation explained was proposed as a measure of how much habitat selection is hierarchical.
Effects of aggregative behaviour on the bioenergetics of the freshwater predatory leech Nephelopsis obscura (Erpobdellidae)
Authors: SMITH D.E.C. , DAVIES RONALD
Published: November 2003

1. Supplied with ad libitum prey, the effects of different group sizes (one, five, ten, twenty‐five, fifty or 100) on the acquisition and allocation of energy were examined over the entire life cycle of the freshwater predatory leech Nephelopsis obscura, to evaluate the bioenergetic costs and/or benefits of aggregation.

2. In terms of growth, asymptotic biomass and ingestion, group sizes larger than one and less than ten are optimal. As group size increases from ten to 100, N. obscura has slower growth and lower weekly food ingestion, suggesting interference competition. Single leeches had lower food consumption than group sizes of less than 100 animals. With a lower asymptotic biomass, single leeches have lower fecundity and presumed lower fitness. Lipid deposition was unaffected by group size.

3. Size‐ and time‐specific respiration rates declined with increasing group size. For group sizes between five and fifty, the same relative proportion of ingested energy was allocated to respiration. Above this threshold group size, leeches allocated a higher proportion of ingested energy to growth, i.e. had higher growth efficiency, as did leeches cultured individually.

4. In the largest group size, total time spent in activity was highest (reflecting the high degree of interference between conspecifics), but as a result of the lower hourly costs of respiration they allocated a lower proportion of ingested energy to total respiration.

5. Optimum group size of N. obscura in the laboratory is within the typical range of group sizes found on stony shores in the field.
Differential behavioural responses of mayflies from streams with and without fish to trout odour
Authors: McINTOSH ANGUS , PECKARSKY BARBARA
Published: November 2003

1. In streams, mayflies (Order Ephemeroptera) are at risk from fish feeding visually in the water column. The effect of fish odour on the behaviour of Baetis bicaudatus from a fishless stream and a trout stream was investigated in four large oval tanks supplied with water from the fishless stream.

2. For each mayfly population, mayfly positioning on the substratum and movement in the water column (drift) were measured during the day and night, over 3 days. Brook trout (Salvelinus fontinalis) odour was added to two tanks to test the effect of a threat from fish.

3. Throughout the experiment more mayflies from the trout stream were observed on the substratum surface and in the water column during the night than the day, but the magnitude of night drift was less in tanks with fish odour.

4. Baetis from the fishless stream also displayed a nocturnal periodicity in drift and positioning, but their night‐time drift was not affected by the presence of fish odour. On the first day of the experiment, however, more mayflies were observed on the substratum surface and drifting in tanks without fish odour during the day.

5. Sensitivity to fish odour may enable mayflies to alter their behaviour according to the risk of predation from fish.
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.
Functional consequences of trophic specialization in pufferfishes
Authors: RALSTON K. R. , WAINWRIGHT P. C.
Published: November 2003

1. Trophic breadth may be correlated with behavioural and functional versatility or flexibility (Liem 1984), such that species with limited diets would be predicted to be less versatile or flexible in their feeding capabilities than would trophic generalists. The relationship was examined between the trophic breadth of a species and the degree to which muscle activity is influenced by prey type in two species of pufferfishes: Chilomycterus schoepfi, a specialist on hard‐shelled prey, and Sphoeroides nephalus, a generalist predator. It was predicted that the specialist would show a decreased ability to alter its motor pattern in response to prey type and an increased amount of motor‐pattern variability when feeding on different prey.

2. Electromyographic recordings of five feeding muscles were made from five individuals per species feeding on four prey types that differed in their hardness and escape abilities. Muscle‐activity duration, relative onset and integrated rectified area were analysed for prey capture and manipulation behaviours for each prey type.

3. Prey‐type effects on mean motor‐pattern variables for capture were limited to one of 14 variables in each species. Prey effects on buccal manipulation were not significant for any of the 14 variables for C. schoepfi, but S. nephalus exhibited prey effects for seven out of 14 variables. No differences in motor‐pattern variation were found for the strike, but species differed significantly in overall motor‐pattern variability during buccal manipulation; C. schoepfi, the dietary specialist, exhibited greater motor variability than S. nephalus, the dietary generalist.

4. The results therefore support a direct relationship between the trophic breadth of a species and its functional versatility for buccal manipulation. In contrast, prey capture was a relatively stereotyped behaviour for both species, as few prey‐type effects were found.
In situ effects of elevated CO2 on the carbon and nitrogen status of alpine plants
Authors: SCHÄPPI B. , KÖRNER CH.
Published: November 2003

1. The effect of elevated CO2 on tissue composition in an alpine grassland (Swiss Central Alps, 2500m) under both natural and increased nutrient supply (NPK) is summarized.

2. During 3 years of CO2 enrichment the concentration of total non‐structural carbohydrates (TNC) in leaves increased by 32% in Leontodon helveticus (largely sugar) and by 56% in Trifolium alpinum (largely starch) but did not change significantly in the dominant sedge Carex curvula and in Poa alpina, currently a rare species at this site.

3. Enhanced mineral nutrient supply (unlike elevated CO2) greatly stimulated growth but did not reduce the CO2‐induced TNC accumulation.

4. Under elevated CO2 nitrogen concentrations (per g TNC‐free dry matter) of green leaves decreased in Leontodon (–21%) and in Trifolium (–24%) but not or only slightly in Carex and in Poa. NPK addition compensated this CO2 effect on nitrogen concentration in Trifolium but not in the other species.

5. In below‐ground tissue neither TNC nor nitrogen concentration responded to CO2 fertilization.

6. The nitrogen pool per unit land area at peak season biomass remained unaffected by the CO2 treatment.

7. Overall our results suggest that the late successional dominant sedge Carex curvula remains unaffected by elevated CO2, independently of mineral nutrient supply, whereas the co‐dominant and sub‐dominant forbs Leontodon helveticus and Trifolium alpinum show both an increase of TNC as well as N depletion under elevated CO2.

8. None of these changes in active plant tissue translate into compositional changes in naturally senesced litter suggesting caution with predictions of CO2 effects on decomposition based on data from green plant material.
Host selection by virgin and inseminated females of the parasitic wasp, Dinarmus basalis (Pteromalidae, Hymenoptera)
Authors: NISHIMURA K.
Published: November 2003

1. Fitness is related to reproduction and survival. There apparently exists a negative correlation between the numbers of male and female offspring. There also exists a trade‐off between survival and reproduction. This paper investigates optimal decisions with the reproduction and survival trade‐off in host selection by wasps.

2. Whereas inseminated female wasps could manipulate the sex of their offspring, virgin females produced only male offspring. I surveyed behavioural differences and the consequences of oviposition by inseminated and virgin females of a solitary parasitic wasp in host choice situations.

3. Two host types were available at the same time to both inseminated and virgin female wasps: one (a 17‐day‐old host in one bean) presenting difficulties for the laying of eggs, but more benefits for the offspring and the other (five 12‐ or 13‐day‐old hosts in one bean) easier for the female wasp for laying of eggs but less beneficial for the offspring.

4. Inseminated female wasps chose more 17‐day‐old hosts than 12‐day‐old hosts, but more 13‐day‐old hosts than 17‐day‐old hosts in each pair‐wise choice. Virgin females chose the smaller hosts in both situations.

5. Virgin females, having greater longevity than inseminated females, laid larger numbers of eggs than the inseminated females during their lifetime by adopting an energy‐saving host choice that had little effect on male offspring fitness.
Light stress effects and antioxidative protection in two desert plants
Authors: STREB P. , TEL‐OR E. , FEIERABEND J.
Published: November 2003

1. The enzyme catalase was investigated as a sensitive marker of light stress in Retama raetam stems and Atriplex halimus leaves. While the activity of catalase was readily photoinactivated in vitro when crude extracts from these tissues were exposed to a photon flux of 500μmolm–2s–1 photosynthetic active radiation (PAR), no apparent losses of the extractable catalase activities were observed when tissues were harvested from desert plants at noon when light levels were as high as 2200μmolm–2s–1 PAR.

2. When stems of R. raetam or leaves of A. halimus were exposed to natural daylight of 1000μmolm–2s–1 PAR in the presence of cycloheximide (CHI), in order to prevent the new synthesis of catalase, or at a temperature of 42–44°C, only minor losses of catalase activity occurred in stems of R. raetam, but a marked apparent photoinactivation of catalase was observed in leaves of A. halimus.

3. Similarly, stronger declines of the ratio Fv/Fm, indicating more severe photoinhibition of photosystem II (PSII), were observed in A. halimus, compared with R. raetam.

4. For R. raetam, activities of some antioxidative enzymes and the carotenoid contents were higher in plants growing in the desert than in plants collected from non‐desert locations.

5. During the daily increase of light and temperature the antioxidants ascorbate and glutathione became more oxidized and violaxanthin was converted to zeaxanthin in R. raetam stems, while these antioxidants became more reduced and zeaxanthin was not notably accumulated in A. halimus leaves.

6. The results suggest that the desert plants R. raetam and A. halimus apply different strategies of protection against light‐stress damage. In the stems of R. raetam antioxidative protection appears to play the major role, while A. halimus appears to avoid light damage in the field by the mutual shading of leaves and reflection of light at the leaf surface.