bluuebunny/crossref_metadata_2025 huggingface dataset:
Macroinvertebrate functional feeding groups in the middle and lower reaches of the Buffalo River, eastern Cape, South Africa. I. Dietary variability
Authors: PALMER CAROLYN , O'KEEFFE JAY , PALMER ANTHONY , DUNNE TIMOTHY , RADLOFF SARAH
Published: May 2006

The question of whether the diets of twelve abundant macroinvertebrate taxa from the middle and lower reaches of the Buffalo River (eastern Cape, South Africa) were too variable to allow them to be assigned to functional feeding groups (FFGs) was addressed.

 Spatial, temporal and developmental variations in diet were assessed. Foregut content analysis was used as an index to compare diets.

 Foregut contents were compared from early (small) and late (large) instar larvae collected from riffles at thirteen sites in summer, and from riffles, stony backwaters and sediments at four of these sites in spring, summer, autumn and winter, in 1987.

 For all individuals of all taxa, fine amorphous detritus (0.5–250 μm), was the most common dietary item. Differences in diet followed a similar pattern for all taxa. The most frequent differences in dietary content were between large and small larvae. The foreguts of large larvae contained more material, and a wider variety of rare items than small larvae. Neither species nor FFGs could be distinguished on the basis of foregut contents.

 Two dietary types were recognized. The eight mayfly larvae were fine detritivores, having ingested fine detritus almost exclusively. In contrast, the two hydropsychid caddisfly larvae had ingested a mixed diet; their gut contents included chirinous invertebrate remains and other items as well as fine detritus.

 Intra‐specific dietary variability was not so great as to prevent these taxa from being assigned to FFGs. On the contrary, inter‐specific dietary content was so similar that gut content analysis could not provide a positive basis upon which to identify FFGs.
The infection ofMoina macrocopaby a colonial peritrich,Epistylis daphniae, and its effects on the host
Authors: XU ZHENKANG
Published: May 2006

The effects of infection byEpistylis daphniaeon its host,Moina macrocopa, were studied in the laboratory at 28°C by comparing the growth, reproduction and survival between infected and uninfected hosts.

 Infestation by epizoites had little or no effect on the survival of the dadoceran hosts when adequate food was present.

 The infected cladocerans had lower growth rates as juveniles, lower net reproduction rates as adults, and smaller body size at death than uninfected hosts.

 The index of infection at different stages in the life cycle was related to the durations of intermoult period. Ranked in order of both index of infection and intermoult duration, the development stages were: old adult > young adult > juvenile.
Hatching of Daphnia sexual eggs. II. The effect of age and a second stimulus
Authors: DE MEESTER LUC , DE JAGER HILDE
Published: May 2006

We examined the effect of age on the hatching response of Daphnia magna sexual eggs of specific families. For old eggs (>2 years), hatching characteristics were compared at two storage temperatures (4°C and 20°C). Also, the hatching response after a second dark incubation and subsequent incubation under conditions favourable for hatching was compared with that after the first stimulus.

  Daphnia sexual eggs were found to remain viable for several (at least 4.5) years. The effect of age on the hatching rate was family dependent. At least in some families, hatching rate was higher for old (>2 years) than for young (<5 months) eggs. Low temperature (4°C) during dark incubation resulted in a higher hatching rate compared with incubation at 20°C.

 The application of a second hatching stimulus resulted in a renewed hatching response. The overall hatching rate after the second stimulus was, however, lower than that of the first stimulus.

 More than 80% of the hatchlings of young eggs appeared on Day 3 or 4, with minor between‐family differences in time distribution of hatching. The timing of the response to hatching stimuli was more variable in old than in young eggs, with the average time at hatching being 6.4 instead of 4.0 days. The response to the application of hatching stimuli was also slower after the second stimulus compared with the first stimulus.
Random patch dynamics of larval Chironomidae (Diptera) in the bed sediments of a gravel stream
Authors: SCHMID P.E.
Published: May 2006

The larval chironomid community of the sediment surface and the hyporheic inters titial was investigated in two longitudinal transects of an alpine gravel stream between September 1984 and August 1985. Eighty larval species and species groups were identified, most of which belonged to the subfamily Orthocladiinae. Of all larval individuals 51.1% inhabited the first 10cm of the bed sediments, and 93.2% occurred between the surface and 40cm depth.

 The spatial species turnover showed marked variations between horizontally adjacent sampling sites in each of the four sediment depth layers. In both transects the species composition showed a significantly lower turnover in the upper 10cm of the bed sediments than in the deeper layers.

 Spatial community stability showed an oscillating pattern between all sampling sites due to density shifts of larvae between depth layers. Temporal differences in resilience (local stability) were significantly and positively related to changes in the cumulative discharge pattern in the gravel brook, thus indicating the apparent ability of the community to recover quickly following disturbances.

 The five abundant species, Corynoneura lobata, Synorthocladius semivirens, Tvetenia calvescens, Micropsectra atrofasciata and Rheotanytarsus nigricauda, exhibited significant differences in their sediment depth distribution, with density maxima shifting between depth layers. Spatial autocorrelations suggest that these larvae form patches between neighbouring sampling sites with varying sizes and inter‐patch distances in each of four sediment layers. A simulation test, in which individuals of each species were randomly permuted between microhabitats of each depth layer separately, indicated that the patches might have arisen by chance.

 To evaluate the significance of observed spatial resource overlap values amongst these five chironomid species, neutral models were developed based on 300 randomizations of each possible species pair‐wise association of individuals and patches of species. The spatial organization of a larval chironomid assemblage in the stream Oberer Seebach seemed to be governed by coexistence due to random patch formation and dispersal patterns within the interstitial habitats, which reduce the probability of strong competitive interactions.
Potential importance of algae in the diet of adult Cyclops vicinus
Authors: SANTER BARBARA
Published: May 2006

The potential importance of phytoplankton to the nutrition of adult Cyclops vicinus was studied.

 The flagellate Chlamydomonas reinhardii was ingested and digested at a higher rate than the coccale green alga Monoraphidium minutum.

 The predation rate on the rotifer Brachionus rubens decreased if C. reinhardii was also available as food. No significant reduction of predation was found when M. minutum was offered together with B. rubens.

 The species of available phytoplankton influenced egg production. Females which were allowed to feed on B. rubens and C. reinhardii produced more eggs than females which fed on rotifers only or a diet containing rotifers and M. minutum. Egg production was also possible when rotifers were absent from the diet.

 Production efficiency was higher when C. reinhardii was the only food resource than on a diet containing rotifers only.
Limitations of FST hemispheres in lotic benthos research
Authors: FRUTIGER A. , SCHIB J.‐L.
Published: May 2006

FST hemispheres have been proposed as a method for assessing flow characteristics near the river bottom. We suspected that the hemispheres were too big for this goai and that the ground plate would significantly affect near‐bottom microhydraulics.

 The results we present have confirmed our assumption about the limitations of this method: the correlation between FST results and current velocity (measured by an anemometer, φ= 1.2cm) was best at 40% of depth (‘mean current velocity’, coefficient of determination r2= 0,58) and decreased to r2= 0.24 at 0.6 cm above the bottom; the correlation with (calculated) shear stress was only r2= 0.23. A correlation between FST results and macroinvertebrate abundance was found for only four of eight investigated taxa and was similar to the correlation between abundance and ‘mean current velocity’.

 We conclude that for fieldwork the FST hemispheres have about the same limitations as has a conventional (i.e. propeller‐type) anemometer. With the hemispheres we could not obtain better data than with other methods.
The influence of phosphorus enrichment on lotic bryophytes
Authors: STEINMAN ALAN D.
Published: May 2006

Phosphorus enrichments of 5 weeks' duration were performed in two woodland streams in eastern Tennessee, U.S.A. to determine their effect on the dominant stream bryophyte, Porella pinnata.

 In a second‐order reach of Walker Branch, which had an N:P ratio (by atoms) of 3.5:1 in the stream water, the P:C ratio of Porella was not significantly affected by enrichment, but the P:N ratio did increase significantly. In Sludge Creek, which had an N:P ratio of 21.6:1 in the stream water, both P:C and P:N ratios of Porella increased significantly following phosphorus addition. Increased phosphorus ratios may have resulted from either assimilation or adsorption.

 Absolute phosphorus concentrations in Porella tissue were significantly greater prior to enrichment in the control reach of Walker Branch, confounding the effect of phosphorus enrichment. In Sludge Creek, absolute phosphorus content in Porella tissue increased significantly in the treated reach and showed no significant difference in the control reach.

 Although mean primary production increased by approximately 15% following enrichment, the increase was not significantly different from that prior to enrichment.

 Epiphyte structure and abundance were not significantly influenced by enrichment in either stream. It is suggested that grazing pressure by snails may have masked any potential epiphyte response to enrichment.
Predation by Neomysis mercedis: effects of temperature, Daphnia magna size and prey density on ingestion rate and size selectivity
Authors: CHIGBU PAULINUS , SIBLEY THOMAS H.
Published: May 2006

1. Neomysis mercedis predation rates on Daphnia magna were determined under laboratory conditions. There were generally no consistent differences between the number of Daphnia ingested at 10 and 14°C.

2. At each temperature, the number of prey consumed increased with mysid size and decreased with Daphnia size.

3. For small prey the relationship between ingestion rate and prey density represented a Type II functional response. However, for larger prey there was no significant relationship between density of prey and consumption by mysids.

4. The pattern of size‐selective predation by Neomysis was studied to test the optimal foraging hypothesis. For prey populations with mixed size classes, the smallest size of prey was consumed most frequently but intermediate size prey provided the greatest biomass. These observations are contrary to our predictions based on calculations of profitability of different sizes of prey.
Disturbance to a stream food web by a bacterial larvicide specific to black flies: feeding responses of predatory macroinvertebrates
Authors: WIPFLI MARK S. , MERRITT RICHARD W.
Published: May 2006

1. A field study was conducted to: (i) assess feeding habit changes of two predatory stoneflies following the loss of larval black fly (Diptera: Simuliidae) prey from two streams; and (ii) determine the relative importance of black fly larvae as prey for these and other selected predatory benthic macroinvertebrates.

2. Acroneuria lycorias and Paragnetina media (Plecoptera: Perlidae) diets were monitored in response to local reductions in larval black fly populations caused by Bacillus thuringiensis var. israelensis (B.t.i.) in two Michigan streams. These predators were collected from B.t.i.‐treated and control sections of the streams, and their foreguts inspected for prey.

3. Black flies were the major dietary component of both predators collected from the control sections, but the number of black flies ingested was significantly less for predators collected from B.t.i.‐treated habitats. Total number of prey ingested significantly decreased for A. lycorias, but not for P. media, and non‐black fly prey consumption significantly increased for P. media, but not for A, lycorias, following B.t.i. applications.

4. In prey choice trials conducted in experimental channels, A. lycorias and P. media showed no preference between prey types (black flies and mayflies). Body mass gain of individual A. lycorias nymphs was measured, and was similar for nymphs in black fly‐rich and black fly‐poor environments. Conversely, Isoperla signata and I. dicala (Plecoptera: Perlodidae) ingested significantly more Simulium vittatum (Diptera: Simuliidae) than Baetis flavistriga (Ephemeroptera: Baetidae) or Epeorus vitrea (Heptageniidae) prey. Boyeria vinosa (Odonata: Aeshnidae) ingested significantly more B. flavistriga than S. vittatum prey.

5. Reducing black fly densities in these streams, using B.t.i., indirectly and differentially affected predators. In black fly‐poor environments, feeding habits of specialist predators were most affected, and generalist predators least affected because the latter consumed alternative prey. Predator—predator and predator‐prey interactions, and prey community structure may be affected indirectly by disturbances such as B.t.i. applications by reducing food resources and forcing predation onto less preferred prey.
Feeding plasticity of two detritivore‐shredders
Authors: FRIBERG NIKOLAI , JACOBSEN DEAN
Published: May 2006

1. The feeding preferences of the trichopteran shredder Sericostoma personatum Spence and the amphipod shredder Gammarus pulex L. were studied using specimens collected in a springbrook where the major food source was beech litter (Fagus sylvatica L.). Six food items were tested: conditioned beech leaves, conditioned alder leaves (Alnus glutinosa L.), conditioned Sitka spruce needles [Picea sitchensis (Bong.) Carr], fresh beech leaves, a fresh macrophyte (Potamogeton perfoliatus L.) and a fresh filamentous green alga (Microspora sp.).

2. The overall preference pattern shown by the two shredders was the same: both preferred conditioned Alnus most, followed by fresh Microspora. The least preferred food items were conditioned Fagus leaves and Picea needles.

3. The feeding preference of the two shredders proved to be unrelated to food source fibre content, toughness, total phosphorus, C:N ratio and total nitrogen (P>0.05).

4. Despite the overall similarity in their feeding preferences, Gammarus was more selective than Sericostoma. The reason for this difference is discussed.

5. We interpret our findings as indicating that detritivore‐shredders do not per se prefer leaf litter, but in fact actively select other food items such as filamentous green algae or macrophytes, even when terrestrial leaf litter is abundant. Most shredders in Danish forest streams thus seem to live on a growth‐limiting food resource that they do not prefer. This may have important implications for secondary production in such streams.
Pattern, process and prediction in aquatic ecology. A limnological view of some general ecological problems
Authors: HARRIS GRAHAM P.
Published: May 2006

1. New scientific concepts such as models of chaos, complex dynamics and non‐linear interactions have the potential to contribute to an improved understanding of ecological patterns and processes. This paper discusses some of the known dynamics of phytoplankton, pelagic food chains and nutrient cycles in the light of some of these new concepts. The paper brings these new conceptual models together with data from a wide range of sources in an attempt to produce a synthesis of system behaviour which allows us to understand why some things are inherently more predictable than others. In particular it looks at the limnological management tools of empirical biomass models and biomanipulation and at the need for prediction of species composition.

2. The structures observed in ecosystems (nutrient pools, sizes, species, temporal/spatial patterns) show properties at a spectrum of scales, as do the processes (fluxes, grazing, competition). Both respond to a spectrum of external perturbations that may be climatologically or anthropogenically induced. Empirical biomass models work because of the annual averaging of pattern and process and because of some inherent properties of the functioning of pelagic ecosystems. Many aspects of ecosystem pattern and process vary in a regular way with trophic state. Examination of empirical data sets can lead to an improved understanding of system behaviour if questions are asked about why things happen the way they do.

3. Feedbacks between pattern, process and periodicity are seen to be an inherent property of the system. Understanding the fundamental dynamics of non‐linear interactions in ecosystems may make it possible to exploit the external spectrum of environmental perturbations and to control system function. For example, by imposing external physical perturbations on pelagic systems it may be possible to manipulate the species composition of the phytoplankton community. Because of the complexity of possible interactions both ‘horizontally’ between species and ‘vertically’ within the food chain, any prediction of species composition will necessarily be probabilistic.
Stress responses and metal exchange kinetics following transplant of the aquatic moss Fontinalis antipyretica
Authors: LOPEZ JESUS , VAZQUEZ M. DOLORES , CARBALLEIRA ALEJO
Published: May 2006

1. We studied stress responses and metal exchange (uptake and loss) kinetics in the aquatic moss Fontinalis antipyretica Hedw. following transplant (in plastic mesh bags) to clean and metal‐contaminated river sites and under laboratory conditions.

2. The stress response (estimated on the basis of chlorophyll:phaeophytin ratio) was more pronounced, and the moss took longer to recover, following transplant to heavily contaminated sites.

3. Metal uptake over the 28 day exposure period was predicted well by a two‐compartment kinetic model: uptake velocity was initially high and gradually declined, with metal concentration in the moss showing a tendency to reach an equilibrium with metal concentration in the water. Mean uptake rate, time to reach equilibrium and metal concentration in moss at equilibrium all increased with increasing metal concentration in the water.

4. Bioconcentration constants calculated on the basis of our data rank the metals studied in the order Zn < Ni < Co < Cu < Pb < Cd.

5. Following retransplant of mosses to a clean site, metal loss was not predicted well by a passive exchange mode of the above type; instead, two phases (rapid and slow) were apparent. Loss rates during both phases, and proportion of metal load lost during the rapid phase, were proportional to the concentration of metal in the moss at the start of the recuperation trial.

6. We present nomograms to allow estimation of severity of contamination on the basis of metal concentration in moss and duration of transplant.
Latitudinal patterns in leaf litter breakdown: is temperature really important?
Authors: IRONS JOHN G. , OSWOOD MARK W. , STOUT R. JEAN , PRINGLE CATHY M.
Published: May 2006

1. Forest stream food webs depend largely on input of dead riparian zone leaves for their energy, which is converted into living biomass by microbes, macroinvertebrates and fish.

2. Temperature has been invoked as important in controlling breakdown rates, and aquatic biologists have suggested that by normalizing processing rates to degree days rather than days, one can ‘factor out’ the effect of temperature and compare processing rates in streams with different thermal regimes (e.g. different seasons or study sites in different biomes).

3. We examined processing rates (k) along a latitudinal (i.e. thermal) gradient by using reciprocal transplants of leafpacks. We placed leafpacks of ten tree species (representing a large range of leaf litter quality) in streams in Costa Rica, Michigan and Alaska using coarse‐mesh (20mm) litter bags. We then examined both the ‘per day’(kday) and ‘per degree day’ (kdegree day) models of leaf litter processing. While processing rates (per day) were fastest at the Costa Rica site (as expected), rates at the Alaska and Michigan sites were similar to each other, which we would not predict if temperature were the principal factor controlling breakdown rate. If using degree days eliminates any effect of differing thermal regimes, rates should be similar across latitudes; however, rates at the Alaska site were much faster (per degree day) than rates at the sites in Costa Rica and Michigan.

4. We compared our data with studies in the North American literature. Regression analysis of kday and kdegree day against latitude of the study site revealed that processing rates (kday) of leaves (from a wide range of tree species in a wide range of stream types) showed no significant change with increasing latitude. However, when normalized for temperature (kDegree day), a positive correlation was found between processing rates and latitude, causing us to reject the hypothesis that normalizing processing rates to cumulative degree days removes the effect of temperature.

5. We suggest three hypotheses: (i) shredding insect populations have adapted to the local thermal regime, and invertebrate‐mediated processing rates are either similar between regions (showing no latitudinal pattern), or increase with latitude; (ii) microbial populations are less active at colder temperatures, and the rate of microbially mediated processing of leaf litter will show a decrease with latitude, and consequently (iii) the relative importance of invertebrate v microbial processing changes on a latitudinal gradient, with invertebrates being more important at high latitudes.
Behavioural and genetic differences in populations of Daphnia subjected to different levels of predation
Authors: YOUNG STEPHEN , WATT PENELOPE J.
Published: May 2006

1. Predictions based on a genetic control mechanism for vertical migration were tested by monitoring the vertical migration behaviour of electro‐phoretically distinct clones of Daphnia longispina and Daphnia magna collected from ponds with different levels of predation.

2. The number of predator species in a pond (a measure of predation) had a significant effect on the vertical migration behaviour of the clones found within that pond, and a phenogram constructed on the basis of the percentage dissimilarity between the genotypes of the clones indicated that clones from the same site were more closely related genetically than clones from different sites.

3. There were significantly different vertical migration behaviour patterns between clones from different sites and between‐site variation in behaviour was significantly greater than that found within a site.

4. Clones differed in the average depth they maintained in the waterbody regardless of the pond from which they were collected, but clones from the same site did have similar behavioural profiles suggesting a tendency to show the same behavioural patterns.

5. These findings, which support predictions based on a genetic control mechanism, are discussed in relation to phenotypically plastic mechanisms of vertical migration control widely reported in the literature.
The critical thermal limits for the stone loach, Noemacheilus barbatulus, from three populations in north‐west England
Authors: ELLIOTT J.M. , ELLIOTT J.A. , ALLONBY J.D.
Published: May 2006

1. The chief objective was to determine the upper and lower thermal limits for feeding and survival in the stone loach, Noemacheilus barbatulus, using juveniles (total length 30–45 mm, live weight 0.25–0.80 g) from one population and adults (total length 77–100 mm, live weight 3.6–7.9 g) from three populations.

2. Fish were acclimatized to constant temperatures of 3, 7, 10, 15, 20, 25 and 27°C; then the temperature was changed at a rate of 1°C/30min to determine the critical limits for feeding, survival over 7 days (incipient lethal temperature), or survival for 10 min or less (ultimate lethal temperature). The rate of 1°C/30min was the optimum value from preliminary experiments, using nine rates from 0.5°C/48h to 18°Ch−1. As values for adults were not significantly different between populations, they were pooled to provide arithmetic means (with 95% CL) for the thermal limits at each acclimation temperature.

3. Feeding limits increased with acclimation temperature to upper and lower mean values of 28.0 ± 0.15°C and 5.1 ± 0.55°C for adults, 25.0 ± 0.54°C and 6.1 ± 0.92°C for juveniles. Incipient lethal levels defined a tolerance zone within which stone loach survive for a considerable time; upper limits increased with acclimation temperature to reach a maximum plateau of 29.1 ± 0.18°C for adults and 29.0 ± 0.40°C for juveniles; lower limits also increased from near 0°C to 3.0 ± 0.40°C for adults and juveniles. Upper limits for the ultimate lethal level increased with acclimation temperature to a maximum plateau of 33.5°C for adults (95% CL ± 0.19) and juveniles (95% CL ± 0.40), whilst the lower limits increased from near 0°C to 2.5 ± 0.30°C. At acclimation temperatures below 20°C, upper incipient and ultimate lethal values were significantly lower for juveniles than those for adults.

4. The thermal tolerance of stone loach was higher than that of juvenile Atlantic salmon or brown trout, one or both of these species often being dominant in streams with stone loach.
Species traits in relation to a habitat templet for river systems
Authors: TOWNSEND COLIN R. , HILDREW ALAN G.
Published: May 2006

This paper focuses on the premise that the habitat provides the templet upon which evolution forges characteristic species traits. Alternative hypotheses are that there are historic and phylogenetic constraints on the match between organism and environment.

In our analysis of river systems, as one dimension of the templet we choose temporal heterogeneity and assume some relationship between this and the frequency of disturbance. The second dimension is spatial heterogeneity in the physicochemical environment and we pay particular attention to the way such variation can ameliorate the influence of disturbances through the provision of refugia.

We derive predictions about the traits of species, including size, generation time, reproductive tactics, body form, mobility and potential for regeneration, that are likely to occur in particular regions of the two‐dimensional templet. We also present predictions about community‐level characteristics such as number of species per resource category and total species richness. The general predictions are intended to apply to a wide range of plants, micro‐organisms and animals, provided the measurements have been made at a scale appropriate to them.

Hypotheses can be tested by comparing traits predicted for particular habitats, whose spatial and temporal heterogeneity have been quantified, with those actually observed. If the fit turns out to be good, we will be able to conclude that the habitat templet approach offers a sound framework within which to pose questions in river ecology.
Theoretical habitat templets, species traits, and species richness: Plecoptera and Ephemeroptera in the Upper Rhône River and its floodplain
Authors: USSEGLIO‐POLATERA PHILIPPE , TACHET HENRI
Published: May 2006

Ephemeroptera and Plecoptera in two sites of the Upper Rhône River (France) were examined using multivariate analyses to determine: (i) relationships among seventeen species traits; (ii) habitat utilization of the fifty‐five species present; (iii) the relationship between species traits and habitat utilization; (iv) trends of species traits and species richness in a framework of spatial and temporal habitat variability.

The species traits having the highest correlation ratios correspond to reproduction or life cycle, behavioural, and morphological characteristics. According to their traits, species of Baetidae, Caenidae, and Leptophlebiidae (Ephemeroptera) are opposite species of Perlidae and Perlodidae (Plecoptera).

The distribution of species in thirteen habitat types of the Upper Rhône River floodplain demonstrates a transverse gradient from the main channel to the oxbow lakes. Plecoptera are restricted to the different main channel habitats; in contrast, Ephemeroptera families have a broader distribution with Baetidae and Leptophlebiidae occurring in most floodplain habitats.

Plecoptera exhibit a significant relationship between species traits and habitat utilization but no relationship is evident for Ephemeroptera. Baetidae use many habitat types and have diverse species traits; in contrast, Leptophlebiidae, Heptageniidae, and Caenidae use many habitat types but each family has a rather uniform set of traits.

Trends in species traits were significantly related to both the spatial and temporal variability of habitats. Considering only temporal variability, the distribution of species trait modalities (= categories) corresponded well to predictions on trends in the river habitat templet for ‘minimum age at reproduction’ and ‘potential longevity’, and in general for ‘descendants per reproductive cycle’, ‘reproductive cycles per year’, ‘potential size’, and ‘body flexibility’ trends in six other traits did not match predictions.

No trends in species richness were evident in spatial–temporal framework of habitat variability.
Theoretical habitat templets, species traits, and species richness: aquatic insects in the Upper Rhône River and its floodplain
Authors: USSEGLIO‐POLATERA PHILIPPE
Published: May 2006

For five orders of Insecta (Plecoptera, Ephemeroptera, Odonata, Trichoptera, and Coleoptera) in two sites of the Upper Rhône River (France), the following are examined: (i) relationships among nineteen species traits; (ii) habitat utilization of species; (iii) the relationship between species traits and habitat utilization; and (iv) trends of species traits and species richness in a templet of spatial‐temporal habitat variability.

The species traits having the highest correlations correspond to reproduction, life cycle, nutritional, and morphological features. Species trait characteristics of Coleoptera are distinctly contrasted with those of Plecoptera and Ephemeroptera; Odonata and Trichoptera are intermediate to these orders.

The distribution of species in fourteen habitat types of the Upper Rhône River floodplain demonstrates a transverse gradient from the main channel to the oxbow lakes and the temporary water habitats, and a vertical gradient from interstitial to superficial habitats.

Despite a significant relationship between species traits and habitat utilization, superposition between species traits and habitat utilization is limited. At the order level, species form usually one (Ephemeroptera, Trichoptera, Odonata) or several (Coleoptera) groups of relatively homogeneous species traits; however, the species of each of these groups utilize rather different habitat types.

Only for some life history traits, e.g. the minimum age of reproduction or the number of reproductive cycles per year, do the trends observed in the framework of spatial—temporal variability of habitat types agree with the predictions from the river habitat templet. This mismatch mainly results from the unique phylogenetic history of the Coleoptera compared with that of the other four orders.

Species richness peaks at an intermediate level of temporal variability; however, it does not gradually increase with increasing spatial variability, nor increase from low to intermediate temporal variability.
Theoretical habitat templets, species traits, and species richness: aquatic macrophytes in the Upper Rhône River and its floodplain
Authors: BORNETTE GUDRUN , HENRY CHRISTOPHE , BARRAT MARIE‐HÉLÈNE , AMOROS CLAUDE
Published: May 2006

The objective of this study, which is based on forty‐two species of hydrophytes and helophytes, is to investigate: (i) relationships among species traits; (ii) habitat utilization by species; (iii) the relationship between species traits and habitat utilization; (iv) trends in species traits in the framework of spatial–temporal habitat variability, and if trends match predictions from the river habitat templet; and (v) trends in species richness in the framework of spatial–temporal habitat variability, and if trends match predictions of the patch dynamics concept.

Two data sets were used for this analysis: species traits (mainly reproductive and morphological characteristics) were documented from the literature; and species distribution across eight habitat types was from field surveys conducted in the floodplain of the Upper Rhone River, France. This information was structured by a fuzzy coding technique and analysed by ordination methods.

Several species traits, which are related to disturbances and reflect resistance (e.g. attachment to soil or substrate) or resilience (e.g. potential for regeneration of an individual), are closely related for aquatic macrophytes.

Habitat utilization by aquatic macrophytes separates the habitat types along a gradient of connectivity with the main channel, which corresponds to a gradient in flood disturbance frequency and the permanence of the different water‐bodies.

The relationship between species traits and habitat utilization is highly significant, indicating that a particular set of habitat types is used by taxa with a particular set of species trait modalities.

Observations in one habitat templet (in which scaling of the templet is primarily based on water level fluctuations for the temporal variability axis and on substrate characteristics for the spatial variability axis) generally do not support predictions on trends in species traits but do support predictions on trends in species richness.

Observations in an alternative habitat templet (in which scaling of the templet is based on frequency of flood scouring for the temporal variability axis and on heterogeneity of the substrate for the spatial variability axis) support theoretical predictions on trends for about half of the species traits for which predictions were available. However, trends in species richness in this alternative habitat templet are only partly in agreement with predictions.
Spatial and temporal variability in filament length of a toxic cyanobacterium (Anabaena affinis)
Authors: SMITH ALISON D. , GILBERT JOHN J.
Published: May 2006

1. This study examines the distribution of Anabaena affinis filament lengths under natural conditions as a function of depth and season, and in the laboratory as a function of growth phase. Because Anabaena affinis is only toxic when consumed, both its filament length and position in the water column are important determinants of its potential impact on zooplankton populations.

2. Star Lake (Norwich, Vermont, U.S.A.), a natural, eutrophic pond, remained thermally stratified throughout the Anabaena bloom. Filament number and length differed significantly with both sampling date and water depth. Most filaments occurred at 0.5 m, particularly at the height of the bloom. Throughout the entire water column average filament length decreased from approximately 0.53 mm in May to 0.14 mm in July. The shortest filaments occurred at the 2.5 m depth. Filament length distributions (combined for all depths) for 29 May, 12 June and 3 July, corresponding to the beginning, middle and end of the bloom, respectively, differed significantly among the three dates. These patterns most likely reflect variable growth conditions, both during the season and in the water column.

3. In the laboratory, Anabaena filament length was affected by medium composition and growth phase. Filaments were significantly longer when grown in MBL than in ASM medium. Also, the average length of Anabaena filaments grown in MBL changed significantly as cultures aged; by day 13 filament length (2.01 ± 0.38 mm, mean ± SD) was twice that on day 0 (0.97 ± 0.71 mm). As cell concentration continued to increase, mean filament length gradually decreased.
Alpine newts (Triturus alpestris) as top predators in a high‐altitude karst lake: daily food consumption and impact on the copepod Arctodiaptomus alpinus
Authors: SCHABETSBERGER ROBERT , JERSABEK CHRISTIAN D.
Published: May 2006

1. Population dynamics and feeding ecology of adult and larval alpine newts (Triturus alpestris, Laurenti) were investigated in a high‐altitude karts lake to estimate their feeding pressure on the copepod Arctodiaptomus alpinuf (Imhof). Estimates of population size for reproducing adults ranged from 666 to 864 individuals in the lake during July and August. Total abundance of larvae before the onset of ice cover varied considerably between 4400 and 25400 individuals in different years.

2. Arctodiaptomus alpinus was an important prey item for adult and larval alpine newts. During the second half of their aquatic period, adult newts moved to deeper water where the copepod reached its highest densities near the sediment. Adults and larvae exhibited no periodic feeding pattern. The feeding rhythm was more synchronized among the larvae than among the adults.

3. Daily food consumption, estimated using the Elliott & Persson (1978) model, reached 4–21 mg dry biomass in adults. The daily ration of larvae was about 7% of body dry weight in the temperature range 6‐11°C. Compared to published estimates of daily food consumption in salmonid fishes, the feeding pressure of newts appears low.
Effect of zinc on four populations and two generations of Gammarus pulex (L.)
Authors: CRANE MARK
Published: May 2006

1. The amphipod Gammarus pulex (L.) is increasingly used in toxicity assessments and is usually obtained from wild populations. Interpopulation variability in response to toxicants may be due to genetic or phenotypic differences and could be large in wild‐caught organisms exposed to different environmental conditions. This paper describes an investigation designed to assess the extent of lethal and sublethal variability between four different G. pulex populations when exposed to zinc, and to determine whether differences observed in the parental generation were also apparent in offspring bred in the laboratory.

2. The mortality of G. pulex from one of the four field‐caught populations (Crags Stream) was significantly lower than for animals from the other three populations for the first 2 days of exposure. After 6 days’ exposure the LC50 values for all four populations did not differ significantly, and were approximately 1.0 mg Zn 1‐−1. Sublethal effects on feeding rate after 6 days’ exposure were also similar for all four populations (feeding rate EC50 approximately 0.5 mg Zn 1‐−1).

3. Lethal effects on the F1 generation were similar among the four populations, in contrast to the short‐term differences observed in the parental generation. These results suggest that interpopulation differences in zinc tolerance in G. pulex are short‐lived, and phenotypically rather than genetically based.
Local effects of a sedentary grazer on stream algae
Authors: BERGEY ELIZABETH A.
Published: May 2006

1. Larvae of the sedentary aquatic caterpillar Petrophila confusalis (Walker) construct silken retreats around which they feed; outside these clearly demarcated grazed areas, stream algae are exposed to a variety of mobile grazers. Comparisons of the algal community inside and just outside grazed zones were made for third‐ and fifth‐instar Petrophila in the South Fork of the Eel River, California.

2. Densities of both the filamentous macroalga Cladophora and diatom assemblages were significantly reduced within the grazed areas during both larval instars. Grazing of diatoms was taxonomically non‐selective.

3. In spring, the grazed zones were relatively large (mean = 22.7 cm2) and visibly increased epilithic spatial patchiness.

4. Per cent composition of diatom assemblages inside and outside the grazed areas differed during the third instar but not during the fifth instar. During the third instar, the grazed zone contained more Synedra ulna (a common immigrant) and less Gomphonema olivaceum (a late‐successional species).
The critical thermal limits for the bullhead, Cottus gobio, from three populations in north‐west England
Authors: ELLIOTT J.M. , ELLIOTT J.A.
Published: May 2006

1. The objective was to determine the thermal limits for feeding and survival in the bullhead, Cottus gobio, using juveniles (total length 20–30 mm, live weight 0.5–1.5 g) from one population and adults (50–70 mm, 3.5–5.5 g) from three populations.

2. Fish were acclimated to constant temperatures (3, 7, 10, 15, 20, 25 or 27 °C) and the temperature was then changed at a rate of 1 °C /30 min to determine the critical limits for feeding, survival over 7 days (incipient lethal temperature), or survival for 10 min or less (ultimate lethal temperature). The rate of 1 °C/30 min was the optimum value from preliminary experiments, using nine rates from 0.5 °C/48 h to 18 °C h−1. As values for adults were not significantly different between populations, they were pooled to provide arithmetic means (with 95% CL) for the thermal limits at each acclimation temperature.

3. Feeding limits increased with acclimation temperature to upper and lower mean values (± 95% CL) of 26.5 ± 0.16 °C and 4.2 ± 0.20 °C for adults, 26.6 ± 0.59 °C and 5.0 ± 0.55 °C for juveniles. Incipient lethal levels defined a tolerance zone within which fish survive indefinitely; upper limits increased with acclimation temperature to a plateau of 27.6 ± 0.22 °C for adults and 27.5 ± 0.47 °C for juveniles, lower limits increased from near 0 °C to 2.5 ± 0.31 °C for adults and 2.7 ± 0.47 °C for juveniles. Ultimate lethal levels increased with acclimation temperature to a plateau of 32.5 ± 0.24 °C for adults and 32.6 ± 0.46 °C for juveniles, whilst the lower limits increased from near 0 to 0.9 ± 0.29 °C. Upper feeding, incipient and ultimate lethal values were significantly lower for juveniles than those for adults at acclimation temperatures < 20, < 20 and < 15 °C, respectively.

4. The thermal tolerance of bullheads was slightly lower than that of stone loach, similar to that of juvenile Atlantic salmon and higher than that of brown trout; the thermal limits for feeding were much wider than those for salmon or trout.
Spatial patterns in benthic invertebrate community structure: products of habitat stability or are they habitat specific?
Authors: DEATH R.G.
Published: May 2006

1. The effects of habitat stability on benthic invertebrate community structure were examined at eleven sites (ten streams and a wind‐swept lake shore) with similar physicochemical characteristics but differing stability.

2. Habitat characteristics were assessed to place the study sites within the framework of the disturbance‐productivity‐diversity model, the intermediate disturbance hypothesis and a variant of the habitat templet model to examine their predictions with respect to community structure.

3. Many of the most common invertebrate species were present at all the study site, although their relative abundance and density differed markedly between sites. Thus, while stability did not appear to affect colonization of the study sites by these taxa, it did affect their relative success.

4. Communities at unstable sites were very similar and shared a number of taxa such as Deleatidium, Austrosimulium and several species of chironomid, presumably well‐adapted to surviving and recolonizing after flood events.

5. Communities at the stable sites differed markedly, both from each other and the group of unstable sites. The characteristic fauna at each of the stable sites seemed to be a result of the site's intrinsic character and possibly biotic interactions.

6. Although stability was a pervading influence on community structure, acting as a bottleneck to the development of a site‐specific suite of taxa, none of the above models could adequately explain the observed patterns.
Life cycle and production of Chironomidae (Diptera) from Lake Banyoles (NE Spain)
Authors: PRAT NARCÍS , RIERADEVALL MARIA
Published: May 2006

1. The life cycles and annual production of the eight most abundant species of chironomids (Prodadius cf. choreus, Tanypus punctipennis, Chironomus bernensis, Chironomus gr. plumosus, Cladopelma virescens, Microchironomus tencr, Tanytarsus gr. lestagei, and Cladotanytarsus atridorsum) were studied from sublittoral and profundal samples taken monthly in Lake Banyoles during 1987 at five sampling stations (depths ranging from 5 to 20 m).

2. The number of generations per year deduced from instar‐frequency data varied from one to four, depending on the species, lake basin and depth. Annual temperature range, dissolved oxygen in the stratified period and presence of sulphide are the key factors that may explain the differences in the number of generations.

3. Production estimates were calculated using the size‐frequency (SF) method corrected for the number of generations (SFG), and the increment‐summation method (IS) when cohorts could be clearly deduced.

4. Production calculated with the SFG method gave results which were comparable with those of the IS method using smoothed‐survivorship curves in the three species for which the use of the IS method was possible (C. virescens, M. tener and C. atridorsum). Using these methods production was estimated to range from 23–70 mg AFDW (ash‐free dry weight) m−2 yr−1 at 12 m to 74–275 mg AFDW m−2 yr−1 in the sublittoral zone of the lake (5‐m depth).

5. Calculation of production for the other five species using the size‐frequency method with the number of generations (SFG) deduced from monthly instar‐frequency data gave values ranging from 12 mg AFDW m−2 yr−1 (Chironomus bernensis at 20 m depth) to 3.75 g AFDW m−2 yr−1(Prodadius cf. choreus at 12 m).

6. Total chironomid production (with the SFG method) varied from 0.8 to 5 g AFDW m−2 yr−1 in the profundal and sublittoral, respectively. At each sampling station two species groups accounted for most of the production: Prodadius cf. choreus and Chironomus spp. Annual production/biomass ratio (P/B) varied from very high values for Prodadius (between 11 and 27, as four generations completed each year) to very low values for Chironomus gr. plumosus (2.20), which completed only one generation each year. The annual production of P. cf. choreus in Lake Banyoles is higher than any reported in the literature due to the completion of four generations and to the high densities of this species.
Microhabitat selection by larval Chironomus tentans (Diptera: Chironomidae): effects of predators, food, cover and light
Authors: BAKER ROBERT L. , BALL SHELLEY L.
Published: May 2006

1. As part of a study designed to estimate the developmental costs of antipredator behaviour of larval chironomids, we used laboratory experiments to study effects of food and factors that could influence predation risk [presence of fish, cover from fish (simulated debris) and light level], on microhabitat selection by Chironomus tentans larvae in the third and fourth instar.

2. Larvae were more likely to build tubes where there was more food although their ability to move far to find food appeared limited.

3. Larvae did not avoid areas with fish and the presence of fish did not alter larval response to food.

4. Larvae avoided areas of cover (simulated debris) but cover did not alter larval response to food.

5. When provided with a choice between light and dark areas, larvae initially without tubes were found more often in the dark areas. Light level had no effect on location of larvae that had begun the experiment with tubes.

6. Results suggest the tubicolous life‐style of larval Chironomus tentans limits their ability to select microhabitats that could alter their risk of predation.