bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationships of marsh seed banks to vegetation patterns along environmental gradients
Authors: WILSON SCOTT D. , MOORE DWAYNE R.J. , KEDDY PAUL A. 
Published: May 2006

SUMMARY

The relationship of the seed bank to the vegetation of a freshwater marsh was studied along gradients of water depth and soil organic matter content. Characters examined included standing crop, seedling density, and species composition, distribution and richness.
The seed bank differed from the vegetation in that only nine of twenty‐seven species were present in both, abundant seed‐bank species were uncommon as adults, and adults showed different distributions along a gradient of soil organic matter content whereas their seeds were most abundant in soils with high organic matter.
The seed bank resembled the vegetation in that separate multivariate analyses of the communities revealed that variation in the species composition of each was significantly correlated with water depth and soil organic matter content. Further, species richness in both communities decreased with water depth and increased with soil organic matter content. Lastly, the standing crop of the vegetation and the number of seedlings both decreased with water depth and increased with soil organic matter.
Consideration of spatial patterns and environmental gradients revealed more similarities between vegetation and seed banks than were obtained by comparing species lists. The results suggest that artificial stimulation of seed bank germination for management purposes will not produce vegetation changes as large as those suggested by differences in species lists.
Influence of submergence on growth of seedlings of Scirpus lacustris and Phragmites australis
Authors: WEISNER STEFAN E.B. , GRANÉLI WILHELM , EKSTAM BÖRJE 
Published: May 2006

SUMMARY

Seeds of Scirpus lacustris and Phragmites australis were germinated in early June, and twenty‐four seedlings of each species were subsequently exposed to submerged conditions (eight seedlings at each of the water depths 0.2, 0.4 and 0.8m), in outdoor 500–1 tanks in southern Sweden. Weight and shoot length of the plants were measured in September.
The Phragmites seedlings did not show any significant growth when submerged. The Scirpus seedlings, however, developed submerged leaves and exhibited considerable submerged growth. One Scirpus plant, in shallow water (0.2m), had developed an aerial shoot by September. Shoot length of the remaining (submerged) Scirpus plants was positively related to plant weight within water depth treatments, and was higher, in relation to plant weight, in deeper water. Mean weight in September of the submerged Scirpus plants decreased with increased water depth.
In south Swedish lakes with a lowered water table, Scirpus often occupies large areas on the lakeward side of the reed belt, which is generally dominated by Phragmites. The differences between the two species, in performance of submerged seedlings, suggest that this zonation may be created through successful submerged seedling establishment of Scirpus on the lakeward side of Phragmites.
Field techniques for the classification of near‐bed flow regimes
Authors: YOUNG W.J. 
Published: May 2006

SUMMARY

The equipment and methods needed for collecting the data required for near‐bed flow regime classification are detailed.
To illustrate appropriate procedures for data analysis, data collected from four cobble bed streams are used to classify near‐bed flow regimes both at the measured depth and at estimated bankfull depth.
Implications of the resulting classifications are discussed from a limnological perspective. It is concluded that while the biological relevance of near‐bed flow regimes has not been formally established, the terms ‘pool’, ‘run’, and ‘riffle’ are not always useful for differentiating between habitats in the near‐bed zone.
The effect of suspended clay on ciliate population growth rates
Authors: JACK JEFFREY D. , GILBERT JOHN J. 
Published: May 2006

SUMMARY

Renewed batch cultures of three algivorous and one bacterivorous ciliate showed that ciliate reproductive rates increase with increasing food concentration up to an asymptote. Maximum rm values for Strobilidium gyrans, Bursaridium difficile and Euplotes eurystomus feeding on the cryptomonad alga Rhodomonas minuta were 0.87, 0.86 and 0.45 day‐1, respectively, while Paramecium aurelia feeding on the bacterium Enterobactor aerogenes had an rm of 0.40 day‐1. B. difficile had a food threshold (rm= 0) of 0.38 μg Cml‐1 and P. aurelia had a threshold of 1.6μg Cml‐1.
The presence of suspended fine (particle size <1 μm) and coarse (particle size 1–2μm) clay suppressed the half maximum reproductive rate of the ciliate Strobilidium gyrans by up to 69% but had no effect on B. difficile, E. eurystomus or P. aurelia. Populations of ciliates unaffected by clay may be released in situations where suspended particles negatively affect their metazooplankton predators and competitors.
Substrate interstices as a habitat for larval Thraulus bellus (Ephemeroptera) in a temporary floodplain pond
Authors: TABACCHI E. , DÉCAMPS H. , THOMAS A. 
Published: May 2006

SUMMARY

Larvae of the ephemeropteran Thraulus bellus were sampled from the substrate interstices of a floodplain pond along the River Adour (south‐west France). Quantitative sampling was carried out using traps arranged in five transects of four traps each, made up of five vertical compartments between +20 and ‐80cm from the surface of the substrate. The 100 compartments thus obtained were each 2.861 volume, and were sampled once a month from January 1988 to January 1989.
An influx of young larvae coming from the permanently flooded deep substrate invaded the upper 80cm of the substrate on and after mid‐January. An increase in larval density and frequency of occurrence in the compartments occurred until May before emergence of the adults. A second colonization phase by young larvae took place from July to September, and was followed by reductions in larval density and frequency of occurrence during the autumn/winter drop in water level.
Horizontal and vertical movements of the larval population within the interstitial habitat of the pond were clearly linked to the water level fluctuations. However, differences between the five transects indicated a control of these movements by factors such as slope of the substratum, macrophytic vegetation, and the influence of springs. A relationship was found between population density and probability of submergence of the compartments, indicating that the larvae avoided locations most influenced by the fluctuating water levels.
The temporarily flooded substrate interstices appear to be a refuge for the larvae of T. bellus, preventing them from overlapping with two other abundant ephemeropterans, namely Cacnis horaria from silt habitats and Cloeon gr. simile from macrophyte beds.
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

SUMMARY

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

SUMMARY 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

SUMMARY

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

SUMMARY

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

SUMMARY

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

SUMMARY

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

SUMMARY

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

SUMMARY1. 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

SUMMARY1. 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

SUMMARY1. 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.