bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local effects of a sedentary grazer on stream algae
Authors: BERGEY ELIZABETH A. 
Published: May 2006

SUMMARY1. 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

SUMMARY1. 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

SUMMARY1. 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

SUMMARY1. 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

SUMMARY1. 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.
Indicating shear stress with FST‐hemispheres ‐ effects of stream‐bottom topography and water depth
Authors: DITTRICH ANDREAS , SCHMEDTJE URSULA 
Published: May 2006

SUMMARY1. In order to quantify the effects of substratum roughness on shear stress and Fliesswasserstammtisch‐(FST)‐hemisphere movement, hemispheres were calibrated against shear stress in a laboratory flume with fully developed turbulent flow. In five different runs, substratum roughness, water depth and location of hemispheres in relation to the surrounding particles, were varied.2. FST‐hemisphere results were strongly influenced by bottom topography. In the case of hydraulically rough flow a linear relationship exists between shear stress (χc) and hemisphere density (ρh), whereas in the case of quasi‐smooth flow a power law was obtained for the χc/ρh, relationship. Shear stress for a given hemisphere and relative roughness h/k > 4 (h= water depth; k= height of the roughness elements) deviated up to one order of magnitude between roughnesses. In water depths, where h/k 4, the χc/ρh relationships are dependent on the ratio h/k, due to water surface effects on hemisphere movement. In the case of k = d90=rh (d90= characteristic diameter of the largest particles of the bottom substratum; rh= radius of the hemispheres), the location of the hemispheres in respect to the roughness elements is of secondary importance.3. In the case of hydraulically rough flow and wake interference between the roughness elements, the turbulent flow field close to the substratum is three‐layered, each layer being characterized by its own velocity distribution laws (Dittrich & Hammann de Salazar, 1993). Depending on the height of the roughness elements, FST‐hemispheres will be subjected mainly to flow forces of the near‐bed layer (in rough substrata) or to flow forces distant from the near‐bed zone (in fine substrata). The dominant flow forces acting on bottom particles, organisms, or FST‐hemispheres are shear force and lift force.4. The Local Shear Stress Model (Lamouroux et al., 1992) leads to a correct prediction of hemisphere distribution in a stream with a cobble size substratum, but to an overestimation of hemisphere numbers in a sandy‐bottom stream. The substratum‐dependent shear stress values therefore need to be entered into the model and a measure of substratum roughness included.5. Macroinvertebrate abundance correlates well with the movement of FST‐hemispheres. Samples from points with very high or very low roughness did not contribute to scatter in the data, indicating that the sum of the near‐bed flow forces is relevant to macroinvertebrate distribution, not shear stress alone. We conclude, that FST‐hemispheres are well suited to characterize near‐bottom hydraulics and therefore the microhabitat of the benthos.
The effects of catchment liming on the chemistry and biology of upland Welsh streams: testing model predictions
Authors: RUNDLE S.D. , WEATHERLEY N.S. , ORMEROD S.J. 
Published: May 2006

SUMMARY1. The catchments of three acidified streams in mid Wales were limed in 1987/88. Here we assess their chemical and biological response in comparison with unmanipulated reference streams over a period of 5 years post‐liming.2. Stream chemistry was measured weekly/fortnightly between 1985 and 1992, while macroinvertebrates were sampled annually. Colonization by acid‐sensitive taxa was assessed and trends in community structure were monitored by TWINSPAN. Real biological responses were compared with those predicted by an empirical model constructed using chemical data.3. There were marked changes in stream chemistry following liming: calcium concentrations and pH values increased, while aluminium concentrations decreased to levels similar to those in naturally circumneutral streams. These conditions have persisted since liming.4. Empirical models predicted that stream invertebrates would respond to the altered stream chemistry, with the establishment of communities typical of circumneutral conditions.5. Following liming, the taxon richness and abundance of acid‐sensitive taxa was significantly higher in limed compared with reference streams. Colonization by, and persistence of acid‐sensitive taxa was patchy, however, and richness was still substantially lower than in naturally circumneutral streams. Moreover, contrary to the model predictions, there were no wholesale changes in the structure of macroinvertebrate communities.6. We conclude that liming has created and maintained chemical conditions suitable for macroinvertebrate communities typical of circumneutral streams, but these chemical changes have not been matched by sustained responses among the biota. The views expressed in this article are those of the authors and do not necessarily reflect those of the NRA.
The role of nutrition in regulation of predator‐induced crests of Daphnia carinata
Authors: BARRY MICHAEL J. 
Published: May 2006

SUMMARY1. The effects of food level on the development of crests by Daphnia carinata in the presence of Anisops grains (Notonectidae) were investigated in two laboratory experiments and in the field.2. In the laboratory experiments D. carinata were grown at different food levels either in the presence of A. gratus or in predator‐free water. In the field study the effects of six variables (temperature, food level, density of Daphnia, density of Anisops, brood size and maternal nutrition) on development of crests in the next generation of Daphnia were investigated over a 12‐month period at a single field site.3. In the laboratory food level had a small but significant effect on relative crest height of D. carinata. In the presence of notonectid predators the rate of crest growth relative to body length was higher than for control D. carinata only during embryogenesis and/or the first two neonatal instars. Beyond this age the rate of crest growth was similar in both morphs.4. In the field study, crest height was negatively correlated with density of Daphnia and positively correlated with density of Anisops and maternal nutrition (maternal nutrition was defined as the somatic weight of a female with a body length of 2.5 mm, calculated from the length‐dry weight regression based on a sample of the population). However, these data were biased by a short period when no Anisops were present in the pond. When these data were excluded, the only factor which significantly correlated with crest height was maternal nutrition. This finding indicated that relative crest height of the next generation was determined primarily during embryogenesis on the basis of maternal feeding success and possibly on food availability during the first two instars.
Seasonal dynamics of picophytoplankton in Lake Kinneret, Israel
Authors: MALINSKY‐RUSHANSKY N. , BERMAN T. , DUBINSKY Z. 
Published: May 2006

SUMMARY1. Picophytoplankton (picocyanobacteria and picoeukaryotes) communities in Lake Kinneret were studied from 1988 to 1992. No prochlorophytes were observed in the lake.2. Picocyanobacteria were a prominent and ubiquitous component of the phytoplankton, being present at all depths throughout the year, with concentrations ranging from 2 ± 10–8 ± 105 cells ml−1. Low cell numbers in winter and spring were followed at the end of the annual dinoflagellate bloom by maximal abundances in summer‐autumn in the epilimnion. High cell numbers (> 104 cells ml−1) were sometimes also found in the anaerobic hypolimnion. Net growth rates for picocyanobacteria ranged from 0.29 to 0.60 divisions day−1.3. Picoeukaryotes were a very minor constituent of the picoplankton, mostly present in winter and spring, and sometimes at the end of autumn, with concentrations ranging from 44 to 5700 cells ml−1. Higher cell numbers tended to occur in the near surface water layers. In August‐September, picoeukaryotes were found only in the hypolimnion. In December, the occurrence of picoeukaryotes in the deep water layers probably resulted from advection with cold water currents from the Jordan river. Net growth rates for picoeukaryotes ranged from 0.26 to 0.43 divisions day−1.4. Overall, the contribution of picophytoplankton to the phytoplankton standing crop in Lake Kinneret was limited; picocyanobacteria and picoeukaryotes accounted for no more than 7.0 and 0.1% of total algal biomass (semiannual average), respectively.5. Picophytoplankton cell numbers in pelagic waters were usually similar to those in shallower lake stations.6. Picocyanobacteria appear to be an autochthonous population, whereas picoeukaryotes are probably brought annually by the Jordan River and do not maintain themselves in the lake.
Distribution fields for aquatic ecosystem components: method of identification of correlation zones
Authors: KALIKHMAN I. , OSTROVSKY I. , WALLINE P. , GOPHEN M. , YACOBI Y. Z. 
Published: May 2006

SUMMARY1. Data from the two multidisciplinary surveys of Lake Kinneret (Israel), including acoustic surveys of fish concentrations and concurrent sampling of plankton at stations, were used to reconstruct fish and plankton distributions. No significant lake‐wide correlations for the distribution fields were found. With respect to patchiness of the fish and plankton distributions, we hypothesized that they might be correlated in localized zones.2. A method is suggested for the identification of areas where there are strong correlations of two distribution fields. The method is based on outlining zones where the gradients of the two fields of interest are in the same direction (or are opposite). Only areas larger than the autocorrelation circles (or ellipses) for the fields are considered. The correlation of the fields is calculated for each of the zones selected.3. The method was used in analysing data from the multidisciplinary surveys. We were able to detect areas of the lake where there were correlations for fish and plankton distributions. Analysis of specific conditions inside the correlation zones made it possible to construct hypotheses concerning the causes for the observed patterns of fish and plankton distributions.
Temporal scale, phytoplankton ecology and palaeolimnology
Authors: ANDERSON N. J. 
Published: May 2006

SUMMARY1. Scales of temporal analysis in limnology generally cover dial through to interannual changes, with occasional longer studies with up to 50 years continuous sampling data. Lakes, however, have been changing over much longer time periods than this, as is apparent from palaeolimnological studies. Temporal scales are, however, largely relative, with an individual's perspective controlling what is deemed short or long term.2. Phytoplankton populations are variable over a variety of timescales, and the sediment record can readily record these changes from interannual through to 103‐year timescales. Because of anthropogenic influences, such as acidification and eutrophication, phytoplankton communities probably have been altered dramatically in many lakes, often before routine sampling began. Records of changing phytoplankton populations at timescales relevant to limnologists can be derived from, for example, varved sediments and used to address specific problems, such as the degree of long‐term interannual variability and timescales of sexual reproduction.3. Palaeolimnologists tend to interpret changes in sediment assemblages in terms of ecological and physiological processes which are relevant at scales that may not be resolvable in lake sediments. There is a clear need for sediment records to be interpreted in terms of the processes which operate at timescales that match the resolution of that sediment sequence.4. Increasingly fine sampling resolutions are being attempted by palaeolimnologists, often without consideration of the reasons for such an approach or to the repeatability of the results. The increased variability associated with high‐resolution sampling can make it difficult to separate noise from the ecological signal. There is a clear need for replication.5. The necessary temporal resolution is defined by the aim of any given palaeolimnological study. If the main emphasis of a study is, for example, establishing background phosphorus concentrations, a coarser sampling resolution is probably acceptable than that required for many ‘ecological’studies.
Growth limitation of submerged aquatic macrophytes by inorganic carbon
Authors: VADSTRUP METTE , MADSEN TOM VINDBÆK 
Published: May 2006

SUMMARY1. This study determined the effects of CO2and HCO3‐ enrichment onin situgrowth of two submerged macrophytes,Elodea canadensisandCallitriche cophocarpa, in two Danish lakes: Lake Hampen and Lake Væng. Lake Hampen is an oligotrophic low‐alkaline lake (0.4 meq−1) and Lake Væng is mesotrophic with an alkalinity of 1.1 meq 1‐−1. In Lake Hampen experiments were carried out throughout the growth season, whereas experiments in Lake Væng were restricted to late summer. The CO2and HCO3‐enrichment procedures used increased the concentration of free‐CO2by 500–1000 μM and the concentration of HCO3‐ by about 80 μM.2. The concentration of free‐CO2in Lake Hampen was about five times atmospheric equilibrium concentration (55 μM) in early summer declining to virtually zero at the end of summer.3. Under ambient conditionsCallitriche, which is restricted to CO2use, was unable to grow and survive in both lakes. In contrast,Elodea, which has the potential to use HCO3‐ in photosynthesis, grew at rates varying from 0.046 to 0.080 day−1over the season.4. Under CO2enrichment the growth rate ofCallitrichevaried from 0.089 to 0.124 day−1and forElodeafrom 0.076 to 0.117 day−1over the season. Enrichment with HCO3‐affectedElodeaonly and only to a limited extent. This may be a result of insufficient increase in [HCO3‐] upon enrichment or to a limited capacity of the plants to take up HCO3‐.5. The substantial stimulation ofin situgrowth ofElodeaandCallitricheby enhanced concentrations of free‐CO2shows that inorganic carbon is an important determinant of growth of submerged macrophytes and that inorganic carbon limitation ofin situgrowth may be a common phenomenon in nature, even in lakes with an alkalinity as high a 1 meq 1‐−1. Inorganic carbon, however, is only one of many parameters important for growth, and the growth rates ofElodeaat both ambient and high free‐CO2were closely coupled to day length and photon irradiance, indicating that light had an ultimate control on growth.
Empirically estimating the lateral transport of riparian leaf litter to lakes
Authors: FRANCE R.L. 
Published: May 2006

SUMMARY1. An experimental study found the lateral transport of riparian leaf litter to increase in relation to surface slope, exposure to precipitation, and absence of ground flora. Deciduous leaves displayed greater lateral redistribution than did coniferous needles.2. When these results were combined with the proportional representation of different slopes, canopy exposures and ground roughness measured from transects throughout the riparian zones of sixteen north‐western Ontario lakes, the average annual lateral transport distance of coniferous needles was estimated to be 0.3 m and that of deciduous leaves to be 0.5 m.3. Data on the annual riparian litterfall and distributional proximity of trees to the shorelines suggested that the lateral input of riparian litter was 2 g m−1 forested shoreline yr−1, an amount which represents 6% of the total annual allochthonous input of leaf‐fall to these study lakes.