bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of microhabitat on availability of drifting invertebrate prey to a net‐spinning caddisfly
Authors: SMITH‐CUFFNEY FRANCIE L. , WALLACE J. BRUCE 
Published: May 2006

SUMMARY. 1. Invertebrate drift was sampled at both a rockface and a deep pebble riffle site in streams draining both a clearcut and a forested catchment.2. A sampler was designed to separate the bottom 2 cm of flow, encompassing the effective range of caddisfly (Hydropsychidae: Trichoptera) catchnets. from upper flow.3. No significant difference in drift density (numbers per cubie metre) was seen between sites within each stream. However, numbers per square centimetre intake area per day at the rockface sites were 4 times higher in the clearcut and 10 times higher in the forested stream than at the pebble‐riffle site.4. Rockface habitat which had highest drift availability was also the site of maximum secondary production of the predaceous collector‐ filterer Parapsyche cardis in both streams studied.5. Increased sediment load in the clearcut stream may influence the efficiency of utilization of invertebrate drift by collector‐filterers.
Age‐specific Chaoborus predation on rotifer prey
Authors: MOORE MARIANNE V. , GILBERT JOHN J. 
Published: May 2006

SUMMARY. 1. This is the first study to examine predator‐prey interactions between Chaoborm instars and rotifer prey. The predatory behaviour of instars I–III of Chaoborus pimctipennis and the diet selectivity of instars I—IV feeding on rotifers were examined in the laboratory. Prey used in direct observations of predatory behaviour included a variety of rotifers (Symhacta pectlnata, S. ohUmga, Polyarthra remata, Asplanchna girodi, Keratella crassa, spined and unspined forms of Keratella cochlearis) and two crustaceans (Bosmitia longirostris, Mesocyclops edax nauplii.2. In general, strike efficiencies (percentage of strikes resulting in inges‐ tion) increased in successive instars I—III. Early instar (I and II) strike efficiencies were low when compared with other invertebrate predators. For a given instar. mean prey handling times varied among prey species more than strike efficiencies. Mean handling times for small, soft‐bodied rotifers were lowest and those for wide, hard‐bodied prey were highest.3. Instar I exhibited significantly greater selectivity for the small, soft‐ bodied S. obUmga than for the larger S. pectinata, hard‐bodied K. crassa, and spined and unspined forms of K. cochlearis. Instars II—IV positively selected both the large and small Symhaeta species over all Keratella species. The relationship between Chaobortts selectivity and prey value (weight of prey per unit handling time) can be described by a power function. Ingestion rates of rotifers by older instars (III and IV) are among the highest reported for invertebrate predators.4. Rotifer vulnerability to Chaoborus predation probably depended on rotifer cuticle texture, body width, and hydrodynamic disturbances. Spined rotifers were not necessarily protected from Chaoborus predation because Chaohorus can manipulate and swallow them. Giguere et al.'s 1982) encounter rate model must be modified to predict encounter rates of slow‐moving rotifer prey with Chaohorus.
The influence of predation on horizontal distribution of zooplankton species
Authors: JAKOBSEN PER JOHAN , JOHNSEN GEIR HELGE 
Published: May 2006

SUMMARY. 1. The horizontal distributions of Daphnia longispina and Bosmina tongispina in Lake Kvernavatn (Norway) were investigated twice in 1982. In late spring, when populations were small, the two species inhabited the same areas, and they were evenly distributed from the littoral to the pelagic. At high population densities, during midsummer, the species were spatially segregated, D. longispina being pelagic and B. longispina littoral in distribution.2. The distribution and feeding of three‐spined sticklebacks (Gasteros‐teus aculeatus) were also studied. The sticklebacks were apparently forced into littoral areas by larger piscivorous predators in the pelagic and they were consequently restricted to foraging primarily on B. longispina, which formed dense swarms during daytime in summer.3. We suggest that predation and competition influence the spatial distribution of zooplankton species. The feeding efficiency of fish foraging on high‐density zooplankton populations can be reduced by spatial segregation of zooplankton species. Where high local densities occur, due to swarm formation, predation is changed from size‐selective feeding to consumption of spatially isolated individuals.
Occurrence of phosphorus and its potential remohilization in the littoral sediments of a productive English lake
Authors: DRAKE JOHN C. , HEANEY S. IVAN 
Published: May 2006

SUMMARY. 1. Vertical profiles of pH were measured at nine shallow water (<5m) locations in Esthwaite Water. These indicate strong gradients of pH near the sediment water interface suggesting a marked buffering capacity of the sediments.2. Thirteen littoral sediment cores were horizontally sectioned and sequentially extracted (0.5 M NaHCO3, 0.1 M NaOH, 1 M HCI) and analysed for soluble reactive phosphorus. The core sections were also analysed for total phosphorus and per cent organic content to determine the vertical and areal variability of phosphorus within the littoral sediments of Esthwaite Water.3. The rate of release of phosphorus from intact sediment cores was measured in the laboratory as a function of the pH of overlying water, yielding the relationship log K=0.54 pH−3.94, K=mg Pm−2day−1. The maximum release rate measured was 75 mg P m−2 day−2 at pH = 10.5.4. Experiments on sediment slurries indicate that the release of phosphorus at pH 10 is rapid with approximately 50% of the total NaHCO3+ NaOH extractable phosphorus being released within 3 h.5. Phosphorus release from the littoral sediments may equal or exceed external sources plus hypolimnetic inputs during periods of high pH associated with times of maximum algal biomass.
Dissolved organic carbon, seston and macroinvertebrate drift in an acidified and limed humic stream
Authors: KULLBERG ANDERS , PETERSEN ROBERT C. 
Published: May 2006

SUMMARY. 1. Total seston, and invertebrate drift were studied before and after lime addition to Fyllean River, a stream‐iake system in Halland county, southwest Sweden, with poorly buffered waters undergoing acidification.2. The largest effect of liming was on the chemistry of the water. Following liming with 23 mg CaCO3 l−1 the pH of the water changed from 5.8 to 6.8 and alkalinity from 0.04 to 0.13 meq l−1.Turbidity increased from 3.4 to 4.7 JTU with no change in colour.3. Dissolved organic carbon (DOC) concentration of all samples was in the range 10.7–13.3 mg C l−1 with no significant change occurring due to liming.4. Total seston increased from 4.35 mg DM 1−1 in unlimed conditions to 6.25 mg DM l−1 after lime addition. All significant changes in seston occurred in the smaller size fraction (0.45–25 μm).5. Liming reduced the organic content of the partieulate material from an average of 61% to 39% immediately downstream of a lime silo (within 1 km) but had little effect when the river course was interrupted by lakes and impoundments.6. The lakes in the river system had a larger effect on seston concentration than any effect of the lime addition by itself. Particle concentrations were reduced by 50–55% and DOC by about 1 mg C l−1as the water passed through the lakes.7. Macroinvertebrate drift density was low in all samples before and after liming and typical of oligotrophic streams. Drift was significantly lower at limed (0.024 ind. m−3) than at unlimed (0.083 ind. m−3) locations. The decrease was only in total drift density with no significant change in the relative abundance of functional groups or in densities of single taxa, except for a reduction in drift of predators in the limed condition.
Seasonal change in the respiration of the dobsonfly larva, Protohermes grandis(Megaloptera: Corydalidae)
Authors: HAYASHI FUMIO , YOSHIDA TOSHIO 
Published: May 2006

SUMMARY 1. Seasonal change in the respiration of the dobsonfly larva, Protohermes grandis,was studied by measuring the oxygen consumption rate (resting metabolism) bimonthly for 2 years. The respiratory rate of the larva was significantly lower during the summer season when the stream temperature rose to 30°C.2. Summer depression of respiration was confirmed by measuring the rate of carbon dioxide evolution. The mean value of the respiratory quotient was estimated to be 0.76 ± 0.05 SE. The larva is believed to conserve energy by this reduction in respiratory rate,3. In other seasons, however, the larva maintained a higher respiratory rate and remained active even in the winter when the stream temperature decreased near to 0°C. In fact, significant growth in weight occurred from mid‐October to late March.4. This acclimation to temperature may enable the efficient allocation of energy during the long larval period (3 years) in streams which have large annual fluctuations in temperature.
The effect of nitrate in stream water on the relationship between gentrification and nitrification in a stream‐sediment microcosm
Authors: COOKE JAMES G. , WHITE ROBERT E. 
Published: May 2006

SUMMARY 1. Microcosm experiments were carried out to simulate, in the laboratory, the conditions occurring at the water‐sediment interface of a stream draining agricultural land. Constant boundary conditions were attained by passing synthetic 'stream water', saturated with dissolved oxygen and containing 1 mmol NO3−N dm−3 (or 1 mmol Cl− dm−3, control), once only over the sediment surface.2. Measurements were made of inorganic‐N (nitrate, nitrite, ammonium), redox potential, potential denitrification and nitrification activities, and readily mineralizable carbon sediment profiles at three incubation times up to 24 days. The peaks in denitrification and nitrification activity moved down the profile with time in the nitrate‐treated sediment, but stayed relatively stationary in the control treatment. Although the zone of nitrification was restricted to the top 2–3 mm of sediment in the control treatment, high fluxes of both dissolved oxygen and NH4−N maintained a high nitrifier activity within this zone for the duration of the experiment.3. Increases in denitrifier activity immediately below the nitrifier activity peak indicated that a coupled nitrification‐denitrification sequence was operating in both the control and nitrate‐treated sediment. The greater depth of nitrification when nitrate was present in the ‘stream water’ was attributed to a feedback mechanism in which enhanced denitrification in the sediment reduced the local demand for oxygen and permitted dissolved oxygen to diffuse further into the sediment. The progressively greater depth to which oxygen penetrated caused the contiguous peaks of potential nitrifier and denitrifier enzyme activity to migrate farther from the interface. However, diffusion rates of the reactants limited the depth to which these coupled reactions could extend.4. The possible effect of this feedback mechanism on the nitrate status of natural sediment‐stream water systems is briefly discussed.
Leaf‐pack dynamics in a southern African mountain stream
Authors: KING J. M. , HENSHALL‐HOWARD M‐P , DAY J. A. , DAVIES B. R. 
Published: May 2006

SUMMARY 1. The occurrence, composition and invertebrate fauna of naturally‐occurring leaf packs were studied over 24 months in Langrivier, a second‐order mountain stream in the south‐western Cape, South Africa. Langrivier is shallow and fast‐flowing and stores very low levels of allochthonous detritus, although natural leaf packs form an obvious part of the energy base in the stream throughout the year.2. The occurrence and size of the packs were influenced mainly by stream discharge and by the timing and character of leaf fall from riparian trees. Packs were smallest (minimum dry mass 17 g, minimum volume 1.7–10−5 m3) in winter when discharge was high, and largest (maximum dry mass 191 g, maximum volume 4.2–10−3 m3) in spring when discharge decreased and leaf fall from the evergreen riparian trees began. Through the year the packs covered a mean 0.41 % of the stream bed and had a mean abundance of 0.46 packs m−2 of stream bed. They were ephemeral, lasting on average <1.7 months and yet accounted for 29% of the stored detritus in the system. Wood was the dominant component of packs, and leaves at ali stages of decomposition were present throughout the year.3. The ratio of numbers of invertebrates in packs: numbers of individuals in the benthos was very low (0.002–0.030), presumably because of the rarity and small size of the packs. Nevertheless, the density of invertebrates per unit area covered by leaf packs was consistently much higher than the density in an equivalent area of the benthos, except during peak leaf fall (October to December).4. Experiments were undertaken with artificial leaf packs in order to determine the extent to which these simulated natural packs. Although both natural and artificial leaf packs contained a high proportion of Plecoptera (46% and 29% respectively), the natural packs contained high numbers of simuliid larvae (33% of total), whereas artificial packs had a high percentage of chironomid larvae (62%), Several other taxa regularly occurred in both types of pack but in very low numbers. In addition,
Microbial activity associated with seston in headwater streams: effects of nitrogen, phosphorus and temperature
Authors: PETERS G. T. , WEBSTER J. R. , BENFIELD E. F. 
Published: May 2006

SUMMARY 1. The influences of temperature and dissolved nitrates and phosphates on microbial activity associated with suspended fine particulate organic matter (seston) were evaluated in four headwater streams in the southern Appalachian Mountains.2. Temperature manipulations of ± 5°C always induced significant changes in [14C] glucose mineralization (ANOVA; P<0.05) and [3H]thymidine incorporation (ANOVA; P<0.05).3. Nutrient amendments of 1.0 mg NO3 I−1 and 0.05 mg PO4I−1 induced no significant alterations in bacterial mineralization of [14C]glucose (ANOVA; P>0.05) or incorporation of [3H]thymidine (ANOVA; P>0.05) in short‐term (i.e. 3 h) experiments.4. Microorganisms attached to refractory particulate organic matter do not appear to be limited by nitrogen or phosphorus even in streams with ambient nutrient concentrations as low as 0.06 mg NO3 I−1 and <0.03 mg PO4 I−1.5. Our results indicate that variations in water temperature resulting from diurnal and seasonal temperature fluctuations, forest clear‐cutting, and catchment elevation and aspect can have marked effects upon microbial activity and production, while short‐term alterations in nutrient regime appear to have no significant effect on microbial activity associated with seston.
Evidence for the use of non‐detrital dissolved organic matter by microheterotrophs on plant detritus in a woodland stream
Authors: MILLER J. CLARK 
Published: May 2006

SUMMARY 1. Recent studies provide evidence for the use of exudates from living plants by epilithic microheterotrophs in streams. This study investigated the possible use of such non‐detrital sources of dissolved organic matter (DOM) by streatn microheterotrophs colonizing leaf litter. Biomass of bacteria and of fungi accumulating in situ on autumn‐shed leaves in flow‐through troughs from which light was excluded was compared to that accumulating on leaves in troughs open to natural illumination.2. In experiments repeated at different times of year and in different stream sections, greater biomass of microheterotrophs consistently accumulated on the leaf detritus in troughs open to natural illumination. Differences in water temperature or in grazing of leaf surfaces by macroinvertebrates could not account for these consistent differences. Further, greater microheterotroph biomass accumulated on light‐ and dark‐incubated leaves in a stream section relatively open to sunlight, compared to corresponding leaves in a section heavily shaded by canopy and understorey vegetation.3. These and other results suggest that, to some yet undetermined extent, detritus‐associated microheterotrophs use non‐detrital DOM. This conclusion is consistent with a priori predictions based on consideration of microbial energetics involved in the use of detrital versus non‐detrital DOM.4. Studies of trophic pathways in streams and other aquatic habitats have failed to assess some potentially important sources of non‐detrital DOM. The ability of available techniques to assess the relative roles of detrital and non‐detrital sources of DOM is evaluated, and alternative approaches to this problem are suggested.
Prediction, from temperature, of eyeing, hatching and ‘swim‐up’ times for salmonid embryos
Authors: CRISP D. T. 
Published: May 2006

SUMMARY. 1. The literature contains a number of curves relating time (days) required for median hatch (=D2) to water temperature (T,°C) for the eggs of several salmonid fishes. There are relatively few data on the relationships between time to median eyed (= D1), days) or time to median swim‐up (= D3, days) and temperature.2. From published data, over most of the range 0‐9.5°C, approximate relationships are D,=0.5D2 for Atlantic salmon (Salmo salar L.) and D3 = 1.7D2 for eight species of Salmo and Oncorhynchus.3. Field and hatchery tests suggest that these are useful empirical models for approximate prediction of D1 and D3 from D2 for most salmonids.
Cyclomorphosis in Daphnia galeata mendotae Birge and D. retrocurva Forbes as a predator‐induced response
Authors: DODSON STANLEY I. 
Published: May 2006

SUMMARY. 1. Populations of Daphnia galeata mendotae and D. retrocurva were exposed for one generation to predators enclosed in mesh bags. The exposed Daphnia showed adaptive morphological changes that mimic cyclomorphosis in nature. The invertebrate predators Chaoborus and Notonecta induced longer helmets, while the fish Lepomis induced shorter bodies but had no effect on helmet length. Longer tail spines (relative to body length) were induced by Notonecta and Lepomis.2. The responses of D. retrocurva were influenced by algae concentration, with the more extreme responses occurring at a higher food concentration and higher lipid index.
The distribution of Ephemerella ignita (Ephemeroptera) in streams: the role of pH and food resources
Authors: WILLOUGHBY L. G. , MAPPIN R. G. 
Published: May 2006

SUMMARY. 1. The mayfly Ephemerella ignita does not occur in upland streams of the River Duddon catchment which have waters with low pH values of 4.8‐5.2, negative alkalinities and low ionic contents. However, it does occur in lowland streams of the catchment which have waters with higher pH values of 6.6 and above, large positive alkalinities and high ionic contents. This study addresses the question of whether the absence of the animal in the acid water streams is due directly to the water chemistry or to the absence of suitable food.2. In comparative experiments using unfed animals of several species it was shown that E. ignita has a considerable tolerance of low pH, low ion water. In this it is similar to Amphinemura sulcicollis (Plecoptera), a stonefly which occurs in the acid water streams of the River Duddon catchment.3. Growth rates in laboratory experiments with E. ignita were equally good whether the food supplied was that available in the low pH water streams (bryophyte Nardia compressa plus filamentous alga Hormidium subtile) or typical of that available in high pH water streams (moss Rhynchostegium riparioides with the epiphytic diatom Cocconeis placentula). However, a consideration of the natural habits of the animal suggests that it is the inaccessibility of the H. subtile algal food, rather than its unsuitability, which is relevant to the exclusion of E. ignita from the low pH streams. In addition, the very limited diversity of other algae in the low pH water streams, in the summer season, may well be influential in inhibiting the establishment of E. ignita.4. The comparative experiments using unfed animals suggested that, contrary to the findings for E. ignita, the mayflies Baetis muticus and Beatis rhodani are probably excluded from the acid water streams of the Upper Duddon because of water chemistry.
Alkalinity and pH of tarns and streams in the English Lake District (Cumbria)
Authors: SUTCLIFFE D. W. , CARRICK T. R. 
Published: May 2006

SUMMARY. 1. The distribution of softwater and acid tarns and streams in central Cumbria is briefly summarized and compared for the periods 1983‐85 and 1949‐56.2. Fifty‐three upland tarns (altitude >350m) and forty lowland tarns (altitude <320m) were sampled on Skiddaw Slates, the Borrowdale Volcanic Series, and igneous intrusions. On these bedrocks, tarns and streams would be highly sensitive to further acidification if acid deposition increases above current levels. Twenty‐six upland and seven lowland tarns are permanently acid with zero or negative alkalinity values throughout the year; mean pH ranged from 5.3 to 4.2. The other sixty upland and lowland tarns had positive mean Alk in the summers of 1983‐85, ranging from 7 to 1227μequiv. I−1 Alk and mean pH5.7 to >7.0. Thirty‐one of the sixty tarns had mean Alk < 100μequiv. I−1 in summer (May‐September); sixteen became temporarily acid (negative Alk) for varying periods in winter. Acid episodes also occurred in the tarns in 1949‐56.3. Acid and very low alkalinity tarns and streams commonly occur on the high western, central and northern fells. Few occur on the high eastern felts, where there are veins of calcite in exposed rocks.4. Seventy‐five lowland tarns were sampled on Silurian Slates in southern Lakeland. On these bedrocks, tarns and streams are not highly sensitive to further acidification. Only six tarns had summer mean Alk <100μequiv. 1−1. No permanently acid tarns or streams were found.5. Over a mean span of about 30 years. Eel Tarn appears to have become slightly more acid and Harrop Tarn slightly less acid. The remainder of all tarns surveyed in 1983‐85 have altered little, although there is a heavy load of acidic deposition on to the catchments and some tarns contain very low concentrations of Alk. Rapid acidification in recent years has been prevented by the neutralizing capacity of volcanic and sedimentary rocks. These rocks produce relatively high concentrations of Alk, up to 650μequiv.l−1 in some spring‐fed streams on the central fells and even more at lower altitudes. Absence of coniferous
Life history variation in a dobsonfly, Protohermes grandis (Megaloptera: Corydalidae): effects of prey availability and temperature
Authors: HAYASHI FUMIO 
Published: May 2006

SUMMARY. 1. The life cycle of a predatory insect, Protohermes grandis (Megaloptera: Corydalidae), was compared in four streams in central Japan. The effects of annual temperature regime and prey availability on life history characteristics were also assessed.2. The larval period was 2 years and small adults emerged in the Morito River, where summer water temperature was high and large prey scarce.3. In the Nagura River, rich in large prey, the larval period was also 2 years in spite of slightly lower temperature, and the adult size was largest among the streams.4. In Anado Fork with a low summer temperature, the larval development took 3 years, and large adults emerged. Large prey were abundant in this stream.5. Seasonal abundance of large prey also affected the time large larvae left the stream to pupate. Larvae emigrated earlier in streams where the density of large prey sharply decreased after spring, than in streams where large prey were available throughout the year.