bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential use of food resources by the instars of Chaoborus punctipennis
Authors: MOORE MARIANNE V. 
Published: May 2006

SUMMARY. 1. Differential use of food resources by instars I‐1V of Chaoborus punctipennis was examined in a mesotrophic New Hampshire lake during midsummer when all instars coexisted. Diet composition and prey preference were quantified first, at night when all instars were feeding at the same depth, and second, during the day when the early instars (I‐II) and instar III were segregated by depth. Relative abundance, per cent biomass, and per cent frequency of occurrence of soft and hard‐bodied rotifers, flagellated phytoplankton, protozoans, and crustaceans in C. punctipennis diets were quantified using crop content analyses.2. All four instars ingested large, flagellated phytoplankton (mainly Dinobryon and Ceratium). This unexpected result suggests that the effects of phytoplankton on Chaoborus growth and survival should be investigated. All instars also consumed rotifers (mainly Kellicottia, Gastropus, Polyarthra), but only instars III and IV fed upon crustaceans (mainly Daphnia, Bosmina and Diaphanosoma). Small rotifers (Gastropus spp., Keratella cochlearis, Trichocerca similis) occurred more frequently and were more abundant in early instar diets than late instar (III and IV) diets, whereas large rotifers (Asplanchna priodonta and Keratella crassa) were eaten only by instars III and IV. Zooplankton with gelatinous sheaths (e.g. Ascomorpha, Collotheca and Holopedium) were rarely ingested.3. Developmental increase in gape diameter of C. punctipennis seemed to be the major proximate mechanism causing dietary differences among instars. Body widths of hard‐bodied prey in C. punctipennis crops were always less than gape diameter. The relationship between prey body width and Chaoborus gape diameter, coupled with knowledge of prey escape behaviour, should be useful for predicting the presence of hard‐bodied prey taxa in diets of other Chaoborus species.4. All four instars of C. punctipennis selected soft‐bodied, or weakly loricate, rotifer prey over crustaceans and phytoplankton. Early instars preferred the small rotifer T. similis and the protozoan Difflugia sp. to other rotifers and phytoplankton when feeding in the epilimnion or thermocline during the day or night. Late instars positively selected the rotifer, Asplanchna. Prey value (prey weight ingested per unit handling
Input, movement and exchange of organic matter within a subtropical coastal black water river‐flood plain system
Authors: CUFFNEY THOMAS F. 
Published: May 2006

SUMMARY. 1. Inputs, movements and exchanges of particulate organic matter were measured on two contrasting floodplains of the Ogeechee River, Georgia, U.S.A. A model, which incorporated measurements of standing crop, respiration, litterfall, inundation, and litter processing rates, was used to estimate annual exchanges of organic matter between the river and floodplains.2. Annual litterfall was higher on the East floodplain than on the lower elevation West floodplain (902 v. 784 g ash‐free‐dry‐mass [AFDM] m−2).3. Experiments with tagged leaves and sticks demonstrated that litter was readily displaced during floods. The distance and direction of displacement varied within and between floodplains but tended to be higher closer to the river and was generally parallel to the river.4. The model indicated that both floodplains lost organic matter to the river. The lower elevation floodplain (East) lost more organic matter to the river (208 g AFDM m−2 year−1) than did the higher elevation (West) floodplain (79g AFDM m−2 year−1).5. Inputs of organic matter from the floodplain to the river exceeded the amount of litterfall typically entering heavily forested high gradient headwater streams (5.5 v. 0.4‐0.6 kg AFDM m−2 year−1).6. Floodplain organic matter inputs may exert a greater influence upon structure and function within these streams than do upstream inputs or primary production. Consequently, current conceptualizations of stream structure and function need to be modified to account for the effects of floodplain inputs on stream channel processes within large, low‐gradient rivers.
The phytoplankton of an enriched, soft‐water lake subject to intermittent hydraulic flushing (Grasmere, English Lake District)
Authors: REYNOLDS C. S. , LUND J. W. G. 
Published: May 2006

SUMMARY. 1. The abundance and species composition of the phytoplankton of Grasmere were monitored over a 12‐year period following the commissioning of a small sewage treatment works, upstream of the lake.2. Although Grasmere has been subject to increased phosphorus‐loading and has quickly developed many features associated with eutrophication, the composition of its plankton has retained the characteristics of a mesotrophic, soft‐water lake: a vernal diatom maximum, generally dominated by Asterionella, is followed by summer growths of nanoplanktonic species, of various colonial Chlorophyceae, before a substantial return to Asterionella‐dominance in the autumn. In cooler summers there have been episodes of renewed diatom growth. followed by truncated recapitulations of the essential summer sequence. Anabaena solitaria was relatively common in drier summers when dissolved inorganic nitrogen fell to low concentrations, although many of the ‘larger’ algal species associated with stratified eutrophic lakes (Aphanizomenon, Microcystis, Ceratium spp.) have failed to become abundant in Grasmere.3. Mean biomass levels (as indicated by chlorophyll concentration) have increased in response to the enrichment, though they do not conform well with most chlorophyll/phosphorus regression‐models.4. The key factor resisting a more complete transition to a typical eutrophic plankton appears to be the efficiency of episodic flushing of the lake during periods of high fluvial discharge sustained by heavy rainfall over the extensive, mountainous catchment. The probabilities that these limnological conditions might fail to deter the development of ‘nuisance’ blooms are briefly assessed.
In vitro studies on sulphate reduction and acidification in sediments of shallow soft water lakes
Authors: SCHUURKES J. A. A. R. , KOK C. J. 
Published: May 2006

SUMMARY. 1. The sulphate reduction capacity of six shallow soft water sediments, differing in pH and organic matter content, was studied under controlled pH adjustments ranging from pH 3 to pH 8.2. In the acid sediments, relatively rich in organic matter, the sulphate reduction capacity reached values of 0.09‐0.12 μmol g−1 d−1. In the circumneutral mineral sediments the values ranged between 0.04 and 0.08 μmol g−1 d−1.3. The latter group of sediments was very sensitive to the effects of experimental acidification as sulphate reduction was almost fully inhibited when pH decreased from 7 to 5. In the acid sediments inhibition occurred at lower pH values, in the range pH 5 to pH 3.4. Sulphate reduction governed the production of free sulphides, whereas putrefaction processes were only of minor importance. It is suggested that in acid sediments, relatively rich in organic matter, the sulphate reducing bacterial population is less sensitive to acidification than in circumneutral mineral sediments.5. The presence of organic matter appeared to be important in counteracting the inhibiting effects of acidification on sulphate reduction. This is important for the in situ sulphate reduction in sediments of soft waters which become enriched with organic matter during the long‐term process of acidification.
Community structure of Trichoptera in a mountain stream: spatial patterns of production and functional organization
Authors: HURYN ALEXANDER D. , WALLACE J. BRUCE 
Published: May 2006

SUMMARY. 1. Annual production was estimated for Trichoptera occurring in each of three distinct habitats of a mountain stream: bedrock‐outcrops, riffles and pools. Production was greatest on bedrock‐outcrops (2608 mg ash‐free dry weight m−2), followed by riffles (1038) and pools (950).2. Annual production in bedrock‐outcrops and pools was dominated by single functional groups, with collector‐filterers and shredders contributing 73% and 75% of the annual production, respectively. Production in riffles was due primarily to shredders (46%), followed by collector‐filterers (27%).3. Taking account of the amount of stream area occupied by each habitat type, total annual production was estimated at 1336 mg AFDW m−2. 53% of this production was attributable to four taxa: Parapsyche cardis Ross (25%), Pycnopsyche gentilis (MacLachlan) (10%), Neophylax mitchelli Carpenter (9%) and Rhyacophila nigrita Banks (9%).4. Habitat‐weighted production was distributed among functional groups as follows: collector‐filterers (41%), shredders (29%), engulfing‐predators (15%), scrapers (13%) and collector‐gatherers (2%).5. The distinct taxonomic and functional structures of trichopteran sub‐communities were shaped by the distinct physical characteristics of their principal habitats. Bedrock‐outcrops were characterized by low roughness and high current and were sites of low deposition or organic matter; thus the predominance of collector‐filterers. In contrast, the other habitats of greater roughness (riffles) and/or lower current (pools) were sites of deposition of food (e.g. leaf litter) and greatest shredder production.6. By distinguishing discrete mesoscale habitats, each with a functionally distinct caddisfly sub‐community, we speculate that small mountain streams provided the diverse physical templates essential for the evolution of the major feeding tactics (e.g. scraping, shredding, filter‐feeding) of the. Trichoptera.
Effects of turbidity on life history parameters of two species of Daphnia
Authors: SCHOLTZ S. , SEAMAN M. T. , PIETERSE A. J. H. 
Published: May 2006

SUMMARY.1. Life table experiments were carried out in a range of turbidities onD. pulex, representing a ‘clear‐water’, and onD. barbata, representing a ‘turbid‐water’ species.2. In contrast to predictions based on seasonal occurrence patterns,D. pulexhad a higher intrinsic rate of increase (rc)s over most of the turbidity range thanD. barbata.Consistent differences in life history between the two species were found, but life history characteristics were rather insensitive to turbidity levels. Although turbidityper seappears to have little direct effect on life history parameters, it could influence the seasonal succession of these two species by interacting with other factors.3. It is suggested that visual predation by fish rather than turbidityper seprobably influenced the seasonality ofDaphniaspecies. During the warmer months, selective removal ofD. pulexby visually foraging fishes may allowD. barbatato gain dominance. Effects of temperature and nutrition also merit further study.
Impact of biological activity on detritus transported in the lower river Rhine: an exercise in ecosystem analysis
Authors: ADMIRAAL WIM , VAN ZANTEN BOB 
Published: May 2006

SUMMARY. 1. Published data are used to construct a tentative carbon budget for the ecosystem of the lower river Rhine and its sedimentation areas in The Netherlands.2. It is estimated that 287 × 106kg Cy−1 of particulate organic material is transported by the river Rhine, and 100 × 106 kgCy−1 of this material is deposited in the delta.3. Phytoplankton and nitrifying bacteria seem to contribute significantly to the carbon budget, by producing c. 78 × 106kgCy−l.4. The mineralization in the water (estimated from routine determinations of biological oxygen demand and from in situ diurnal fluctuations of oxygen) and in the bottom (estimated from the denitrification rates in the delta, from the production rate of methane and from overall oxygen consumption) is shown to degrade c. 50% of the carbon input plus autochthonous production.5. The carbon budget and oxygen regime in the lower Rhine suggest that after decades of severe organic pollution the river has more or less resumed the normal, slightly heterotrophic state of a large lowland river.
Rapid flow through the sediments of a headwater stream in the southern Appalachians
Authors: MUNN NANCY L. , MEYER JUDY L. 
Published: May 2006

SUMMARY. 1. The flow of water through the sediment layer (underflow) of streams can influence nutrient uptake dynamics and the supply of materials to microbes, meiofauna and macroinvertebrates living within stream sediments. We examined the extent of underflow in Hugh White Creek, a headwater stream in the southern Appalachian Mountains and compared underflow at different depths and at different sites within the stream.2. Initially rhodamine dye was used to trace the flow of water through the sediments; however, the dye was strongly absorbed by the sediments in Hugh White Creek. Thus rhodamine was not suitable as a tracer of water flow. Chloride reacted conservatively in laboratory experiments and was used as a tracer.3. The tracer infiltrated the sediments within 5 min to depths of 10 cm at all six sites. Chloride infiltration tended to decrease with depth of sediments at all sites although there was no consistent statistical pattern in chloride concentration with depth for the different sites. Equilibrium between the water column and sediments was reached rapidly, within minutes for the sites with coarse sediments and within a few hours for sites with finer sediments. Minimum rates of chloride infiltration into the sediments ranged between 1.0 cm min−1 for the sites with cobble substrate to 0.2 cm min−1 for sites with fine sand sediments associated with debris dams. These data suggest that underflow may be a major component in the functioning of Appalachian mountain streams.
Exoenzyme activity associated with lotic epilithon
Authors: SINSABAUGH R. L. , LINKINS A. E. 
Published: May 2006

SUMMARY. 1. Epilithic communities were developed on glass slides under four regimes of relative current velocity and light exposure, designated as slow‐light, slow‐dark, fast‐light and fast‐dark, in a fourth‐order boreal stream. Ten samples were collected over an 8‐month period and analysed for biomass, chlorophyll and exoenzyme activity. Fourteen assays were used to monitor the activity of eleven types of exoenzymes involved in the degradation of cellulose, lignin, chitin, xylan, protein, glycogen, organic phosphates and organic sulphates.2. The communities that developed under each current and light regime were distinct in structure and species composition, but had similar patterns of exoenzyme activity. Overall, exoenzyme activity was closely correlated with biomass. The most readily detected enzymes were phenol oxidase, phosphatase, alpha‐1, 4‐glucosidase, beta‐1, 4‐N‐acetylglucosamidase, and beta‐1, 4‐glucosidase.3. Calculating exoenzyme activities per unit biomass eliminated the covariance between biomass and enzyme activity, revealing quantitative differences in exoenzyme activity among communities. The highest exoenzyme activity was associated with the slow‐dark epilithon and the least with the slow‐light. Fast‐light and fast‐dark were intermediate.4. Biomass, chlorophyll and exoenzyme activity showed marked seasonal variations. In general, carbohydrases and the phenol oxidases had different seasonal activity patterns with carbohydrase activity peaking in the summer and phenol oxidase activity increasing markedly in the autumn.5. Differences among epithilic communities could not be readily accounted for by single factors. Community development was determined by the interactions among current, light, macroinvertebrates and season.
An inexpensive, deep‐water limnocorral that compensates for wave action
Authors: SPENCER CRAIG N. 
Published: May 2006

SUMMARY. 1. A large reusable limnocorral is described, suitable for use in water bodies with substantial wave action. The clear plastic enclosure is 1 m in diameter, 25m deep, lightweight (∼50 kg), and inexpensive ($350 U.S.A.).2. The lower portion of the limnocorral is designed to hang motionless below the water surface, while an expandable floating collar section moves freely up and down with any wave action.3. Two limnocorrals, equipped with removable sedimentation traps at the bottom, were field tested successfully for 6 weeks in Flathead Lake, Montana, withstanding wave heights up to 1m. Chlorophyll levels and profiles of various physical‐chemical parameters measured inside the limnocorrals were comparable to Flathead Lake values.4. Despite their large size, the limnocorrals are relatively easy to transport, install and retrieve.
Phytoplankton nutrient limitation in Colorado mountain lakes
Authors: MORRIS DONALD P. , LEWIS WILLIAM M. 
Published: May 2006

SUMMARY. 1. Limiting nutrients for phytoplankton were studied experimentally in eight mountain lakes of central Colorado between May and November of 1984.2. Five categories of phytoplankton limitation were identified: no limitation, N limitation, P limitation, concurrent limitation (stimulation only by simultaneous additions of N and P), and reciprocal limitation (stimulation by addition of either N or P). The phytoplankton communities of three lakes were primarily N‐limited, one was primarily phosphorus‐limited, and four showed primarily combined limitation (concurrent or reciprocal). Switching between categories of limitation was also observed within lakes. Nitrogen was the most frequently limiting nutrient; N, either alone or in combination with P, accounted for 79% of all observed instances of limitation.3. Nine indices were tested for effectiveness in predicting phytoplankton limitation by N and P. The best indices for discriminating all limitations were ratios of dissolved inorganic N: total P (84% accuracy) and dissolved inorganic N:total dissolved P (80% accuracy). The effectiveness of these indices may be explained by the degree to which they represent N and P fractions actually available to the phytoplankton.
In vivo algal fluorescence, spectral change due to light intensity changes and the automatic characterization of algae
Authors: HILTON J. , RIGG E. , JAWORSKI G. 
Published: May 2006

SUMMARY. 1 Total fluorescence spectra of thirty‐two freshwater algae show that the majority of the information is contained in the excitation spectrum of emission at 680 nm.2. Previously suggested characteristics for the automatic identification of blue‐green algae from their fluorescence properties, i.e. the presence of high phycoerythrin fluorescence and low chlorophyll fluorescence, are shown to be inapplicable to the freshwater blue‐green algae studied here.
Predation and the prey community of a headwater stream
Authors: SCHOFIELD K. , TOWNSEND C. R. , HILDREW A. G. 
Published: May 2006

SUMMARY 1. Predatory, net‐spinning larvae of the caddis Plectrocne‐mia conspersa (Curtis) were abundant in the acid headwaters of some southern English streams where fish were absent, but were scarce or absent downstream where brown trout (Salmo trutta L.) occurred.2. Field enclosure experiments showed that both underyearling and older brown trout reduced the density of P. conspersa. However, whereas small trout affected the overall density of caddis, older fish reduced that of large larvae only.3. Although P. conspersa is itself an important invertebrate predator there was little evidence of an indirect effect of brown trout on the prey of P. conspersa. Perhaps the diets of brown trout and P. conspersa are so similar that fish simply replaced the caddis as top predator.
The temperature dependence of embryonic and larval development in Protonemura intricata (Plecoptera: Nemouridae)
Authors: MARTEN MICHAEL , ZWICK PETER 
Published: May 2006

SUMMARY. 1. Egg development and larval growth of Protonemura intricata (Ris, 1902) (Plecoptera: Nemouridae) were studied in the laboratory and in the Breitenbach, a small stream‐in Germany (F.R.G.).2. The mean number of eggs in batches collected from the field was 627 (S=314).3. Mean batching success in the laboratory was 60–100% at 2–18°C. Cumulative hatch in individual batches could be described by asymmetrically sigmoid curves. The length of the hatching period was positively correlated with the length of the incubation period.4. The incubation period of I', intricata normally consists of an initial dormancy followed by subsequent development. The length of embryonic development (Y. days) is strongly inversely temperature (T, °C) dependent and can be described by the equation:

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5. The length of dormancy is dependent on oviposition dale, and is shorter the later that the eggs are laid. It also depends on temperature during incubation and is increased by rising temperatures. As a consequence, larvae hatch more or less synchronously in the field during autumn. Total incubation period, i.e. dormancy and actual development, exhibits a complex dependence on both incubation temperature and oviposition date. Under constant laboratory temperatures, a late sharp fall in temperature can terminate dormancy earlier.6. Photoperiod probably induces dormancy and may already act on the last larval instars of the parent generation. The dormancy of P. intricata is classified as an oligopause (Müller. 1970, 1976).7. In the laboratory. P. intricata larvae from early batches with long dormancy grew faster than larvae from late batches with direct development. Final size was the same in both cases. This acted against the population synchrony induced through egg dormancy. Benthos samples suggest the same in the field.8. Avoidance of the suboptimal summer conditions in streams by the cold stenothermous P. intricata is suggested to partly explain the success of the species, which contributes more to total emergence biomass than do other Plecoptera in the Breitenbach.
Decomposition of leaf litter exposed to simulated acid rain in a buffered lotic system
Authors: GARDEN ANNE , DAVIES RONALD W. 
Published: May 2006

SUMMARY. 1. Exposure to simulated acid rain resulted in changes in the chemical content of riparian vegetation and terrestrial leaf litter and had significant effects on leaf litter decay rates in a well‐buffered lotic ecosystem.2. Foliar nitrogen and phosphorus decreased with decreasing pH of the simulated acid rain and microbial activity was greater on leaf litter exposed to rain of pi I 5.4 than on leaf litter exposed to pH 3.0 or pH 4.0.3. Detritivore numbers and biomass were significantly higher on leaf litter exposed to pH 5.4, probably due to the greater palatability of the leaf substrate.4. Decay rates of leaf litter processed in the summer months were significantly lower than decay rates of leaf litter processed during the autumn/winter due to reduction in nitrogen content and microbial respiration.
Macroinvertebrate movements in a large European river*
Authors: CELLOT BERNARD 
Published: May 2006

SUMMARY. 1. Quantitative variations in downstream movements of benthic macroinvertebrates were studied in a large European river, the Rhône, upstream from Lyon. Artificial substrates were suspended at three depths in the water column, both near a bunk and in mid‐channel, monthly from December 1978 to March 1980. Drift nets were used to determine the diurnal rhythm in drift and to investigate the efficiency of our suspended artificial substrates in capturing the drifting macrofauna.2. Drift densities (number and biomass) reached a maximum during summer, especially near the river bank, and at night. Mean individual weight of organisms was higher close to the bottom and at night.3. Artificial substrates were reliable, but underestimated drift by about a quarter in number and a sixth in biomass. compared with drift nets. Two detailed analyses of the drift distribution across the width of the river revealed similar densities along both banks, and uniformity in the channel as a whole.4. Mean annual drift densities estimated for the section of river were 100 individuals, per 100 m3 and 60 mg dry weight per 100 m3. These densities are similar to those obtained from other temperate rivers.