bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determinants of ingestion rates in filter‐feeding larval blackflies (Diptera: Simuliidae)
Authors: HART DAVID D. , LATTA STEVEN C. 
Published: May 2006

SUMMARY
1. The functional response of the filter‐feeding blackfly larva Frosimulium mixtum/fuscum was examined in laboratory experiments. We focused on the relationship between a component of the particle handling process (the cephalic fan flick rate) and ingestion rate, to determine whether ingestion rate is limited by handling‐time. The influence of food deprivation on ingestion rate and feeding efficiency also was assessed.2. Ingestion rate rose asymptotically with increasing food availability, leveling off at a concentration of about 100 mg1−1. Satiation did not account for this plateau. Flick rate (the frequency with which larvae open and close their cephalic fans) increased in a similar fashion, though flick rate only accounted for about two‐thirds of the variation in ingestion rate.3. A simple equation describing the components of the feeding process in blackfly larvae was developed to investigate alternate flick rate ‘decision rules’ capable of predicting relationships between food concentration, flick rate and ingestion rate. The flick rate did not follow a fixed time rule, in which larvae allow particles to accumulate in the fan for a fixed amount of time prior to retraction. For most food densities, flick rate patterns more closely approximated a fixed number rule, in which fans are retracted after a fixed number of particles accumulate.4. Flick rate rose with increasing food concentration even after the ingestion rate had levelled off, whereas several optimal filter‐feeding models predict that filtering rate should decline as food concentration increases above this level. This predicted behavior was not observed because the number of particles ingested per flick failed to increase with increasing food concentration.5. The efficiency of particle ingestion (number ingested × number available−1× 100) was very low (<0.1%), and declined with increasing food concentration.6. An increase in food deprivation time prior to a feeding trial produced a significant increase in flick rate, ingestion rate and feeding efficiency. This adjustment of feeding behaviour allowed animals to replace their gut contents more quickly following longer periods of food deprivation, which agrees with the qualitative predictions of optimal digestion‐time models.
Peat and peat water chemistry of a flood‐plain fen in Broadland, Norfolk, U.K.
Authors: GILLER KENNETH E. , WHEELER BRYAN D. 
Published: May 2006

SUMMARY. 1. Dominant chemical gradients in the peats of a flood‐plain fen in Broadland, Norfolk were poor‐fen (oligotrophic)  rich‐fen (minerotrophic) and freshwater  brackish water. These gradients were to some extent obscured by a complex of factors governing the concentrations of ions in the peats and peat waters.2. The peats were almost totally organic and cation exchange capacities (CEC) varied with their macrofossil composition. Cladium mariscits L. peats had higher CEC than Phragmites communis Trin. peats of similar bulk density.3. Amounts of dissolved and extractable N and P were very low. but total amounts of N and P were high and closely related to bulk density.4. Large seasonal variation in concentrations of ions in the peat waters was due to dilution at times of flooding. There was strong evidence that little river water penetrated directly across the study area, contrary to classical descriptions of flood‐plain mires.5. Amplitude of fluctuations in concentration varied between study sites although the pattern of change was similar. Fluctuations were small in poor‐fen. Sphagnum dominated sites.6. An incursion of brackish water up river due to unusually high tides was observed, but it is likely that brackish conditions in the fens are caused by release of ions from underlying estuarine clays.
A pump sampler study of microdistribution in Walker Lake, Arizona, U.S.A.: a senescent crater lake
Authors: BLINN DEAN W. , GREEN J. 
Published: May 2006

SUMMARY. 1. The seasonal microdistribution of physico‐chemical features and plankton were examined at close intervals in a high elevation (2493m) senescent crateri lake (1m deep) in the arid southwestern U.S.A.2. The protective volcanic rim and dense growth of provided highly stable thermal conditions throughout much of the year with the thermocline frequently in the top 30cm of the water column during the summer and dissolved oxygen typically <3.0mgl−1 in surface waters and <1.0mgl−1 below 50cm.3. The microdistribution of both phytoplankton and zooplankton was examined at close intervals (10cm) throughout the water column with the aid of a peristaltic pump.4. Aglaodiaptomus leptopus, along with Dinobryon sertularia and certain diatom species, were largely restricted to the top 30cm, while the colonial phytoflagellate, Pyrobotrys elongata and certain euglenoids were mostly located in the anaerobic lower strata.5. Cryptomonas obovata demonstrated subsurface maxima at various locations within the water column depending upon season.6. The distribution of plankton was also compared during daylight and darkness on one date.
Contribution of fungal biomass to the diet of a freshwater isopod (Lirceus sp.)
Authors: FINDLAY STUART , MEYER JUDY L. , SMITH PHILLIP J. 
Published: May 2006

SUMMARY. 1. The direct contribution of fungal biomass to the carbon needs of a freshwater isopod (Lirceus sp.) was measured using 14C‐labelled fungi on leaf material. 14C‐glucose was added to fungus‐inoculated leaf discs periodically throughout the growth of the fungus. Amount of label incorporated into fungal biomass, radioactivity appearing in Lirceus after feeding on labeled fungus and the standing stock of fungus were used to calculate incorporation of fungal C by the consumer.2. Incorporation rates ranged from 0.06 to 70 ng fungal C mg wet wt isopod‐1h‐1. These rates of incorporation represent from 0.05 to 57% of C respired by the isopod.3. Fungal C does not meet the carbon needs of this consumer and the role of fungi as modifiers of the leaf substrate may be more significant than their role as a food source.
Spatial variation of water temperature characteristics and behavior in a Devon river system
Authors: WEBB B. W. , WALLING D. E. 
Published: May 2006

SUMMARY. 1. The results of 5 years of continuous monitoring of river water temperatures at seventeen stations within the Exe basin, Devon, U.K., are presented and discussed.2. Systematic spatial variation in mean annual water temperature was evident and was strongly related to the topographic variable of elevation. Deviations from this relationship reflect local influences of vegetation shading, runoff source and channel character.3. Considerable spatial variation in temperature extremes was also apparent, and the Exe basin differs from several other British river systems in exhibiting highest peak temperatures at downstream sites on the mainstream. Discharge from Wimbleball Reservoir exerted a significant influence on annual maxima and minima.4. A clear seasonal cycle characterized all stations and was objectively defined by second‐order harmonic functions which varied in amplitude and phase across the study area. Marked spatial variability in the magnitude and timing of diurnal temperature fluctuations, in temperature duration curves and in accumulated temperatures was also recorded.5. The implications of the spatial variation in thermal regime for the growth of brown trout was also investigated.
The occurrence of metacercariae of the trematode, Cyathocotyle opaca (Wisniewski), in three species of lake‐dwelling leeches
Authors: SPELLING S. M. , YOUNG J. O. 
Published: May 2006

SUMMARY. 1. The leeches, Erpobdella octoculata, Glossiphonia complanata and Helobdella stagnalis, were collected at monthly intervals over a 2‐year period from a eutrophic English lake, and examined for the presence of metacercariae of the trematode. Cyathocotyle opaca.2. Only one specimen of each of H. stagnalis and G. complanata was recorded with the parasite. Seasonal changes in prevalence levels in E. octoculata were similar for each of the three cohorts identified during the study period. Values, low in young leeches recruited in the autumn, rose slowly until the following spring, and then increased more rapidly till the autumn, when the cohort died out. Mean intensity and relative density showed similar patterns of seasonal change to that of prevalence.There was no evidence of parasite induced mortality in E. octoculata. Attainment of sexual maturity did not differ between infected and uninfected leeches.
Gradients in the distribution of riverine benthos
Authors: SCHAEFFER DAVID J. , PERRY JAMES A. 
Published: May 2006

SUMMARY. 1. Numerous hypotheses regarding the controls on species distributions in streams depend on longitudinal analyses of collections of stream organisms. Techniques for the detection of trends and for the detection of station groupings among biological collections have been widely reported, but rarely compared with each other. We have conducted an analysis of ten or eleven samples from each of thirteen stations along a stream abiotic gradient, and have compared several techniques.2. An analysis of longitudinal distribution must first assess the existence of a gradient in biotic composition. Random skewers on species proportions were the most sensitive in demonstrating such a gradient. Q and M statistics were most useful in further describing the trend due to their additive properties; i.e. the importance of one or more stations in dictating the trend may be determined. Cluster analysis, as well as percent faunal similarity, was most efficient at isolating station groupings. Techniques such as faunal replacement and species loss calculations are generally more useful in testing hypotheses about controls on species distributions, and should be employed where potential causal factors may be isolated.
Polymixis and algal production in a tropical lake: latitudinal effects on the seasonality of photosynthesis
Authors: VINCENT W.F. , WURTSBAUGH W. , NEALE P.J. , RICHERSON P. J. 
Published: May 2006

SUMMARY. 1. Phytoplankton production was measured during 1981–82 in Bahia de Puno. a large polymictic system that is part of LakeTiticaca in the tropical Andes (Peru‐Bolivia), Photosynthesis followed aweak seasonal pattern through each 12‐month cycle but the largestvariations occurrud between years.2. The large temporal variations in productivity appeared to becontrolled by biological events rather than by the direct effeets ofseasonal or aseasonal physical processes. Major shifts in production overthe 2‐year period were attributable to the proportional abundance andactivity of N2‐fixing blue‐green algae. Production was uncorrelated withthe seasonal radiation cycle.3. In vivo fluorescence and photosynthetic assays revealed largechanges in phytoplankton community structure over time and depth.The shifts in vertical structure were associated with changes in transparency and water column stabilily.Physiological as well as floristiceffects dictated the variations in fluorescence per unit chlorophyll a.4. An analysis of twenty‐seven primary productivity data sets fromdifferent latitudes shtiwed that Bahia dc Puno resembled other tropicallakes in its relatively weak coupling between algal photosynthesis andseasonal variations in light. Productivity in the temperate zone correlated with the annual cycle of incoming radiation while the tropicalproduction data did not. For many of the tropical lakes, but fewtemperate lakes, the between‐month variance in primary production wassignificantly higher than the between‐month variance for incomingradiation. There was a significant positive relationship between maximum production variance explained hy light (maximum r2 for each dataset) and latitude.5. As in many tropical lakes. Bahia de Puno experiences moderatelylarge variations in algal photosynthesis.The muted seasonal cycle of light explains only a small portion of the total variation In productivity, and other factors such as weuther‐related events are disproportionately important.
Diatom flora of an Australian river system:spatial patterns and environmental relationships
Authors: CHESSMAN BRUCE C. 
Published: May 2006

SUMMARY. 1. Qualitative diatom samples from various microhabitatswere collected at fifty‐three sites on the La Trobe River. Victoria, and itstributaries in late summer and early autumn. Measurements of severalphysico‐chemical variables of likely significance to diatom distributionwere also made.2. Principal components analysis of the physico‐chemical data showedthat the dominant environmental pattern in the river system was agradient from cool, dilute upland streams to warmer, more turbid andenriched lowland waters.3. A total of 267 diatom species was recorded; most were cosmopolitan and Navicula and Nitzschia were the dominant genera. Clusteranalysis allowed the sampling sites to be divided into six groups on the basis of their floras. These groupings corresponded closely to flow. landuse and wastewater discharge patterns and there were clearphysico‐chemical differences between the groups. Multiple discriminant analysisfound thataltitude. temperature. biochemical oxygen demand. turbidity, non‐filterable residue, pH. major ions, phosphorus and nitrogenwere important factors in distinguishing between site groups.4. Diatom species richness was lowest in relatively undisturbed, forested upland streams, probably as a result of nutrient limitation. Forthe catchment as a whole significantcorrelations were establishedbetween species richness and altitude, temperature, biochemical oxygendemand, turbidity. non‐filterable residue, conductivity, calcium, alkalinity, organic nitrogen and phosphorus.
Predation on leeches in a weedy pond
Authors: YOUNG JOHNSTONE O. 
Published: May 2006

SUMMARY. 1. A range of sizes of Erpobdelta octoculata fL.), Glossiphonia complanata(L.) and Helobdella stagnalis(L.) were introduced to a small weeded pond harbouring invertebrate and amphibian predators. Control leeches were kept in protective cages. Subsequently, gut contents of potential predators were tested against three anti‐leech sera, using the precipitin test. Five of fifteen species tested had fed on leeches; Agabus, Pyrrhosoma, Aeshna, Sympetrum and larval Trilurus.2. The size distributions of introduced and surviving leeches were compared. Predation pressure had been greatest on smaller leeches and this may have accounted for the observed differential mortality between leech species.3. It is concluded that predation may cause significant mortality in leech populations in weeded ponds, with severity determined by the types and abundance of predators present.
Metabolism of a sub‐tropical low gradient black water river
Authors: EDWARDS R. T. , MEYER J. L. 
Published: May 2006

SUMMARY. 1. Single‐station diel oxygen curves were used to monitor the oxygen metabolism of the Ogeechee River, a sixth‐order blackwater river in the Coastal Plain of southeastern U.S.A., over a period of 4 years. Ecosystem production (P) and respiration (R) were estimated, and P/R ratios calculated to determine the extent of autotrophy characteristic of this type of river. The potential error in oxygen metabolism caused by photo‐oxidation of dissolved organic carbon (DOC) in the water was measured and found to be minor.2. Rates of ecosystem primary production measured were intermediate compared to other rivers, ranging from 0.49 to 13.99g O2m−2 day −1.Primary production rates were highest during the summer when water levels were low. Regression analysis indicated that water depth and light absorption by DOM were significant predictors of primary production in this river. Incident light intensities were not significantly correlated with production rate.3. Respiration rates were unusually high, varying between 3.70 and 11.5 g O2 m−2 day − 1. System respiration also varied seasonally, but less than primary production. Rates were slightly higher in spring and summer.4. With one exception, P/R ratios were considerably lower than l throughout the study period, indicating that the Ogeechee River was highly heterotrophic. PIR ratios ranged from 0.09 to 1.3, and averaged 0.25.5. A carbon budget calculated for this river showed floodplain inputs were 7 times autochthonous production. Organic carbon turnover length was 690 km, considerably longer than has been reported for lower‐order rivers.
Grazing by oligochaetes and snails on epiphytes
Authors: KAIRESALO TIMO , KOSKIMIES IRMA 
Published: May 2006

SUMMARY. 1. The isotope 33P was used to assess the effect of grazitig by oligochaetes (mainly Stylaria lacttstris L.) and the snail, Lymnaea peregra(Muller), on epiphytes within an Equisetum fluviatile L. stand.2. Two 1 m2 polystyrene enclosures were set up within the emergent macrophyte zone of the lake. At the start of the experiment 33P‐solution was mixed with the water in both tanks. Algal and animal samples for 33P‐ analysis were collected during the peak occurrence of epiphytes in June.3. Phosphorus release rates from the animals through defaecation and excretion were measured in the laboratory. The grazing rate of oligochaetes was 2.2–4.1 mg P m−2 (of bottom) d−1 of which about two ‐ thirds was released and recycled. The oligochaete density ranged from 13,400 to 20,900 m−2. The snails (25 ind. m−2) grazed 1.2‐1.5 mg P m−2d−1of whieh about a quarter was released through defaecation and excretion.4. Daily consumption by the oligochaetes and snails corresponded to 22–45% of the average phosphorus uptake by the epiphytes.
Short‐term experimental acidification of a Welsh stream: comparing the biological effects of hydrogen ions and aluminium
Authors: ORMEROD S. J. , BOOLE P. , McCAHON C. P. , WEATHERLEY N. S. , PASCOE D. , EDWARDS R. W. 
Published: May 2006

SUMMARY. 1. A soft‐water stream iti upland Wales was dosed with sulphuric acid and aluminiutn sulphate at two successive points to create sitnultaneous episodes of low pH, and low pH with increased aluminiutn. Chemical atid biological responses were measured before, during and after the episode and were compared with a reference zone.2. The pH fell frotn ∼7.0 to 4.28 (±0.18 SD) and 5.02 (±0.10) respectively in the acid and aluminium zones. Corresponding aluminium concentrations during the episode were 0.052 g Al m−3 (±0.008) and 0.347 g Al nr3 (±0.047), the former not differing significantly from the reference zone. The concentration of cadmium rose to 0.002‐ 0.011 g Cd m−3in both treated areas, but the concentrations of other metals were unchanged.3. In situ toxicity tests were performed with macroinvertebrates and fish. Chironomus riparius. Hydropsyche angustipennis and Dinocras cephalotes suffered no mortality. Ecdyonurus venosus, Baetis rhodani and Gammarus pulex showed up to 25% mortality in both treatment zones and further mortalities occurred after the episode. Brown trout Salmo trutta and salmon Valmo salar s howed 7–10% mortality in the acid zone, but 50–87% in the aluminium zone, where salmon had a significantly shorter LT50than trout.4. The drift of Simuliidae increased during treatment in both acid and aluminium zones. Drift densities of Dixa puherula, Protonemura meyeri, Ephemeralla ignita and Dicranota sp. increased in the aluminium zone. The most pronounced response was by Baetis rhodani in the aluminium zone where drift density increased by ×8.4 during the episode.5. Baetis rhodani was the only taxon to show a significant decline in benthic density during the treatment, and then only in the aluminium zone. Drift could account for most of the losses.6. The depth distribution of invertebrates in the substratum differed between zones following treatment. More individuals were present at the surface of the reference zone (1287 m−2±747) than at the surface of the other zones (<400 m−2); however, densities at greater depths were similar. These patterns probably reflected differences prior to the treatments.
Faunal and chemical dynamics of some acid and alkaline New Zealand streams
Authors: COLLIER K. J. , WINTERBOURN M. J. 
Published: May 2006

SUMMARY 1. Water from acid (pH 4.3–5.7), brown water streams was low in alkalinity (0–2.3 g m−3 CaCO3) and conductivity (2.5–4.1 mS m−1) but contained relatively high concentrations of dissolved organic carbon (6.6–16.3 gm−3). In contrast, alkaline (pH 6.6–8.0), clearwater streams had high CaCO3 (12.6–57.6 g m−3) and conductivity (3.7–22.3 mS m−1) but low dissolved organic carbon concentrations (0.3–4.7 g m−3).2. Total reactive aluminium (Al) concentrations were high in acid streams (123–363 mg m−3) but never exceeded 84 mg m−3 in alkaline streams. Acid‐soluble and organic monomeric Al were the major Al species in the acid streams (31–168 and 84–178mg m−3, respectively). Concentrations of toxic inorganic monomeric Al were low in all streams (<50mg m−3).3. Sixty‐four invertebrate taxa were collected from the alkaline streams compared to forty‐seven from the acid sites. Numbers of taxa in specific insect orders were similar at all sites, however. Benthic faunas at most sites were dominated by the mayfly Deleatidium sp. and chironomids.4. Overall, mean densities of benthic invertebrates were 2.4–4.8 times higher in alkaline streams than acid streams. No seasonal patterns of abundance were evident at any site.5. Temporal variability of invertebrate densities was correlated with stream channel stability such that fluctuations in densities declined as stability increased.6. Sources of dissolved organic carbon and aluminium in acid, brown water streams are discussed. We suggest that changes in the food supply available in acid streams account for the depauperate faunas found there.
Gut passage and insect grazer selectivity of lotic diatoms
Authors: PETERSON CHRISTOPHER G. 
Published: May 2006

SUMMARY 1. Grazing experiments were conducted in a small Kentucky stream to determine if epilithic diatom taxa differed in susceptibility to grazing by the larval caddisfly, Neophylax autumnus, and whether ingested taxa varied in digestibility. Live/dead ratios of diatom cells from N. autumnus faecal material were compared with live/dead ratios of cells taken from adjacent epilithic habitats to determine diatom digestibility. Selectivity was studied by comparing relative abundances of diatom taxa on substrata with the relative abundances of these taxa in grazer faecal material.2. 73% of the diatoms collected from epilithic habitats contained intact chloroplasts and were characterized as live cells. Only 42% of diatoms eliminated in caddisfly faeces were living. The five dominant diatom taxa did not differ in digestibility. Elimination of viable diatoms in grazer faecal material may contribute to diatom drift in streams, and thus supply individuals for downstream recolonization. Failure to document live/dead ratios of diatoms from grazed substrata can lead to overestimation of the digestibility of taxa and misinterpretation of results.3. Grazers in this investigation were more successful at ingesting large, high‐profile diatom taxa (i.e. Cymbella, Meridion and Gomphonema) and less able to remove small, adnate forms (Achnanthes minutissima). Such 'selectivity’may be one mechanism by which A. minutissima maintains dominance in this system.