bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potentiometric measurements of carbon dioxide flux of submerged aquatic macrophytes in pH‐statted natural waters
Authors: DENNY PATRICK , ORR PHILIP T. , CSIRO DAVID J. C. ERSKINE 
Published: May 2006

SUMMARY. 1, An apparatus has been described that is suitable for potentiometric measurement of carbon dioxide flux in photosynthesizing shoots of submerged aquatic macrophytes2. The procedure, based on methods described by Tailing (1973) for measurement of phytoplankton photosynthesis, relies upon the continuous pH‐statting of the solution surrounding the tissues. The pH of the solution is monitored by electrodes from a pH meter which is linked to an auto‐titrator. The rise in pH during photosynthesis is then compensated tor by controlled, small titrant additions of CO2‐ennched solution (titrant water). This replaces the CO2 removed by the tissues without affecting the total alkalinity of the solution. If the concentration of CO2 in the titrant water, and the volume of titrant added arc known precisely, the CO2 flux can be calculated.3. Total alkalinity, total CO2 and free‐CO2 acidity of the bathing solutions and titrant waters are estimated by Gran titrations and the pH: tilre‐volume data pairs are analysed by computer to provide rapid data feed‐back. A modification to Tailing's equation for calculation of F1functions has been necessary for accurate calibration of the CO2enriched tilrant water.4. The photosynthesis cuvette, which is surrounded by a water‐jacket, is approximately I dm3 in capacity and has six compartments for the shoots. An impeller at the base of the cuvette rapidly mixes and cycles the bathing solution and flushes it over the tissues.5. Information on temperature, light flux density, oxygen concentration. pH and titre‐volume is continuously recorded into a data‐logger and is fed into a computer which is programmed for data analyses.6. Results from a typical experiment show the system to be sound and the method has considerable potential, especially in the study of aquatic plant photosynthesis in natural waters.
Reproduction and growth of Craterocephalus marjoriae and C. stercusmuscarum (Pisces: Atherinidae) in south‐eastern Queensland, Australia
Authors: MILTON D. A. , ARTHINGTON A. H. 
Published: May 2006

SUMMARY. 1. The reproductive cycle and growth of Craterocephalus marjoriae and Craterocephalus stercusmuscarum (Atherinidae) were studied in Brisbane, south‐eastern Queensland, over a 17‐month period (1981–82).2. Both species had a 5‐month breeding season in spring and summer, with a breeding peak in spring (September‐October). Multiple spawning occurred but life time fecundity was not determined.3. Gonosomatic index values and mean fecundity per female were higher in Craterocephalus marjoriae than in C. stercusmuscarum. Fecundity increased with body length in both species according to the relationship, F=aLb. Growth rates were similar and growth was adequately described by the von Bertalanffy equation. Both species grew rapidly during the first year and reached maturity the following season. Reproductive strategies are considered in relation to seasonal flooding in the streams inhabited.
Anomalies in hydropsychid capture nets from polluted streams
Authors: PETERSEN LENA B.‐M. , PETERSEN ROBERT C. 
Published: May 2006

Members of the genus Hydropsyche, net‐spinning caddisfly larvae, exhibit anomalies in the structure of their capture nets when collected from stream localities receiving heavy metal and toxic chemical wastes.
The number of nets showing anomalies was positively correlated with the number of anomalies per net suggesting a graded response to the toxic wastes.
Frequency of anomalies in a hydropsychid population increased the closer the nets were collected to a pollution source. Anomaly frequency was negatively correlated to total macroinvertebrate community structure as measured by the Shannon function. It is suggested that net anomaly frequeney by hydropsychids may be a useful tool in ecological monitoring.
The cocoon and hatchling of Nais variabilis (Naididae: Oligochaeta)
Authors: LOCHHEAD G. , LEARNER M. A. 
Published: May 2006

SUMMARY. 1. The cocoon of Nais variabilis is ovoid with an average length of 527.6±8.4 μm (95% CL) and an average breadth of 378.1±9.9 μm. The cocoon wall is about 7 μm thick and the average volume of the cocoon cavity is 0.035±0.002 mm3. Most cocoons contain one ovum; only single‐ovum cocoons developed.2. Cocoons hatch in about 80 days at room temperature (average 20°C. range 17–23°C). Hatchlings emerged posterior end first and were, on hatching, about one‐third the adult live length of 8.5±10.3 mm.3. It is estimated that adult Nais variabilis are unlikely to produce more than an average of ten cocoons each. Adults ceased asexual budding on becoming nature and died shortly after the completion of cocoon production. There was a brief co‐existence of generations.
A preliminary classification of running‐water sites in Great Britain based on macro‐invertebrate species and the prediction of community type using environmental data
Authors: WRIGHT J. F , MOSS D. , ARMITAGE P. D. , FURSE M. T. 
Published: May 2006

SUMMARY. 1. Macro‐invertebrate species lists were obtained for 268 sites on forty‐one river systems throughout Great Britain by qualitative sampling in spring, summer and autumn. Information on twenty‐eight environmental variables was also collated for each site. The sites were ordinated on the basis of their species content using detrended correspondence analysis (DCA) and classified by two‐way indicator species analysis (TWINSPAN). Correlation coefficients between ordination scores and single environmental variables indicated that Axis 1 distinguished between types of rivers and Axis 2 reflected variation along the length of rivers. A preliminary classification of sites into sixteen groups has been proposed, together with a key which allows new sites to be classified. Information on the species and environmental features which characterize each group is also presented.2. Multiple discriminant analysis (MDA) was employed to predict the group membership of the 268 sites using the twenty‐eight environmental variables. 76.1% of sites were classified correctly. An independent assessment of predictive ability using forty test sites yielded a 50% success rate. Predictive ability was higher for the classification presented in this paper than in fifteen additional classifications produced using data from single seasons and/or different taxonomic treatments.3. TWINSPAN and MDA were found to be useful approaches to the classification of running‐water sites by their macro‐invertebrate fauna and the prediction of community type (as indicated by the occurrence of species in the sites comprising the group) using environmental variables. Extension of the scope of the classification, coupled with the use of additional environmental variables to increase predictive ability, is now in progress.
Effects of copper on species composition of periphyton in a Sierra Nevada, California, stream
Authors: LELAND HARRY V. , CARTER JAMES L. 
Published: May 2006

SUMMARY. 1. Changes in species composition of the periphyton of an oligotrophic. Sierra Nevada stream continuously dosed for 1 year at three concentrations of copper (2.5, 5 and 10 μg 1−1 CuT; approximately 12, 25 and 50 ng 1−1 Cu2+) were determined.2. The numerically most abundant taxa were Bacillariophyceae (Achnanthes minutissima, Cocconeis placentula, Cymbella microcephala, C. sinuata, Fragilaria conslruens, F. crotonensis. Navicula spp., Synedra acus and S. rumpens), and the Cyanophyta Lyngbya spp., a co‐dominant during spring and summer.3. Population densities of Lyngbya spp. were markedly reduced at all test concentrations of copper. Population densities of the principal Chlorophyta (Spirogyra spp. and Cladophora spp.) and the diatom Amphipleura pellucida were reduced at 5 μg 1−1 CUT. Of the twenty‐two most abundant taxa, sixteen were reduced in abundance by continuous exposure to 10 μg 1−1 CuT.4. There was no commensurate reduction in standing crop (total number of individuals of all taxa). Achnanthes minutissima, a co‐dominant in the control, was the primary replacement species. Other taxa that were more abundant at 5 μg1−1 CuT than in the control were Ceratoneis arcus, Cocconeis placentula, Navicula spp. and Synedra rumpens. Only A. minutissima and Calothrix spp. were more abundant at 10 μg 1−1 than in the control.5. Three resemblance measures (Canberra metric, Bray‐Curtis and Dice) and diversity (Brillouin's) were evaluated for detecting differences in species composition among experimental stream sections. The Canberra metric, an index sensitive to proportional rather than absolute differences, was the most informative of these indices.
The macroinvertebrates and fish of a Colorado stream during a period of fluctuating discharge
Authors: CANTON STEVEN P. , CLINE LEO D. , SHORT ROBERTA. , WARD JAMES V. 
Published: May 2006

SUMMARY. 1. During a 2‐year study of the fish and macroinvertebrates of a third‐order montane stream, a severe drought in the first year resulted in a temporary cessation of surface flow. Flow was continuous during the second year.2. Some taxa (e.g. Ophiogomphus severus) exhibited higher density during the drought year, others declined in abundance during low flow (e.g. Baetis spp.), whereas a few (e.g. Tricorythodes minutus) appeared unaffected. Total macroinvertebrate density decreased by 50% during the low flow year compared to the normal flow year. Mayflies were most severely affected, but also exhibited the most dramatic recovery.3. The collector‐gatherer functional feeding group was abundant only during the normal flow year, whereas shredders and predators exhibited increased relative abundance during low flow.4. Fish populations were severely reduced in the low flow year. However, fishes rapidly invaded the area following resumption of normal flow.
Adaptive head coloration in case‐making caddis larvae
Authors: OTTO C. 
Published: May 2006

SUMMARY. 1. In daylight conditions brown trout preferably attacked head capsules with a contrasting colour pattern compared to those which were more uniformly coloured. This preference was reversed under reduced illumination. It is argued that striped head capsules are cryptic to predators at low light intensities.2. In caddis larvae contrasting head patterns are found mainly in lentic species, whilst the heads of lotic larvae are usually more uniformly coloured. Lentic species dwell in conditions of more diffuse illumination than lotic one, and each category thus achieves high crypsis with respect to head capsule coloration.3. Lentic molannid and phryganeid larvae often dwell at considerable depths, and these species also have the most sharply defined head patterns. These species are predatory and, besides being cryptic to larger predators, may also be cryptic to their prey.4. Intraspecific variation in head capsule coloration in relation to habitat type is also discussed.
Cellulolytic decomposition in streams of contrasting pH and its relationship with invertebrate community structure
Authors: HILDREW ALAN G. , TOWNSEND COLIN R. , FRANCIS JEANETTE , FINCH KAREN 
Published: May 2006

SUMMARY. 1. Ceilulolytic decomposition, measured by loss of tensile strength in strips of cellulose test cloth, was estimated in thirty‐four stream sites in experiments in summer, autumn and winter.2. The results of multiple regression analyses showed that strength loss was most closely related to temperature in summer, when the model accounted for only 38% of the variation, and to stream pH in autumn and winter, when the models accounted for 52% and 75% of the variation, respectively.3. The relationship between decomposition rate and the structure of invertebrate communities in streams of dissimilar pH is discussed. We argue that a very rapid rate of decomposition of coarse particulate organic matter may profit consumers of fine particulate organic matter at the expense of coarse particle shredders.
Cadmium in freshwaters: concentrations and chemistry
Authors: LAXEN DUNCAN P. H. 
Published: May 2006

SUMMARY. 1. Concentrations of cadmium are reported for twenty largely unpolluted freshwaters in north‐western England. They range from 15 to 117 ng l−1 total Cd in the rivers and streams and from 18to51 ng l−1 in the lakes, lying on the low side of values reported in the literature. The care required to obtain reliable data is stressed.2. A comparison is made between the fraction of Cd found to be particulate (>0.2 μm) and that which is calculated to be adsorbed on particulate matter. This provides further insight into the speciation of Cd, as well as a test of the application of a simple adsorption model to the prediction of the observed speciation.3.The adsorption model is found to be a poor predictor of the measured fraction of particulate Cd. Possible reasons for this are explored and the potentially important role of slow desorption kinetics is emphasized.
Sinking rates of planktonic diatoms in an unstratified lake: a comparison of field and laboratory observations
Authors: GIBSON C. E. 
Published: May 2006

SUMMARY. 1. Natural population sinking rates were calculated by fitting an exponential regression to 6 years’observations on declining crops of Melosira italica subarctica O. Müll. and Stephanodiscus astraea (Ehr.) Grun.2. Losses were described by an exponential model which yielded still water sinking rates of 0.86 md−1 for M. italica and 0.45md−1 for S. astraea.3. Laboratory measurements of the sinking rate of natural populations showed that the rate increased abruptly from less than 0.2 m d−1 in growing populations to 0.4 m d−1 after silica depletion.4. The measured sinking rate of S. astraea agreed well with that observed in the field. Where as populations of M. italica appeared to sink more quickly in the lake than could be accounted for by laboratory observations.
The stable carbon isotope ratios of fish and their invertebrate prey in four New Zealand rivers
Authors: ROUNICK J. S. , HICKS B. J. 
Published: May 2006

SUMMARY.

Sources of carbon utilized by invertebrates and fish in four New Zealand streams were investigated using stable carbon isotope analysis. Complementary analyses were made to determine σ13C alteration (fractionation) by fish reared on a known food and to examine the distribution of 13C/12C ratios in different tissues.
σ13C values of hatchery‐reared rainbow trout (white muscle tissue) were 13C‐enriched compared with their food (trout pellets) by an average of 1.7%0. σ13C values of different organs and tissues never differed by more than 1.8%o in any fish species; white muscle always had an intermediate value.
σ13C values of invertebrates ranged from‐28.4 to –20.4%o– At the more open sites invertebrates were 13C‐depleted, reflecting some use of algal carbon. However, invertebrates from the most heavily shaded stream site were unusually enriched in 13C. An undetected carbon source of terrestrial origin, perhaps 13C‐enriched dissolved organic carbon in groundwater, may have been contributing indirectly to invertebrate biomass carbon.
σ13C values for fish were not closely linked to aquatic invertebrate ratios; instead, at all sites their carbon was isotopically similar to terrestrial organic carbon. The reasons for this apparent anomaly are unclear.
The denitrification capacity of sediment from a hypereutrophic lake
Authors: KASPAR HEINRICH F. 
Published: May 2006

SUMMARY.

In sediment from Wintergreen Lake, Michigan, denitrification was not detectable by the acetylene inhibition method at in situ nitrate concentrations. When nitrate was added to sediment slurries, denitrification capacities up to 18.8μg N g‐1 h‐1 were measured. The denitrification capacities decreased with increasing sediment depth and distance from shore.
The high denitrification capacities in these sediments which under natural conditions had no supply of nitrate and oxygen suggested that denitrifies with alternative mechanisms for anaerobic energy conversion were present. Nitrous oxide was a significant portion of the N‐gas produced immediately after the nitrate addition. Small amounts (4–5% of the total N‐gas production) of nitric oxide accumulated in the early phase of nitrate reduction. Presumably after depletion of nitrate and nitrite both N2O and NO were further reduced to N2.
About 70%r of the added nitrate was denitrified, and the remainder was assumed to have been reduced to ammonium.
Life history and ecological role of the xylophagous aquatic beetle,Lara avaraLeConte (Dryopoidea: Elmidae)
Authors: STEEDMAN R. J. , ANDERSON N. H. 
Published: May 2006

SUMMARY.This study documents the life history of the xylophagous elmid beetle,Lara avara, and estimates its contribution to wood degradation in Oregon streams. The life cycle was found to be 4 to 6 or more years long, with all but 2–3 months of that spent in the larval stage.Larvae grow through seven instars, taking about 1 year for instars 1–3, and from 3 to 5 or more years for instars 4–7.Last‐instar larvae leave the water to pupate. Adults live approximately 3 weeks and occur from May to August. The eggs are deposited on submerged wood.Larvae probably obtain their nutrition by absorbing substances liberated into decaying wood by microbial activity. They do not produce their own cellulase, nor do they have a symbiotic gut flora similar to that of xylophagous cranefly (Tipulidae) larvae.Faecal production byL. avaralarvae averaged 13% dry body wt d‐1. This yields an estimate of faecal production of 1.6 g m‐2y‐1in Oregon Coast Range streams (about 0.3% y‐1of wood standing crop).
A choice chamber experiment on the selection of algae as food and substrata by Nais elinguis (Oligochaeta: Naididae)
Authors: BOWKER D. W. , WAREHAM M. T. , LEARNER M. A. 
Published: May 2006

SUMMARY.

A choice chamber experiment was performed in the laboratory to quantify the selection of benthic algae as food and substrata by Nais elinguis.
Most worms actively chose filamentous algae and/or diatoms as substrata whereas unicellular or colonial chiorophycean algae were discriminated against. Diatoms were selected in preference to latex beads but the worms could not discriminate between living filaments and nylon monofilaments. A thigmotactic response to filaments and a chemotactic response to diatoms may be implicated.
The worms ingested unicellular algae at a greater rate than colonial and filamentous algae. The rates at which the algae were ingested were negatively correlated with the lengths of the algae. A filament 200 μm long was the largest item ingested, representing about 63% of the length of the pharynx of the worm.
Ivlev's electlvity indices were positive when the rates at which the algae were ingested exceeded about 20 individuals h‐1. The index was negatively correlated with the lengths of the algae, but the time periods spent by the worms in association with the algae were unrelated to the electivity index.
The data confirmed previous observations on the selection of algae as food and substrata by Nais elinguis in a natural habitat.
The effect of invertebrate and vertebrate predators on the foraging movements of Ischnura elegans larvae (Odonata: Zygoptera)
Authors: HEADS P. A. 
Published: May 2006

SUMMARY.

The foraging movements of late instar Ischnura elegans larvae were monitored in laboratory experiments to study the effects of predators on larval feeding behaviour.
Ischnura larvae are sit‐atid‐wait, or ambush, foragers, moving occasionally between perches in search of profitable feeding sites. Larval foraging movements, monitored at different densities of Daphnia prey, increased significantly when prey were absent.
In experiments without prey, larval movement was inhibited by the presence of fish predators, as well as by invertebrate predators (Notonecta glauca), but not by closely related, non‐predatory invertebrates (Corixa punctata) or physical disturbance of the water (intermittent air bubbles).
Further experiments varied Ischnura hunger levels (0–8 days without food) and illumination (light or dark) with and without notonectid predators. Hunger had no consistent effect on penultimate instar behaviour but final instar foraging activity was significantly modified: movements increased after 4 days starvation and decreased again after 8 days. This response was suppressed by the presence of predators. Both larval instars moved significantly less often in the light, even when predators were absent.
These phenotypically flexible predator‐avoidance responses are likely to decrease the risk of predation by both visual and tactile predators. However, predators clearly have an important influence on the feeding niche of Ischnura larvae, and may decrease the overall feeding efficiency, growth rate, and survival of larvae by constraining their movement in search of profitable feeding sites.
Determination of biologically available phosphorus using a radiobioassay technique
Authors: JORDAN C. , DINSMORE P. 
Published: May 2006

SUMMARY.

A kinetic approach in which the uptake rate of simultaneous additions of orthophosphate and carrier‐free phosphorus‐ 32 by a standard culture of the green alga Selenastrum capricornutum under near neutral conditions was used to obtain an estimate of the readily available components of the total phosphorus pool in natural freshwater samples.
A comparison was made between the values of the biologically available phosphorus obtained using this radiobioassay technique and those obtained by the soluble reactive phosphorus procedure for thirty‐one freshwater samples. Only about three‐quarters of the phosphorus measured as soluble reactive phosphorus was readily available to algae. The results agreed with those obtained in an earlier study in which an enzymatic procedure was used to determine orthophosphate.
The results of tests carried out on the water samples used in this study were consistent with the conclusion that the presence of a hydrous ferric oxide‐orthophosphale complex in the samples caused the soluble reactive phosphorus value to be greater than the corresponding biologically available phosphorus value.