bluuebunny/crossref_metadata_2025_split huggingface dataset:
Periphyton responses to a hydraulic gradient in a regulated river in New Zealand
Authors: BIGGS BARRY J.F. , HICKEY CHRISTOPHER W. 
Published: May 2006

SUMMARY1. Periphyton species composition, chlorophyll a concentration, organic matter biomass, and metabolic activity were analysed at a site in a regulated river with low nutrient concentrations to investigate population and community level responses to a spatial gradient in hydraulic conditions. The communities were dominated by diatoms over the full hydraulic range [0.1–0.5m depth, 0.1–1.5ms−1 velocity, and 0.01–1.5 Froude number (Fr)] with Cymbella kappii, Synedra ulna, and Gomphoneis herculeana having the highest relative biovolumes.2. Unexpectedly, Cymbella kappii and Synedra ulna were abundant or co‐dominant at all levels of velocity and Fr. Gomphoneis herculeana was most abundant within the mid‐velocity range (velocity = 0.8–1.2ms−1).3. The physiognomy of the communities changed with a change in hydraulic conditions. There was progressively more diatom mucilage as velocity and Fr increased which resulted in a macroscopic change from relatively thin films (1–2mm) at low velocities and Fr (in pool habitats), to thick (approximately 10mm) mats at higher velocities and Fr (in riffle habitats). Associated with this, ash‐free dry mass (APDM) increased strongly, but chlorophyll a concentration did not, resulting in a decrease in % chlorophyll a over the gradient.4. The results of experiments conducted in an in situ benthic chamber showed no significant differences in gross primary production between two communities of different biomass, but indicated a slightly decreasing trend with increasing velocity (0.14 to 0.38 ms−1). In contrast, community respiration increased greatly with mat biomass and also as a function of increased water velocity. The combined AFDM, chlorophyll a and metabolic results indicated that the zone of photosynthesis was maintained at the surface of the mats, with variable amounts of mucilage being secreted below, depending on hydraulic conditions.5. The diatom community had considerable physiognomic plasticity through the accumulation of mucilage. It is suggested that this high mucilage secretion may be an active feedback mechanism to help ameliorate environmental stress. If so, present theory on velocity control of periphytic algal development in streams, which is essentially based on passive responses, needs expanding. It is concluded that the response of periphyton to spatial differences in habitat hydraulics in streams is highly complex and it may be difficult to define clear hydraulic habitat preference curves for periphyton communities in nutrient‐poor streams.
Effects of benthivorous bream (Abramis brama) and carp (Cyprinus carpio) on sediment resuspension and concentrations of nutrients and chlorophyll a
Authors: BREUKELAAR ANDRÉ W. , LAMMENS EDDY H.R.R. , BRETELER JAN G.P. KLEIN , TÁTRAI ISTVAN 
Published: May 2006

SUMMARY1. The effect of benthivorous bream and carp on sediment resuspension and the concentrations of nutrients and chlorophyll a were studied in sixteen experimental ponds (mean depth 1m, mean area 0.1 ha, sandy clay/clay sediment), stocked with bream or carp at densities varying from 0 to 500 kg ha−1. Planktivorous perch (Perca fluviatilis L.) were added to some ponds to suppress zooplankton.2. Suspended sediment concentrations increased linearly with biomass of benthivorous fish. Bream caused an increase of 46 g sediment m−2 day−1 per 100kg bream ha−1 and a reduction of 0.38m−1 in reciprocal Secchi disc depth, corresponding to an increase in the extinction coefficient of 0.34m−1.3. No relationship was found between size of fish and amount of resuspension, but the effect of bream was twice as great as that of carp. Benthivorous feeding was reduced in May because alternative food (zooplankton) was available.4. Assuming a linear relationship, chlorophyll a level increased by 9.0 μgI−1, total P by 0.03mgl−1 and Kjeldahl‐N by 0.48mgl−1 per 100kg bream ha−1. Silicate, chlorophyll a, total P and total N were all positively correlated with fish biomass, but orthophosphate showed no correlation.
Hydraulic parameters and benthic invertebrate distributions in two gravel‐bed New Zealand rivers
Authors: QUINN JOHN M. , HICKEY CHRISTOPHER W. 
Published: May 2006

SUMMARY1. Benthic invertebrates were sampled over a matrix of about eighty combinations of mean velocity (10–150cms−1) and depth (10–150cm) in two rivers that differed in substrate size variability. Vertical velocity profiles were measured at each sample site and substratum roughness was measured and estimated from percentage cover by stone size classes. The influence of depth on periphyton biomass was also measured.2. The hydraulic and substrate data were used to investigate the correlations between conventional (mean velocity, depth, substrate size) and complex hydraulic variables (Froude number, shear velocity, and water column and boundary Reynolds number) that were either calculated from direct measurements or inferred from mean velocity, depth, kinematic viscosity and substrate roughness. The ecological relevance of these hydraulic variables was investigated by comparing their degree of correlation with invertebrate densities and community metrics.3. The invertebrate variables had similar correlations with mean velocity and the complex near‐bed hydraulic variables in the river with uniform cobble substrates. In the river with diverse substrates, however, average correlations with Froude number, and inferred shear velocity and boundary Reynolds number were 25–45% higher than with velocity. Of all the individual hydraulic parameters, the boundary Reynolds number, calculated from simple measures, was most strongly correlated with benthic invertebrate distributions and taxa richness. However, invertebrate distributions were more strongly correlated with predictions of multiple regression models, incorporating substrate size, depth and mean velocity, than with any single hydraulic variable.4. Hydraulic influences on food availability and oxygen concentration in the benthos are likely mechanisms affecting the hydraulic preferences of several taxa. Lower periphyton biomass with depth, partly attributable to light attenuation, appeared to have a non‐hydraulic influence on a collector‐browser species.
Microhabitat as a determinant of diversity: stream invertebrates colonizing leaf packs
Authors: DOBSON MIKE 
Published: May 2006

SUMMARY1. Macroinvertebrate colonization of artificial leaf packs of differing palatability to detritivores was measured in a low‐order stream.2. The most palatable leaf types—alder and young beech—were colonized mainly by detritivores and consumed rapidly, so that species diversity on the substrate remained low. In the case of the less palatable old beech and paper ‘leaves’, however, colonization was slower but species diversity approached that of the surrounding benthos.3. After 1 week, species diversity in paper ‘leaf packs was equivalent to that of the benthos, but species composition was dissimilar.4. I argue that species diversity of a patch of stream bed may be inversely related to the abundance or palatability of a given food resource, and that this relationship is maintained by the instability of the stream bed habitat, precluding a long‐term community response to increased food availability. It may be, however, that the dispersal abilities of many aquatic insects allow a rapid response to the creation of novel habitats.
Laboratory studies on the population dynamics of Anuraeopsis fissa (Rotifera) in relation to food density
Authors: DUMONT HENRI J. , SARMA S.S.S. , ALI A. JAWAHAR 
Published: May 2006

SUMMARY1. We offered Scenedesmus obliquus in five densities, from 0.5 to 8 ± 106 cells ml−1, to the rotifer Anuraeopsis fissa. Growth rates (r) during the exponential phase (first 7 days) were significantly and positively related to food density. The r values (mean ± SD) varied between 0.454 ± 0.067 and 0,856 ± 0.090, from the lowest to the highest food concentration, respectively. Population growth went through a phase of exponential increase which lasted from 7 to 10 days before a plateau and, in some cases, a decrease occurred.2. There was a linear relation between food density and rotifer plateau density. At the highest food density, a peak abundance (mean ± SD) of 2312 ± 226 individuals ml−1 was reached, while at the lowest food density there was no identifiable single peak but a plateau, at a density of 361 ± 62 ind. ml−1.3. The egg ratio decreased with increasing population density. The ratio of loose eggs to eggs attached to females indicated that more eggs became detached at higher food densities.4. As in many other rotifer species studied so far, population density of A. fissa was less stable at higher algal food concentrations. Numerically, A. fissa could be grown at twice the density achieved in Brachionus.
Comparison of phosphorus deficiency indices during a spring phytoplankton bloom in a eutrophic reservoir
Authors: VRBA JAROSLAV , ÁLEK VOJTĚCH VYHN , HEJZLAR JOSEF , NEDOMA JIŘÍ 
Published: May 2006

SUMMARY1. Phosphorus limitation was studied along the eutrophic, canyon‐type Římov reservoir (Czech Republic) during a spring phytoplankton bloom. Concentration of soluble reactive phosphorus (SRP), C:P molar ratio in seston, extracellular alkaline phosphatase activity (APA), and P limitation (bioassay) were used as indices for phosphorus deficiency in the phytoplankton.2. SRP, C:P, APA, and P limitation indicated a moderate P deficiency in the downstream, but not upper, part of the reservoir.3. Significant correlations between these parameters were found in the downstream part. Chlorophyll a concentration correlated with APA and P limitation in the upper part.4. APA was significantly enhanced in the phosphorus‐deficient phytoplankton. However, APA was apparently not related to total biomass or species composition of the phytoplankton.5. Generally, APA was closely correlated with pH in the reservoir. However, extracellular alkaline phosphatases, with a pH optimum above 9.0, were induced and active only during the phytoplankton bloom, whereas low background activity of extracellular phosphatases was found at low chlorophyll a concentrations (winter, clear‐water phase).
Death, detritus, and energy flow in aquatic ecosystems
Authors: WETZEL ROBERT G. 
Published: May 2006

SUMMARY1. Pelagic trophic structure and energy fluxes are evaluated predominantly on the basis of ingestion of particulate organic matter by living organisms and the effects of consumption on the population dynamics of trophic levels.2. Population fluxes are not representative of the material and energy fluxes of either the composite pelagic region or the lake ecosystem. Metabolism of particulate and especially dissolved organic detritus from many pelagic and non‐pelagic autochthonous and from allochthonous sources dominates both material and energy fluxes. Because of the very large magnitudes and relative chemical recalcitrance of these detrital sources, the large but slow metabolism of detritus provides an inherent ecosystem stability that energetically dampens the ephemeral, volatile fluctuations of higher trophic levels.3. The annual time period is the only meaningful interval in comparative quantitative analyses of material and energy fluxes at population, community, and ecosystem levels.4. Non‐predatory death and metabolism by prokaryotic and protistian heterotrophs dominate. Continued application of animal‐orientated relationships to the integrated, process‐driven couplings of the aquatic ecosystems impedes understanding of quantitative ecosystem pathways and control mechanisms.
Distribution and abundance of blackflies (Diptera: Simuliidae) in relation to impoundments in the Buffalo River, eastern Cape, South Africa
Authors: PALMER ROBERT , O'KEEFFE JAY 
Published: May 2006

SUMMARY1. The abundance of blackfly species along the length (140 km) of the multiply impounded Buffalo River, eastern Cape, South Africa, was studied between 1986 and 1988.2. Twenty‐three species of blackflies were recorded, most of which (95%) were usually found 5–10 km from the source.3. Impoundments favoured five lower‐reach (pest) blackfly species at the expense of two upper‐reach (non‐pest) species. Impoundments have therefore shifted the distribution of blackfly species ‘upstream’, and have increased the distribution of pest blackflies.4. The smallest impoundment, situated in the Upper Foothill Stony Run Zone, had the greatest effect on blackfly distribution.5. There was no typical filter‐feeding guild below impoundments. Possible reasons for this included the discharge of toxic algae from impoundments, the lack of compensatory releases, the sudden drying of impoundment tailwaters and the paucity of natural lakes in southern Africa which precludes a pre‐adapted ‘outlet’ fauna.
Use of fluorescently labelled algae to measure the clearance rate of the rotifer Keratella cochlearis
Authors: TELESH IRENA V. , OOMS‐WILMS ANJA L. , GULATI RAMESH D. 
Published: May 2006

SUMMARY1. Fluorescently labelled algae (FLA) were used to measure clearance rates of the rotifer Keratella cochlearis. The freshwater algae Chlorella vulgaris and Stichococcus bacillaris were labelled with a fluorescent dye, 5‐(4,6‐dichlorotriazin‐2‐yl) aminofluorescein (DTAF), following a modified staining procedure.2. Keratella cochlearis ingested both algal species. Clearance rates on tracer foods varied between 2.4 and 6.9 μl ind−1 h−1, which are comparable with those determined using other techniques.3. The main drawback of the FLA technique was that only a little more than one‐third of the total amount of algal cells of both C, vulgaris and S. bacillaris were well stained with the dye (DTAF), despite the use of a higher concentration of dye and a longer staining period than recommended in the literature.4. The FLA method can be successfully applied in grazing studies involving size selection and competition for food among zooplankton. The method complements existing techniques for measuring the clearance and ingestion rates of filter‐feeders.
The parabolic pattern of animal growth: determination of equation parameters and their temperature dependencies
Authors: OSTROVSKY ILIA 
Published: May 2006

SUMMARY1. Parabolic (power) growth is characteristic of many aquatic poikilothermic animals for certain stages of their development. The parabolic pattern describing growth in weight (or length) under constant ambient conditions can be expressed in the following general form:
image
where Y is growth rate (or specific growth rate), X is animal size, and Ω and τ are coefficients. The constancy of ambient conditions is of cardinal importance in determining τ. The problem of maintaining a constant level of nutrition can be reliably solved only by the presence of food in excess of demand. Data satisfying these requirements have demonstrated that τ does not depend on factors such as temperature, and can be assumed to be independent of ambient conditions. In the growth rate‐weight equation, τ ranges between 0.5 and 0.85 for animals representing a variety of taxonomic groups.2. The coefficient Ω. is affected by ambient conditions (e. g. temperature, amount of food). Its value reflects the ‘level’ of the growth rate‐size relationship under given conditions. For a specific time period, Ω can be computed from the following formula:
image

where X1 and X2 are the animal sizes (weights, lengths) at time t1 and t2, the beginning and end of the time period. The calculated value of Ω corresponds to the average intensity of the ambient factor (F) affecting the growth during the period between the two observations. If the values of the Ω are calculated for wide range of the factor, the relationship between the Ω. and F, Ω=f(F), can be determined. The function can be then incorporated into the parabolic equation of growth, as

image
3. Dependence of the development rate (1/D, where D is time interval needed to complete a given stage) on temperature (T), and dependence of Ω on T, are both described by sigmoid‐shape curves. The broad intermediate part of these curves, a range to which animals are adapted in nature, can be approximated by straight line functions. For two groups, pan‐size sockeye salmon (Oncorhynchus nerka) and different species of chironomid larvae, it was shown that an equation combining parabolic growth and linear temperature patterns describes accurately the variability observed in growth rates under experimental and natural conditions.
Substance budgets of an upland catchment: the significance of atmospheric phosphorus inputs
Authors: GIBSON C.E. , WU Y. , PINKERTON D. 
Published: May 2006

SUMMARY1. Precipitation inputs and outflow stream outputs are presented for 1993 in an upland lake and catchment system on the Antrim Plateau, Northern Ireland.2. Phosphorus, potassium, chloride and possibly sulphate behaved conservatively inputs were approximately balanced by outputs. Combined nitrogen outputs were very much less than inputs, whereas there was a net export of calcium, magnesium, sodium and silica from the catchment.3. Precipitation phosphorus inputs (22 kg P km−2yr−1) are compared with literature data and are shown to be near the median value.4. The phosphorus budget is discussed in relation to the fact that there are few oligotrophic lakes in Northern Ireland. It is suggested this is due to the rainfall inputs, low phosphorus retention by the catchment and rapid flushing rates in the lakes.
The non‐lethal effects of predators and the influence of food availability on life history of adultChironomus tentans(Diptera: Chironomidae)
Authors: BALL S. L. , BAKER R. L. 
Published: May 2006

SUMMARY1. We used a laboratory experiment to determine effects of a predator (other than straightforward prey consumption) and food availability, during the larval stage, on adult size, age at emergence and fecundity ofChironomus tentans.2. Predator presence and decreased food availability resulted in reduced adult emergence.3. Predator presence and food availability resulted in smaller size and greater age at emergence of male and female chironomids. There were no significant interactions between effects of predator presence and food availability.4. Predator presence had no significant effect on fecundity.5. Smaller size and greater age at emergence can have important implications for adult survival, size and age at first reproduction and, thus, intrinsic rate of population growth.
Food value of introduced eucalypt leaves for a Mediterranean stream detritivore: Tipula lateralis
Authors: CANHOTO C. , GRAÇA M.A.S. 
Published: May 2006

SUMMARY1. Food preference, consumption and growth of Tipula lateralis feeding on leaves of one exotic (Eucalyptus globulus) and three native trees of central Portugal (Alnus glutinosa, Castanea saliva and Quercus faginea) were investigated.2. Larvae preferred and consumed more alder than the other three species. Larvae fed oak and eucalyptus did not grow, while those fed alder had a faster mean specific growth than those fed chestnut. Alder also provided a higher and earlier peak growth rate, which occurred at 35 days vs. 91 days for chestnut.3. High values of survivorship to 126 days were observed in larvae fed alder and chestnut. All larvae fed oak died within 63 days; those fed eucalyptus died within 91 days.4. Leaf utilization by Tipula lateralis seems to be negatively correlated with cuticle thickness and polyphenolic content and positively correlated with microbial colonization and nutrient content of the leaves. We hypothesize that the replacement of the original deciduous forest by eucalyptus plantations may induce deleterious changes in the associated invertebrate communities and stream ecosystem processes.
Image analysis of aerial photography to quantify changes in channel morphology and instream habitat following placer mining in interior Alaska
Authors: GILVEAR DAVID J. , WATERS TERTIA M. , MILNER ALEXANDER M. 
Published: May 2006

SUMMARY1. ‘Placer’ mining for alluvial deposits of gold in a number of stream systems in interior Alaska represents a major disturbance to the stream bed and affects habitat for biotic communities.2. The potential of analysing aerial photographs to map changes in channel habitat and morphology within gravel‐bed rivers is outlined with reference to the impact and recovery of Faith Creek, a second‐order stream with a history of placer mining.3. A strong correlation between the reflectance of the channel bed and water depth is necessary to use the technique succesfully, together with a knowledge of the effects of ‘broken’water on the spectral characteristics of rivers.4. Image analysis demonstrated that a wide range of water depths and instream mesoscale habitats existed prior to mining. During mining, the stream was confined to a channellized reach with negligible deep water or habitat diversity.5. Since mining ceased the stream has abandoned its channellized course and formed a new channel with few deep pools. It is suggested that geomorphological recovery and associated habitat recovery takes a number of large flood events and is likely to require more than 10 years.
Bacterial metabolism in the River Danube: parameters influencing bacterial production
Authors: BERGER BARBARA , HOCH BIRGIT , KAVKA GERHARD , HERNDL GERHARD J. 
Published: May 2006

SUMMARY1. Microbial parameters were determined at five sampling sites in the River Danube up‐and downstream of Vienna, Austria, twice monthly over an annual cycle. Bacterial production (BP) was estimated from thymidine and leucine incorporations; additionally, the effect of turbulence on BP and the conversion factors for converting incorporation rates into bacterial cell production were determined using the cumulative approach.2. BP under turbulent conditions was not significantly different from that under stagnant conditions. For thymidine, a mean annual conversion factor of 3.2 ± 1018 cells mol−1 thymidine incorporated was calculated. For leucine, the corresponding factor was 0.07 ± 1018 cells mol−1 leucine. Average annual BP calculated by thymidine incorporation was significantly higher than BP calculated from leucine incorporation and ranged from 47.2 to 77.5 μg C 1‐−1 day−1 depending on the tracer and the conversion factor used.3. Bacterial growth rates ranged from 0.1 day−1 during winter to 1.7 day−1 in the summer. A strong correlation was found between temperature as well as chlorophyll a and bacterial growth when temperature was greater than 5 °C; a major spring phytoplankton bloom at a temperature below 5 °C did not increase BP.4. Dissolved organic carbon (DOC) concentrations varied between 2 and 7.2 mg C 1‐−1 and comprised between 50 and 92% of the total organic carbon pool in the River Danube, Based on the DOC concentration and an assumed bacterial growth yield of 20% we calculated mean DOC turnover times of around 60 days in the winter and less than 8 days during the summer.