bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genetic control of predator avoidance behaviour in Daphnia
Authors: WATT PENELOPE J. , YOUNG STEPHEN 
Published: May 2006

SUMMARY1. The vertical migration behaviour in electrophoretically distinguishable clones of Daphnia magna Straus was investigated.2. Clones differed significantly in their tendency to stay near the surface of the tank during the light phase of the daily light/dark cycle, indicating that vertical migration has a genetic component.3. There was a significant difference in behaviour between juvenile and adult Daphnia: overall the juveniles stayed closer to the water surface than the adults, but the characteristic pattern of clonal differences persisted in the juveniles.4. When an adult population of each clone was exposed to a fish predator in an experimental tank, the position a clone maintained in the tank at the start of the day had a direct effect on its survival. Clones remaining near to the surface of the water suffered greatest predarion.
The morphometry and hydrology of Oak Mere, a lowland kataglacial lake in the north‐west Midlands, England
Authors: SAVAGE A.A. , BRADBURNE S.J.A. , MACPHERSON A.A. 
Published: May 2006

SUMMARY1. This paper presents geological, climatic, morphometric and hydrological data, collected from 1941 to 1991, on a lowland kataglacial lake and its catchment, as a basis for the development of a descriptive hydrological model.2. The catchment occupies an area of 2.56 km2, at altitudes of 73–130 m above sea level, and receives an average annual net precipitation of 558 000 m3. The surface geology consists principally of sandy glacial drift and peat overlying Triassic strata which are exposed at the western extremity of the catchment.3. The mere (lake) has an asymmetrical basin lying in sandy glacial drift and peat. The area (18.4–22.9 ha), depth (7–8 m) and volume (320000–453000m3) fluctuate in relation to net precipitation in at least two ways: an immediate response and a response with a rime lag of approximately 2 years.4. The pH, normally <5.5 but varying from 4.0 to 7,8, and ionic composition of the mere fluctuate. The evidence suggests that the fluctuation is a response to at least two essentially separate types of water supply: a base‐poor surface supply and a base‐richer supply entering at a depth of 4m.5. Essentially, the descriptive model postulates that the mere waters are controlled by a water‐table of varying level, in relation to net precipitation, which is base poor at the surface but becomes increasingly base rich with depth.
Distribution and feeding of the predatory nematode Anatonchus dolichurus (Mononchoidea) in the Dokka delta (Norway) and its impact on the benthic meiofauna
Authors: PREJS KRYSTYNA 
Published: May 2006

SUMMARY

A dense population of a large (over 6.5mm long), semiaquatic, predatory nematode Anatonchus dolichurus was found in the delta of the River Dokka, Norway. This is the first time it has been reported in surface fresh waters.
Nematode distribution was related to water depth, with maximum abundance (over 24000 ind.m−2) occurring in shallow areas (0.5–2.0m). Sediments at all stations with a high density of A. dolichurus were dry and exposed to air and ice during winter and early spring, and overgrown with macrophytes during summer.
This predator contributed a greater fraction of total numbers and biomass of the nematode fauna than predatory forms in other known freshwater nematode assemblages. It constituted up to 15.6% of numbers and up to 90% of total nematode biomass.
Anatonchus dolichurus preyed on Nematoda, small Oligochaeta (mainly Enchyrraeidae) and Chironomidae. It was able to reduce the density of these meiofaunal taxa when present in large numbers in experimental cores.
An investigation of allelopathic effects of Daphnia
Authors: MATVEEV VLADIMIR 
Published: May 2006

SUMMARY

The hypothesis is tested that large daphnids are able to suppress their own and other species' feeding and reproduction by means of excreting an inhibitory chemical (or chemicals).
In laboratory experiments with an Australian species, Daphnia carinata, water preconditioned with 3–67 daphnids 1‐−1 for 30 h had the effect of reducing feeding rates of D. carinata and D. lumholtzi provided with Selenastrum capricornutum.
For the two Daphnia species, there were highly significant negative correlations between feeding rate and the preconditioning density of D. carinata.
Water preconditioned with 20–30 daphnids 1‐−1 for 1–2 weeks reduced the grazing rates of Daphnia, Moina, and Diaphanosoma 2–3‐fold.
Moina kept in such water for 2 days stopped feeding. Conditioned water kept for 3 days without animals still inhibited grazing by Moina. Hearing to 100°C removed the inhibitory effect.
Given excess food, and in non‐renewed water, a gradient of D. carinata densities developed a strong negative correlation between clutch size and daphnid density after a 6‐day time lag. This result may help explain the direct density‐dependent regulation of cladoceran reproduction observed earlier in a subtropical lake.
Patterns of hydrological exchange and nutrient transformation in the hyporheic zone of a gravel‐bottom stream: examining terrestrial—aquatic linkages
Authors: TRISKA FRANK J. , DUFF JOHN H. , AVANZINO RONALD J. 
Published: May 2006

SUMMARY

The terrestrial‐aquatic interface beneath a riparian corridor was investigated as a region of hydrological and biological control of nutrient flux. Subsurface flow paths were defined from the channel toward the riparian zone and also from the riparian zone toward the channel using tracer‐injection studies. Solute transport had a rapid channel component (m min−1) and a slow hyporheic flow component (mh−1, m day−1). Subsurface flow beneath the riparian zone approximated a straight path entering at meanders but could also cross beneath the stream, possibly using relic channels.
Dissolved oxygen (DO) concentration in the hyporheic zone ranged from <1.0 to 9.5mgl−1 due to permeability variations in bankside sediments. DO concentration was related to the proportion of stream water in the lateral hyporheic zone, indicating that the channel water was the DO source.
The magnitude and riming of lateral water exchange was linked to previously published studies of nitrification and denitrificarion. Both nitrification potential and channel exchange decreased with distance from the channel and were absent at sites lacking effective exchange, due to low DO. Field amendment of ammonium to an aerobic flow path indicated nitrification potential under natural hydrological conditions. Denitrification potential was inversely related to channel exchange and was insignificant in channel sediments. Field amendment of acetylene plus nitrate to a flow path with low DO and minimal channel exchange indicated denitrificarion of amended nitrate.
Comparison of hydraulic head to distribution of the biologically important solutes DO, ammonium, and nitrate was useful for interpreting previous findings and conceptualizing the riparian zone as a functioning ecotone between terrestrial and aquatic systems.
The influence of larval case design on vulnerability of Limnephilus frijole (Trichoptera) to predation
Authors: NISLOW KEITH H. , MOLLES MANUEL C. 
Published: May 2006

SUMMARY

We examined the potential selective pressures exerted by different types of predators on morphological prey defences using the case‐building larvae of the limnephilid caddisfly, Limnephilus frijole. The predators were a predaceous minnow, Gila pandora, and an aeschnid dragonfly naiad, Oplonaeschna armata.
The influence of larval case design on vulnerability to predators was evaluated in a series of laboratory experiments. Larval L. frijole were collected from a stream without fish or dragonflies. In the laboratory, larvae still occupying their field‐built cases were exposed to the two predators, with which L. frijole co‐occurs in other streams. Following 24 h exposure of caddisfly larvae to a specific predator, the pre‐trial case length, case strength, case width, and case composition of victims and survivors were compared.
Principal components analysis (PCA) indicated substantial independent variation for all four case parameters in the study population. The cases of larvae surviving exposure to either dragonfly naiads or fish were significantly stronger and wider than cases of victims of predation. Cases of survivors were also longer and had a greater mineral fraction than those of victims, but differences were either marginally significant or not significant.
These results demonstrate that specific aspects of case design affect the vulnerability of caddisfly larvae. In addition, predaceous fish and predaceous invertebrates, using different predation techniques, may exert similar selective pressures on these defenses. Case aspects influencing vulnerability in these experiments are broadly consistent with natural variation in case design associated with predator‐rich and predator‐free habitats for related caddisfly species.
The impact of small chironomid grazers on epiphytic algal abundance and dispersion
Authors: BOTTS P. SILVER 
Published: May 2006

SUMMARY

A combination of field and laboratory experiments was used to assess the impact of chironomid grazers on taxonomic composition, abundance and dispersion of epiphytic algal assemblages.
In the laboratory, Psectrodadius sp. reduced the biovolume of algal species preferred as food and increased the degree of clumping of non‐preferred species. Thienemanniella cf. fusca had both positive and negative effects (depending on the algal species) on the biovolumes of algal species preferred as food and increased the degree of clumping of non‐preferred species.
In field exclosures, no effect of removal of chironomid larvae from the grazer assemblage could be detected in autumn or winter experiments. A third, longer removal experiment, conducted in summer, resulted in increased biovolumes of edible Cosmarium spp. and Aphanocapsa spp., preferred foods of chironomid larvae. Biovolumes of Lyngbya sp., Eulbochaete spp. and Oedogortium spp., filamentous taxa used extensively in larval case construction, also increased. Chironomid larvae had no effect on total algal biovolume or biovolume of large unicellular algae.
Chironomid larvae can influence epiphytic algal assemblages through selective grazing by reducing the biovolumes of preferred foods and through case‐building activity by reducing the biovolumes of construction materials.
Juvenile survival of a planktonic insect: effects of food limitation and predation
Authors: FISCHER JANET M. , MOORE MARIANNE V. 
Published: May 2006

SUMMARY

An experiment was conducted to investigate potential impacts of food limitation and copepod predation on juvenile survival of Chaoborus purtctipennis. We tested the hypotheses that: (i) juvenile survival of Chaoborus is influenced more by copepod predation than by starvation in a productive environment, and (ii) food limitation and predation interact to affect survival.
Effects of food concentration (approximately 800, 1400 and 2300 microzooplankton 1‐−1) and predator density (0, 1 and 2 Mesocydops edax 1‐−1) on Chaoborus development and survival were evaluated using a 3 × 3 factorial design. Jars containing lake water, the appropriate food and predator treatments, and two Chaoborus (<12h old) were rotated on a plankton wheel at 25°C. Survival and developmental stage were monitored daily until all individuals had either died or moulted to instar II.
Predation by Mesocydops was the major source of mortality, causing 87.5% of Chaoborus deaths over all treatments. Chaoborus mortality was significantly higher in treatments with Mesocydops (67–100%) than in predator‐free treatment (0–13%).
Development time was significantly longer in the low‐density food treatment than in the highest food treatment.
No significant interaction between food limitation and predation was detected.
These results suggest that predation by copepods may limit recruitment of juvenile Chaoborus in productive lakes.
A simple periphyton sampler for algal biomass estimates in streams
Authors: DAVIES ANNE L. , GEE JOHN H.R. 
Published: May 2006

SUMMARY

A simple periphyton sampler, which is cheap and easy to construct, is described. The key component is a disposable scouring disc which also serves to adsorb detached material.
Field trials show that the scouring sampler is significantly more efficient at removing and retaining periphyton from stones in streams for biomass estimation than other commonly used techniques.
The scouring sampler requires only one operator. Its small size and speed of use facilitate replication of samples. Samples can be collected from stones as small as 30mm diameter.
Behavioural response of fishes to increasing pH and dissolved oxygen: field and laboratory observations
Authors: SERAFY J.E. , HARRELL R.M. 
Published: May 2006

SUMMARY

Freshwater fish assemblages were sampled quantitatively before, during, and after naturally produced conditions of elevated pH and dissolved oxygen (DO) that occurred for 2–6h in two dense macrophyte beds. Field observations were followed by 3–4‐h laboratory behavioural experiments in which banded killifish (Fundulus diaphanus), bluegill (Lepomis macrochirus), and striped bass (Morone saxatilis) were exposed to gradually increasing levels of: (i) pH; (ii) DO; and (iii) pH and DO.
Field results indicated that the macrophyte bed dominated by Hydrilla verticillata had a higher fish density than the mixed‐species (H. verticillata and Vailisneria americana) bed, but beds did not differ significantly in fish species richness or biomass. Within beds, diel changes in fish species composition, richness, density and biomass were minor.
In the laboratory, avoidance of pH levels exceeding 9.5 was exhibited by all species tested. No significant response was observed to either DO increase treatments, or to pH and DO increase treatments.
Results suggest fishes do not avoid areas, such as dense macrophyte beds, when high pH levels (9.5–10.0) are accompanied by high DO levels (200–260% saturation).
A simple water sampler, and a chamber for in situ incubation of plankton samples at discrete depths
Authors: TRANVIK L.J. , TRANVIK P.H. 
Published: May 2006

SUMMARY

A simple water sampler and an incubation chamber are presented. The water sampler is simpler in construction than the Ruttner sampler and other comparable devices. In addition to enclosure of water at a discrete depth, the incubation chamber releases a radioisotope or other substance of experimental interest into the sample.
Tests of performance are presented, demonstrating efficiency in enclosure of water from discrete depths, and time course of mixing of a tracer into the sample after activation of the release mechanism.
Characterizing a zooplankton neighbourhood: small‐scale patterns of association and abundance
Authors: FOLT CAROL , SCHULZE PETER C. , BAUMGARTNER KAREN 
Published: May 2006

SUMMARY

This study compares small‐scale (i.e. neighbourhood) associations among distributions of phytoplankton, zooplankton, and zooplankton grazing rates using a combination of correlations and analyses of spatial patchiness.
All zooplankton and phytoplankton populations had patchy distributions. On average, individuals experienced members of their same taxon at a density that was 42% greater than the mean sample density.
The various zooplankton taxa experienced different average neighbourhoods, even within the same stratum of the lake. For example, Daphnia galeata mendotae (Birge) experienced phytoplankton concentrations that were nearly 50% greater than those experienced by Daphnia pulicaria (Forbes) at the same depth.
The distributions of the various phytoplankton taxa were positively correlated with each other, but the distributions of zooplankton were negatively correlated, or more often, unrelated to each other.
Phytoplankton abundance was negatively correlated with zooplankton grazing rates.
We hypothesize that while phytoplankton distributions are driven by common external factors, the factors that determine horizontal distributions of zooplankton are species specific. In addition, zooplankton grazing appears at least partially responsible for the generation of patchiness in the distribution of phytoplankton.
Carbon and nitrogen dynamics in a maritime Antarctic stream
Authors: DAVEY MARTIN C. 
Published: May 2006

SUMMARY

The carbon and nitrogen dynamics in a maritime Antarctic lake outflow stream were investigated. The stream and the algal communities could be split into two zones: a semi‐aquatic margin consisting of a perennial cyanobacteria/diatom mat and a flowing channel with a similar perennial mat that was overgrown by annual filamentous chlorophytes during the course of the summer.
Neither algal community was limited by nutrient availability. Major nutrients were always available in the stream water. There were slight differences in the atomic ratios of the mats, the N:P ratios in the channel mat being lower than those in the marginal mat. However, both these and the total dissolved N:P ratio in the stream water were all close to those that indicate a balanced supply.
There was no net carbon or nitrogen accumulation by the marginal mat suggesting that uptake processes were balanced by loss processes.
Maximum rates of carbon fixation (0.1–0.5mgCg−1 dry weight h−1) were similar to those of other perennial Antarctic algal mats. Productivity appeared to be limited by physical factors, but the effects of irradiance and temperature could not be separated.
There were no heterocystous cyanobacteria in the mat communities and rates of atmospheric nitrogen fixation were very low (0–10ngNmg−1 mat Nh−1). Fixation accounted for only 0.3% of the nitrogen accumulation of the channel mats, but was higher in the marginal mat where uptake of other sources of nitrogen was also low.
Nitrogen accumulation by the channel mat averaged 0.34gNm−2 day−1. Only 0.05gNm−2 day−1 was accounted for by the uptake of dissolved inorganic nitrogen (nitrate plus ammonium). The major (80%) source of nitrogen appeared to be dissolved organic nitrogen. Recycling of nitrogen within the stream ecosystem may also be important.
The nature of the fluid boundary layer and the selection of parameters for benthic ecology: reply to Lamouroux
Authors: CARLING P.A. 
Published: May 2006

SUMMARY

The near bed flow equations and definitions given originally by Carling (1992) are reviewed and are shown to be correct and unambiguous. The theoretical assumptions inate in deriving the governing equations are violated in non‐uniform, unsteady flow, such as occurs in shallow flow over rough beds, but in practice results obtained from log‐law models are often not significantly different from those derived from functions purporting to represent large‐scale roughness. This point was made carefully in the original paper.
More complex approaches now exist for modelling gradually varying, slightly non‐uniform flow which are modifications of uniform flow models. These are not readily applicable to field data commonly available to ecologists, however, and generally give little additional insight. Advances are only likely to be made when turbulent flow structure is better understood.
Spatial distribution and population dynamics of a benthic rotifer, Embata laticeps (Murray) (Rotifera, Bdelloidea) in the bed sediments of a gravel brook
Authors: SCHMID‐ARAYA J.M. 
Published: May 2006

SUMMARY

The spatial and temporal distributions of the most abundant bdelloid rotifer, Embata laticeps (Murray), inhabiting the sediment surface and the hyporheic interstitial of a gravel stream were investigated between October 1991 and October 1992. Three temporal peaks of population density occurred during the year at the sediment surface differing in their riming from the density peaks detected within the bed sediments.
The depth distributions of E. laticeps in pool and riffle areas differed significantly. Higher abundances were found between 10 and 20 cm depth in the pool and between 20 and 30 cm in the riffle area. In these two sites a significant effect of surface discharge (estimated 1 week before sampling) on rotifer densities was found. Discharge greater than 0.424 m3s−1 significantly reduced the densities in the riffle, while only at values greater than 1.660m3s−1 were abundances influenced in the pool area.
The percentages of egg‐bearing females were higher within the bed sediment than in the surface layer, and in the pool area than in the riffle. Thus, overall mean values of population increase were higher in the pool habitat (x̄= 0.015 ± SE 0.029 day−1) than in the riffle and at the sediment surface (x̄= 0.004 ± 0.025 and 0.005 ± 0.026 day−1, respectively). In addition, population growth fluctuated more strongly at the sediment surface than within the hyporheic intersiritial. Comparison of the observed values of population increase with a randomization test, where observed densities were randomly permuted, revealed no significant differences between those observed and values from a random model. Thus, a clear trend in population growth of E. laticeps over time could not be demonstrated in this gravel stream.
Dispersal of adult Trichoptera at a Danish forest brook
Authors: SODE ANNETTE , WIBERG‐LARSEN PETER 
Published: May 2006

SUMMARY

The dispersal of adult Trichoptera at the small Danish forest brook, Stamperenden, was studied from 10 May to 6 October 1990 using Malaise traps placed across the brook, parallel to the brook at distances of 2, 20 and 40m, and perpendicular to it at a distance of 1–3m.
Of the total of 4175 specimens caught, lotic species breeding in Stamperenden accounted for 95.6%. The dominant species were Agapetus fuscipes, Lype reducta, Plectrocnemia conspersa, Potamophylax nigricornis and Silo pallipes.
The sex ratios in the catches of most species were uneven. Agapetus fuscipes males were in excess, probably because males fly more frequently than females.
The dominant species flew predominantly above the surface of the brook. Whereas both sexes of A. fuscipes, L. reducta and S. pallipes were rarely found even as little as 20–40m from the brook, the dispersal range of P. conspersa was much wider.
The implications of low dispersal for the biological recovery of damaged but subsequently restored streams and stream catchments are discussed. It is concluded that complete biological recovery may be a process requiring decades unless the original aquatic fauna is re‐established artificially.