bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photosynthetic use of inorganic carbon among primary and secondary water plants in streams
Authors: SAND‐JENSEN KAJ , PEDERSEN MORTEN FOLDAGER , NIELSEN SØREN LAURENTIUS 
Published: May 2006

SUMMARY1. We analysed photosynthetic rates and inorganic carbon use of thirty‐five vascular macrophyte species collected submerged in eight nutrient‐ and CO2‐rich Danish lowland streams. The species were classified in four groups as mainly terrestrial, homophyllous and heterophyllous amphibious and truly submerged. These groups represent plant species differently adapted to life in water.2. Photosynthetic rates measured in water increased in the gradual transition from mainly terrestrial, through amphibious to truly submerged species. Species normally in contact with air adapted to submergence by increasing the photosynthetic rate at limiting CO2. Photosynthetic rates of submerged parts of heterophyllous amphibious species were close to those of submerged species. Submerged species with thin or finely dissected leaves had the highest photosynthetic rates, probably because of low diffusional resistance to uptake of nutrients and gases.3. In contrast to submerged species, terrestrial and amphibious species were unable to use HCO3−. Extensive oversaturation with CO2 in the streams allows, however, many amphibious species to photosynthesize well under water, based on CO2‐use alone. Amphibious CO2‐users, with very few structural adaptations to life under water, can therefore be as dominant in the submerged vegetation of lowland streams as HCO3−‐using water plants. Moreover, the streams provide open space for colonization from the dense vegetation ashore.4. Among the 1265 Danish herbaceous species no less than seventy‐five terrestrial species occasionally grow submerged, forty‐five species are amphibious, and fifty‐one are true water plants. These numbers suggest that adaptation to permanent or temporary submergence is an ongoing process involving many species and that the land‐water interface does not represent as difficult a barrier as often believed.
Long‐ and short‐term dynamics of submerged macrophytes in two shallow eutrophk lakes
Authors: BLINDOW IRMGARD 
Published: May 2006

SUMMARY1. Periods with clear water and abundant submerged vegetation have alternated with periods of turbid water and sparse vegetation during recent decades in Lake Tåkern and Lake Krankesjön, two shallow, calcium‐rich, moderately eutrophic lakes in southern Sweden, Between 1983 and 1991, submerged vegetation (predominant species: Chara tomentosa, Nitellopsis obtusa, Myriophyllum spicatum) covered about 50% of the open lake area in Lake Tåkern. In Lake Krankesjön, submerged vegetation was sparse during 1983–84, but increased continuously in the following years and covered about 50% of the open lake area by 1990 and 1991. Potamogeton pectinatus was the first species to expand in Lake Krankesjön, but was later replaced by C. tomentosa.2. During 1983–84, turbidity was high in Lake Krankesjön, which indicated that submerged macrophytes were light‐limited. During 1986–91, there was a negative correlation between the areal coverage of charophytes and angiosperms, indicating that competition for space had become an important limiting factor. The same negative correlation was found in Lake Tåkern for 1983–91.3. Charophytes had much higher biomass per unit area than angiosperms in both lakes and reduced water movement considerably. This was probably one reason for the increase of water transparency in Lake Krankesjön during the spatial expansion of these plants. Charophytes also stored large amounts of phosphorus and nitrogen, Charophytes are probably superior competitors for both space and nutrients and thus have competitive advantage over angiosperms in this lake type.4. In Lake Krankesjön, both P. pectinatus and C. tomentosa were negatively affected by high water level during the growing period. Total disappearance of submerged vegetation occurred in both lakes after catastrophic events (dry‐out during summer or mechanical damage by ice) caused by extremely low water level. Changes in water level are thus one of the most important reasons for among‐year fluctuations in areal coverage of submerged macrophytes in these lakes.
Effects of suspended clay on Daphnia body growth and fitness
Authors: KIRK KEVIN L. 
Published: May 2006

SUMMARY1. Suspended sediments often reduce the abundance, fitness, and feeding rates of planktonic cladocerans. This paper examines the effect of suspended clay particles on the body growth and life‐history parameters of Daphnia ambigua. Cohorts were exposed to zero or 50mgl−1 suspended clay (particle size <2μm). Individuals exposed to clay had significantly lower body lengths at a given age than individuals in the control cohort. Parameters for the von Bertalanffy body growth equation were calculated for each individual; the asymptotic maximum body length (lmax) was reduced, but the growth rate constant (k) was unaffected, by the presence of suspended clay. Body length at reproductive maturity was lower in the presence of suspended clay; this may be an adaptive response and is similar to the response of cladocerans to limiting food concentrations.2. Age‐specific survivorship and fecundity were both reduced, and the ages of maturity and first reproduction were both increased, in the presence of suspended clay. The overall effect of these demographic changes was a 70% decline in the net reproductive rate (Ro), a measure of fitness.3. Suspended clay affected the relationship between body length and fecundity. Animals of a given length produced fewer eggs in the presence of suspended clay. In addition, there was a significant interaction in the effects of body length and clay on brood size: the slope of the regression line of brood size as a function of body length was lower in the presence of clay. This interaction has also been observed in limiting food concentrations, and may be caused by reductions in body length at maturity in low food or high clay environments.4. The similarity between the effects of limiting food concentrations and suspended clay on Daphnia body growth, survivorship, fecundity, and brood size makes sense, given previous observations showing that suspended clay reduces the feeding rate of D. ambigua by up to 70% due to mechanical interference with feeding behaviours.
Effects of temperature and body size on radiocaesium retention in brown trout, Salmo trutta
Authors: UGEDAL O. , JONSSON B. , NJÅSTAD O. , NÆUMANN R. 
Published: May 2006

SUMMARY1. The elimination rate of radiocaesium in brown trout Salmo trutta L. was determined in the laboratory at four water temperatures (range 4.4–15.6°C). In the experiments three or four homogenous size‐groups of fish (mean weights 23–496 g) were studied at each temperature.2. The brown trout received acute oral doses of 134Cs and were killed at intervals for radioactivity counting. The retention versus time curves were composed of two distinct exponential components. The long‐lived component was quantitatively the most important for retention of radiocaesium. Elimination rate increased with increasing water temperature and decreased with increasing body weight.3. The biological half‐life of 134Cs (Tb, days) was related to fresh body weight (W, g) and water temperature (t, °C) by the equation: Tb= 290 ×W°.176× e‐°.106×t. The elimination rate of Cs could be predicted from weight‐specific metabolic rate as given by Elliott's equations for brown trout.
An experimental test of the egg‐ratio method: estimated versus observed death rates
Authors: BRETT MICHAEL T. , MARTIN LISA , KAWECKI TADEUSZ J. 
Published: May 2006

SUMMARY1 The accuracy of death‐rate estimates provided by the egg‐ratio method was assessed by directly measuring the real death rates of six large laboratory Daphnia populations for 40 days.2. Of six models tested the Kawecki iterative model gave the best relationship to real death rates in terms of variance explained, bias, and fit at both 4‐ and 8‐day sampling intervals. Although considered theoretically correct by persons familiar with the mathematics of egg‐ratio models, the Edmondson—Paloheimo model gave slightly worse results in terms of bias and fit.3. Using raw data, as opposed to smoothed data, gave the best fit between estimated and observed rates for both the Kawecki iterative and Edmondson‐Paloheimo models.4. Size‐selective predation did not increase error in estimates of the death rate; however, non‐steady‐state dynamics were correlated with error in model estimates.5. In general, the models gave a relatively good description of real dynamics, but they regularly produced negative death rates, and were grossly wrong for some individual estimates. The present study also gives practical suggestions on application of this technique to field populations.
Extreme cyclomorphosis in Daphnia lumholtzi
Authors: SORENSEN KATHRYN H. , STERNER ROBERT W. 
Published: May 2006

SUMMARY1. Daphnia lumholtzi, not previously reported in North America, was found in a small reservoir in East Texas in January, 1991, This species possesses extremely long spines and large fornices; an allometric study was performed to detect any temporal differences in specific growth rates of the spines relative to the body.2. In nature, mature females attained 1.8mm body length, excluding spines, but when the head and tail spines are included, the total length reached a maximum of 5.6mm.3. Differences in the growth patterns of the head spine and the tail spine relative to the body existed for D. lumholtzi from January to March 1991. Both the head and the tail spines grew at a faster rate than the body during all 3 months although the rates varied between them. The results contradict the invertebrate predation hypothesis (Dodson, 1974) in that D. lumholtzi's head and tail spines continue to grow during adulthood instead of stopping after the juvenile instars.4. The head spines grew at a constant allometric rate over time while the tail spine grew faster as the temperature increased. Both varied significantly in length over the 3 months, with animals having the shortest spines in February and the longest in March.
Sensitivity of mayfly nymphs to red light: implications for behavioural ecology
Authors: HEISE BRIAN A. 
Published: May 2006

SUMMARY1. Visual sensitivity of the mayflies Stenacron interpunctatum (Say) and Stenonema vicarium (Walker) to red (650 nm) and infra‐red (950 nm) light was tested using a behavioural assay. Nymphs were placed in a runway and sequentially exposed to green light, red light, infra‐red light and no light (control) at one end of the runway. The distance run away from the light, and the number of alarm reactions to the light were recorded.2. Both species reacted strongly to both red and green light, running significantly greater distances and reacting more frequently to these wavelengths of light than to either infrared light or the control.3. These results show that unobtrusive observations of mayfly nocturnal behaviour should be made using infra‐red, and not red light, for illumination. Previous studies of aquatic insect nocturnal behaviour may have produced biased results if red light was used.
Simultaneous patterns of temperature, oxygen, zooplankton and fish distribution in Lake Kinneret, Israel
Authors: KALIKHMAN I. , WALLINE P. , GOPHEN M. 
Published: May 2006

SUMMARY1. Temperature, oxygen concentration and zooplankton density were measured simultaneously on 25 December 1990 at twenty‐six stations during an acoustic survey of the fish population of Lake Kinneret, Israel. Data from a preliminary acoustic survey were used to establish the optimal distance between transects (4km).2. The distribution of temperature and oxygen concentration (and their gradients), and zooplankton and fish densities were compared using three‐dimensional plots and correlation analysis. Both fish and zooplankton were concentrated in frontal zones where temperature and oxygen gradients were highest.3. In the south‐eastern part of the lake, where fish abundance was highest, a minimum of zooplankton density was observed, suggesting that predation by fish reduced zooplankton concentrations.
Complex relations between freshwater macro‐ and meiobenthos: interactions between Chironomus riparius and Chydorus piger
Authors: van de Bund WOUTER J. , DAVIDS C. 
Published: May 2006

SUMMARY

The potential importance of interactions between macro‐ and meiobenthos in the littoral zone of takes was studied in a series of laboratory experiments with a chironomid and a chydorid.
In a situation of intraspecific density dependence, Chydorus piger Sars inhibited the growth of Chironomus riparius Meigen, while both second‐ and fourth‐instar C, riparius stimulated the parthenogenetic reproduction of C. piger.
The meiofaunal chydorids may thus have a structuring effect on macrofaunal chironomid populations by interfering with the early‐instar larvae.
With macro‐ and meiofaunal species both operating at the primary consumer‐level of the food web, this kind of complex interaction will affect the magnitude of secondary production available to higher trophic levels.
The importance of fluvial hydraulics to fish‐habitat restoration in low‐gradient alluvial streams
Authors: RABENI CHARLES F. , JACOBSON ROBERT B. 
Published: May 2006

SUMMARY

A major cause of degradation and loss of stream fish is alteration of physical habitat within and adjacent to the channel. We describe a potentially efficient approach to fish restoration based upon the relationship between fluvial hydraulics, geomorphology, and those habitats important to fish.
The aquatic habitat in a low‐gradient, alluvial stream in the Ozark Plateaus physiographical province was classified according to location in the channel, patterns of water flow, and structures that control flow. The resulting habitat types were ranked in terms of their temporal stability and ability to be manipulated.
Delineation and quantification of discrete physical spaces in a stream, termed hydraulic habitat units, are shown to be useful in stream restoration programmes if the ecological importance of each habitat unit is known, and if habitats are defined by fluvial dynamics so that restoration is aided by natural forces.
Examples, using different taxa, are given to illustrate management options.
Role of interaction zones between surface and ground waters in DOC transport and processing: considerations for river restoration
Authors: VERVIER PHILIPPE , DOBSON MIKE , PINAY GILLES 
Published: May 2006

SUMMARY

A study of dissolved organic carbon (DOC), nitrates and total dissolved phosphorus (TDP) concentrations, conductivity and bacterial numbers was undertaken in subsurface water of the Garonne River (France) under low‐flow conditions. The velocity of subsurface flow through a 300‐m gravel bar, during this study, was less than 43 m day−1. DOC, nitrates and TDP concentrations, conductivity and bacterial numbers fluctuated within the gravel bar with no discernible spatial pattern. Bacterial abundance was correlated with DOC concentration. Results were compared to a previous study of the Stillaguamish River (U.S.A.) (Vervier & Naiman, 1992).
These studies provide evidence that gravel bars are important in the processing of DOC by bacteria in the subsurface water. Bacterial activity is, in turn, determined by sources of DOC from upstream at high discharge, and by patchy local microhabitats at low discharge.
Restoration of rivers should incorporate, wherever possible, meanders with associated gravel bars and riffles. These will improve DOC‐processing capacity, in addition to other benefits predicted by the Building Block Model (Petersen, Petersen & Lacoursière, 1992).
Natural rehabilitation of stream fish populations in an Illinois catchment
Authors: BAYLEY P.B. , OSBORNE L.L. 
Published: May 2006

SUMMARY

An extreme drought in 1988 dried first‐ and second‐order streams in the Salt Fork basin (1190 km2) in east‐central Illinois. This event provided a natural experiment in which the natural rehabilitation of fish populations could be measured in the whole catchment following resumption of stream flows.
Fish were sampled before, during, and after the drought (1987–1990) throughout the basin (eighty‐eight samples in July‐September) using methods of known efficiency. Analyses of covariance [using log (distance from source) as the covariate] indicated no significant differences (P>0.2) of biomass or species richness between pre‐drought and post‐drought samples from sites desiccated during 1988 or among pre‐drought, drought, and post‐drought years among samples from perennial Streams. Therefore, recovery occurred within 1 year, but there was no indication of increased biomass or species richness in permanent streams resulting from fish moving down or remaining downstream during the drought.
Fish biomass per unit length of stream segment was modelled as a power function of distance of the segment from the source of each stream to estimate changes in biomass of the whole catchment. Before and subsequent to the drought, 90.0t of fish occupied the total 729km of stream length in the basin, compared with 74.61 in the drought year. Although, the drought affected 80% of total stream length, fish biomass was reduced by only 17% in the drought year because only the lower‐order streams were desiccated and their normal biomass density was lower than in perennial streams.
In conclusion, it is expected that no expenditure on stocking fish would be necessary in restoration projects on these lower‐order, surface runoff streams, providing that they are connected to permanently flowing streams that contain a full complement of species.
Patterns in metal content of submerged aquatic macrophytes: the role of plant growth form*
Authors: JACKSON LELAND J. , KALFF JACOB 
Published: May 2006

SUMMARY

Sediments and eleven species of rooted submerged aquatic macrophytes were sampled from twenty‐five lakes in southern Quebec to examine species patterns in metal content.
Linear regression models relating the content of metals in the macrophytes to their sediments demonstrated that the isoetoid (Eleocharis acicitlaris, Eriacaulon septangulare, Isoetes sp. and Sagittaria graminae) and the non‐isoetoid species had different plant‐sediment relationships. Canopy‐forming (Myriophyllum spicatum, Potamogeton amplifalius, P. crispus and P. perfoliatus) and understory species (Elodea canadensis, P. robbinsii and Vallisneria americana) had similar linear regression model slopes, but the understory species had significantly higher intercepts, indicating higher plant metal contents for a given sediment metal concentration.
We grouped species by their biomass density (biomass (kg)/height (m)), a measure of the packing of the plant canopy, and averaged values for each metal, thereby producing one model per group. Comparison of the models by analysis of covariance revealed no significant differences in metal content. However, the canopy‐forming species that occurred in monospecific and mixed species stands (M. spicatum and P. amplifolius) had significantly higher metal content for a given sediment metal content when an understory was present.
These results show that sediment metal content explains the largest proportion of variation in plant metal content across all sites and species. Deviations from what would be predicted by the most general model are not related to large‐scale differences in sediment geochemistry, but to the physical structure of the weedbed within geochemically similar sediments.
The drag coefficient of cased caddis larvae from running waters: experimental determination and ecological applications
Authors: WARINGER J.A. 
Published: May 2006

SUMMARY

Drag coefficients of cylindrical‐case caddis larvae from running waters were investigated in the laboratory using an artificial stream channel.
Dead larvae of the limnephilids Allogamus auricollis (first to fifth instars), fifth instars of Potamophylax cingulatus, Chaetapteryx fusca, Drusus monticola, Metanoea rhaetica and fourth instars of the brachycentrid Micrasema minimum, were exposed to different current speeds. When the heads of the larvae were directed towards the water flow (frontal position), the current necessary to dislodge the larvae ranged from 3.00cms‐1(A. auricollis, first instar) to 70.50cms‐1 (P. cingulatus). With flow normal to the long axis of the case (lateral position), these speeds ranged from 2.20cms‐1 (M. minimum) to 20.80cms‐1 (P. cingulatus).
In frontal position, individual Reynolds numbers at the moment of dislodgement ranged from 74 (A. auricollis, first instars) to 14100 (P. cingulatus), and from 14 (M. minimum) to 1143 (P. cingulatus) in lateral position. Regression equations correlating case length, mean case width or fresh weight with Reynolds numbers at the moment of dislodgement (frontal and lateral position) were very highly significant with r20.91.
For the range of Reynolds numbers given above, the drag coefficient varied between 5.05 (A. auricollis, first instars) and 0.26 (P. cingulatus) in frontal case position and from 2.97 (M. minimum) to 0.69 (C. fusca) in lateral case position. Furthermore, the relationship between Reynolds number and drag coefficient was found to be linear on a In/In scale for both frontal and lateral case position.
Macroinvertebrate functional feeding groups in the middle and lower reaches of the Buffalo River, eastern Cape, South Africa. II. Functional morphology and behaviour
Authors: PALMER CAROLYN , O'KEEFFE JAY , PALMER ANTHONY 
Published: May 2006

SUMMARY

While it was impossible to assign twelve taxa from the middle and lower reaches of the Buffalo River, eastern Cape, South Africa to functional feeding groups (FFGs) on the basis of their foregut contents alone, we were able to assign these taxa to FFGs, with varying degrees of certainty, on the basis of their mouthpart morphology and feeding behaviour.
The two Hydropsychidae were identified as passive filterers on the basis of their feeding behaviour. The ultrastructure of the labia and maxillae of the ten Ephemeroptera, and observation of the feeding behaviour of five of these, were used to assign them to FFGs.
Only mayfly species whose morphology and behaviour were recorded could be positively assigned to the FFGs active or passive filterer, gatherer, brusher, and scraper. The FFG designation described the predominant feeding behaviour, and all observed taxa exhibited a range of feeding activities.
FFGs are useful descriptive categories which clarify both the nature and distribution of the food eaten, and the role of the organism in the ecosystem. FFGs affect a variety of stream processes, and the role of the FFG concept in understanding stream functions is discussed.