bluuebunny/crossref_metadata_2025_split huggingface dataset:
Environmental significance of ice to streamflow in cold regions
Authors: PROWSE T.D. 
Published: May 2006

SUMMARY1. The five major hydrologic regimes of cold regions are typically classified as proglacial, wetland, spring‐fed, arctic nival and subarctic nival. Each has a distinctive hydrograph determined by the source and timing of runoff.2. The hydrologic response of streams in cold regions is influenced significantly by the source and pathways of moisture from the landscape to the stream channel. Snow and ice masses, such as snow cover, permafrost and icings, play principal and unique roles as major moisture sources, and in affecting runoff pathways.3. Once flow has been routed from the landscape into a channel system, the effects of floating ice begin to control the flow system. Notably, many of the most significant hydrologic events in cold regions, such as floods and low flows, are more the result of in‐channel ice effects than of landscape runoff processes. This has not been adequately recognized in general assessments of cold‐regions water resources.4. Only recently have the broader environmental effects of river ice been addressed in any concerted fashion. This paper reviews the various stages of ice formation, growth and break‐up, and summarizes the major hydrologic and ecological effects associated with each. Priority research topics are also identified.
Altitudinal trends in the diatoms, bryophytes, macroinvertebrates and fish of a Nepalese river system
Authors: ORMEROD S.J. , RUNDLE S.D. , WILKINSON S.M. , DALY G.P. , DALE K.M. , JUTTNER I. 
Published: May 2006

SUMMARY1. Hydrobiological changes were assessed along an altirudinal transect of eighteen to twenty‐three tributaries from 600 to 3750m in two adjacent river systems in east‐central Nepal. The transect incorporated catchments under terraced agriculture at the lowest altitudes in the Likhu Khola, through streams in forest, alpine scrub and tundra at higher altitudes in Langtang.2. Diatoms, bryophytes, macroinvertebrates and fish all showed pronounced altitudinal changes in assemblage composition as shown by TWINSPAN and DECORANA. A few taxa were restricted to streams at high altitude, but many more occurred only at lower altitudes where taxon richness increased substantially despite catchment disturbance by terraced agriculture.3. Diatoms characteristic of lower altitude streams were mostly motile, epipelic or episammic Navicula and Nitzschia spp., which occur typically at greater electrolyte and nutrient concentrations. Those characteristic of higher and steeper sites included attached Fragilaria spp. and prostrate Achnanthes spp., tolerant of turbulent flow.4. Cover by bryophytes varied within catchment type; high altitude springs supported dense mats, unlike streams fed by ice and glaciers. Taxa confined to low altitudes included those characteristic of humid subtropical conditions.5. Invertebrate families occurring only at lower altitudes included a range of burrowers and pool dwellers. Numerically, filter feeding Hydropsychidae and Simuliidae dominated streams in terraced and forested catchments, whereas grazing baetid mayflies dominated higher altitude streams in scrub and tundra.6. The combined density and biomass of at least six fish species in the Likhu Khola were 23–250 (per 100m−2), and 86–1282 g wet mass (per 100 m−2), respectively. No fish were found in Langtang streams, probably because torrential headwaters prevented colonization.7. Our data confirm that altitudinal transitions in stream biota are pronounced in the Himalaya of Nepal, but are likely to reflect a wide array of potential influences.
Benthic ecology of a spring‐fed river of interior Alaska
Authors: LAPERRIERE JACQUELINE D. 
Published: May 2006

SUMMARY1. A massive aquifer between the Gerstle, Tanana and Delta rivers in interior Alaska receives water from them and from smaller streams that flow from the Granite Mountains in the Alaska Range, Groundwater from the aquifer intersects the surface in a mid‐sized (20m3s−1× 10%) spring‐fed stream, Clearwater Creek.2. Mean annual air temperature is about ‐2.6°C. However, even in winter when air temperature often reaches —40°C, the stream does not form a complete ice cover. Water temperature ranges from 0 to 7.8°C. Specific conductance and the concentrations of major ions vary little throughout the year, and summed ionic salinity exceeds 250 mg1‐−1.3. Benthic algal standing crop (as chlorophyll a) was at least an order of magnitude higher than that in a nearby surface‐water stream, the upper Chena River, Standing crop peaked in spring and autumn (about 20mgm−2) and averaged about half this value, although biomass of an early spring bloom of Hydrurus foetid us was underestimated.4. Algal standing crop was inversely related to the concentrations of inorganic nitrogen and orrhophosphate‐phosphorus in the water column. The ratio of total nitrogen to total phosphorus (as mass concentrations) was always about 30. Measurements of primary production made in Clearwater Creek were among the highest reported for streams in subarctic Alaska.5. Macroinvertebrate diversity in Clearwater Creek was low. Numbers of ‘morpho‐species’ in monthly Surber samples (0.09m2) averaged nine, and ranged from three to fourteen. However, benthos and drift densities were similar to those reported from other Alaskan streams. In early spring and autumn, drifting macroinvertebrates were primarily Ephemeroptera, Plecoptera and Trichoptera, but in summer, Diptera dominated the drift. The low diversity of macroinvertebrates is hypothesized to be a consequence of the small annual range in water temperature and the relatively constant discharge of Clearwater Creek.
Colonization and succession of invertebrate communities in a new stream in Glacier Bay National Park, Alaska
Authors: MILNER ALEXANDER M. 
Published: May 2006

SUMMARY1. Invertebrate colonization of a new stream following glacial recession is documented for a 12 year period from 1978 to 1990.2. Invertebrates, particularly Chironomidae, displayed site‐specific temporal succession over the study period, at the end of which a number of the pioneer colonizers were no longer collected.3. Maximum species richness was found in 1988, whereas total invertebrate density was greatest in 1978, 10 years earlier.4. Water temperature appeared to be the most significant factor determining the year of colonization of invertebrate taxa. As a result, deterministic trends were apparent in patterns of invertebrate colonization and succession.5. Salmonids first colonized the stream in 1988. Dietary analyses of juvenile Dolly Varden (Salvelinus malma) showed preferential selection for blackfly and small chironomid larvae.
Effects of agricultural development on processing of tussock leaf litter in high country New Zealand streams
Authors: YOUNG ROGER G. , HURYN ALEXANDER D. , TOWNSEND COLIN R. 
Published: May 2006

SUMMARY1. We compare the rates and mechanisms of processing of tussock (Chionochloa spp.) leaf litter in six New Zealand streams draining grassland catchments that contrast in the extent to which they have been developed for pasture.2. Rates of processing, measured as rate of weight loss of leaf packs and rate of leaf softening, were at the slow end of the spectrum for vascular plant processing. Processing was faster at developed sites, mediated mainly through the influence of oxidized nitrogen concentration on microbial activity.3. Few invertebrate shredders colonized leaf packs and it is unlikely that invertebrates had an appreciable effect on leaf processing in our study streams, which do not effectively retain leaf litter. Very small headwater tributaries appear to retain leaf litter and possess a more abundant shredder community.4. Measures of leaf processing in our six streams were significantly correlated with Petersen's (1992) RCE score of stream condition. We discuss the potential for using rate of leaf litter processing as a method of bioassessment.5. Even the most degraded stream in our study is classed as ‘good’ using the RCE inventory system. Human impact in the Taieri River is relatively small compared with the degradation observed in some parts of the world.
The roles of grass leaf litter in streams draining tussock grassland in New Zealand: retention, food supply and substrate stabilization
Authors: SCARSBROOK MIKE R. , TOWNSEND COLIN R. 
Published: May 2006

SUMMARY1. We investigated the roles of grass litter in streams that drain upland New Zealand tussock grassland, paying particular attention to the ways in which grass leaves differed in their characteristics from much more intensively studied tree leaves.2. The instantaneous retention rates of tussock grass leaves (Chionochloa rigida) on the bed of a second‐order stream (0.157–0.515 m−1) were significantly higher than those of the elliptical leaves of lemonwood trees (Pittosporum eugenioides; 0.068–0.180 m−1).3. Instantaneous retention rates of grass leaves in two third‐order streams were very low. At high discharge, leaf retention rate was greater in Timber Creek (0.0040 m−1), a braided, gravel bed stream, than in the adjacent Kye Burn (0.0010m−1), with its well‐defined channel and large, stable substrate particles. At baseflow, retention rates were similar in the two streams (0.0053–0.0064 m−1 for Timber Creek; 0.0047–0.0058m−1 for Kye Burn). Nevertheless, total coarse particulate organic matter (mainly derived from tussock litter) was present at lower densities in Timber Creek than Kye Bum, reflecting the instability of the bed of the former and its tendency to spread over a wide area at high discharge.4. The results of a colonization tray experiment, in which substrate was mixed with tussock leaves, nylon ribbon or nothing, indicate that tussock leaves do not play an important role as microhabitat or food in the two third‐order streams. This may reflect the poor food quality of grass litter, and/or the relatively low availability and predictability of its supply.5. An in situ experiment revealed that tussock leaves play a role, analogous to that reported for certain seagrasses, in stabilizing substrate and reducing sediment transport, apparently by reducing bed roughness and therefore the force of friction on the bed.
Controls on production of bryophytes in an arctic tundra stream
Authors: FINLAY JACQUES C. , BOWDEN WILLIAM B. 
Published: May 2006

SUMMARY1. Two bryophyte taxa (Hygrohypnum spp. and, to a lesser extent, Fontinalis neomexicana) were abundant in riffles within phosphorus‐fertilized reaches of the Kuparuk River (North Slope, Alaska), but were much less common in fertilized pools and virtually absent in unfertilized reaches of the river. We conducted field experiments using stems and clumps of both species and artificial bryophytes to test the hypotheses that bryophyte growth was strongly limited by low phosphorus concentrations in unfertilized reaches, and limited by epiphytes in fertilized pools.2. Stem tips of Hygrohypnum spp. did not elongate when grown in unfertilized pool and riffle environments. In fertilized reaches, Hygrohypnum elongated significantly, although there was no significant difference in elongation of stem tips placed in pools [2.5 ± 0.9 cm (SD)] as opposed to riffles (2.8 ± 0.9 cm) for 32 days.3. Stem tips of F. neomexicana elongated significantly in all sites. There was a significant difference in elongation of stem tips in control and fertilized riffles (2.1 ± 1.1 and 4.7 ± 0.1 cm, respectively) but not in tips grown in control and fertilized pools (2.8 ± 0.8 and 2.7 ± 0.9 cm, respectively).4. Biomass increments in clumps of these same species followed similar patterns except in fertilized pools. Hygrohypnum spp. lost weight in control riffle environments and did not grow in pools, but accumulated 181 ± 44 and 335 ± 200% of initial biomass in fertilized riffles in 1992 (over 32 days) and 1993 (over 44 days), respectively. F. neomexicana accumulated 38 ± 39 and 98 ± 47% of initial biomass in 1992 in unfertilized and fertilized riffles, respectively. Total phosphorus concentrations of both bryophytes in 1992 were significantly greater when grown in fertilized riffles than control riffles.5. Artificial mosses (untwisted, natural fibre rope) and clumps of Hygrohypnum spp. were used to assess effects of flow regime on derrital and epiphyte accumulation in the fertilized zone. Epiphyte and detrital mass was 4–4.5 times greater on average on artificial mosses in slow‐flowing pool environments than in fast‐flowing riffle environments. Epiphyte chlorophyll a was 4 times greater on Hygrohypnum clumps in pools than in riffles. This difference was probably brought about by increased detrital deposition and reduced grazing by invertebrates in pools. It is likely that both Hygrohypnum spp. and F. neomexicana could grow throughout the river, but are limited strongly by low phosphorus concentrations in unfertilized reaches and secondarily by detritus accumulation and interference competition with epiphytic algae in fertilized pools.
Seasonal variation in composition and production of planktonic communities in the lower River Rhine
Authors: ADMIRAAL W. , BREEBAART L. , TUBBING G.M.J. , VAN ZANTEN B. , DE RUIJTER VAN STEVENINCK E.D. , BIJKERK R. 
Published: May 2006

SUMMARY1. The composition and activity of phytoplankton, zooplankton and bacterioplankton in the lower River Rhine were measured in 1990 as part of an international biological inventory of the river. A seasonal study was carried out on two stations: one in the river mouth (km 1019) and one at the German/Dutch border (km 863).2. High densities of phytoplankton (with up to 140 μg chlorophyll a 1‐−1) and occasional depletion of dissolved silicate were observed at the upstream station. Phosphate concentrations were also lowered during blooms.3. Phytoplankton blooms, dominated by a few species of centric diatoms, declined one order of magnitude during downstream transport. During non‐bloom conditions (low) algal densities were maintained during transport, or increased slightly, indicating the suitability of the river reach for algal growth.4. Bacterial cell number and production (measured by the 3H‐thymidine method) showed a broad summer maximum with activity peaks (0.5 nK < M thymidine h−1) coincident with declining phytoplankton blooms. Winter values of bacterial production (0.02–0.05 n < Mh−1) were substantial, probably as a result of allochthonous input of organic matter.5. Rotifers and crustaceans made up the greater part of the zooplankton biovolume, but at the upstream station the contribution of Dreissena larvae and rhizopods was also substantial. High zooplankton biovolumes, of over 500 × 106μm31‐−1, were observed only during the phytoplankton spring bloom.6. Quantitative relationships between the high phytoplankton production (2.1–3.4 gCm−2 day−1), the high bacterial substrate uptake (0.5–1gCm−2 day−1), and grazing were analysed for the growing season 1990. Algal grazing by metazoan herbivores was substantial only during spring, while the role of phagotrophic microplankton and cell lysis were indicated as major factors responsible for the downstream decline of phytoplankton blooms in the lower Rhine.
Chironomid microdistribution in gravel of an English chalk river
Authors: RUSE LESLIE P. 
Published: May 2006

SUMMARY1. The study aimed to determine the relative importance of certain environmental variables to the distribution of instars of chironomid species in mid‐stream gravels of the River Pang.2. Core samples of gravel substrata were collected over 1 year. Water depth, current, particle size distribution, substratum porosity and detritus were recorded for each sample. The four principal components from a linear ordination of the environmental variables were used to constrain the ordination of chironomid data using the program CANOCO.3. Microdistribution was principally related to a temporal gradient of water depth, current and substratum heterogeneity. There was significant spatial separation of instars along a gradient of fine detritus, silt and substratum porosity. The distributions of early instars of three taxa were also significantly related to particle size. There was a significant relationship between the size distribution of larvae and the spatial distribution of fine sediments and detritus. This relationship was strengthened when restricted to larvae classified as scrapers.
Predator avoidance costs and habituation to fish chemicals by a stream isopod
Authors: HOLOMUZKI JOSEPH R. , HATCHETT LAURA A. 
Published: May 2006

SUMMARY1. We examined whether long‐term exposure to chemical cues of predatory longear sunfish (Lepomis megalottis) affected growth and rates of leaf processing by the isopod, Lirceus fontinalis, an important facultative shredder in low‐order streams in the eastern United States, and whether isopods habituated to sunfish chemicals.2. Long‐term (24 days) exposure to fish chemicals did not affect growth or the extent of leaf processing by isopods in the laboratory. Thus, chemical cues alone may not be important in triggering long‐term predator avoidance behaviours that could potentially reduce fitness or affect community processes like Litter breakdown.3. Isopods exposed to fish chemicals for 3, 9 and 15 days were significantly more active than individuals unexposed to fish chemicals, when transferred to another environment with fish chemicals. This result, coupled with results of the growth experiment, suggests that isopods habituate to fish chemical stimuli and that time to habituation is c. 3 days or less. Because fish chemicals can mislead prey about predator presence, and hence be a non‐threatening stimulus, they are probably important in eliciting only short‐term antipredatory behaviours by isopods.
Invertebrate communities and turnover in wetland ponds affected by drought
Authors: JEFFRIES MICHAEL 
Published: May 2006

SUMMARY1. Changes to the macroinvertebrate fauna found in small ponds on a freshwater marsh (Aberlady Bay, Scotland) in 1986, 1987 and 1992 were used to assess the impact of the 1988–92 drought on taxon turnover in pond communities.2. Permanent ponds accumulated taxa over the study period. Ponds that were wet throughout 1986–87 but dried in 1992 lost some of the many taxa associated with permanent water but acquired a reduced fauna typical of temporary ponds. Ponds that were temporary in 1986–87 were dry during most of 1992 and lost almost all aquatic taxa.3. Faunal turnover was considerable even in permanent ponds. Extinction rates were high for taxa typical of permanent or temporary ponds. Colonization rates were poor for the taxa from permanent water, but high for the taxa from temporary ponds.4. The importance of colonization and extinction rates as main predictors of the distribution of species between the ponds was looked at using metapopulation incidence functions, where observed incidence of a taxon can be used to predict colonization and extinction rates. Predicted rates were then compared with observed rates. Incidence functions gave reasonable predictions of observed colonization rates but were poor predictors of extinction, even for taxa that appeared likely to be true metapopulations.5. For the pond fauna, including fugitive species adapted to temporary ponds, whilst colonization may well depend on environmental stochasricity (how long a pond holds water), subsequent survival depends on other, demographic, processes (e.g. finding a mate, predation) rather than the pond drying out.
The relationship between invertebrate assemblages and available food at forest and pasture sites in three southeastern Australian streams
Authors: REED JULIA L. , CAMPBELL IAN C. , BAILEY PAUL C.E. 
Published: May 2006

SUMMARY1. Levels of ash‐free dry matter (AFDM) and chlorophyll a in epilithon, benthic participate organic matter (BPOM), invertebrate assemblage composition, and biomass of functional feeding groups were compared in winter and summer at forest and pasture sites in three Victorian streams.2. Chlorophyll a concentrations of epilithon were significantly higher at pasture than forest sites in winter but not in summer while BPOM was not significantly greater at forest sites in either season. Epilithic biomass as AFDM did not show consistent differences between land uses or seasons.3. Total biomass of invertebrates did not differ between forest and pasture sites but the biomass of shredders was significantly higher, and that of grazers significantly lower, at forest than pasture sites. A site shaded with an artificial canopy behaved as a forest site for grazers but as a pasture site for shredders.4. Cluster analyses of invertebrate assemblages grouped pasture sites with forest sites on the same stream at the same season, indicating that assemblage composition was less influenced by land‐use differences than by between‐stream and seasonal differences.5. Biomass of functional feeding groups appeared to be a more sensitive indicator of invertebrate assemblage response to land‐use alteration than either species diversity/ richness measures, or multivariate assemblage composition measures.
Prey selection by Asplanchna girodi (Rotifera): the importance of prey defence mechanisms
Authors: CONDE‐PORCUNA J.M. , SARMA S.S.S. 
Published: May 2006

SUMMARY1. Predator (laboratory‐grown Asplanchna girodi and prey (several field‐collected non‐carnivorous rotifer species) interactions were studied in the laboratory as a function of both predator and prey densities. The clearance rates of A, girodi decreased with increasing prey density. Predator density had no effect on the feeding of A. girodi.2. Asplanchna girodi selectively fed on Keratella cochlearis. Its clearance rates for K. cochlearis were much higher than those for Polyarthra and Brachionus. Short‐spined forms (spine length less than 25 μm) showed a significantly higher susceptibility to predation than either the non‐spined or the long‐spined forms.3. Large Asplanchna individuals fed selectively on reproductive females of K. cochlearis, thereby reducing the fecundity of their prey.
The effects of hydropsychid colonization on algal response to nutrient enrichment in a small Michigan stream, U.S.A.
Authors: PAN YANGDONG , LOWE REX L. 
Published: May 2006

SUMMARY1. We tested the hypothesis that the indirect effects of colonization by Hydropsyche spp. (Trichoptera: Hydropsychidae) may be greater than direct effects of nutrients on the benthic algal community growth. Two sets of nutrient‐releasing substrates (a total of twenty‐four) were deployed into a small pristine stream in northern Michigan. Each set was composed of four treatments replicated three times: (i) no nutrient enrichment (C), (ii) 0.5 M phosphate‐P enrichment (P), (iii) 0.5 M nitrate‐N enrichment (N) and (iv) 0.5 M phosphate‐P plus 0.5 M nitrate‐N enrichment (P + N). All hydropsychids colonizing on the substrate in one set (twelve substrates) were removed regularly and the other set (twelve substrates) with undisturbed hydropsychids served as the controls.2. Algal biomass and gross primary productivity were estimated as chlorophyll a (chl a) concentration, algal biovolume, and carbon fixation rate, respectively. There was a significant interactive effect of hydropsychid colonization and P enrichment on algal biomass measured as chl a concentration. With removal of hydropsychids, chl a concentration increased 11‐fold in the P enrichment treatments relative to the controls. The effects of P on chl a was, however, not significant in the presence of hydropsychids. Such interactive effects were not observed when algal responses were measured as biovolume and carbon fixation rate (GPP).3. It is recommended that algal responses to nutrient enrichment should be measured as biovolume or carbon fixation rate in small streams where hydropsychids are commonly present.