bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secondary production of Chironomidae (Diptera) in a north temperate stream
Authors: BERG MARTIN B. , HELLENTHAL RONALD A. 
Published: May 2006

SUMMARY 1. Secondary production of chironomids (Diptera: Chironomidae) in a third‐order northern Indiana stream was estimated using species‐specific, and in most cases cohort‐specific, life‐history data from the field.2. Chironomid life‐history patterns were diverse, ranging from one to four generations per year in addition to asynchronous development. Cohort production intervals (CPI) for all taxa ranged from 56 to 266 days. CPI for cohorts of conspecifics differed up to 3‐fold.3. Annual secondary production was estimated using the instantaneous growth method or the size—frequency method depending on whether cohorts were distinguishable or not. Total annual chironomid production was 29 700 mg dry mass m−2, which is the highest value reported for chironomids from a north temperate stream.4. Eighty per cent of the total chironomid production was attributed to five species: Diamesa nivoriunda (33.9%), Cricotopus bicinctus (16.6%), Pagastia sp. (10.2%), C. trifascia (9.7%) and Orthodadius obumbratus (9.6%).5. The annual P:B ratio ranged from 4.7 to 21.9. Thus, high secondary production was due to high mean annual standing stocks and not to rapid biomass turnover.
Phosphorus retention in streams draining pine and hardwood catchments in the southern Appalachian Mountains
Authors: D'ANGELO D.J. , WEBSTER J.R. 
Published: May 2006

SUMMARY.
1. This study was designed to determine how catchment use affects stream phosphorus retention by comparing retention in streams draining three mixed hardwood catchments and three catchments that were planted in white pine in the 1950s.2. Catchments of similar area and stream discharge were chosen and phosphorus uptake was measured monthly in each catchment along with temperature, discharge, velocity, coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM), and microbial respiration associated with FPOM.3. On an annual basis, average phosphorus retention was not different between streams draining pine and hardwood catchments nor were there significant differences between physical (temperature, velocity and discharge) or biological (CPOM, FPOM and respiration) parameters based on catchment type. However, discharge was more variable in streams draining pine catchments.4. Because phosphorus uptake was correlated with discharge, phosphorus retention was also more variable in streams draining pine catchments. Storms caused a greater increar.e in discharge and loss of phosphorus in pine streams than in mixed hardwood streams, but discharge returned to baseline more quickly in pine streams.5. We suggest that discharge regimes and phosphorus dynamics of streams draining pine catchments are less resistant to change but more resilient than streams draining mixed hardwood forests.
The influence of summer/winter conditions of temperature and irradiance on diel oscillations in photosynthesis by Fragilaria crotonensis
Authors: WALLEN D.G. 
Published: May 2006

SUMMARY.
1. The common pennate diatom (Bacillaryiophyta) Fragilaria crotonensis Kitton showed strong periodicity in its photosynthesis ‐irradiance (P—I) relationship under summer conditions of high irradiance and temperature which damped progressively throughout the growth phase. Under winter conditions of low irradiance and temperature, weak periodicity was observed.2. The amplitude of diel oscillations in photosynthesis as a function of irradiance under winter conditions showed only slight variation throughout the growth phase. Under summer conditions, however, amplitudes for both α and Pmax were highest in the early exponential phase, declining progressively during growth.3. These results indicate that the occurrence of periodicity is dependent, in part, on the growth phase of the cells and, in part, on environmental parameters of irradiance and temperature variations under simulated summer and winter conditions.
Differences in processing dynamics of fresh and dried leaf litter in a stream ecosystem
Authors: GESSNER MARK O. 
Published: May 2006

SUMMARY.
1. Although the bulk of litter input to stream ecosystems is in the form of fresh leaves, current understanding of organic matter processing is largely founded on experimental studies made with pre‐dried leaves. This paradox points to the critical need for evaluating to what extent those experiments with dried leaves reflect natural litter decomposition.2. The mass loss rates, patterns of mass loss, and chemical changes during processing of fresh leaf litter were compared with air‐dried leaf litter in a stream ecosystem.3. Although overall mass loss rates were similar between treatments (k= 0.0213 day−1 and 0.0206 day−1), fresh leaves lost mass at a constant rate, whereas the decay of dried leaves proceeded in two distinct phases. Soluble organic carbon, phosphorus, and potassium were rapidly leached from dried litter, but were largely retained in fresh material for more than a week. Kinetics of concentrations of cellulose and changes in amounts of lignin remaining per leaf pack revealed further differences in decomposition dynamics between treatments, apparently related, either directly or indirectly, to differences in leaching behaviour.4. Dynamics of nitrogen and protein contents were similar between treatments, indicating that microbial colonization was not greatly delayed on fresh leaves.5. It is concluded that the retention of labile carbon and nutrients in fresh leaf litter facilitates their utilization by leaf‐associated micro‐organisms and invertebrates, resulting in an increased importance of biotic processes relative to physical processes such as leaching.6. At the ecosystem level, retention of carbon and nutrients in streams would be increased, allowing greater overall productivity. Conversely, the availability of labile organic carbon would be reduced in compartments such as the epilithon, fine sediments, and the water column.
Asymmetric resource competition in a filter‐feeding stream insect (Hydropsyche siltalai; Trichoptera)
Authors: ENGLUND GÖRAN 
Published: May 2006

SUMMARY.
1. Field experiments in a lake outlet stream were carried out on filter‐feeding larvae of the caddisfly Hydropsyche siltalai Döhler, to assess whether microhabitat quality, establishment and growth rate is affected by position (upstream—downstream) within a dense aggregation of larvae.2. Artificial substrates holding high‐density aggregations of hydropsychid larvae were used. Marked III‐instar H. siltalai larvae were implanted either in the upstream end or in the downstream end of an aggregation and recovered after 17 days.3. Larvae recovered from the downstream end of an aggregation were smaller than those that had been implanted in the upstream end.4. Fewer larvae had settled in the downstream end of aggregations compared to the exposed upstream part.5. Naturally colonizing H. sitalai larvae were, in contrast to implanted larvae, more numerous behind aggregations. Small (first and second instar) Hydropsyche angustipennis (Curtis) and/or H. pellucidula (Curtis) larvae were more numerous in front of aggregations.6. Current velocities, measured with a microcurrent velocity meter, and density of drifting prey, were significantly lower behind aggregations of hydropsychid larvae. Food availability decreased by about 50% behind aggregations.
The effect of food on protein content in rotifer and cladoceran species
Authors: GUISANDE C. , TOJA J. , MAZUELOS N. 
Published: May 2006

SUMMARY.
1. The protein content of individuals of four species of cladoceran and two species of rotifer in eight ponds was measured over several time periods. The protein content in coarsely filtered water, which includes particulate (less than 31 μm for cladoceran and less than 10μm for rotifers) and dissolved proteins, was also analysed to estimate the amount of food available to the animals.2. A positive relationship between protein content of individuals and protein in the food was found for all the species. The increase in protein content of the animals was less pronounced when food was more abundant.3. When food concentration was lower, a greater reduction in protein content was observed in two species of rotifers than in four cladoceran species. Moreover, when comparing among species of Cladocera, the reduction in protein content at low food concentrations was more marked in the small‐bodied than in the large‐bodied species. These results are consistent with the size‐efficiency hypothesis.
Life history, growth and production of Mysis relicta in the large, fiord‐type Lake Mjøsa, Norway
Authors: KJELLBERG GØSTA , HESSEN DAG O. , NILSSEN JENS PETTER 
Published: May 2006

SUMMARY.
Biomass, production and life history of Mysis relicta were studied in the large Lake Mjøsa during the years 1976–80. Biomass fluctuations were large, but biomass averaged about 1 g wet wt m−2 or 200 ind. m−2. Cumulative net production during summer ranged from 1.6 to 2.1 g wet wt m−2. Mean population P/B‐ratio was close to 2.
Neither production or biomass of Mysis were correlated with the biomass of phytoplankton or the main Zooplankton prey species (Daphnia and Bosmina), suggesting a predominant ‘top down’ control of Mysis in this lake.
The life cycle was well synchronized with development of food items, but predation pressure also affected life‐history patterns. The proportion of juveniles apparently increased in years with strong fish predation pressure, producing a predominantly 1‐year life‐cycle pattern the following year.
Mysis had a predominant 2‐year life history, but a traction of the population may reproduce after 1 or 3 years. Reproduction occurred exclusively during winter. Even in such a large and stable system, where Mysis has coexisted with its main food items and predators for 8–10 000 years, a flexible life history is maintained and is probably an important buffer against year‐to‐year fluctuations in food and predator abundance.
Dynamics of surface water/groundwater ecotones in a karstic aquifer
Authors: VERVIER Ph. , GIBERT J. 
Published: May 2006

SUMMARY.Interactions between surface waters and groundwaters were analysed by studying degrees of similarity between a surface stream and groundwater in a karstic system.Exchange of water and solutes (‘abiotic interactions’) and living organisms (‘biotic interactions’) were quantified by characteristic parameters measured at the outlet of the karstic system during hydrological changes across the year as well as during a flood.The ratio of bicarbonate to calcium described abiotic interactions. In the seasonal study, biotic interactions were estimated from the proportion of epigean organisms in the communities sampled at the outlet. These interactions during the flood were estimated by comparing numbers of Cladocera, epigean organisms, with numbers ofNiphargus virei, hypogean organisms.The location of the ecotone created by interactions between the surface stream and the karstic system showed marked spatial fluctuations according to the prevailing hydrology. Interactions were strong during high‐water periods whereas they were negligible during low‐water. Similar fluctuations occurred within a few hours during the flood.Results are compared with those from fluvial systems to discuss the importance of the dynamics of these surface/underground ecotones in the functioning of lotie ecosystems.
Life history and production of the predatory caddisfly Rhyacophila vao Milne in a spring‐fed stream
Authors: DIXON R.W. JAMIESON , WRONA FREDERICK J. 
Published: May 2006

SUMMARY1. The predatory caddisfly Rhyacophila vao Milne (Rhyacophilidae) displayed a 2‐year, semivoltine life cycle in a small, spring‐fed stream in southern Alberta, Canada. Three overlapping cohorts were identified throughout the 2‐year sampling program, with five larval instars recognized. Larvae overwintered in instars I —ELI, developed to instar IV by summer and instar V by autumn. The second winter was spent in instar V, Pupation occurred from late May to August and did not commence until stream temperature exceeded 3°C. Adults were collected from mid‐June to early September.2. Larvae displayed a diphasic growth pattern: Phase I, a positive, non‐linear growth rate for instars I‐IV; Phase II, a constant growth rate during instar V. Phase I coincided with increasing stream temperatures in late winter and spring, where mean instantaneous growth rates (maximum of 2.78% dry wt day−1) were significantly correlated with stream temperatures. Although the duration of Phase II spanned a temperature range similar to that in Phase I, the instantaneous growth rate remained temperature‐independent at 0.87% dry wt day−1.3. Larvae exhibited a type III survivorship curve (i.e. an exponential decrease on an arithmetic scale), with the finite rate of mortality averaging 0.80% larvae day−1.4. Cohort 1 (later part of 1983 year class) displayed lower total production compared with the equivalent growth phase in the 1984 year class (Cohort 2). In contrast, production of the non‐linear and linear growth phases of Cohort 2 was similar. Periods of similar growth characteristics for Cohorts 1 and 2 had comparable P/B ratios for both the unadjusted and time‐adjusted annual estimates, although higher ratios were observed for the non‐linear growth phase of Cohort 2. Total cohort production (linear + non‐linear growth phases) could only be calculated for Cohort 2, and was 870.2 ± 1011.4 mg dry wt m−2. The corresponding cohort P/B ratio was 5.01 and the adjusted annual P/B, 3.01.5. Annual larval production (±SE) for the first and second years of the study was similar (Year 1, 480.0 ± 387.5mg dry wt m−2; Year 2, 526.9 ± 967.5mg dry wt m−2) as were unadjusted and annual P/B ratios.
Development and composition of the epixylic biofilm in a blackwater river
Authors: COUCH CAROL A. , MEYER JUDY L. 
Published: May 2006

SUMMARY1. Comparisons of chlorophyll a, bacterial density, frequencies of dividing cells, ash‐free dry mass (AFDM) and extracellular polysaccharide content were made for biofilm developing on wood (Salix) submerged in replicated stream‐side flumes exposed to either ambient light (light treatment) or covered to exclude light (dark treatment). Biofilm was sampled on days 3, 6, 9 and 14 during experimental periods occurring irrMay, September, November and December.2. There were no significant differences in bacterial cell densities, frequencies of dividing cells, AFDM or extracellular poiysaccharide content between light and dark treatments. Ash content and bacterial biomass was similar to seston, suggesting the importance of seston as a source of material accumulating in the biofilm.3. Of total epixylic organic carbon 7.2% was estimated to be extracellular polysaccharide, and 0.8% was bacterial carbon. At least nine times more carbon was contained in extracellular polysaccharide than in bacterial biomass.4. In the epixylon of the Ogeechee River, bacterial dynamics appear to be controlled by factors other than the availability of algal substrates.
Seasonal migration by larvae of an epiphytic chironomid
Authors: KORNIJÓW RYSZARD 
Published: May 2006

SUMMARY1. A clear seasonal alternation of Endochiranomus albipennis larvae between submerged plants and the bottom sediment was observed in the littoral of a deep mesotrophic and a shallow eutrophic lake. The analysis of change in larval density and of occurrence of pupae suggests that larvae migrated from plants to the bottom sediment in early autumn and back to the plants, where they pupate, in spring.2. Up to 95% of the third and fourth instar larvae overwintered in the bottom sediment in special cocoons. Larvae staying in the sediment without cocoons were also dormant. The timing of cocoon formation was different in the two lakes.3. Migration may have a significant influence on the seasonal changes in dominance structure and density of epiphytic and benthic faunas.
The ecology of two intermittent streams in Victoria, Australia
Authors: BOULTON A.J. , LAKE P.S. 
Published: May 2006

SUMMARY1. We compared aquatic macroinvertebrate assemblage composition within and between habitats (pools and riffles) at four sites on two intermittent streams in Victoria, Australia during a drought year followed by a wetter year to see how different spatial and temporal scales influenced patterns of community structure detected by multivariate techniques of ordination and classification. We also examined the fit between faunal groups and ‘flow phases’ characterized by multivariate analyses of physicochemical variables in an earlier paper.2. Pools contained more taxa and individuals than riffles. At the more temporary site, there was considerable overlap between the faunal composition of pools and riffles, whereas habitat‐specific assemblages consistently occurred at the more permanent sites. Most taxa were either tolerant, permanent stream forms able to persist in streams that dry briefly, or facultative species that occur in lotic or lentic habitats. Few species appeared specifically adapted to temporary waters.3. Within habitats, there were some matches between faunal groups and flow phases, especially with the onset of the ‘diminishing flow’ phase, characterized by rising water temperature and conductivity, and declining pH and dissolved oxygen. However, disjunctions among faunal groups were less marked than those between flow phases, and were absent at an intermediate scale when habitats were pooled within sites. At the broadest scale of analysis (within habitats between sites and years), historical events (e.g. whether pools upstream dried completely during the previous summer) apparently influenced community composition as much as site‐specific abiotic differences.
The ecology of two intermittent streams in Victoria, Australia
Authors: BOULTON A.J. , LAKE P.S. 
Published: May 2006

SUMMARY1. Temporal changes in species richness, total abundance, and numbers of individuals in seven functional feeding groups were compared between pools and riffles at four sites on two intermittent streams in Victoria sampled during a drought year followed by a wetter year.2. Species richness increased steadily over time, peaking in the riffles just before flow ceased. Maximum species richness occurred in the pools shortly after flow stopped, implying emigration from the drying riffles. There were two peaks in total numbers, first in autumn when flow commenced and again in late summer as flow diminished. Generalist feeders (collector‐gatherers and collector‐scrapers) were usually abundant throughout the year. Scraper densities rose in late spring‐early summer in conjunction with enhanced periphyton growth, whereas predator numbers steadily increased during the year, peaking in all habitats just before they dried.3. Several floods in spring significantly reduced species richness and total numbers of individuals but recovery to pre‐flood levels was generally complete within 2 weeks. Although floods had little effect upon succession, as indicated by trajectories in ordination space, the dry period interrupted otherwise cyclical sequences, consistently resulting in arch‐shaped trajectories. Faunal change appeared to be allogenic, driven by the seasonal cycle of environmental phases.4. A group of early colonists or ‘pioneer’ species was replaced after several weeks by heterogeneous groups of ‘mid‐successional’ taxa responsible for differences in faunal composition between riffles and pools. When flow diminished, these groups were replaced by ‘summer’ species, apparently capable of tolerating deteriorating environmental conditions, and potentially intensifying biotic interactions.5. We suggest that the cyclical temporal changes in assemblage composition observed in this study represent ‘seasonal periodicity’, whereas recovery after unpredictable disturbances such as floods that temporarily disrupt the cycle fits the definition of ‘succession’. Succession rate is a measure of resilience, recovering to the cyclical trajectory that would exist in the absence of disturbance. ‘Lag effects’ brought about by reduced recruitment during the drought were not evident until the following year, emphasizing the significance of historical events and the need for long‐term studies to describe the ecology of intermittent streams adequately.
Community structure of larval Chironomidae (Diptera) in a backwater area of the River Danube
Authors: SCHMID P.E. 
Published: May 2006

SUMMARY1. The larval chironomid community was studied quantitatively in three cross‐sections of an impounded area of the River Danube between July 1985 and July 1986.2. Sixty‐six species were identified, most of which belonged to the subfamily Orthocladiinae, but species of the tribe Chironomini were numerically dominant.3. The sections differed distinctly in terms of species number and diversity; a tendency towards increasing species richness and diversity was observed in the upstream sections of the impoundment. Marked fluctuations in these two parameters characterized the area close to the dam; the temporal oscillations in diversity values differed significantly between the sections (ANOVA: P<0.05).4. Clear differences were found between sampling sites in terms of community resilience, the minimum eigenvalue of the community matrix defined as the rate of return of a disturbed system. Longer return times after ‘disturbances’ could be expected at sites further upstream from the dam.5. Temporal persistence of species composition was estimated for each section with Kendal's correlation coefficient from 1985 to 1986. Sites further upstream of the dam illustrated a significantly greater temporal species persistence over time and a smaller degree of fluctuation, compared to the dam area (ANOVA: P<0.05). A significant negative relationship was found between overall persistence and cumulative monthly water discharge, at the dam site (P<0.01).6. Classification of the larval chironomid community gave evidence of generally low spatio‐temporal overlap between species in the impoundment area.
Food, microhabitat, or both? Macroinvertebrate use of leaf accumulations in a montane stream
Authors: RICHARDSON J.S. 
Published: May 2006

SUMMARY1. Leaf packs in streams may serve as food and substrate to many macroinvertebrates, but the relative importance of these two functions has not been disentangled. To test the hypothesis that leaf packs are colonized primarily for their food value rather than as microhabitat, the colonization of leaf packs of red alder and of polyester cloth in a natural stream was compared.2. Species of shredders showed large differences in the colonization of the two types of leaf pack with almost no use of artificial leaf packs. Non‐shredders were also more abundant on natural leaf packs, however, they colonized artificial leaf packs six to eighty times proportionally more than shredders.3. The effect of different leaf types was virtually eliminated for non‐shredders when the amount of fine parriculate detritus (food for many non‐shredders) trapped in the leaf pack was added to the analysis as a covariate. Therefore, to non‐shredders, leaf types differed only in the retention of fine particulate organic matter.4. Comparisons of the use of both kinds of leaf packs in riffles versus pools revealed that significantly fewer animals colonized pool leaf packs.5. These results suggest that food value, and not microhabitat, is the primary determinant of leaf pack use for most shredders and non‐shredders.