bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microhabitat selection by a stream‐dwelling amphipod: a muitivariate analysis approach
Authors: WILLIAMS D. DUDLEY , MOORE KATHRYN A. 
Published: May 2006

SUMMARY. 1. Colonization of microhabitat implants by the amphipod Gammarus pseudolimmnaeus in a small southern Ontario stream was studied in order to analyses the factors controlling habitat selection. The variables substrate particle size, current speed, presence of food and light were used in an analysis of covariance, with percentage weight of organic matter of silt and percentage interstitial space occluded by silt as the covariates.2. Greatest numbers of amphipods settled on microhabitats featuring large substrate particles, no current and presence of food. There was also a positive relationship between total numbers and the volume of silt deposited on the microhabitats by the stream; small quantities of silt had a beneficial effect on colonization but larger quantities became detrimental.3. The change from a positive effect occurred at approximately 25% occlusion of the interstitial space in large gravel (x̄ diameter=3.2 cm) and at approximately 55% occlusion in small gravel (x̄ diameter = 0.34 cm).4. Large animals (6–16.0 mm long) were found predominantly in microhabitats featuring food and large substrate. Medium‐sized animals (3–6.0 mm) were most commonly associated with no current and presence of food, and were positively affected by the amount of silt but, at the same time, were negatively affected by increasing occlusion of interstitial spaces by silt. Numbers of small Gammarus (<3.0 mm) were affected only by silt and in a similar manner to medium‐sized animals.5. Amphipod biomass was greatest in microhabitats featuring food and no current. Previous data on the behaviour of this species in laboratory stream‐tanks are compared with the microhabitat selections seen.
Effects of overhead canopy on macroinvertebrate production in a Utah stream
Authors: BEHMER DAVID J. , HAWKINS CHARLES P. 
Published: May 2006

SUMMARY. 1. Macroinvertebrate abundance and production were compared between an open and shaded site of a stream in the Wasatch Mountains, Utah. Mean biomass was significantly higher at the open site for midges (Chironomidae), 4.6×; Baetis bicaudatus, 5.7×; Baetis tricaudatus, 2.3×; Drunella coloradensis, 12× and Cinygmula sp., 1.6×, Abundance of most other macroinvertebrates (except black flies: Simuliidae) was also greater at the open site, but differences were not significant. Black fly biomass was 1.7× greater at the shaded site.2. Seasonal production, estimated by the size‐frequency and instantaneous growth rate methods, was greater at the open site than the shaded site for most taxa (except black flies) and reflected differences in standing crops between the sites rather than differences in rate of growth. Excluding black flies, production at the open site was twice as high as at the shaded site.3. The greater abundance and production of most invertebrate taxa at the open site is probably associated with either higher quality food (algae and algal detritus), or a phototactic attraction to sunlit areas.4. Sampling of large cobbles was an efficient method of sampling all taxa except Cinygmula sp. which was more abundant on smaller substrate particles.
Quantitative observations on the ability of epiphytic bacteria to contribute to the populations of suspended bacteria in two dissimilar headstreams
Authors: RIMES CARRIE A. , GOULDER R. 
Published: May 2006

SUMMARY. 1. Concentration of suspended bacteria in a calcareous headstream increased linearly from the source to 48 m; this indicated a diffuse origin of bacteria.2. Drift loss of suspended bacteria and glucose‐mineralization capacity from this length of stream were measured, and estimates were also made of the total number and glucose‐mineralization capacity of epiphytic bacteria associated with the luxuriant submerged aquatic vegetation.3. Mean drift loss per day represented 11–12% of total epiphytic bacteria and 8–18% of epiphyte glucose‐mineralization capacity, hence the epiphytic population should be well able to sustain the observed downstream losses.4. In a 90 m length of a contrasting acid, granitic, headstream, in which submerged vegetation was principally a leafy liverwort, there was no downstream change in concentration of suspended bacteria.5. A substantial population of epiphytic bacteria was found in the acid stream, sufficient for only a 1–2% daily release to produce a doubling in concentration of suspended bacteria; reasons are suggested for the apparent non‐release of epiphytes.
Population dynamics, life histories and species richness in an epiphytic chironomid community
Authors: TOKESHI MUTSUNORI 
Published: May 2006

SUMMARY. 1. The chironomid fauna on the spiked water‐milfoil Myriophyllum spicatum was studied quantitatively for a year in a small lowland stream in eastern England.2. A total of nineteen species, comprising fourteen Orthocladiinae, four Chironominae and one Tanypodinae, was recorded. Population dynamics and life histories of the eight most abundant species were described: Orthocladius (O.) Pe 9, O. (O.) sp. A, Cricotopus (C.) annulator, Rheocricotopus chalybeatus, Tvetenia calvescens, Eukiefferiella ilkleyensis, Thienemanniella majuscula and Rheotanytarsus curtistylus. The number of generations per year ranged from one (O. (O.) Pe 9, O. (O.) sp. A, C, (C.) annulator) to five (T. calvescens, T. majuscula). Temporal variation in population density often reflected characteristic patterns of the life cycle of each species.3. Species richness (number of species) for each month ranged between six and fifteen. These observed species richnesses were compared with a null species occurrence model and it was revealed that a significantly higher number of species than expected coexisted in April and May. This may be related to the abundance of diatoms in spring.
Population dynamics of the gastropod Theodoxus jordani (Sowerby) in the Shatt Al‐Arab river
Authors: AL‐DABBAGH KHALID Y. , LUKA JAMAL Y. 
Published: May 2006

SUMMARY. 1. Measurements of the population density of Theodoxus jordani were made for the period July 1980 until June 1981. Numbers showed a well‐defined pattern of fluctuation and varied between 390 in February and 1804 snails m−2 in May after recruitment.2. The population age structure revealed that the snail was semelparous, and that one generation dominated the population for most of the year.3. The breeding season was long. Snails laid eggs from early December to the end of April. Eggs were laid in protective capsules and one snail developed per capsule. Total population natality estimated from field samples was 9813 snails m−2.4. Age specific mortality was high immediately after recruitment, low during the juvenile stages, and increased sharply at the adult stage with the onset of reproduction.
The effects of temperature and photoperiod on life history parameters of Daphnia magna (Crustacea: Cladocera)
Authors: KORPELAINEN HELENA 
Published: May 2006

SUMMARY. 1. The life history responses of two common and three rare Daphnia magna clones to constant conditions of temperature and photoperiod were investigated, and intraspecific variation in the genes controlling growth, survivorship and reproduction was observed.2. Rearing temperature had a significant effect on growth, survivorship and on all reproductive parameters measured (generation time, intrinsic rate of increase and male production), while photoperiod influenced significantly only survivorship and male production.3. The maximum proportion of male offspring was produced at a low temperature (14°C) and at a mid‐range photoperiod (L:D16:8).4. The likely mechanism whereby clones with different life histories are maintained in the population is discussed.
Spatial and temporal variation in the macroinvertebrate fauna of streams of the northern jarrah forest, Western Australia: functional organization
Authors: BUNN STUART E. 
Published: May 2006

SUMMARY. 1. Spatial and temporal changes in functional organization of the invertebrate community of streams of the northern jarrah forest, Western Australia, were examined in the light of predictions of the river continuum concept (Vannote et al., 1980).2. The composition of the fauna was largely as predicted for forested headwater streams with detritivores, principally collectors, dominating the fauna. Although shredders are generally considered to be codominant in such streams, they were not abundant in the riffle areas sampled in this study.3. Some of the observed temporal changes in the composition of functional feeding groups were in agreement with those predicted by the generalized model. The abundance and richness of collectors were higher during the summer than winter, whereas the converse was true for filterers. This corresponded to the presumed availability of deposit and suspended fine‐particulate organic matter during summer and winter respectively. Scrapers and predators showed no consistent temporal pattern among sites. However, the density of the latter was highly correlated with the density of other invertebrates, particularly collectors.4. Temporal changes in the abundance and richness of shredders were not synchronized with the marked summer input of coarseparticulate organic matter. The possible reasons for this, and the role of shredders in Australian stream systems, are discussed.
Ammonium and phosphate regenerationby the zooplankton of an Amazon floodplain lake
Authors: LENZ PETRA H. , MELACK JOHN M. , ROBERTSON BARBARA , HARDY ELSA A. 
Published: May 2006

SUMMARY. 1. Regeneration of ammonium and phosphate by macro‐zooplankton (Cladocera. adult copepods. and copepodites) was measured in Lake Calado. an Amazon floodplain lake, Macrozooplanktonabundances ranged between 1×104 and 3×105 individuals m−2.2. Phosphate regeneration ranged from 0.2 to 1.3μ mol PO4 m−2 b−1at station 1. located 2 km from the Solimoes River, and from 1.6 to8.3 μ mol PO4 m−2 h −1 at station 3, located 7 km from the SolimoesRiver. Ammonium regeneration at stations 1 and 3 ranged from 1.7 to11.9 and from 13.4 to 77.2 μ mol NH4 m−2 h−1. respectively.3. Zooplankton regenerated ammonium and phosphate at similarrates during rising and falling waier. Regeneration by macrozooplankton was low compared to other tropical lakes and compared to microbesand microzooplankton in Lake Calado.
Egg development of the stoneflies Siphonoperla burmeisteri(Chloroperlidae) and Dinocras cepùnalotes(Perlidae)
Authors: LILLEHAMMER ALBERT 
Published: May 2006

SUMMARY. 1. The duration of egg incubation (Y) in Dinocras cephalotes and Siphonoperla burmeisteri was related to constant temperatures from 4 to 24°C, by the regression equations Y=2382 T −1, 402(r2=0.992, P<0.001) and y= 2683 T−1.667 (r2=0.994, P<0.001), respectively. No diapause was observed in either species.2. Egg incubation in D. cephaloles was slow and took 784.9±92.7 (mean ± SD) degree days between 12 and 20°C. significantly more than in S. burmeisteri(445±76.17 degree days: t= 7.44. d.f.=13,P<0.001).3. For D. cephalotes hatching occurred at temperatures between 12 and 24°C, and for S. burmeisteri between 8 and 20°C. The mean volume of the eggs of D. cephalotes was about 5 times greater than that of S. burmeisteri and the mean body lengths of the newly‐hatched nymphs were 1.13 mm and 0.95 mm respectively.4. This study shows that the freshwater fauna of northern Fennoscan‐ dia also contains species with warm stenotherm eggs. D. cephalotes. which is of a Mediterranean origin (Zwick, 1981a), may exist at the limit of its distribution in northern Fennoscandia.
Unsuitability of introduced tiles for sampling blackfly larvae (Diptera: Simuliidae)*
Authors: MORIN ANTOINE 
Published: May 2006

SUMMARY. 1. Blackfly larvae were collected from twenty‐one stations in five lake outlets in Southern Quebec. Tiles (total area=500cm2) were introduced in early March, and collected 4 weeks later: randomly selected rocks (30–500cm) from the surrounding area were collected at the same time.2. Larval densities on tiles were significantly less variable than on rocks. The variance of density estimates on tiles averaged 36% of the observed variance on natural rocks, or 67% when variance on rocks was corrected for average rock size.3. Tiles significantly overestimated densities on rocks in some streams, and significantly underestimated them in others. These differences could not be explained by microhabitat differences (distance from the lake, depth, current velocity) between rock and tile samples. The bias that tiles introduce in density estimates precludes their use in comparisons among sites.
Zooplankton grazing on [methyl‐3H]thymidine‐labeIled natural particle assemblages: determination of filtering rates and food selectivity
Authors: BERN LARS 
Published: May 2006

SUMMARY. 1. The grazing of [methyl‐3H]thymidine‐labelled bacteria by zooplankton was studied in Lake Norrviken. Sweden.2. Animals did not ingest bacteria attached to large colonies of the cyanobacterium Microcystis wesenbergii Kom. but small aggregates of hacteria and free bacteria were readily consumed.3. Diaphanosoma brachyurum (Liévin). Daphnia cucullata Sars. and Daphnia galeata Sars grazed free bacteria more quickly than aggregates, but Endiaptomus gracilis (Sars), Chydorus sphaericus Müll. and Bosmi‐ na coregoni s.l. Baird grazed the aggregates more readily.4. Filtering rate determinations varied from LA to 123 μl ind. −1h − 1for various species.
Factors affecting the microdistribution of Gammarus pulex (Amphipoda): an experimental study
Authors: ADAMS JONATHAN , GEE JOHN , GREENWOOD PAUL , McKELVEY SIMON , PERRY RICHARD 
Published: May 2006

SUMMARY. 1. The tnierodistribution of Gammarus species is size assortative: larger animals are associated with larger substrate particles. Using an artificial stream with scrubbed substrate we investigate the hypothesis that the assortative mechanism is stimulated by current avoidance rather than food searching.2. In uniformly mixed substrate, G. pulex tend to move upstream, but in patchy substrate they are found in a predictable substrate grade. There is no discrimination between patches by different size classes of G. pulex in static water. The size assortative field pattern can only be reproduced under flow conditions in the laboratory. It occurs in the absence of food and irrespective of the sequence or location of substrate patches.3. As density increases, G. pulex are displaced from the optimal patches but move into the open stream rather than into the cover of alternative patch types.4. We discuss the significance of these results and suggest that some earlier models explaining mechanisms for microdistribution patterns tnay have been unnecessarily complex. Contrasts between natural and simulated stream situations and their experimental advantages are noted.
Importance of dissolved organic matter produced by duckweed (Lemna minor) in a southern English river
Authors: BAKER J. H. , FARR I. S. 
Published: May 2006

SUMMARY. 1. The quantity of dissolved organic carbon (DOC) released by axenic Lemna minor cultures in the laboratory has been determined by an absolute method and by 14C labelling.2. Good agreement was obtained between the two methods and from 1.1% to 2.6% of the total carbon fixed was released.3. The DOC produced by L. minor has been analysed by ultrafiltra‐ tion and compared with a similar analysis of DOC in natural river water.4. The results of ullrafiltration analyses indicate that the proportion of low molecular weight (<1000 Daltons) material in DOM produced by axenic L. minor is significantly greater than is found in its natural habitat.
Field experiments on the relationship between drift and henthic densities of aquatic insects in tropical streams (Ivory Coast). III Trichoptera
Authors: STATZNER BERNHARD , ELOUARD JEAN‐MARC , DEJOUX CLAUDE 
Published: May 2006

SUMMARY. 1. Based on in situ gutter trials we related the drift of caddis flies to their benthic densities and to various abiotic factors in streams in the Ivory Coast (West Africa). Members of the families Hydropsychidae, Philopotamidae. Hydroptilidae and Leptoceridae were considered in detail.2. The drift of larvae peaked at night in both early and late larval instars.3. Drift of a larval group (a certain instar, species or higher taxon) was more often related to the benthic density of other larval groups than to its own benthic density.4. Self‐regulation of an upper benthic density of a larval group by emigration through drift was not statistically evident.5. There was no straightforward relationship between drift and abiotic factors.6. Drift rates differed between taxa as well as between larval instars (size groups) within a taxon. Newly hatched larvae had very high drift rates, whereas the last larval instar usually had the lowest drift rate.7. We related these results to the violently fluctuating discharge of the streams in the study area and the consequent variability of space for lotic insects.8. Drift estimates, made at the same time as a monitoring programme on possible side‐effects of insecticides (Onchocerciasis Control Programme), failed to reflect benthic densities except in the night drift of Hydropsychidae.
An inexpensive water circulation system for studies of chemical exchange using intact sediment cores
Authors: FOWLER B. , DRAKE J. , HEMENWAY D. , HEANEY S. I. 
Published: May 2006

SUMMARY. 1. An inexpensive pumping and reservoir system has been developed for circulating water over intact sediment cores. The system facilitates both measurement and manipulation of supernatant properties and flow velocities.2. The apparatus has been used to evaluate the effect of flow velocity and pH on nutrient exchange at the sediment‐water interface.
The influence of fish on leaf breakdown in a Virginia pond
Authors: TAYLOR FRANK , HENDRICKS ALBERT C. 
Published: May 2006

1. To find if fish affect leaf breakdown, sugar maple leaves (Acer sacchrum March) were placed in a soft‐water, farm pond at a depth of 1 m for up to 3 months in four treatment groups: (1) enclosure with sunfish (Lepomis macrochirus Rafinesque) (SUNFISH treatment); (2) enclosure with catfish (Ictalurus punctatus Rafinesque) (CATFISH treatment); (3) enclosure without fish (NO FISH treatment); and (4) no enclosure (OPEN treatment). The study was conducted in spring and autumn.2. The leaf breakdown rates, k±95% CL, for SUNFISH (0.0082± 0.00059 and 0.0111±0.00162 d−1) and CATFISH (0.0072±0.00096 and 0.0103±0.00077 d−1) were greater in spring and summer, respectively, than in the OPEN treatments (0.0065 ±0.00048 and 0.0105± 0.00141 d−1) and NO FISH (0.0067±0.00039 and 0.0088±0.00099 d−1). However, only k for SUNFISH was significantly different from NO FISH and OPEN treatments.3. Fish in the pond did not appear to affect breakdown rates of OPEN leaf packs in the first replicate but k approached that of the fish treatments in the second replicate.4. Fish may have promoted leaf breakdown directly by fragmentation of leaves while foraging for food and, indirectly, by agitation of leaves, leading to increased microbial activity.
Diet of the leeches Erpobdella octoculata (L) and Helobdella stagnalis (L) in a lotic habitat subject to organic pollution
Authors: BRADLEY M. D. K. , REYNOLDS J. D. 
Published: May 2006

SUMMARY 1. A study of the diet of E. octoculata (L) and H. stagnalis (L) using a serological technique was carried out in a lot ic habitat subject to organic pollution and seasonal sewage fungus growth.2. The results indicate that E. octoculata consumed predominantly Chironomidae and Oligochaeta, while H. stagttalis had a less pronounced prey preference, consuming rather similar proportions of chironomids, oligochaetes, Asellus and gastropod snails.3. At enriched sites, E. ocioculata consumed relatively more chironomids and fewer oligochaetes, while H. stagnalis took more gastropods and fewer chironomids.4. Seasonal differences were noted in the diet of both leeches with chironomids predominating chiefly from April to August, and molluscs, oligochaetes and Asellus at other times of the year. Intra‐specific differences (on a weight‐age basis) were only seen for E. octoculata, small forms consuming chiefly oligochaetes and larger ones concentrating on chironomids.
Vertical partitioning of the phytoplankton assemblage in ultraoligotrophic Crater Lake, Oregon, U.S.A.
Authors: LARSON D.W. , DAHM C. N. , GEIGER N. S. 
Published: May 2006

SUMMARY 1. The summertime phytoplankton assemblage in abysmally deep (Zmax: 589 m) Crater Lake, Oregon, consists of over 100 species, which are variously distributed in the upper 200 m of the vertical water column. The depth distribution of the lake's three most prevalent species follows a predictabk pattern: Nitzschia gracilis in the 0–20 m stratum, Tribonema sp. at mid–depth (80–20 m), and Stephanodiscus hantzschii in the lowermost stratum (160–200 m). These major species, which account for approximately 80% or more of the lake's total phytoplankton biomass and primary production, exist under atypical temperature, light, and nutrient conditions.2. The spatial distribution of phytoplankton in Crater Lake resembles a three‐tier structure. Unlike most lakes, where the entire phytoplankton communities exist in less disparate environmental conditions, or are vertically mixed periodically by storm events and seasonal lake turnover. the Crater Lake community is partitioned into stratified environments.5. The disparate and unusual characteristics of these environments, and the hydrological and limnological stability of the lake basin, are perhaps important factors regulating the diversity, dominance. and partitioning of the lake's phytoplankton populations.
Spatial distribution of Trichoptera larvae in the sediments of an Austrian mountain brook
Authors: WARINGER J. A. 
Published: May 2006

SUMMARY 1. A set of thirty‐six permanently installed standpipc traps was used over 2 years to sample caddis larvae at various depths in the gravel bed of an Austrian brook. From a total of 805 specimens caught, the most abundant species were Sericostoma sp. (Sericostomatidae), and the three limnephilids Potamophylax cingulatus Steph., Allgamus auricollisPictet and Allogamus uncatus Brauer.2. Sericostoma sp. and Ecclisopteryx guttulata Pictet were collected down to a seditnent depth of l m. In Sericostoma sp., a burrowing species, tiny larvae were found in sediments at 20–60 em, where most of the life cycle is spent; fully grown larvae were mostly collected at a depth of 0–20 em. All instars of Potamophylax cingulatus, Allogamus auricollis and Allogamus uncatus larvae were most abundant at the sediment surface.3. The horizontal distribution of the most abundant species was studied at the 20 cm depth stratum. Larvae were most abundant in midstream areas.4. Factors probably responsible for the observed spatial distribution pattern are briefly diseussed.