bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on Chironomidae in experimental recirculating stream systems. II. The growth, development and production of a spring generation of Orthocladius (Euorthodadius) calvus Pinder
Authors: LADLE M. , COOLING D. A. , WELTON J. S. , BASS J. A. B. 
Published: May 2006

SUMMARY.

Orthodadius (Euorthodadius) calvus Pinder. similar to Orthocladius (Euorthodadius) thienemanni Kieffer. colonized a new gravel substratum in two recirculating stream channels. A maximum population density of 68.621 m‐2 was attained after only 16 days. This had fallen to a negligible density by the thirty‐third day.
Some recruitment occurred over most of the study period (April‐May 1981) and no single sharply defined cohort was evident. There was a large range of body lengths within each instar. and considerable overlap between instars. The population density estimates for instars I and II were low compared with instars III and IV.
The relationship between instantaneous growth rate (g) and geometric mean length indicated that growth was best described by a Gompertz curve. Growth rate decreased with increasing length from a value of about 40% length day‐1 at 2 mm body length to about 5% length day‐1 at 9 mm.
Growth rates for individual larvae, kept in culture, were very variable with maximum rates close to the values determined from the field data. Mean duration of larval life was 16 days.
Estimates of production for the study period ranged from 13.5 g dry wt m‐2 (Channel III, size‐frequency method) to 34.2 g dry wt m‐2 (Channel II, Allen's graphical method, values corrected for non‐linear growth).
Gut contents were estimated to represent about 55% of the total weight therefore production values should be reduced by this amount.
Cycling and retention of nitrogen and phosphorus in wetlands: a theoretical and applied perspective
Authors: HOWARD‐WILLIAMS CLIVE 
Published: May 2006

SUMMARY.This review considers the internal fluxes and transformations of nitrogen and phosphorus in wetland ecosystems. Emphasis is placed on the dynamic nature of nutrient cycling and the review is slanted towards an applied perspective, namely the possible use of wetlands as sinks for unwanted nutrients.A number of basic concepts pertaining to wetland ecosystems are first explained. These are: successional time scales, exchange equilibria and the concepts of storage and through flow, resource consumption and supply including the ideas of new and regenerated nutrients and the nutrient spiralling concept. Much of the following review material is referenced back to these concepts.Descriptions of the basic pathways of nutrients through different types of wetland systems are given with the emphasis placed on the movement into and out of the major storage compartments of wetland systems.The problems of conversion of qualitative information (or data in concentration units) on nutrient movements and transformations, into data on mass flows are then discussed. The importance of understanding groundwater, evapotranspiration processes and the effects of floods and seasonality on mass flow calculations can be significant. Unidentified groundwater sources can dilute nutrient concentrations, and evapotranspiration can increase concentrations. The pattern of through flow can also alter nutrient levels. Increasing residence time has the effect of decreasing nutrients in the wetland outflow.The review then considers the effects of adding nutrients to wetlands. The concept of the loading capacity is discussed in relation to the length of time a wetland can continue to remove nutrients from through flow. Sediment accumulation and degassing are seen as the major long‐term nutrient sinks. Nutrient enrichment results in biological changes to wetlands. These involve both changes in species composition and productivity. Not all are deleterious.The literature indicates that natural wetlands are not particularly effective as nutrient sinks when compared with conventional stripping plants but their value lies in removal of diffuse nutrient runoff at low concentrations. Dealing with this type of runoff by conventional means is not generally feasible.Recent studies show that artificially created wetlands can he effective systems for nutrient (particularly N) removal only if their internal removed mechanisms are understood and if these are optimized by management techniques.
Limnological investigations on the Rosetta branch of the Nile. III. Phytoplankton
Authors: SAAD MASSOUD A. H. , ABBAS MAHDI H. 
Published: May 2006

SUMMARY.

Seasonal qualitative and quantitative studies of the phytoplankton of the Rosetta branch of the River Nile are reported. Most of the genera were Bacillariophyceae, with Chlorophyceae and Cyanophyceae second and third. Only two genera of Dinophyceae were present. The phytoplankton can be broadly described as eurythermal and euryhaline.
Phytoplankton tended to be more concentrated in surface waters and showed large variations from station to station, with noticeably lower values in the estuarine region except in January.
Most of the genera were recorded at all times but seasonally the highest numbers of diatoms and green algae were found in July during a period of high temperature and low discharge whereas blue‐greens achieved maximum density in October.
Microhabitat selection and life cycle patterns of two Rhyacophila species (Trichoptera: Rhyacophilidae) in southern Ontario streams
Authors: MARTIN IAN D. 
Published: May 2006

SUMMARY.

Two species of predatory caddisfly larvae—Rhyacophila fuscula (Walker) and R. melita Ross—have overlapping longitudinal distributions in southern Ontario streams.
The populations were studied at sites in areas of overlap (sympatry) and allopatry to determine what resources were partitioned, and if partitioning varied in the zones of overlap.
Life cycle and species size variation resulted in substantial physical differences between these univoltine species for most months of the year.
In May, when larvae of both species were not significantly different in size, a detailed microhabitat field study found no difference in microhabitat use between allopatric populations of R. fuscula and R. melita. Microhabitat selection by R. fuscula remained constant at sympatric sites but R. melita showed a significant change resulting in reduced microhabitat overlap with R. fuscula.
Nitrate cycling in Lake Titicaca (Peru‐Bolivia): the effects of high‐altitude and tropicality
Authors: VINCENT W. F. , VINCENT C. L. , DOWNES M. T. , RICHERSON P. J. 
Published: May 2006

SUMMARY.

The vertical distribution of dissolved oxygen and inorganic nitrogen differed considerably between three stratification cycles in Lake Titicaca, a tropical lake (latitude 16°S) in the high Andes (3800 m altitude). In 1980/81 an anoxic layer of water extended from 200 to 275 m and contained high levels of NH4 but zero NO3. During the annual deep mixing period in 1981 this layer was substantially eroded, and was completely eliminated during deep‐mixing in 1982.
Nitrapyrin assays of nitrification demonstrated highest activity in the surface mixed layer, lowest activity just beneath the thermocline, and then increasing nitrification rates with increasing depth towards the bottom anoxic zone. Denitrification rates were slow, but detectable, in the surficial sediments of Lake Titicaca during late 1982. Much faster rates were estimated for the periods of water column anoxia.
Lake Titicaca is a productive lake with low saturation levels of oxygen because of its high altitude. These features favour hypolimnetic anoxia, and thus denitrification which varies in magnitude from year to year.
Zooplankton dynamics in Lake Mendota: short‐term versus long‐term changes
Authors: PEDROS‐ALIO CARLOS , BROCK THOMAS D. 
Published: May 2006

SUMMARY.

A study of zooplankton dynamics was carried out in Lake Mendota, Wisconsin, for the years 1976–80. The data were compared with those of E. A. Birge, obtained in the years 1894–96.
The zooplankton annual cycles and sizes of standing crop were similar in both studies. There was more year‐to‐year variation within each study than there was between the two studies separated by over 80 years.
The data are discussed in relation to the prediction of long‐term change in lakes. The value of a historical data set for long‐term ecological studies is emphasized.
Seasonal variation in the abundance and heterotrophic activity of suspended bacteria in two lowland rivers
Authors: GOULDER R. 
Published: May 2006

SUMMARY. 1. Water samples were collected over two years from the Yorkshire Ouse and Yorkshire Derwent and the following were measured: (i) concentration of directly‐counted bacteria (free‐living and particle‐bound), (ii) concentration of colony‐forming units, (iii) bacterial heterotrophic activity (turnover rate for glucose assimilation), (iv) specific activity (turnover rate per bacterium), (v) a range of environmental variables.2. The abundance and activity of suspended bacteria showed similar seasonal periodicities in both rivers.3. Free‐living bacteria were usually more numerous than particle‐bound bacteria; low concentration of free‐living bacteria and maxima of particle‐bound bacteria usually occurred in winter.4. Concentration of colony‐forming units varied irregularly, but lowest levels were found in summer.5. Turnover rate and turnover rate per bacterium showed distinct summer maxima.6. Multiple‐regression analysis was used to relate bacterial variables to subsets (chosen by factor analysis) of environmental variables; up to 89% of variation in bacterial variables was related to the combined effects of variation by variables in the chosen subsets.
The relative importance of temperature and diet to larval development and adult size of the winter stonefly, Soyedina carolinensis (Piecoptera: Nemouridae)
Authors: SWEENEY BERNARD W. , VANNOTE ROBIN L. , DODDS PETER J. 
Published: May 2006

SUMMARY. 1. Soyedina carolinensis Claassen, a leaf shredding stonefly, was reared in a series of three laboratory experiments from early instar to adult on different species of deciduous leaves and at various constant and fluctuating temperature regimes.2. Experiment 1, which involved rearing larvae on fourteen different leaf diets at ambient stream temperatures, showed that diet significantly affected larval growth and adult size but did not affect overall developmental time.3. Experiment 2, which involved rearing larvae on five different leaf diets at each of three fluctuating temperature regimes (viz ambient White Clay Creek (WCC), ambient WCC+3°C, and ambient WCC+6°C), showed that: (i) adding 6°C to the normal temperature regime of WCC was lethal to 99% of the larvae regardless of diet; and (ii) warming WCC by 3°C did not affect developmental time but did significantly reduce adult size relative to adults reared at WCC temperatures on certain diets.4. Experiment 3, which involved rearing larvae on five different leaf diets at each of five constant temperatures (viz 5, 10, 15, 20, 25°C), showed that: (i) temperature significantly affected the mortality, growth, and development time of larvae whereas diet only affected larval growth and mortality; (ii) temperatures at or near 10°C yielded maximum larval growth and survival for most diets; (iii) at 5°C, larval mortality was high and growth was low resulting in a few small adults for most diets; (iv) larval mortality was at or near 100% at 15°C regardless of diet; and (v) no larvae survived at 20 and 25°C.
Spatial and temporal variation in the macroinvertebrate fauna of streams of the northern jarrah forest, Western Australia: community structure
Authors: BUNN S. E. , EDWARD D. H. , LONERAGAN N. R. 
Published: May 2006

SUMMARY. 1. Streams of the northern jarrah forest, Western Australia, were sampled at twelve sites from December 1981 to December 1982 to examine spatial and temporal changes in the structure of the macroinvertebrate community.2. The climate of this region is quite predictable by Australian standards and each year a hot, dry summer is followed by a mild, wet winter. Highest stream discharge occurs during winter (June‐November) reducing to negligible flow over late summer and autumn (January‐May). The low flows in summer were associated with warm water, lower dissolved oxygen, increased concentrations of cations and, in many cases, lower pH.3. Temporal changes in abundance, diversity and evenness indicated that the invertebrate fauna became dominated by a few taxa during the summer months. Major spatial and temporal changes in the composition of the fauna were detected by classification and ordination. Summer and winter faunas were identified at most sites and were clearly associated with the seasonal changes in the physical and chemical environment. This seasonality is not typical of stream systems previously studied in Australia. Large spatial differences also occurred over small distances among sites in two similar‐sized forested catchments.4. Multiple discriminant analysis and stepwise multiple regression analysis showed that velocity and depth were highly associated with the observed temporal changes in the fauna, though other variables, including concentrations of cations and water temperature, were also important. Spatial differences were correlated with concentrations of cations which may simply reflect differences in the geologies of the catchments.
Patterns of pupal mortality in field populations of Hydropsyche and Cheumatopsyche (Trichoptera: Hydropsychidae)
Authors: RUTHERFORD JANE E. , MACKAY ROSEMARY J. 
Published: May 2006

SUMMARY. 1. Up to 40% of hydropsychid pupal cases (from three stations on the Credit and Humber Rivers, Ontario, Canada) contained insects already dead when collected; chironomid infestation accounted for up to 82% of total mortality within a taxon from any one station. The remaining mortality appeared to be due to siltation.2. For all taxa (Cheumatopsyche Wallengren and four species of Hydropsyche Pictet), and at all stations, prepupae suffered significantly more chironomid‐related mortality than did fully‐developed pupae.3. Chironomid infestation generally affected all species of Hydropsyche equally; at some stations, Cheumatopsyche pupae appeared to suffer less chironomid‐related mortality than did co‐existing Hydropsyche species.4. Chironomid infestation affected a greater proportion of pupae at the station where the density of pupal cases (per sampling quadrat) was greatest.5. Vertical distribution of the pupation site had no apparent influence on mortality attributed to either siltation or chironomid infestation.6. Chironomid infestation varied seasonally; it was greatest in May and July‐August at an upstream station, and peaked in June at the downstream stations.7. Mortality attributed to siltation was relatively constant for all stages and taxa, at all stations, throughout the sampling programme.
Zooplankton abundance, community structure and dynamics in relation to inorganic turbidity, and their implications for a potential fishery in subtropical Lake le Roux, South Africa
Authors: HART R. C. 
Published: May 2006

SUMMARY. 1. The abundance and composition of entomostracan zooplankton were studied between 1977 and 1984 in relation to abiotic and biotic conditions in Lake le Roux (LLR), a large silt‐laden reservoir on the Orange River formed in 1976. The community consisted of Metadiaptomus meridianus, Lovenula excellens (Calanoida), Daphnia gibba, D. barbata, D. longispina and Moina brachiata (Cladocera), and various Cyclopoida.2. Zooplankton biomass varied seasonally from winter lows below 50 mg m−2 dry wt at temperatures of 9–10°C to summer peaks generally above 1000 mg m−2 at 21–23°C. It correlated strongly and positively with prevailing water temperature and transparency but only weakly with chlorophyll concentration.3. Mean annual zooplankton biomass, which varied four‐fold (97–408 mg m−2) in 7 years, increased with annual mean transparency (23–75 cm Secchi depth) and especially with summer heat content (33–230 degree‐days above 20°C) which was itself positively correlated with transparency.4. Daphnid species showed most annual variation in abundance. Large forms(D. gibba and D. barbata) were scarce or absent in two years of very low transparency and low planktivore abundance. The smaller D. longispina developed once during clearer conditions when more fish were present. Copepod biomass also varied inversely with turbidity, but was not as severely reduced at high turbidities.5. Smallmouth yellowfish(Barbus aeneus: Cyprinidae) is the principal planktivore and candidate fishery species in LLR. It feeds selectively on Lovenula and large daphnids. Catches and growth rates of yellowfish varied directly with the abundance of zooplankton, particularly large food forms, and with water transparency. High turbidity and associated food limitation seems to reduce standing stocks especially of the daphnid zooplankton more than the effects of fish predation.6. Spawning of yellowfish depends upon the release of water from an upstream reservoir which concurrently reduces transparency and thus zooplankton availability in LLR. Transparency values above 30–35cm SD appear necessary for the development of sufficient and suitable zooplankton to benefit the fishery.
The effects of temperature, atmospheric pressure and season on the swimming activity of the medicinal leech, Hirudo medicinalis (Hirudinea; Hirudinidae), in a Lake District tarn
Authors: ELLIOTT J. M. , TULLETT P. A. 
Published: May 2006

SUMMARY. 1. The chief objective was to determine the major environmental factors affecting the swimming activity of Hirudo medicinalis L. because the latter will affect the feeding and growth periods. 841 leeches were caught in samples taken every 2 weeks in 1982, 1983 and 1984.2. There were four major size groups, probably corresponding to year‐classes. Only nine leeches were in their fourth year (Group IV), most leeches found on stones were in their first year (Group I) and most swimming leeches were in their second or third year (Groups II, and III). Size groups I‐III overlapped considerably and could not be treated separately in subsequent analyses.3. Water temperature appeared to be the dominant factor affecting swimming activity, the threshold for activity being 7°C (range 5–9°C). A curvilinear regression provided the best description of the relationship between temperature and catches of swimming leeches; 62% (range 50–75%) of the catch variation could be explained by temperature.4. Atmospheric pressure at the time of sampling and its rate of change over 24 h preceding sampling had no significant effect on catches of swimming leeches, not even on the residuals of catches after the dominant effect of temperature had been removed. Similar analyses showed that there were no significant seasonal effects on swimming activity.5. From a discussion of the implications of this study, it is concluded that the absence of the medicinal leech from many water bodies may be due partially to the relatively high temperatures required for swimming activity in a large proportion of the population (11.9°C, 19.0°C, 22.7°C for 10%, 50%, 90% active respectively).
Initial colonization of periphyton on natural and artificial apices ofMyriophyllum heterophyllumMichx
Authors: MORIN JOANNE O'NEILL 
Published: May 2006

SUMMARY.1. The initial colonization of periphyton on natural and artificial apices ofMyriophyllum heterophyllumMichx was compared at three depths in the littoral zone of Lake Winnipesaukee, a soft‐water New England lake. After a 1 week incubation period, the apices were sampled and the periphyton was removed and counted as numbers of periphyton organisms per centimetre of stem.2. Initial colonization on both substrates was characterized by diatoms, particularly small single‐celled species, throughout the spring and summer. Blue‐green and green algae occurred in low numbers on both substrates during mid‐summer, usually forming a greater percentage of the population of the natural apices. Blooms of the green algaZygnemasp. dominated both substrates in late August.3. Community composition generally did not differ significantly by depth or substrate on the natural and artificial apices: however, total abundance was significantly greater on the natural apices.M. heterophyllumappeared to serve as a neutral substrate in terms of community composition but had a positive effect on the total numbers of algae.
Selective grazing on periphyton: a determinant of freshwater gastropod microdistributions
Authors: LODGE DAVID M. 
Published: May 2006

SUMMARY. 1. In a cuirophic pond in southern England. the snail Lymnaca peregra(Mull.) is associated with submersed macrophyies, mainly Elodea canadensis Michx. In contrast, the snail Planorbis vortex(Linn.) is associated with the emergent macrophyte Glyceria maxima(Hartm.) Holmberg.2. L. peregra grazed selectively on filamentous green algae found only on E. camtdensis. P. vortex selected diatoms. Detritus, which was 5 times more abundant on G. maxima than on E. canadensis. comprised about 60% of the diet of P. vortex.3. Results of experiments giving both snail species a choice between periphyton‐detritus removed from the two macrophytes were consistent with the field observations. L. peregra c hose pcriphyton‐detritus from E. canadensis whereas P. vortex chose that from G. maxima.4. Although other factors may have influenced the distributions of L. peregru and P mriex in Radley Pond, food choice was probably the most important proximate factor.
Sources of the lipids in the bottom sediments of an English oligo‐mesotrophic lake
Authors: ROBINSON NEIL , CRANWELL PETER A. , EGLINTON GEOFEREY 
Published: May 2006

SUMMARY. 1. The organic geochemistry of Coniston Water, a low productivity lake, has been investigated.2. The relative inputs of the various known sources to different compound classes suggest terrestrial higher plants as the major source of sedimentary organic matter.3. Early lipid diagenesis, proceeding in the bottom sediments as a result of microbial activity, produces relatively rapid changes, with shorter chain and unsaturated compounds being preferentially degraded.4. Free and bound (acid liberated) lipids exhibit significant differences in composition, related to their respective sources and stability towards degradation.5. The lipid composition of an aquatic higher plant, growing in the margins of the lake, has been determined; comparison with the sedimentary lipids reveal it not to be a significant source.
The prediction of the macro‐invertebrate fauna of unpolluted running‐water sites in Great Britain using environmental data
Authors: MOSS D. , FURSE M. T. , WRIGHT J. F. , ARMITAGE P. D. 
Published: May 2006

SUMMARY. 1. A procedure has been developed which uses environmental data to predict the probabilities of macro‐invertebrate taxa occurring at running‐water sites in Great Britain.2. Biological, physical and chemical data were collected from twenty‐ one sites on three river systems in order to evaluate the procedure.3. For most sites the number and type of taxa recorded, using a standard sampling programme, were very close to those predicted using twenty‐eight environmental variables.4. Comparison with other studies at the same sites showed that most taxa whose probability of occurrence was ≥0.5 could be found with more intensive sampling.5. Reducing the number of variables used in making the predictions from twenty‐eight to five resulted in only a slight loss of predictive accuracy.6. Combinations of chemical and physical variables gave better predictions than equivalent numbers of physical variables only but the latter may be more appropriate where chemical pollution is known, or suspected to occur.7. The procedure is of practical value in the detection and assessment of pollution.8. It may also be used to explore patterns in the structure and functioning of stream communities.