bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new quantitative air‐lift sampler for collecting macroinvertebrates on stony bottoms in deep rivers
Authors: DRAKE C. M. , ELLIOTT J. M. 
Published: May 2006

SUMMARY. 1. As three previous comparative studies of deep‐water samplers for benthic macroinvertebrates in rivers highlighted the need for a quantitative sampler for use on stony substrata, a new air‐lift sampler was developed. It can be operated from a small boat by two people, weighs 13.5–20.0 kg, depending on the length of riser used, and extends the maximum range of substrata that may be sampled quantitatively from 16–32 mm to 128—256 mm. The sampling area is isolated by forcing a collecting cylinder into the substratum, and rapid evacuation of the contents is assisted by a vibrator.2. All the major specifications of the sampler were determined experimentally in a large tank using three sizes of substrata and plastic pellets to represent invertebrates. The sampler performed accurately to a depth of at least 8 cm on substrata ranging from gravel (2–4 mm) to large stones (32–36 mm long).3. The performance of the sampler was compared with that of a Ponar grab and Pearson el at. air‐lift sampler at two sites on a large river and also with a Naturalist's dredge and a diver‐operated Hess‐Waters sampler at one of the sites where there were large stones up to 280 mm long. In terms of both mean taxa per sample and mean numbers m−2, samples taken using the new air‐lift sampler provided estimates comparable to or belter than those obtained with the other samplers.
Some factors regulating cohort production of the crayfish, Orconectes virilis
Authors: MOMOT WALTER T. , GOWING HOWARD 
Published: May 2006

SUMMARY. Cohort production of the crayfish. Orconectes virilis, ranged from 148.8 to 70.2 kg in North Twin Lake (surface area 1.9 ha) and from 151.9 to 84.9 kg in West Lost Lake (surface area 1.4 ha). Both cohort production (P) and cohort mean biomass (B) showed a long‐term decrease with time. The cohort P/B ratios did not show such a trend but remained steady. The P/B ratio approximated the life cycle instantaneous rate of growth (G) which could then be used for estimating cohort production from mean biomass.Production remained consistently higher in West Lost Lake. Analysis of horizontal life table data revealed no inherent difference between survival and fecundity rates of the crayfish population in each lake. Slight differences in basin morphometry between the two lakes determined nursery habitat availability and this affected recruitment of young from each female brood stock. Small differences in carrying capacity between two similar sized nearby lakes, along with a decrease in carrying capacity over time, were sufficient to nullify attempts to manage these populations using a maximum sustainable yield model.
A simplified 1,10‐phenanthroline technique suitable for the determination of dissolved iron in remote sources of water
Authors: WRIGHT R. C. 
Published: May 2006

A simple technique is described for the determination of dissolved iron in water. It is useful for investigating remote sources and avoids errors due to post‐sampling precipitation of hydrated ferric oxides.
A small sample is added to a mixed 1.10‐phenanthroline‐i‐acetate buffer solution in the field and this‘developed sample” can then be stored for up to 4 weeks before the absorbancc value is read.
Chemical composition of water‐bodies in the English Lake District: relationships between chloride and other major ions related to solid geology, and a tentative budget for Windermere
Authors: SUTCLIFFE D. W. , CARRICK T. R. 
Published: May 2006

SUMMARY.Mean tarnwater concentrations of CI‐and other ions (Na+, K+, Ca2+, Mg2+, SO42‐+ NO3‐) decrease with increasing distance from the sea and altitude but are also related to solid geology. Lowest concentrations occur on slow‐weathering igneous rocks (Borrow‐dale Volcanics); minima of c. 100 μequiv. CI‐I‐1are similar to the volume‐weighted mean for bulk precipitation. At least 10–20% of Na+is leached from upland catchments, giving Na+/CI‐ratios greater than the equivalent ratio (0.86) in seawater and precipitation. Evapotranspiration at 20–30% annual rainfall accounts for CI‐concentrations in many tarns on igneous rocks but not all; some CI‐may be leached from the rocks in upland catchments and come from groundwaters at low altitudes near the sea. Sea‐spray has little influence on tarnwaters near the coast.On sedimentary rocks overall mean CI‐concentrations are 27–73% higher than equivalent means on Borrowdale Volcanics; concentrations of other ions are also higher. A 5‐fold to 10‐fold range of CI‐concentrations is not simply due to increased evapotranspiration. Na+/CI‐ratios are < 0.86, especially on Skiddaw Slates where tarnwaters contain 10% or more excess CI‐balanced by Ca2+, apparently derived from groundwaters rich in CaCI2. On other sedimentary rocks (Silurian Slates and Carboniferous, Triassic and Permian series) tarn waters display a similar but less pronounced excess of CI‐and Ca2‐+relative to Na+. Some extra CI‐may be captured by dry deposition on vegetation but a portion, perhaps 15–30% of the total, apparently comes from the rocks or from groundwaters via deep aquifers in contact with seawater or connate water.Anthropogenic sources on the catchments are also considered: deicing salt used on highways in winter accounts for a 27% increase of CI‐in Windermere South Basin over a 20‐year period.
ATP as a biomass indicator in eight North Island Lakes, New Zealand
Authors: PRIDMORE R. D. , COOPER A. B. , HEWITT J. E. 
Published: May 2006

SUMMARY. 1. The relationship between microbial ATP and biomass‐ carbon in the near surface waters (0.5–5 m) of eight New Zealand lakes was studied to determine the constancy of the carbon:ATP ratio under natural growth conditions. Concentrations of microbial carbon were estimated indirectly from cell volume determinations.2. The carbon:ATP ratio remained reasonably constant (interquartile range 248–291, n= 50), except during periods of nitrogen/phosphorus deficiency when carbon: ATP ratios increased to values greater than 400.3. During periods of nitrogen/phosphorus sufficiency, corresponding estimates of microbial ATP and biomass‐carbon were strongly correlated (r=0.97, n=47) and related by the equation carbon = (287±20) ATP‐(22±41) where carbon and ATP are expressed in mg m−3. From this relationship an average carbon:ATP ratio of 267 (SE=5) was calculated.4. This ratio was not significantly affected by the relative proportions of bacterial and algal biomass in the surface water samples. However, because of the marked deviation of the carbon:ATP ratio during periods of nitrogen/phosphorus deficiency, the routine use of ATP as a biomass indicator is discouraged.
Use of ATP and carbon: nitrogen ratio as indicators of food quality of stream detritus
Authors: TAYLOR B. R. , ROFF J. C. 
Published: May 2006

SUMMARY. 1. Differences in food quality of suspended and benthic organic detritus, as measured by ATP content and C/N ratio, were assessed along three contrasting headwater streams in southern Ontario.2. Large differences in ATP content of sediments between cooler upstream reaches and warmer downstream reaches were detected. Sediment ATP content was highly correlated with stream temperature, presumably as a result of faster microbial growth, and with stream gradient. C/N ratios of sediments showed much the same pattern of differences as ATP, but were less variable.3. By contrast, the ATP content (or BIOC/POM ratio) and C/N ratios of suspended organic matter showed no systematic variation between upstream and downstream or between warmer open and cooler shaded areas, probably due to the very short residence time of suspended particles.
The influence of seasonal and taxonomic factors on the ordination and classification of running‐water sites in Great Britain and on the prediction of their macro‐invertebrate communities
Authors: FURSE M. T. , MOSS D. , WRIGHT J. F. , ARMITAGE P. D. 
Published: May 2006

SUMMARY. 1. Macro‐invertebrate samples were collected from 268 running‐water sites in Great Britain in each of three seasons (spring, summer and autumn). A combined seasons’treatment was generated by amalgamating the individual seasons’data. These four seasonal options were each subjected to four distinct taxonomic analyses differing in level of identification and whether the data were quantitative or qualitative. Thus sixteen data‐sets were available for analysis. Environmental data on physical and chemical variables, macrophyte cover and date of sampling were also recorded for each site.2. All sixteen data‐sets were ordinated by detrended correspondence analysis and classified by two‐way indicator species analysis. There were strong correlations between the sixteen ordinations and significant concordance between classifications.3. The relationships between ordination scores and single environmental variables were investigated. Muhiple discriminant analysis was used to fit environmental data to eight selected classifications covering the full range of seasonal and taxonomic treatments. The environmental variables most useful in distinguishing between rivers were substratum characteristics, alkalinity and total oxidized nitrogen. Within‐river differences were often highly correlated with discharge, distance from source, width and depth. Slope and altitude contributed strongly to both between‐river and within‐river distinctions.4. Between‐site variation (beta diversity), eigenvalues of ordination, the reliability of classifications, the proportion of sites correctly assigned to their biological group using environmental data and the standardized similarity between observed and predicted fauna were all higher when identifications were taken to species level, rather than one of three family treatments. Qualitative data on a reduced list of families gave comparable or better results than more detailed family treatments.5. Combined seasons’data enabled better categorization and prediction than single season's.6. The values of the Czekanowski Index of Similarity between the observed and predicted fauna of test sites were close to realistic maximum values.7. Recommendations are made concerning potential usages of the various classifications. The species level classification has uses in the field of conservation and in the prediction of biological response to environmental change. The family level classifications have value in developing local site inventories and in the interpretation of pollution surveillance programmes.
A seasonal sequence of diel distribution patterns for the planktonic dinoflagellate Ceratium hirundinella in a eutrophic lake
Authors: FREMPONG E. 
Published: May 2006

SUMMARY. 1. Diel depth distribution patterns of Ceratium hirundinella were studied during eleven sampling periods, covering the seasonal growth cycle. They were shown to result from short‐term periodic or non‐periodic external factors, endogenous responses of the alga, and interactions between these.2. Diel variations in wind stress resulted in the net transport of algae into or out of the sampling position due to lateral water movements. A progressive surface accumulation of Ceratium, leading to a 3‐fold increase in cell numbers at the sampling site over a 24 h period, was due to wind‐induced upwelling of deeper cells. Near‐surface accumulation of Ceratium on a completely overcast afternoon, similar to that associated with migrations, was attributable to advection.3. Under sufficiently calm conditions, depth‐differentiation of Ceratium was regulated by its vertical swimming movements with a diel periodicity. Migration patterns observed in earlier work were confirmed and extended. The alga migrated towards the surface during the daytime and downward during the night; this rhythm had an endogenous component.4. At high surface illumination, the alga retreated from the surface and formed discrete sub‐surface maxima; at low irradiance Ceratium showed positive phototaxis and concentrated near the surface. Under either condition of irradiance Ceratium actively aggregated at depths associated with irradiance levels of about 125–155 μEinsteins m −2 s −1. Downward movement was restricted by anoxic conditions and possibly by thermal/ density gradients. However, given sufficient light penetration, dissolved oxygen and nutrient availability, the thermal density gradient does not apparently eliminate downward movement by Ceratium.
Haemoglobin synthesis in Daphnia magna Straus (Crustacea: Cladocera): ecological differentiation between neighbouring populations
Authors: CARVALHO GARY R. 
Published: May 2006

SUMMARY. 1. Variations in the haemoglobin index of two neighbouring populations of Daphnia magna were recorded over a range of dissolved oxygen concentrations (0.5–4.0ml O2 1−1, 20°C). Reciprocal transfer experiments between habitats compared haemoglobin synthesis in situ.2. An inverse relationship was found between the oxygen content of pond water and the haemoglobin indices of laboratory and natural populations.3. Significant genetic differences in the synthesis of haemoglobin were found between the two populations. Animals from the poorly oxygenated habitat (0.8±0.18ml O2 1−1) had consistently higher haemoglobin contents (maximum HI, 87.7±4.5) at all experimental and in situ oxygen levels. D. magna from the well oxygenated pond (4.3±0.59 ml O21−1) had a lowered physiological ability to synthesize haemoglobin (maximum HI, 48.3±4.2). The process of ecological differentiation in Daphnia populations is discussed.
The invertebrate fauna of four macrophytes in a lotic system
Authors: ROOKE J. BRIAN 
Published: May 2006

SUMMARY. 1. Invertebrates associated with four species of aquatic plants and on the adjacent substrate were investigated in a riffle/run section of a hard‐water stream.2. Invertebrates were more numerous on stones than on any species of plant (> 17,000m−2 versus 1000–4000 m−2). Gatherers were more abundant on Ranunculus longirostris, where proportionally more fine detritus was trapped in the leaf bundles than on other plants. Scrapers were most numerous on Charu vulgaris, where attached diatoms were also most prevalent.3. Invertebrate community structure on three plant speeies was quite different from that on stones. This was not the case for Potamogeton amplifolius which appeared to be used by the organisms as a mere extension of the substrate.
Seasonal and comparative aspects of chemical stratification in some tropical crater lakes, Ethiopia
Authors: WOOD R. B. , BAXTER R. M. , PROSSER M. V. 
Published: May 2006

SUMMARY. 1. Measurements of oxygen, pH, phosphate, nitrate, nitrite, hydroxylamine. ammonium and sulphide were made in four Ethiopian crater lakes during 1964, 1965 and 1966 at fairly regular intervals. The seasonal pattern of the dynamics of these chemical constituents is described for depth and time and relates closely to the pattern of thermal stratification and mixing previously described.2. Interactions between the chemical constituents are examined and comparisons are made between the four lakes which differ widely in their depth, exposure to wind and standing crops of phytoplankton.3. The vertical distribution of the chemical constituents is used to help define the limits of circulation of surface waters and the need to understand the seasonality of chemical stratification in relating climatic, morphometric and biological events, especially in tropical lakes, is stressed.
Nitrate respiration by Protozoa (Loxodes spp.) in the hypolimnetic nitrite maximum of a productive freshwater pond
Authors: FINLAY B. J. 
Published: May 2006

SUMMARY.

The ciliated protozoon Loxodes dominated the microfaunal community living in the anoxic hypolimnion of Priest Pot, a small productive pond. Its peak abundance close to the oxic‐anoxic boundary was always associated with a peak in nitrite (NO2) concentration. Both peaks were usually found in water containing μ1 μmol O2 1‐1.
The microfauna were concentrated on a 30 μim sieve. The number of Loxodes in the sieve retentate correlated well with the activity of nitrate reductase in the same material, implying that the enzyme was located in Loxodes. It is unlikely that residual bacterial contamination could have accounted for the activity.
A doubling of specific electron transport system activity was associated with the transition across the oxic–anoxic boundary. This is consistent with the switch to nitrate respiration and the lower energy yield it provides.
Dissimilatory nitrate reduction was deduced to be the source of the nitrite peak. Nitrate was supplied by both run‐off and nitrification.
It is suggested that Loxodes participates in the dissimilatory sequence of a condensed nitrogen cycle functioning across the oxic—anoxic boundary.
Structure and grazing of stone surface organic layers in some acid streams of southern England
Authors: WINTERBOURN MICHAEL J. , HILDREW ALAN G. , BOX ALAN 
Published: May 2006

SUMMARY.

Stone surface organic layers were investigated at five sites on small, acid streams in the Ashdown Forest, southern England. Sites differed in stream water pH (means 4.3–6.6) and some other physicochemical features.
Organic layers at the stream bed surface differed between sites in structure and in the amount of organic carbon present. Algae were abundant at the sites with higher conductivity and pH, iron bacteria (mainly Leptothrix sp.) predominated in the iron‐rich Broadstone stream, whereas the surface layer at the most acid site was predominantly a rather structure less organic film with few living organisms.
Amounts of organic carbon on stones buried within the stream bed for 3 months were almost identical at all sites. When viewed with the scanning electron microscope (SEM), organic layers on buried stones were rather structure less with some amorphous, floceulent material. The paucity of microflora suggests that these layers may have been formed primarily by abiotic mechanisms.
X‐ray microanalysis of organic layers indicated that complexes of organic matter with the metals iron, aluminium and manganese were present.
Laboratory experiments with seven species of invertebrates showed that all were able to remove and at least partially ingest organic layers and underlying sandstone. The weight of material removed was highest on microbially impoverished layers from the most acid site, and was substantially lower where algae were abundant.6. The role of stone surface organic layers in stream systems is discussed. They may be important sites of dissolved organic matter (DOM) uptake and transfer to the benthos. A major impact of acidity on running water could be through its effect on the structure and function of organic layers.
The forces on microorganisms at surfaces in flowing water
Authors: SILVESTER N. R. , SLEIGH M. A. 
Published: May 2006

SUMMARY.

Surfaces in flowing water are covered by boundary layers within which the velocity of flow ranges between zero at the surface and the velocity of the main stream at the limits of the boundary layer.
Many organisms are small enough to live entirely within the boundary layer and so are subjected to much smaller drag forces than if they were exposed to the main stream velocity.
The form and extent of boundary layers at different stream velocities around selected structures, representing leaves and stems, have been calculated and presented graphically.
These data provide a basis for the estimation of shear stresses on substrate surfaces and of forces exerted upon organisms of different sizes that live within the boundary layers around such surfaces, when exposed to different current velocities. Values for shear stresses on bacteria calculated in this way lie within the range of shear stresses required to detach bacteria from surfaces experimentally.
Environmental cues for cyclomorphosis in Daphnia retrocurva Forbes
Authors: HAVEL JOHN E. , DODSON STANLEY I. 
Published: May 2006

SUMMARY.

The invertebrate predators. Chaohorus, Leptodora, Hydra, Utricularia, and cyclopoid copepods were ineffective as inducers of high helmets in laboratory reared Daphnia retrocurva. Lako water from different sources, when used as culture medium, was also ineffective.
High helmets were induced when clones were grown under warm and turbulent conditions. Presence or absence of illumination and varying photoperiod did not affect helmet growth in warm turbulent cultures. Different clones grown under warm turbulent conditions differed in their responsiveness to the treatment, but no relationship between helmet size in clones and helmet size in the field on the dates of clone isolation was demonstrated. Laboratory‐induced phenotypes were rarely as extreme as those of field animals.
Phosphorus inactivation in a eutrophic lake by the direct addition of ferric aluminium sulphate: impact on iron and phosphorus
Authors: FOY R. H. 
Published: May 2006

SUMMARY.

Following addition of ferric aluminium sulphate (FAS) in February 1980 to a eutrophic lake, White Lough, Northern Ireland, the cycles of phosphorus (P) and iron (Fe) over 34 months were compared to those in the 18 months preceding the application.
During the summer of 1980, P release to the hypolimnion was reduced by 92% compared to 1979 but by 1982 had returned to pre‐treatment levels. Phosphorus budget calculations for the post‐ treatment period indicated that P was accumulating in the sediment at a rate sufficient to permit the recovery of P release.
In the three summers following FAS addition, Fe released into the hypolimnion increased by 56–71% compared to 1979 but this increase represented less than 10% of Fe added in the FAS.
Prior to FAS treatment, hypolimnetic Fe and P were mixed throughout the lake at overturn, resulting in high winter concentrations, but after treatment, overturn was accompanied by large reductions in the lake Fe and P content due to precipitation. As a result, overwintering P concentrations in 1980/81 and 1981/82 were in the range 31–53μg P1‐1 compared to 111–194μg P1‐1in 1978/79 and 1979/80.
The reduction of hypolimnetic P release in 1980 and 1981 and lower overwintering P had little impact on summer epilimnetic P concentrations which for 1979–82 were 51, 36, 47 and 48μg P1‐1respectively. Phosphorus concentrations in the epilimnion were raised between April and June in each year by a release of P into the epilimnion. August and September was the only period when reductions in hypolimnetic P were reflected in lower P concentrations in the epilimnion.
A dissolved oxygen budget model for Lake Erie in summer
Authors: PATTERSON J. C. , ALLANSON B. R. , IVEY G. N. 
Published: May 2006

SUMMARY.

In this paper we extend a vertical mixing model of Lake Erie with an oxygen budget model. The model was tested against data gathered in the summers of 1979 and 1980 with good results, showing that it is capable of simulating vertical distributions of temperature and dissolved oxygen over relatively short time periods.
The results underline the importance of turbulent mixing in distributing oxygen throughout the water column in the Central Basin of the lake. In addition, the results indicate that production and respiration processes dominate the budget under the influence of low wind speeds, while surface fluxes dominate during periods of high wind.
Bottom mixing delays the onset of anoxic conditions at the sediment/water interface by distributing the sediment demand over the 5–6 m depth of the bottom mixed layer.