bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparative study of three air‐lift samplers used for sampling benthic macro‐invertebrates in rivers
Authors: DRAKE C. M. , ELLIOTT J. M. 
Published: May 2006

SUMMARY. From 16 air‐lift samplers described in the literature, three were selected for operation from a small boat: Mackey, Pearson et al. and Verollet & Tachet samplers. Random samples (number of sampling units n= 10) were taken in a large tank with a known number of dried peas, representing invertebrates, amongst stones of uniform size. Separate experiments were performed with three sizes of stones (modal sizes 2–4, 16–20 and 32–36 mm). Stratified‐random samples (usually n= 10) were taken in rivers at lour sites with modal particle sizes of < 0.1 2–4. 32–128 and 64–128 mm. The samplers were compared with a Ponar grab in the tank experiments and the field, and with a Naturalist's dredge in the field.Rates of pumping at different air‐flows were established for each sampler. Water‐How increased with increasing air‐How and increasing submergence of the riser‐pipe. The Mackey sampler achieved the highest water‐flow and lifted more substratum and larger stones (64–128 mm) than the other samplers. The Verollet & Tachet sampler had the lowest pumping rate and failed to lift stones > 8 mm long, whilst the Pearson et al. sampler, with an intermediate performance, lifted mud and stones < 32 mm long.In the tank experiments, the area from which the Mackey and Pearson et al. samplers collected peas varied with air‐flow, operating time and type of substratum. The Maekey sampler over‐sampled and the Pearson et al. sampler usually under‐sampled their respective sampling areas, except the latter sampler at high air‐flows gave approximately quantitative results comparable to those of the Ponar grab for peas on the surface of stones 16–20 mm. No sampler collected much at a depth of 3 cm on larger stones (32–36 mm), and the Verollet & Tachet sampler failed completely on all substrata.In field trials, the Mackey and Pearson et al. samplers provided good qualitative samples except on large stones (32–128mm). The Verollet & Tachet sampler lifted little material. The relative abundance of taxa often differed between samplers. Estimates of the number of invertebrates per m2 differed widely between samplers except for the Pearson et al. and Ponar grab which gave similar quantitative results at three sites. Values were very low for the Verollet & Tachet sampler and Naturalist's dredge and always very high for the Mackey sampler which often grossly over‐sampled its sampling area. Therefore, these three samplers cannot be considered as quantitative. The relationship between the variances and the means of samples of peas in the tank and most invertebrates in the field followed a power law with values of the exponent b in the range 1.13–2.51.The present study completes the evaluation of 14 samplers used to sample benthic macro‐invertebrates in deep rivers, and the more important conclusions from the comparative studies of seven grabs, four dredges and three air‐lift samplers are summarized in a table.
Comparison of benthic macroinvertebrate fauna and substratum composition in riffles and pools in the impounded River Elan and the unregulated River Wye, mid‐Wales
Authors: SCULLION J. , PARISH C. A. , MORGAN N. , EDWARDS R. W. 
Published: May 2006

SUMMARY. The macro‐invertebrate fauna and substrate were studied in a riffle and pool from a regulated (Elan) and an unregulated (Wye) river in summer. There were some differences in the substrate particle size distribution of the two rivers and between the riffle and the pool on the Wye. There was more detritus in pools than in riffles in both rivers and generally more in the Elan than the Wye. Deposits on the bed of the Elan were rich in iron and manganese.On the Wye. there was a greater density of invertebrates in the riffle than in the pool, but species richness was similar. Most species showed some preferences for either the riffle or the pool. The riffle contained a substantial number of Ephemeroptera, Trichoptera, Plecoptera and Simuliidae (52%) whilst the pool was dominated by chironomids (71%). Compared with the Wye, total invertebrate density and species richness were reduced in the Elan. Some species characteristic of riffles were reduced or absent on the Elan. Invertebrate density on the Elan was similar in the riffle and pool; species richness was greater in the riffle. The distribution and abundance of invertebrates is discussed in relation to such environmental factors as water velocity through the substrate and dissolved oxygen supply in interstitial habitats.
Community structure in some southern English streams: the influence of physicochemical factors
Authors: TOWNSEND COLIN R. , HILDREW ALAN G. , FRANCIS JEANETTE 
Published: May 2006

SUMMARY. 1. Invertebrates and fish were surveyed during October 1976 in thirty‐four stony riffle stream sites in Ashdown Forest, Sussex.2. A variety of physicochemical factors were also measured in an attempt to assess the importance of each in determining the distribution of species and the structure of communities.3. Three analytical techniques—stepwise multiple regression analysis, ordination and community classification—revealed that the structure of these communities was strongly related to variation in stream pH. Acid sites had low numbers of individuals, low species richness and low equitabilities. Summer temperature and stream discharge also appeared to play significant roles. The pattern of catchment land use was shown to have an important bearing on stream pH.4. In the most acid sites only collectors, shredders and predators occurred. In more basic sites the number of species in collector and predator categories increased and these were joined by grazer/scrapers and filter feeders.5. A theoretical basis for explaining stream community structure is discussed.
The influence of elevated nitrate concentration on rate of leaf decomposition in a stream
Authors: MEYER JUDY L. , JOHNSON CAROL 
Published: May 2006

SUMMARY.

Leaf decomposition was compared in two streams at the Coweeta Hydrologic Laboratory, North Carolina. U.S.A. One stream drains an undisturbed hardwood watershed, while the other drains a successional watershed subject to an insect outbreak. The successional watershed has elevated nitrate concentrations in the streamwater.
Both black locust (Robinia pseudo‐acacia) and sweet birch (Betula lenta) leaf litter decomposed 2.8 times more rapidly in the stream with high nitrate concentrations.
The more rapid decay rates appeared to be partly due to accelerated microbial processing in response to nitrate enrichment, because microbial biomass (as ATP) was higher in the nitrate‐enriched stream.
At each point in time, nitrogen and phosphorus content of the litter was lower in the high nitrate stream; however, there was no significant difference in nitrogen or phosphorus content at the same state of leaf decay in the two streams.
The effect of fungal parasitism on the succession of diatoms in Lake Maarsseveen I (The Netherlands)
Authors: DONK ELLEN VAN , RINGELBERG J. 
Published: May 2006

SUMMARY. During late winter and early spring, diatoms are predominant in Lake Maarsseveen I and show a succession in blooming. To elucidate the role of parasitism in this succession, samples were taken once a week in 1978, 1979and 1980 and examined for fungal parasites, further, factors which presumably influenced the phytoplankton growth. including temperature and chemical compounds, were studied. Parasites were found on Asterionella formosa Hass., Stephanodiscus astraea (Ehr) Grun. and Cyclotella comta (Ehr) Kütz. The chytrid fungus Zygorhizidium planktonicumCanter was parasitic tin Asterionella formosa. This was the only case where high infection percentages were registered. The developmental phases of Zygorhizidium plunktonicum on Asterionella formosa were studied. The fungus was capable of affecting the spring increase and bringing about a premature end to the bloom. Only when the fungus was temporarily inhibited in its parasitic activity (this phenomenon coincided with periods of frost) was A. formosa able to reach a high abundance. Severe parasitism on A. formosa favoured the development of other diatoms (mainly of Fragilaria crotoriensis Kitt., Stephanodiscus hantzschii Grun. and Stephanodiscus astraea).Host‐parasite interrelationship studies performed in the laboratory showed that temperature can be an important environmental factor associated with epidemics of Zygorhizidium plankiomcum on Asterionella formosa. At very low temepratures (1.5. 1) the fungal activity was inhibited while Asterionella fortnosa still grew well. However, at 5, 10 and 18 the fungus manifested a high infection rate and was able to overtake Asterionella.
The effects of surface geology and stream size on freshwater mussel (Bivalvia, Unionidae) distribution in southeastern Michigan, U.S.A.
Authors: STRAYER DAVID 
Published: May 2006

Stream size and surface geology are the two major environmental features thai control the distributions of the thirty‐four species of unionid mussels living in the streams of southeastern Michigan.
Surface geology, a previously unrecognized factor in the ecology of freshwater mussels, acts lo regulate the hydrology, slope and turbidity of streams in the study area.
Reciprocal averaging ordinations are used to aid the description of the habitats occupied by each mussel species.
The influence of feeding habits on whole‐body metal concentrations in aquatic insects
Authors: SMOCK LEONARD A. 
Published: May 2006

SUMMARY.

Concentrations of seven metals in forty taxa of aquatic insects were determined in order to examine the influence of the insects’ feeding habits on their whole‐body metal content. Species were grouped into five feeding categories which reflected both the type of material the organisms ingested and their contact with sediments during feeding.
Species such as the burrowing mayflies (Ephemeridae) and some of the Chironomidae, which indiscriminately ingest sediment along with detritus, had the highest concentrations of most metals. Filter feeders (e.g. Hydropsychidae) had the next highest concentrations, followed by species which to some degree selectively ingest detritus and periphyton (e.g. many Ephemeroptera, Plecoptera and Trichoptera). Carnivores and surface feeding species, such as the Gerridae and Gyrinidae, had the lowest metal concentrations.
Analysis of metal concentrations of both gut contents and bodies of individuals from each of these feeding types explain these differences. Gut material was enriched in most metals (Co, Cr, Fe, Sb, Sc) relative to their concentrations in the organism's body and it often constituted a major proportion of an organism's whole‐body burden of a metal.
Both the concentrations of metals in the gut material and the proportion of the whole‐body burden of a metal that was associated with gut contents varied with the feeding habit of a species. This was because of differences in the amount of inorganic material ingested by the species in each feeding category, higher concentrations occurring in organisms which ingested relatively greater amounts of sediment.
Organism concentrations of K and Na were less affected by feeding habits since the majority of the whole‐body burden of these metals was associated with an organism's tissue and surface rather than with gut material.
The physical limnology of Augher Lough (Northern Ireland)
Authors: RIPPEY BRIAN 
Published: May 2006

SUMMARY.

The physical limnology of Augher Lough, Northern Ireland (area=9.25 ha. z=5.5 m), including stratification pattern, heat budget, thermocline erosion rate, eddy diffusion rate in the thermocline and hypolimnion and areal hypolimnetic oxygen deficit is described.
Oxygen and temperature profiles, recorded at two sites during 1978 and four sites during 1979, showed that spatial variability of these quantities was low and allowed the following lake characteristics to be estimated. Heat budgel was 5.30 kcal cm‐2 (standard deviation=s=0.26) in 1978 and 5.00 (s= 0.26) in 1979. The thermocline depth was 3.5–6.5 m with an erosion rate of 1.9X10‐7 m s‐1 in 1979. Eddy diffusion coefficients of heat in the thermocline and hypolimnion normally ranged from 0.48X 10‐2 cm2 s‐1 (s=0.20X10‐2) to 5.4X10‐2 (s=2.6X10‐2), but reached 10X10‐2 cm2s‐l (s=9X10‐2) in early July 1978 after a cooling‐mixing episode in the epilimnion. The hypolimnetic oxygen deficit was 680 mg O2 m‐2 d‐1 (s=76) and varied strongly with depth.
A cooling‐mixing episode in the epilimnion in June‐July 1978 caused the movement of heat down to 8 m, movement of oxygen down to 6 m and increased the eddy diffusion coefficients of heat by an order of magnitude.
Biomass and production of phyto‐ and bacterio‐plankton in eutrophic Lake Tystrup, Denmark
Authors: RIEMANN BO 
Published: May 2006

SUMMARY.

Phytoplankton primary production and biomass were compared with bacterial secondary production estimated by means of frequency of dividing cells (FDC) in eutrophic Lake Tystrup. Denmark.
In the upper part of the photic zone, bacterial secondary production constituted 12% of the carbon fixed by the phytoplankton. In vertical profiles, bacterial secondary production ranged from 7.6% (early spring) to 121% (during August) of the carbon fixed by the algae.
A close relationship was found between occurrence and activity of bacteria and algae, suggesting that released organic products are of primary importance to the bacteria.
The annual phytoplankton primary production was estimated as 227 g C m‐2 compared to 102 g C m‐2 assimilated by the bacteria, so 45% of the carbon fixed by the phytoplankton went through pelagic bacteria.
On the biology of the catfish Chrysichthys auratus (Geoffory) in the man‐made Tiga Lake in Northern Nigeria
Authors: STURM M. G. de L. 
Published: May 2006

SUMMARY. (1) A study was made of the biology of Chrysichthys auratus, a bottom‐feeding omnivore, in Tiga Lake, a man‐made lake in Northern Nigeria.(2) Ripe females were present from April to September, coinciding with the hot season and rise in water level. First spawning took place at age II in females. No ripe males were found, and this was attributed to their spatial separation. Absolute fecundity was related to length and ranged from 327 to 1466 in forty‐six females.(3) Hyaline rings on the centra of lumbar vertebrae were counted to age 235 fish. The first ring is laid down at the end of the second year, after which the rings were formed annually, probably during the breeding season. The fish live for up to 6 years. There is a good fit of the growth curve to the von Bertalanffy equation. Growth is slow and a smaller maximum size is attained than in rivers.
Seasonal changes in the concentration and colour of humic substances in some aquatic environments
Authors: VISSER S. A. 
Published: May 2006

SUMMARY. 1. Between February and September 1974, concentrations of fulvic and humic acids in waters from a cryoboreal region of the Precambrian Shield in Quebec varied between 0.5–6.1 mg 1−1 and 0.1–6.5 mg 1−1 respectively. Whereas the fulvic acids usually remained relatively constant during this period, humic acids showed appreciable increases.2. The number and weight average molecular weights of the fulvic acids (∼5000 and ∼22,000 daltons respectively) were lower than those of the humic acids (∼20,000 and ∼75,000 daltons respectively). The average molecular weight of the aquatic humic matter often decreased during late summer and early autumn. During spring floods the molecular weight of fulvic acids increased and that of humic acids declined.3. Because the aquatic humic acids were more intensely coloured than fulvic acids, they contributed more than 30% of the colour of the water even though they accounted for only 15% of the concentration of humic matter. The colour intensity of both fulvic and humic acids generally appeared to increase during the latter part of the summer, when there was normally a decrease in the value of the colour quotient (E4/E6 ratio), indicating the accumulation in the waters of more humified material.
The influence of drought on the fish and invertebrate populations of an upland stream in Wales
Authors: COWX I. G. , YOUNG W. O. , HELLAWELL J. M. 
Published: May 2006

SUMMARY. 1. The exceptionally dry summer of 1976 presented an opportunity to assess the impact of drought on the fauna of an unregulated stream in Wales.2. Total number of macroinvertebrates varied from 1808 m−2 in September 1976 to 7412m−2 in August 1977. Two main effects of drought were observed: an initial reduction in abundance during the drought and a change in community structure in the following year, probably through impaired reproduction.3. Trout density ranged from 0.075±0.028 to 0.402±0.093 m−2 and salmon parr density varied between 0.014±0.004 and 0.414±0.119 m−2. The only detrimental effect of the drought on the fish fauna was the elimination of the 1976 year class of young salmon. probably due to prolonged high water temperature.
Errors in instar determination of mayflies (Ephemeroptera) and stoneflies (Plecoptera) using the simple frequency, Janetschek, Cassie and Dyar's law methods
Authors: FINK THOMAS J. 
Published: May 2006

SUMMARY. 1. The reliability of the simple frequency, Janetschek, Cassie and Dyar's law methods for determining or corroborating instars of mayflies and stoneflies was evaluated using data from published studies, a population of Baetisca rogersi and populations simulated through use of random numbers and generated normal distributions.2. The Janetschek and Cassie methods are variations of the simple frequency method that offer no significant advantage. Modes of the Cassie method, thought to represent instars, are much more difficult or impossible to detect than are the corresponding peaks of the other two methods.3. Overlap in size between adjacent instars can lead to false instar peaks or modes in frequency plots. The potential for overlap in mayflies and stoneflies is greatly increased, compared to other insects, because of their large number of instars and known developmental variability. The normal distribution simulations demonstrated that instar size variability as low as 5–7.5% COV (coefficient of variability) may lead to false instar peaks when the number of instars is in the typical range. These simulations also indicated that even simple frequency plots with distinct peaks may result in inaccurate instar determinations.4. The number of size classes used in an analysis was correlated with the number of peaks or modes revealed. The number of peaks greater than zero in the Janetschek plots for the Baetisca rogersi population varied from 5 to 53 as the number of size classes was varied from 20 to 188. Similarly for the random number simulations. the number of peaks varied from 6 to 41 as the number of size classes varied from 22 to 127.5. Dyar's law semi‐logarithmic plots do not corroborate instars determined through frequency methods, because the uniform spacing of‘instar’data points is the direct result of the uniform spacing of peaks in frequency plots of most data sources (including random numbers), whether or not peaks actually indicate instars. Also Dyar's law plots will‘corroborate’different numbers of instars depending on the peak selection criteria used. The potential for corroborating instars through supplemental rearing and best‐fit analysis is discussed.6. The future of mayfly—stonefly instar determination lies in the increased and more rigorous application of the rearing and Palmen body (mayflies only) methods.
Lake restoration by biomanipulation: Round Lake, Minnesota, the first two years
Authors: With JOSEPH SHAPIRO , WRIGHT DAVID I. 
Published: May 2006

SUMMARY. 1. Rotenone was applied to Round Lake in the autumn of 1980 in order to eliminate predominantly planktivorous and benthivorous fish. The lake was subsequently restocked with a higher population density of piscivores. The effect of this biomanipulation on the phytoplankton and zooplankton communities and on total nutrient concentrations was monitored at fortnightly intervals during the summers, from May 1980 to September 1982.2. The abundance of phytoplankton was much lower after biomanipulation and was consistent with observed changes in Secchi disc transparency, total attenuation coefficient and chlorophyll a concentration. Zooplankters were also less abundant in 1981 and 1982 but the decrease in numbers was more than offset by the large increase in the mean sizes of the zooplankters present, so that the estimated grazing pressures in 1981 and 1982 were at least double the 1980 value.3. Daphnia, rare in 1980, became the dominant genus in 1981 and 1982, and a shift to progressively larger‐bodied Daphnia species was observed.4. Although total nitrogen and total phosphorus levels were generally lower after biomanipulation, their decline could not explain the reduction in phytoplankton abundance which was attributed to the increased grazing pressure. Possible causes of the observed declines in nutrient concentrations are discussed.
Concentrations and annual loading of dissolved organic matter in a small moorland stream
Authors: GRIEVE IAN C. 
Published: May 2006

SUMMARY. 1. Dissolved organic matter (DOM) was measured at 8h intervals over a 1 year period in a stream draining 51 ha of moorland with peaty soils.2. DOM concentrations increased with increasing stream discharge from low flow values of 0–3 mg 1−1 to maximum values of 30 mg 1−1. There were also seasonal differences of up to 13mgl−1 between August (maximum) and February, and differences of about 2.5 mg l−1 between rising and falling stage samples.3. Seasonal variation was closely related to mean temperature.4. Total loss over the year was 168 kg ha−1 DOM (84 kg ha−1 C), larger than previous estimates for upland sites.
Influence of food quality and temperature on life history characteristics of the parthenogenetic mayfly, Cloeon triangulifer
Authors: SWEENEY BERNARD W. , VANNOTE ROBIN L. 
Published: May 2006

SUMMARY. 1. Laboratory and field data indicate that Cloeon triangulifer McDunnough has at least three generations per year in White Clay Creek (Pennsylvania, U.S.A.).2. The duration of the egg stage ranged from 5 days at 30°C to about 90 days at 10°C.3. Larvae completed development (i.e. first instar to adult) in 27 days at 25°C, 45 days at 20°C, and 179 days at 10°C on an algal diet dominated by diatoms.4. Larvae reared on hickory leaves completed development in 30 days at 25°C but died prior to metamorphosis at 10, 15 and 20°C.5. Adult size (i.e. body length, wing length and dry mass) and fecundity were inversely related to rearing temperature for all laboratory and field experiments.6. The significant interaction of food quality and temperature suggest that these factors may be important in understanding geographic variation in the life history of C. triangulifer.