bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of a serological technique to examine host selection in a natural population of the medicinal leech, Hirudo medicinalis
Authors: WILKIN P. J. , SCOFIELD A. M. 
Published: May 2006

SUMMARY. 1. Serological examinations were made of the bloodmeals of medicinal leeches, Hirudo medicinalis L., collected from two sites at Dungeness, Kent, in order to determine their host range.2. A modified miniature Ouchterlony agar diffusion method was used with antisera raised in rabbits against fish, bird, frog and mammal blood sera.3. The results suggest that the marsh frog. Rana ridibunda Pall., was the most important host with smaller contributions from birds and fishes. Mammals appeared to be very rare hosts. These results reflect the availability of hosts as determined by field studies. Many leeches showed evidence of blood meals from more than one host.4. Field observations indicated the importance of the smooth newt, Triturus vulgaris L., as a host for the leech, particularly early in the season. Predation on the newt appeared invariably to be fatal.
Change to a diatom assemblage in a eutrophic lake following point source nutrient re‐direction: a palaeolimnological approach
Authors: ANDERSON N. J. , RIPPEY B. , STEVENSON A. C. 
Published: May 2006

SUMMARY. 1. Lough Augher, Co. Tyrone, Northern Ireland, underwent eutrophication as a result of untreated effluent disposal by a local creamery, from 1900 until 1972–73, when primary sewage treatment began. When this remedial action met with limited success the effluent was redirected to the River Blackwater, downstream of the lake2. A sediment core taken in July 1981 shows an unambiguous record of the diatom response to this eutrophication; the species succession represents a clear eutrophication gradient, with a shift from mesotrophic plankton forms (Aulacoseira ambigua, Asterionella formosa, Fragilaria crotonensis, Diatoma tenue var. elongatum) to a variety of small Stephanodiscus spp. typical of very eutrophic conditions (S. parvus, S. hantzschii). The succession is in reasonable agreement with that predicted by changing Si:P ratios.3. A second, short core, taken in September 1985, shows dramatic changes in the diatom plankton after 1981, with resurgences and rapid increases of species present early in the lake's eutrophication, and representative of mesotrophic conditions. There is clear agreement between the biostratigraphic record of the two cores, for the time period during which they overlap, c. 1970–81.4. The available chemical data post‐dates the re‐direction of the creamery effluent. However, it indicates that the phosphorus concentration is in equilibrium with the loading, and has stabilized following effluent re‐direction. There were no significant differences for chlorophyll a and total phosphorus between the years for which data are available. The mean concentrations were 10, 14 and 10 g 1−1 chlorophyll a, and 61, 63 and 58 g TP 1−1 in 1978, 1979 and 1982 respectively.5. A Correspondence Analysis Joint‐plot is used to summarize the biostratigraphy of the two cores. It serves as an ecological summary of the responses of the plankton diatoms to changing nutrient concentrations and ratios, following redirection of the creamery effluent, and demonstrates clearly the new direction taken by the planktonic diatoms. Although the phosphorus and chlorophyll a data suggest that the lake returned quickly to an equilibrium state, the diatom community continued to change. suggesting a time‐lag effect and non‐equilibrium responses by the planktonic diatoms to their nutrient environment.6. The potential value of palaeolimnological approaches to long‐ and medium‐term monitoring of diatom plankton changes should not be underestimated; they may provide an important time component for limnological restoration projects.
Interactions among nutrients, algae and invertebrates in a New Zealand mountain stream
Authors: WINTERBOURN M. J. 
Published: May 2006

SUMMARY. 1. Colonization of nutrient‐diffusing substrata by periphyton and invertebrates was investigated at forested and open sites in a small, mountain stream and a spring in the South Island of New Zealand.2. Substrata had colonization surfaces made from 100μm mesh plankton netting that enabled algal assemblages to be removed intact for scanning electron microscopy. They also allowed small volumes of solvent to be used for the extraction of photosynthetic pigments.3. At all sites, periphyton assemblages were dominated by species of Achnanthes, Cocconeis and Gomphonema, and except in the forest in winter, periphyton biomass was always greater on enriched (N + P added) than control substrata.4. Invertebrates colonizing diffusion substrata were principally larval Chironomidae (Orthocladiinac). No larvae were present in winter, but in three spring and summer trials mean larval densities were higher on nutrient‐enriched than control substrata at all sites.5. The inclusion of an insecticide Malathion in diffusion substrata, reduced insect colonization at open and forested sites. After 28 days, no concurrent increases in algal pigment concentration were observed on nutrienl‐enriched or control substrata at the forested site. However, pigment concentrations were higher on substrata incorporating Malathion at the open site suggesting that algal standing crop was depressed by the activities of grazers.
Temporal patterns of grazer‐periphyton interactions in laboratory streams
Authors: De NICOLA DEAN M. , McINTIRE C. DAVID , LAMBERTI GARY A. , GREGORY STANLEY V. , ASHKENAS LINDA R. 
Published: May 2006

SUMMARY. 1. The snail Juga silicuta (500 m−2) and the caddisfly Dicosmoecus gilvipes (50 m−2) were introduced into separate laboratory streams on days 1, 9, 16 and 28 of algal development. The mayfly Baetis spp. (500 m−2) was introduced on days 1 and 16, and two streams did not receive grazers. We assessed the interaction between succession in the pcriphyton, herbivore type and time of encounter in a 40‐day experiment.2. In ungrazed streams, the chlorophyte Scenedesmus obliquus was the most abundant early colonizer. The relative abundance of diatoms increased after day 9, and at day 40 the algal assemblage consisted of a thick mat of diatoms and S. obliquus with an overstorey of filaments of the chlorophyte Stigeoclonium tenue. In general, introductions of grazers at any stage altered this pattern by removing biomass, accelerating the replacement of S. obliquus by diatoms, and suppressing the growth of filaments. Grazing also reduced the relative abundance of the larger diatom Nitzschia oregona but increased the relative abundance of the smaller adnate diatoms Nitzschia frustulum var. perpusilla and Navicula minima.3. Dicosmoecus decreased algal biomass and altered successional trajectories to a greater degree than either Juga or Baetis. Dicosmoecus rapidly grazed the entire substrate, whereas Juga and Baetis only cleared patches in the assemblages. Little alteration in algal development was observed in the Baetis streams after day 16, probably because (he periphyton assemblages attained a size and structure that prevented effective grazing by Baetis.4. The patchy grazing patterns of Juga and Baetis resulted in more diverse algal assemblages than either the Dicosmoecus grazed or ungrazed streams. In natural streams, the temporal and spatial pattern of grazing relative to the developmental stage of the periphyton may contribute to maintaining a mosaic of algal patches in different serai stages.
Grazing interactions between pulmonate snails and epiphytic algae and bacteria
Authors: UNDERWOOD GRAHAM J. C. , THOMAS J. D. 
Published: May 2006

SUMMARY. 1. The effects of grazing by Lymnaca peregra and Planorbis planorbis on Ceratophyllum demersum epiphyton were investigated under simulated natural conditions.2. Grazing resulted in significant reductions in algal cell densities, number of algal taxa and in diversity. Grazing did not influence equi‐tabilily values.3. The use of Ivlev's Electivity index demonstrated positive and negative selection by feeding snails for large, pedunculate, and small, adnate algae, respectively.4. Inoculation of artificial surfaces revealed that 61.1% and 62.5% of the algal taxa presenl in the diet of L. peregra and P. planorbis, respectively (mainly the smaller species), were able to survive passage through the gut, resettle and grow.5. The results are discussed with particular reference to the survival strategies available to the epiphytes, and the possible mutual benefits which algae and snails may derive from coexistence.
Micro‐arthropod seasonally in streams of varying pH
Authors: RUNDLE SIMON D. 
Published: May 2006

SUMMARY. 1. Micro‐arthropods were sampled seasonally (January, May, August and October) during 1986 from ten, stony riffle sites on streams in the Ashdown Forest of southern England, using both standard benthic and interstitial samplers.2. Total densities peaked at most sites in summer. Species richness reached a maximum at acid sites in summer but at cireumneutral sites in autumn, when Hydrachnellae and Cladocera were particularly species rich.3. Individual species showed no obvious differences in seasonally between sites; the majority peaking in summer or autumn, regardless of pH. However, cyclopoid copepods were particularly numerous at acid sites in summer, a pattern not observed at circumneutral sites.4. Multivariate ordination and classification of data sets from the separate seasons, and all four seasons combined, showed that mean site pH, conductivity, and aluminium and calcium concentrations were the most important variables explaining between‐site variation in species composition. This clear distinction between the community structure at acidic and circumneutral sites was evident in all seasons except winter. Species composition was also more predictable throughout the year at low‐pH sites.5. A number of species were taken consistently in interstitial samples and the cyclopoids Diacydops languidus and D. languidoides were restricted to the hyporheos at circumneutral sites. The similar faunal composition of the hyporheos and the epibenthos indicated that the separation of these communities was not well defined in Ashdown Forest streams.
A field and laboratory study of the parasites of the triclad Phagocata vitta (Duges)
Authors: ARMITAGE M. J. , YOUNG J. O. 
Published: May 2006

SUMMARY. 1. Over 13 months, fifty Phagocata vitta were collected from a smalt tributary of the Afon Anafon (Wales) and the occurrence of the ciliate Tetrahymena pyriformis and an unnamed nematode studied.2. During the study, prevalence ranged from 5% to 22% and mean intensity from two to twenty‐nine ciliates per infected triclad, whilst relative density never exceeded three per triclad. There was a trend for these values to be highest in summer and lowest in winter, but a significant positive correlation with field temperature was only found for mean intensity. The mean values of mean intensity and relative density were not significantly correlated with triclad size.3. For the nematode, prevalence varied from 2% to 6% and relative density from 0.02 to 0.08 individuals per triclad, whilst mean intensity remained about one per infected triclad. No significant correlations between seasonal fluctuations of any of these values and field temperature were obtained.4. In laboratory experiments lasting 5 weeks, triclads which had been initially fed tubificid worms infected with T. pyriformis and kept in uninfected water had much higher prevalence and mean intensity values than triclads fed uninfected tubiticids and kept in infected water. The main source of infection by the ciliate in the field seems likely to be through the ingestion of infected food. In infected triclads cultured at either 5, 10, 15 or 20°C, prevalence, mean intensity and relative density values increased with rising temperatures, whilst mortality was negligible at the two lowest temperatures and substantial at the two highest. Laboratory findings are related to field events.5. It is concluded that the ciliate and nematode parasites may not cause significant mortality in the fieid population of P. vitta.
Quantitative relationships between oligochaete communities and phosphorus concentrations in lakes
Authors: LANG CLAUDE 
Published: May 2006

SUMMARY.

The relative abundance of oligotrophic species in tubificid and lumbriculid communities was related to phosphorus concentration in eight lakes of Western Europe and three large lakes of North America.
Mean annual concentrations of total phosphorus, recorded in the whole lake during the 5 years preceding the sampling of worms, were averaged and this mean was used to indicate the trophic state.
Mean relative abundance (%) of oligotrophic species (OS) was negatively correlated with mean concentrations (mg m−3) of total phosphorus (TP):OS = 80.29 – 8.35 TP0.5r2= 0.81
Location and depth from which worms were sampled also influenced values of OS.
Relationships between the physicochemistry and macroinvertebrates of British upland streams: the development of modelling and indicator systems for predicting fauna and detecting acidity
Authors: RUTT G. P. , WEATHERLEY N. S. , ORMEROD S. J. 
Published: May 2006

SUMMARY.

Data on the macroinvertebrate riffle fauna and physicochemistry of 368 upland streams were collated for areas in Wales. Scotland and N.W. England.
TWINSPAN classification of the national macroinvertebrate data at the‘family' level produced either two or four groups of streams which differed markedly in invertebrate fauna and acidity. The analysis also produced an indicator key based on the presence/absence of macroinvertebrate taxa which could be used to allocate new sites to the stream groups.
Multiple Discriminant Analysis (MDA) indicated that sets of environmental variables, which principally included pH or aluminium and calcium concentrations, discriminated effectively between the stream groups defined by TWINSPAN. These variables were incorporated into models which predicted faunal TWINSPAN groups from physicochemical data alone.
TWINSPAN classification and the MDA models were tested by application to new sites either reserved from the initial data set (RESERVED) or sampled during fieldwork in spring 1989 (FIELD).
For the RESERVED data there was 75–80% agreement between the two systems when two TWINSPAN groups were defined and 53–55% with four groups. Agreement was lower for the FIELD data, probably because chemical description was based on only one spot‐sample.
Distributions of pH and aluminium concentration for the groups of test sites classified by macroinvertebrate indicator key corresponded reasonably well to distributions of these determinands at sites in the four original TWINSPAN groups. Correspondence was better for the RESERVED than for the FIELD data set.
Some factors affecting distribution of diatom assemblages in Pyrenean springs
Authors: SABATER SERGI , ROCA JOSEP R. 
Published: May 2006

SUMMARY.

The composition and abundance of diatom assemblages were studied together with physiographical and physicochemical variables in twenty‐eight springs in the Central Pyrenees during the period 1987–88.
Characteristic groupings of diatom taxa are revealed by Principal Components Analysis. One group, made up of assemblages of the taxa Navicula cincta, Caloncis spp. and Niizschia elliptica, is characteristic of springs with waters of high ionic strength. Certain diatom taxa are characteristic of hard water springs, either in quiet waters (Denticula tenuis, Achnanthes minutissima, Eunotia spp.) or fast flowing ones (Fragilaria spp., Diatoma hiemale). Other taxa are representative of relatively quiet, softwater springs: Anomoeoneis bracfiysira, Tabellaria flocculosa, Aulacoseira distans and Fragilaria vaucheriae.
Five different spring types were identified, with respect to diatom assemblages, using discriminant analysis. The first consisted of high mountain springs with cold, fast waters and low ionic strength. The second group, distributed throughout the Pyrenees, had similar environmental characteristics to the first group but with intermediate water velocity and slightly higher mineral content. The third contained springs in calcareous regions of the Pyrenees, mainly slow‐flowing and with hard waters. The fourth was composed of softwater springs, whilst the fifth consisted of two springs which were subject to stressful conditions (limitation of light, abundance of nitrates or high salinity).
Ionic strength and current velocity appeared to be the dominant environmental factors affecting diatom distribution in Pyrenean springs. These factors also seem to determine diatom communities in some other geographical areas. In some springs, however, peculiar environmental factors (dim light, salinity, and high temperature) affect the structure of diatom assemblages.
Changes in phosphorus cycling in a shallow lake due to food web manipulations
Authors: BOERS PAUL , VAN BALLEGOOIJEN LEO , UUNK JAN 
Published: May 2006

SUMMARY.
1. Food web manipulation, by removal of planktivorous or benthivorous fish, is a promising method for reducing phytoplankton concentrations in shallow lakes. The part that nutrients may play in the success of such a measure is not well documented.2. In this study, we analysed the flow of phosphorus through the food web of the shallow, eutrophic Lake Wolderwijd/Nuldernauw. Our studies occurred in the years 1981 (when a bloom of cyanobacteria occurred) and 1987 (no bloom); a hypothetical situation was also examined in which most of the bream are assumed to be removed.3. The analysis shows that the success of biomanipulation is probably due not only to an increased grazing pressure on the phytoplankton, but also to a decreased availability of phosphorus. The reason for this is the removal of detrital phosphorus by increased sedimentation as a result of a predicted increase in growth of macrophytes after biomanipulation.
Prey selectivities of threespine sticklebacks (Gasterosteus aculeatus) and phantom midge larvae (Chaoborus spp.) in Newfoundland lakes
Authors: CAMPBELL CHRISTINE E. 
Published: May 2006

SUMMARY.
1. Threespine stickleback (Gasterosteus aculeatus) and Chaoborus (C. punctipennis and C. trivittatus) planktivore populations were sampled from several oligotrophic lakes on the Avalon Peninsula of Newfoundland, Canada. Pelagic zooplankton communities in these lakes consist of Daphnia catawba, Holopedium gibberum, Eubosmina longispina, Leptodiaptorma minutus, Epischura nordenskioldi, Cyclops scutifer and rotifers (Conochilus unicornis, Keratella and Kellicottia spp.).2. Comparison of gut contents of G. aculeatus and crop contents of later instar Chaoborus larvae with lake zooplankton communities indicated that the vertebrate and invertebrate plank tivores show contrasting species and size selectivities in their choice of zooplankton prey. Prey selectivities were quantified by means of the selectivity index α.3. G. aculeatus showed positive selectivity for larger zooplankton (greater than 0.76 mm in length), typically the cladoceran D. catawba, while Chaoborus larvae showed positive selectivity for smaller zooplankton (less than 0.50 mm in length), typically the cladoceran E. longispina. While rotifers never featured in the diet of the sticklebacks, these zooplankters were a common component of the chaoborid diet. H. gibberum, with its gelatinous sheath, was rarely found in the gut contents of G. aculeatus and was never found in the crop contents of Chaoborus larvae.4. Selective predation by these planklivores in the relatively shallow and well‐mixed oligotrophic Avalon lakes may influence species composition and size structure of the pelagic zooplankton communities.
Comparison of epilithic and epixylic biofilm development in a boreal river
Authors: SINSABAUGH ROBERT L. , GOLLADAY STEPHEN W. , LINKINS ARTHUR E. 
Published: May 2006

SUMMARY.
1. We assessed substratum effects on lotic biofilm development by placing glass and white pine sampling units in a fourth‐order boreal river, and analysing, at 6‐week intervals, upper‐surface biofilms for ATP, chlorophyll, ergosterol, and the activities of nine exoenzymes.2. All parameters, except chlorophyll standing stock (range 80–320 μg dm−2) and β‐xylosidase activity (range 0.4–4.8 μmol h−1 dm−2), were significantly greater for epixylic biofilms than for epilithic ones, but the magnitude of the increases varied from 2 to 5 fold, showing that, even under similar hydrodynamic conditions, epilithic and epixylic biofilms are structurally and functionally distinct. For example, ergosterol concentrations ranged from undetectable to 0.93 μg dm−2 for epilithon and from 11–49 μg dm−2 for epixylon; corresponding ranges for ATP were 1.6–3.7 (epilithon) and 4.2–7.7 μg dm−2 (epixylon), for acid phosphatase activity: 2.3–4.9 and 20–41 μmolh−1dm−2, and for alkaline phosphatase activity: 1.9–8.1 and 29–150 μmol h−1dm−2, respectively.3. The more extensive epixylic development was attributed to utilization of the wood substratum as a supplemental carbon source and to a higher density of microbial attachment sites.
Predation by chaoborids on typical and spined Daphnia pulex
Authors: PAREJKO KEN 
Published: May 2006

SUMMARY.
1. In laboratory predation experiments, predation rates were determined for fourth‐instar larvae of the chaoborids (Insecta: Diptera) Mochlonyx sp. and Chaoborus americanus preying on four juvenile instars and adult Daphnia pulex (clone SBL). In the case of Mochlonyx, predation was most intense on second‐instar juvenile Daphnia while Chaoborus preyed equally on second and third instars.2. Mochlonyx and Chaoborus induced an antipredator defence (neck‐teeth) which was most frequently expressed in second‐instar juvenile Daphnia. Expression of this antipredator phenotype was correlated with a reduced rate of Mochlonyx predation.
Invertebrate grazer‐periphyton interactions in a eutrophic marsh pond
Authors: HANN B.J. 
Published: May 2006

SUMMARY.
1. The effects of two different invertebrate grazer guilds on the periphytic algal community were studied in a marsh pond in Manitoba, Canada over one entire open‐water season.2. Microcrustaceans (cladocerans, copepods, ostracods), which were numerically dominant in the unperturbed grazer community, effectively reduced the periphytic algal biomass to a persistent, depauperate residual assemblage throughout the season.3. The perturbed grazer community, enclosed and treated with ro‐tenone, was composed primarily of chironomids and oligochaetes. This community permitted a more diverse algal community to develop except when grazer numbers peaked.4. When grazer numbers in the perturbed community were at a maximum, the algal assemblage appeared to be ‘overgrazed’. Algal biomass was reduced below the minimum characteristic of the unperturbed community.5. There was an inverse relationship between algal biomass and grazer numbers in both perturbed and unperturbed communities, but variation in degree of response was much greater in the perturbed system than in the unperturbed one.