bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of fish on leaf breakdown in a Virginia pond
Authors: TAYLOR FRANK , HENDRICKS ALBERT C.
Published: May 2006

1. To find if fish affect leaf breakdown, sugar maple leaves (Acer sacchrum March) were placed in a soft‐water, farm pond at a depth of 1 m for up to 3 months in four treatment groups: (1) enclosure with sunfish (Lepomis macrochirus Rafinesque) (SUNFISH treatment); (2) enclosure with catfish (Ictalurus punctatus Rafinesque) (CATFISH treatment); (3) enclosure without fish (NO FISH treatment); and (4) no enclosure (OPEN treatment). The study was conducted in spring and autumn.

2. The leaf breakdown rates, k±95% CL, for SUNFISH (0.0082± 0.00059 and 0.0111±0.00162 d−1) and CATFISH (0.0072±0.00096 and 0.0103±0.00077 d−1) were greater in spring and summer, respectively, than in the OPEN treatments (0.0065 ±0.00048 and 0.0105± 0.00141 d−1) and NO FISH (0.0067±0.00039 and 0.0088±0.00099 d−1). However, only k for SUNFISH was significantly different from NO FISH and OPEN treatments.

3. Fish in the pond did not appear to affect breakdown rates of OPEN leaf packs in the first replicate but k approached that of the fish treatments in the second replicate.

4. Fish may have promoted leaf breakdown directly by fragmentation of leaves while foraging for food and, indirectly, by agitation of leaves, leading to increased microbial activity.
Effects of sample storage and mechanical blending on the quantitative analysis of river perighyton
Authors: BIGGS BARRY J. F.
Published: May 2006

SUMMARY1. Laboratory experiments to test the effects of storage of periphyton samples, at 4°C in the dark, on levels of chlorophyllaand alkaline phosphatase activity (APA) are described. It is concluded that either raw or ethanol extracted samples may be stored for 2–3 days for chlorophyll analyses, but APA should be estimated as soon as possible. 2. Experiments are also described on the efficiency of mechanical blending of periphyton samples in breaking up clumps of periphyton cells to improve subsampling reproducibility. It is concluded that blending is a useful procedure to improve the accuracy of periphyton analyses because the subsampling coefficients of variation decreased for most determinands after blending.
Diet of the leeches Erpobdella octoculata (L) and Helobdella stagnalis (L) in a lotic habitat subject to organic pollution
Authors: BRADLEY M. D. K. , REYNOLDS J. D.
Published: May 2006

SUMMARY 1. A study of the diet of E. octoculata (L) and H. stagnalis (L) using a serological technique was carried out in a lot ic habitat subject to organic pollution and seasonal sewage fungus growth.

2. The results indicate that E. octoculata consumed predominantly Chironomidae and Oligochaeta, while H. stagttalis had a less pronounced prey preference, consuming rather similar proportions of chironomids, oligochaetes, Asellus and gastropod snails.

3. At enriched sites, E. ocioculata consumed relatively more chironomids and fewer oligochaetes, while H. stagnalis took more gastropods and fewer chironomids.

4. Seasonal differences were noted in the diet of both leeches with chironomids predominating chiefly from April to August, and molluscs, oligochaetes and Asellus at other times of the year. Intra‐specific differences (on a weight‐age basis) were only seen for E. octoculata, small forms consuming chiefly oligochaetes and larger ones concentrating on chironomids.
Vertical partitioning of the phytoplankton assemblage in ultraoligotrophic Crater Lake, Oregon, U.S.A.
Authors: LARSON D.W. , DAHM C. N. , GEIGER N. S.
Published: May 2006

SUMMARY 1. The summertime phytoplankton assemblage in abysmally deep (Zmax: 589 m) Crater Lake, Oregon, consists of over 100 species, which are variously distributed in the upper 200 m of the vertical water column. The depth distribution of the lake's three most prevalent species follows a predictabk pattern: Nitzschia gracilis in the 0–20 m stratum, Tribonema sp. at mid–depth (80–20 m), and Stephanodiscus hantzschii in the lowermost stratum (160–200 m). These major species, which account for approximately 80% or more of the lake's total phytoplankton biomass and primary production, exist under atypical temperature, light, and nutrient conditions.

2. The spatial distribution of phytoplankton in Crater Lake resembles a three‐tier structure. Unlike most lakes, where the entire phytoplankton communities exist in less disparate environmental conditions, or are vertically mixed periodically by storm events and seasonal lake turnover. the Crater Lake community is partitioned into stratified environments.

5. The disparate and unusual characteristics of these environments, and the hydrological and limnological stability of the lake basin, are perhaps important factors regulating the diversity, dominance. and partitioning of the lake's phytoplankton populations.
Spatial distribution of Trichoptera larvae in the sediments of an Austrian mountain brook
Authors: WARINGER J. A.
Published: May 2006

SUMMARY 1. A set of thirty‐six permanently installed standpipc traps was used over 2 years to sample caddis larvae at various depths in the gravel bed of an Austrian brook. From a total of 805 specimens caught, the most abundant species were Sericostoma sp. (Sericostomatidae), and the three limnephilids Potamophylax cingulatus Steph., Allgamus auricollisPictet and Allogamus uncatus Brauer.

2. Sericostoma sp. and Ecclisopteryx guttulata Pictet were collected down to a seditnent depth of l m. In Sericostoma sp., a burrowing species, tiny larvae were found in sediments at 20–60 em, where most of the life cycle is spent; fully grown larvae were mostly collected at a depth of 0–20 em. All instars of Potamophylax cingulatus, Allogamus auricollis and Allogamus uncatus larvae were most abundant at the sediment surface.

3. The horizontal distribution of the most abundant species was studied at the 20 cm depth stratum. Larvae were most abundant in midstream areas.

4. Factors probably responsible for the observed spatial distribution pattern are briefly diseussed.
Effects of nutrient (N, P, C) enrichment upon periphyton standing crop, species composition and primary production in an oligotrophic softwater lake
Authors: FAIRCHILD G. WINFIELD , EVERETT ALAN C.
Published: May 2006

SUMMARY. 1. The effects of nutrient addition upon algal periphyton standing crop and benthic community metabolism were investigated in Lake Lacawac, Pennsylvania. Nutrient‐diffusing flower pot substrates were filled with combinations of P (0.015 mol Na2HPO4), N (0.15molNaNO3) and carbon as glucose (0.015mol (LG) or 0.15mol (HG)) or 0.58 mol NaHCO3 (C). Fifty‐two pots representing ten treatments were placed in the lake on 5 May 1985 and sampled after 32‐38 days.

2. Maximum chlorophyll‐a values of 23.82μgcm−2 and 29.72μgcm−2 were obtained on NPC and NPHG pots respectively, compared to 0.82μgcm−2 on control pots. Algal growth was not enhanced unless N and either organic or inorganic carbon were supplied. Ash Free Dry Mass was especially high on NPHG pots.

3. Gross production, net production and community respiration were assessed with light‐dark chambers affixed to the pots using microwinkler measurements of dissolved oxygen. Highest production rates were obtained on NC and NPC pots. Pots with NPLG and NPHG also showed significant increases in gross production compared to control levels (P < 0.01). Specific production (=gross production/chlorophyll‐a) was significantly related to standing crop as chlorophylls (P < 0.001), alkalinity in the chambers (P < 0.00l) and light (P < 0. 05), but not to N or P supplied by the pots.

4. The periphyton community was dominated by Chlorophyta, which averaged 86.1% of total algal biovolume. Enrichment with NC and NPC significantly enhanced the growth of three Chlorophyceae (Stigeoclonium, Scenedesmus and an unidentified coccoid) and two Cryptophyceae (Cryptomonas. Rhodomonas) (all P < 0.05). In contrast, the filamentous green alga Mougeotia dominated other treatments, but declined significantly with NPC enrichment (P < 0.05). Addition of NPHG stimulated an 8‐fold increase in total biovolume and significant increases in growth of Cryptomonas, Rhodomonas and Euglena (all P < 0.05).
An in situ experimental column for the study of vertical migration in plankton
Authors: STEWART L. J , GEORGE D. G.
Published: May 2006

SUMMARY. 1. An experimental column that can be installed in situ to manipulate the behaviour of planktonic organisms is described.

2. The column incorporates a profiling system for collecting water samples and measuring water temperature, oxygen and underwater light, and can be fitted with a battery‐powered lighting unit for ‘photoperiod’ experiments.

3. Tests showed that this equipment can be rapidly deployed from a small boat to enclose a relatively undisturbed column of water.

4. Experiments with planktonic rotifers showed that the pattern of vertical migration recorded inside the column was very similar to that recorded outside.
Phosphorus transformations in the epilimnion of humic lakes: abiotic interactions between dissolved humic materials and phosphate
Authors: JONES R. I. , SALONEN K. , DE HAAN H.
Published: May 2006

SUMMARY. 1. Sephadex gel filtration of filtered water from small, Finnish forest lakes demonstrated abiotic movement of 33P from added PO4 to two higher molecular weight fractions. This movement was most pronounced in waters with high humic content which also had high iron content. The two fractions which took up 13P had nominal molecular weights of > 100,000 and 10,000‐20,000.

2. An equilibrium existed between free PO4 and the two fractions. However, one fraction, at least, appeared to exist in two phases, with one phase in rapid equilibrium with free PO4 but the other in only slow equilibrium.

3. Additions of ferric iron up to 1 mg Fe l−1 to the filtered lake water stimulated movement from free PO4, provided high concentrations of humic materials were present. In the absence of humic materials even 0.1 mg Fe 1−1 would precipitate all added 33PO4.

4. The high molecular weight P was only partially reactive with standard molybdate reagents. Exposure of the high molecular weight P to sunlight caused a small release of PO4 under the experimental conditions employed.

5. Possible implications for biological phosphorus demand of such sequestration of free PO4 by humic materials in combination with iron are discussed.
Spatial distribution, life history and estimates of survivorship in a fourteen‐species assemblage of larval dragonflies (Odonata: Anisoptera)
Authors: WISSINGER SCOTT A.
Published: May 2006

SUMMARY. 1. Spatial and temporal changes in larval densities were used to infer patterns of habitat use and survivorship in a fourteen‐species assemblage of dragonflies (Odonata: Anisoptera) in a small fishless pond. The density of all species combined peaked at >1000 m−2 in late summer, Most species (e.g. Libellula spp.) were restricted to shallow, nearshore habitats (<1.0m in depth), but a few (e.g. Epitheca spp.) also used deeper areas of the pond. Only Perithemis tenera was most abundant in deep habitats.

2. Because many species exhibited temporal shifts in their use of habitats, it was necessary to estimate survival from changes in population size, calculated as the product of density and habitat area, summed across habitats. In most species, periods of high mortality in autumn and spring were separated by 3–4 months of negligible mortality in winter. Survivorship was linear only in the two species that completed all of larval development in summer (Sympetrum vicinum and Pantala flavescens). Average survival rates for these two species (−0.0049 and −0.0079 log density d−1) were similar to those in previous studies (Lawton, 1970; Benke & Benke, 1975).

3. Survivorship in many species was confounded by other life history phenomena such as (i) mixed voltinism, (ii) overlapping migrant and resident cohorts, and (iii) asynchronous development within species. Asynchrony made it difficult to estimate initial and final population sizes, hence total larval survivorship. However, based on emergence data, only 0.4–3% of larvae survived after peak abundance. None of this mortality can be ascribed to vertebrate predation, and only a little to overwintering stress and starvation. Thus, predation by invertebrates might play a major role in the regulation of these populations.
Chlorophyll a determination of periphyton on sediments: identification of problems and recommendation of method
Authors: HANSSON LARS‐ANDERS
Published: May 2006

SUMMARY. 1. The aim of this study was to evaluate the impact of different amounts of water and organic material on the extraction of periphytic algal chlorophyll from lake sediments.

2. Methanol extracted less chlorophyll than acetone from fresh sediment samples. The ratio between the amount of chlorophyll extracted with methanol and acetone increased with decreasing water content of the sample.

3. When sediments were freeze‐dried prior to extraction of chlorophyll, the extraction efficiency increased between 3.4 and 10.0 times compared with fresh samples. It is suggested that the higher extraction efficiency for freeze‐dried samples is due to reduction in water content and pulverization of the sediment, allowing improved exposure to the solvent.

4. As a result of these studies freeze‐drying, prior to extraction in acetone (90%) or ethanol (96%), is recommended as the best available method for quantification of chlorophyll a in sediments.
Measuring Tailing's ‘element of chance in pond populations’
Authors: JEFFRIES MICHAEL
Published: May 2006

SUMMARY. 1. A series of small seasonal pools on a freshwater marsh was used to estimate the element of chance in animal community patterns.

2. The pools were artificially created in 1963. They were all the same age, size, shape, depth and had the same substrate. Other physico‐chemical parameters, and the faunas, were sampled. Community assemblages were analysed using multivariate classification and ordination (TWINSPAN and DECORANA). and related to physico‐chemical characteristics. Communities correlated with distance of pools from permanent water and annual drying/flooding regimes.

3. TWINSPAN analysis in 1987 was used to identify co‐occurring groups of animals and the sets of ponds with which each group was associated. The presence or absence of a taxon from a pool within a set in which it otherwise commonly occurred was used as a measure of the element of chance.

4. The mean occurrence of taxa in pools in which they were expected was 79.6.16.2%. The mean occurrence in pools in which they were not expected was 10.9.10.5% (n=80).
Manipulation of chemistry and phytoplankton by hydrological intervention: a whole lake experiment in the northern Netherlands
Authors: DE HAAN H. , HOOGVELD H. L. , DE BOER T. , VOERMAN J. , MOED J. R. , KRAMER H. A. , SCHROTENBOER J.
Published: May 2006

SUMMARY. 1. The small Lake Negenmad, in the nature reserve ‘De Oude Venen’, was isolated from the canals and lakes of the Frisian lake system. Its chemistry and phytoplankton were monitored 1 year before (1984) and 2 years after (1985–86) isolation. These characteristics were compared with those of the adjacent Lake Veertigmad which was not manipulated.

2. The hydrological intervention prevented the inflow of chloride‐rich IJsselmeer water into Lake Negenmad and made its water table more dependent on evapotranspiration, precipitation and upwelling water. In comparison with the unmanipulated lake. Lake Negenmad became less saline (c. 50%), more humic (c. 50%) and total dissolved (<0.2,μm) iron concentration increased dramatically.

3. During the 2 years of damming no marked differences in the total nutrient concentrations of either lake were observed. However, the maximum phytoplankton density in the dammed lake was half that in the unmanipulated lake. The lower density may have been caused by low P availability after formation of humus‐iron phosphate species.

4. Preventing the inflow of water from the Frisian lake system favoured the occurrence in Lake Negenmad of flagellated species (Chrysophyceae, Cryptophyceae) at the expense of filamentous and nuisance‐causing cyanobacteria (Oscillutoria, Anabaena, Aphanizomenon spp.).

5. The implications of these results for water quality management of reservoirs in peaty areas are briefly discussed.
Two commensals on a host: habitat partitioning by a ciliated protozoan and a chironomid on the burrowing mayfly, Ephemera danica
Authors: TOKESHI MUTSUNORI
Published: May 2006

SUMMARY 1. Two taxonomically unrelated species, the ciliated protozoan Scyphidia sp. and the chironomid Epoicocladius flavens (Malloch), share a commensal mode of life on nymphs of the burrowing mayfly Ephemera danica Müller in a small river in eastern England.

2. Both commensals were present all through the year, with an average level of infestation of 25.1% and 54.7% for Scyphidia sp. and E. flavens, respectively, of the total E. danica population.

3. Scyphidia sp. occurred more frequently on younger, smaller nymphs of E. danica and was totally absent from hosts of more than 10 mm in length. In contrast, E. flavens preferred hosts of larger body size, usually more than 10 mm. Change in dominance of infestation between the two commensals occurred in the host size range of 6–8 mm and this pattern of habitat partitioning on the basis of host size was consistent throughout the study period.

4. Amongst E. danica individuals colonized by E. flavens, larger hosts supported heavier commensal load. A similar trend, though weak, was also observed among hosts harbouring Schyphidia sp.

5. Both commensals are considered to benefit from the association with E. danica in that they gain enhanced mobility and security in otherwise inhospitable habitats. Although plausible on an evolutionary time scale, competition alone cannot constitute a proximate cause for the clear partitioning of habitat observed in the two commensal species.
The seasonal biomass and productivity of the submerged macrophytes in a polluted Wisconsin stream
Authors: MADSEN JOHN D. , ADAMS MICHAEL S.
Published: May 2006

SUMMARY 1. We measured biomass and light/dark bottle productivity of macrophytes in a Wisconsin stream throughout one growing season. Except for a brief period in early spring when a Cladophora glomerata‐filamentous algal community was dominant, Potamogeton pectinatus was the dominant macrophyte species in Badfish Creek.

2. Maximum community biomass was 710 g DW m−2, with a maximum above ground biomass of 620 g DW m−2 and a maximum below ground biomass of 120 g DW m−2. Annual productivity was estimated at 1435 g DW m−2 year−1, with a calculated P/B of 2.01.

3. In situ net production averaged 2.83g C g AFDW−1 h−1 Net positive carbon gain by the P. pectinatus community occurred when water temperatures were above 15°C, and daylength at least 12h. This is correlated to the onset of tuber germination in spring, and the point of maximal biomass decline in autumn.
Floristic changes in shallow soft waters i n relation to underlying environmental factors
Authors: ARTS GERTIE H. P. , LEUVEN ROB S. E. W.
Published: May 2006

SUMMARY 1. Historical and recent data on the occurrence of macrophytes in twenty‐eight lentic soft waters in The Netherlands are summarized. These waters were, and a few still are, characterized by a submerged vegetation of isoetid plants. Changes in the species composition of macrophytes are visualized by means of multivariate analysis and by shifts in species‐spectra.

2. Ordination of the available data shows that the pH, alkalinity, acidity, contents of heavy metals, dissolved organic matter and some important salts and nutrients in water and interstitial water are strongly related to the recent distribution of aquatic plants in waters, which were originally of low alkalinity. In addition, the available inorganic carbon and the redox potential in the sediment are also important environmental parameters in explaining differences in aquatic vegetation.

3. The recorded changes in the macrophyte species composition can be attributed to the effects of acidification and eutrophication. The most important, overall change is a reduction of the number of species.

4. Hydrology proves to be important in controlling the sensitivity of a body of water for acidifying deposition.
Adsorption and release of amino acids from epilithic biofilms in streams
Authors: MARMSTRONG STEPHEN , BÄRLOCHER FELIX
Published: May 2006

SUMMARY. I. Stream sediment with a natural biofilm generally adsorbed more glycine, aspartic acid, and lysine than sterile sediment. Lysine was adsorbed to a greater extent than the other two amino acids.

2. In the presence of Ca2+, adsorption of aspartic acid increased and adsorption of lysine decreased. Glycine was not affected.

3. Stream sediment preferentially removed amino acids with a positive charge or a polar R group from maple leaf leachate.

4. It is estimated that stream invertebrates may have access to a maximum of 7.3% of the amino acids present in epilithic biofilms. More amino acids were available from biofilms exposed to leaf leachate.
Vertical distribution and abundance of invertebrates within the sandy substrate of a low‐gradient headwater stream
Authors: STROMMER JAYNE L. , SMOCK LEONARD A.
Published: May 2006

SUMMARY. 1 The vertical distribution of invertebrates (>0.053 mm) was studied in a sandy‐bottomed, first‐order stream on the Coastal Plain of Virginia, U.S.A. Invertebrate species composition, abundance and bio‐mass were determined monthly over one year at sediment depth intervals of 0–1, 1–5, 5–15,15–30 and 30–40 cm.

2. The subsurface community was numerically dominated by species of Chironomidae, Nematoda and Crustacea, while much of the biomass was due to early instars of several species of Trichoptera.

3. Invertebrate density and biomass decreased significantly with depth in the substrate (ANOVA; P<0.05). Annual mean density decreased from 1,346,844 individuals m−3 at the surface to 13,578 individuals m−3 at 15–30 cm. Annual mean biomass decreased from 66.30 g m−3 at the surface to 0.44 g m−3 at 15–30 cm.

4. Dissolved oxygen decreased markedly from the surface to the 5 cm depth in the substrate, anaerobic conditions often occurring below 10 cm. Density and biomass both showed a significant positive relationship with dissolved oxygen concentration (Linear regression; P<0.05).

5. Physical forces were important in structuring the subsurface invertebrate community. Besides low dissolved oxygen concentration, sediment scouring resulting from storm discharge dramatically reduced density and biomass
Some impacts of human activities on trout, Salmo trutta, populations
Authors: CRISP D. T.
Published: May 2006

SUMMARY. 1. The life cycle of salmonid fishes is described.

2. The performance and environmental requirements of the various life stages of the trout (Salmo trutta L.) are reviewed, (a) The literature gives predictive relationships between water temperature and rate of embryonic development, food requirements and growth rate, (b) Water temperature, intragravel oxygen supply rate, water pH, the occurrence of mechanical shock, disturbance of spawning gravels, sedimentation and water chemistry can all influence the survival of the intragravel stages, (c) The survival and/or well‐being of the free‐swimming stages and the success of spawning are influenced by such factors as dissolved oxygen concentration, pH, water depth, water velocity and water chemistry.

3. Human activities such as impoundment, river transfer, drainage works, land improvement, afforestation and deforestation can all influence trout populations via changes in flow regime (and related effects such as sedimentation), temperature regime and water chemistry.

4. Man can also influence trout populations directly by cropping for food and/or sport and by artificial stocking.

5. Examples of practical application of present knowledge are given and some future research needs are listed.
Genetic differences among brown trout, Salmo trutta, stocks and their importance for the conservation and management of the species
Authors: FERGUSON A.
Published: May 2006

SUMMARY. 1. Review of published studies on genetic variation, as shown by electrophoretic studies of protein variation, in natural brown trout (Salmo trutta L.) populations from Britain and Ireland, Finland, France, Greece, Iceland, Norway, Sweden, U.S.A. and U.S.S.R., revealed abundant geographical variation in gene frequency with individual populations containing only a limited part of the gene diversity of the species.

2. Thirty‐eight (54%) of the seventy gene loci examined have been found to be polymorphic in the species with an average population showing polymorphism at 16% of its loci (range 0‐34.8%).

3. The brown trout is naturally subdivided into a large number of reproductively isolated and genetically distinct populations within, as well as among, drainages.

4. Two independent post‐glacial colonizations, by genetically distinct races, followed by independent evolution in separate drainages over the past 13,000 years is seen as responsible for the genetic diversity of brown trout in north‐western Europe.

5. Many genetically unique populations have been lost in the past 100 years and there is an urgent need to identify and conserve the remaining genetic diversity. Genetically unique populations are an irreplaceable resource for rational management in relation to angling and future aquaculture potential.
Copper complexation in eutrophic and humic Lake Tjeukemeer, The Netherlands
Authors: VERWEIJ W. , HAAN H. DE , BOER T. DE , VOERMAN J.
Published: May 2006

SUMMARY. 1. Copper(II) complexation in the eutrophic. humus‐rich Lake Tjeukemeer was measured fortnightly for several years by copper titration (Ion Selective Electrode) and by copper solubilization. Additionally, the copper speciation during titration was followed by ultrafiltration.

2. The Tjeukemeer showed high ligand concentrations able to complex up to 8.5X10‐5 M Cu.

3. Scatchard plots and affinity spectra of the titration data allowed the discrimination of at least three different binding sites. In Scatchard plots log K values ranged from 5 to 9, in affinity spectra from 4.5 to 8.

4. The highest log K values coincided with relatively low humus concentrations and blooms of algae, mainly Cyanobacteria.

5. The ultrafiltration experiments indicated that relatively small size fractions (<10 nm) have the highest copper binding affinity.
Cyst distribution and excystment conditions for the dinoflagellate Peridinium penardii (Lemm.) Lemm. in a reservoir
Authors: KAWABATA ZEN'ICHIRO , OHTA MASAYUKI
Published: May 2006

SUMMARY. 1. Cyst distribution and a possible excystment site of the dinoflagellate Peridinium penardii (Lemm.) Lemm. in a reservoir were surveyed.

2. The presence of vegetative cells of P. penardii from all lake bottom mud samples, taken from several sites throughout the reservoir and cultured in vitro, showed that viable cysts of P. penardii were ubiquitous on the bottom of the reservoir.

3. Culture bottles containing bottom mud with cysts of P. penardii were suspended at several depths at four stations in the reservoir. Vegetative cells of P. penardii were found in all bottles suspended at 0.5 m and almost none deeper than 20.0 m. Water depth was a critical environmental factor in preventing excystment.

4. The place where P. penardii first excysts annually was predicted to be at the head of the reservoir using the data of cyst distribution, excystment conditions and morphology of the lake basin.
Microhabitat selection by the fishfly larva, Parachauliodes japonicus, in relation to its mode of respiration
Authors: HAYASHI FUMIO
Published: May 2006

SUMMARY. 1. Larvae of Parachauliodes japonicus (Megaloptera: Corydalidae) were tracked in streams using miniature radio‐transmitters.

2. Larvae usually stayed under stones in shallow water for several days, but occasionally moved about on the stream bed at night.

3. Larvae possess a pair of respiratory tubes on abdominal segment VIII, which can be used as a snorkel to obtain oxygen from the atmosphere. Because respiratory rates decreased as dissolved oxygen decreased, larvae turned to air‐breathing under lowered oxygen conditions. When in shallow water, they can alter respiratory mode from aquatic respiration to air breathing instantly by raising their caudal respiratory tubes to the surface of the water.

4. Microhabitat selection and respiratory behaviour are compared with those obtained previously for Protohermes grandis larvae, which belong to the same family and often inhabit the same stream as P. japonicus, but which have gill tufts on abdominal segments I‐VII instead of respiratory tubes. The respiratory constraint on microhabitat preference by aquatic insects is discussed.
Temporal scales of variability in pelagic environments and the response of phytoplankton
Authors: REYNOLDS C. S.
Published: May 2006

SUMMARY. 1. Pelagic environments are inherently and continuously variable. Time scales relevant to phytoplankton behaviour are identified as ranging from the time taken for light to penetrate a cell (10‐−15 s) to the creation and disappearance of lakes (1012 s). Each scale invokes characteristic responses in algae, spanning the activation of biochemical pathways to the extinctions of species.

2. With special, though not exclusive, reference to the Freshwater Biological Association's activities through its first 60 years, scientific investigation has touched each point on the scale. The existing knowledge is used to produce simulations of the behaviour of model planktonic species at every level in the series.

3. Emphasis is placed on scale interaction, upon how variability at one level collapses into the steady state of higher levels and, equally, how the ultimate texture or ‘grain’ of biological systems is determined by the structure at finer scales.
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 lake

2. 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.