bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.