bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biogeochemistry of billabong sediments. I. The effect of macrophytes
Authors: BOON PAUL I. , SORRELL BRIAN K. 
Published: May 2006

SUMMARY.We examined the effects of an emergent macrophyte (Eleocharis sphacelataR. Br., Cyperaceae) and a submerged macrophyte (Vallisneria giganteaGraeb., Hydrocharitaceae) on the biogeochemistry of the sediments of a billabong in south‐eastern Australia.Sediments from anE. sphacelatabed had significantly lower concentrations of exchangeable phosphorus than did sediments from a nearby bare area or aV. giganteabed, but neither macrophyte had a measureable effect on their sediment's exchangeable ammonium content.The redox potential in the upper 10cm ofE. sphacelatasediments was about 100 mV higher than that of bare sediments, or of sediments colonized byV. gigantea.There were few consistent differences between vegetated and bare sediments in terms of the activity of extracellular enzymes, such as α‐amylase, protease, β‐dglucosidase, lipase or alkaline phosphatase. Rates of alkaline phosphatase activity (235–306μmol (g dry wt)−1day−1) were markedly higher than those commonly reported for sediments or soils.Rates of gas release were higher from bare sediments (21–93 ml m−2h−1) than fromE. sphacelataorV. giganteasediments (17–23 and 21‐24ml m−2h−1, respectively). Gas bubbles consisted mainly of methane (26–66%) and nitrogen (15–68%). Rates of methane ebullition varied from 5 to 60ml m−2h−1.In‐vitromethanogenesis was most rapid in samples of the upper flocculent sediment. Methanogenesis was slower inV. giganteasediments than in bare area orE. sphacelatasediments, but was markedly accelerated by additions of acetate and/or H2/CO2in all sites.Profiles of total extractable fatty acids and phospholipid fatty acids demonstrated that material derived from higher plants dominated the sediment organic matter in all sites. Bacteria were also a significant component of sediment organic matter, as fatty acids for which bacteria can be assumed the sole source accounted for 18–30% of total fatty acid content. Biomarkers for sulphate‐reducing bacteria (Desulfobacterspp.) were detected, and for type II methanotrophic bacteria.
Photosynthetic characteristics of Myriophyllum spicatum and six submersed aquatic macrophyte species native to Lake George, New York
Authors: MADSEN J.D. , HARTLEB C.F. , BOYLEN C.W. 
Published: May 2006

SUMMARY.
The macrophyte community of Lake George, New York is diverse, composing of forty‐eight submersed species representing a wide range of habitats, depth ranges and life‐history strategies. The photosynthetic rates of seven representative submersed aquatic macrophytes were determined in laboratory studies using measurements of short‐term changes in oxygen concentration at eight light intensities from 0 to 1000 μmol m−2 s−1 at 20°C. The species examined were: Elodea canadensis, Myriophyllum spicatum, Potamogeton amplifolius, P. gramineus, P. praelongus, P. robbinsii, and Vallisneria americana.
Comparisons of maximum net photosynthesis, Michaelis–Menten Vmax and Km for photosynthesis versus irradiance, and dark respiration rates correlated with changes in community composition and species distribution with depth.
In particular, Myriophyllum spicatum exhibited a high photosynthetic rate (Vmax) and high light requirement (both in compensation point and higher half‐saturation constant (Km) indicative of a high light‐adapted species. In contrast, the native species exhibited shade‐tolerant characteristics.
Simple daily carbon balance models indicate that M. spicatum has a higher positive carbon balance near the surface than the native species, but carbon balance decreased more rapidly with decreased light. All species showed greatly reduced carbon balances under a simulated M. spicatum canopy, indicating that native species might not survive. Myriopyllum spicatum leaves would experience self‐shading and eventual sloughing.
Effects of subacute doses of iron (Fe) on Leptophlebia marginata (Insecta: Ephemeroptera)
Authors: GERHARDT A. 
Published: May 2006

SUMMARY1. The objective of this paper was to reveal the toxicity of Fe3+ and Fe24 at pH 4.5 and 7 on larvae of the mayfly Leptophlebia marginata, by examining survival, motility, gill ventilation, moulting and feeding in experiments.2. Fe2+ was the dominant metal species at pH 4.5, and Fe3+ at pH 7. Precipitation of Fe occurred only at pH 4.5, where Fe‐precipitarions were observed on the thorax and the gills of the larvae.3. Both feeding activity and motility of the animals decreased at pH 4.5 and 10, 20 or 50mg1‐−1 Fetot. After a short period of normal feeding, the animals stopped feeding for approximately 2 weeks and did not start to feed again until the end of the experiment. They were constipated. Survival was >95% in all treatments, except at pH 4.5 and 50 mg Fetot. In this group, about 20% of the animals died after having been constipated for 2 weeks.
Allochthonous coarse particulate organic material in forest and pasture reaches of two south‐eastern Australian streams
Authors: CAMPBELL IAN C. , JAMES KIM R. , HART BARRY T. , DEVEREAUX ANNE 
Published: May 2006

SUMMARY1. Terrestrial plant litter entering two forest and two pasture sites on upland streams in south‐eastern Australia was measured over a 2‐year period using traps suspended above the streams. Laterally transported terrestrial plant litter was also determined in one stream, but found to be only 10% of the total.2. Litter accession to traps suspended above the stream was significantly lower at both forested sites than was litter fall in the adjacent riparian vegetation.3. Litter input was high (600–700g DW m−2yr−1) and seasonal, with 30–50% of the annual total entering the stream during December—February (summer). However, seasonality was not as great as that recorded in Northern Hemisphere deciduous forest streams.4. Leaves comprised the largest litter component, but represented a relatively smaller proportion of the litter than is usually the case in Northern Hemisphere deciduous forest streams; in contrast bark was a relatively large proportion of the litter.5. At the sites flowing through pasture, litter accession was about two orders of magnitude lower than at the forested sites.
Impact of storm‐flow on electron transport system activity in river biofilms
Authors: BLENKINSOPP S.A. , LOCK M.A. 
Published: May 2006

SUMMARY1. The effect of storm‐flow on light‐ and dark‐grown biofilms from a North Wales river was monitored using electron transport system (ETS) activity and epifluorescence cell counts.2. Artificial substrata were colonized in the river, exposed to ambient‐flow (60 cms−1) or storm‐flow (235 cms−1 with suspended sediment addition) for 12h in a laboratory flow tank, and returned to the river to monitor the recovery period.3. Total cell densities decreased in both the light‐ and dark‐grown biofilms as a result of storm‐flow. In addition, storm‐flow ETS activity per cell increased significantly in the light‐grown samples (2.7 times) but did not increase significantly in the dark‐grown samples (1.6 times).5. Within 48 h, storm‐flow total cell densities and ETS activity levels had returned to ambient‐flow levels in both light‐ and dark‐grown biofilms.6. Within each light regime, despite their different histories, both ambient and storm‐flow samples responded the same to daily changes in the river environment, including a second disruption by natural causes, for the remainder of the 24‐day experiment.
A weighted—averaging regression and calibration model for inferring total phosphorus concentration from diatoms in British Columbia (Canada) lakes
Authors: HALL ROLAND I. , SMOL JOHN P. 
Published: May 2006

SUMMARY1. The relationship between surficial sediment diatom taxa (Bacillariophyceae) and measured limnological variables in forty‐six British Columbia lakes was explored using canonical correspondence analysis (CCA). Lake‐water total phosphorus concentration (TP), maximum lake depth, conductivity, and calcium concentration each accounted for independent and statistically significant directions of variation in the distribution of diatom taxa.2. Weighted‐averaging (WA) models were developed to infer lake‐water TP from the relative abundances of 131 diatom taxa in the surficial sediments of thirty‐seven lakes. WA regression and calibration with classical deshrinking provided the best model for TP reconstructions.3. Our quantitative inference model has two major advantages over existing multiple linear‐regression models: (i) inferences are based on the responses of individual taxa to TP, and do not involve grouping the taxa into a small number of ecological categories; and (ii) the model assumes that diatoms respond to TP in a unimodal, rather than a linear, fashion.4. The WA model can now be used to infer past lake‐water TP, within the range 5–28νgr1−1, from diatoms preserved in the sediments of British Columbia lakes. The model can provide quantitative estimates of the onset, rate, and magnitude of lake eutrophication in response to natural processes and human disturbances.
Decline of charophytes during eutrophication: comparison with angiosperms
Authors: BLINDOW IRMGARD 
Published: May 2006

SUMMARY1. Charophytes have disappeared from several enriched lakes in Scania (southern Sweden) since the 1940s. Poor light conditions, rather than a toxic effect of phosphorus or negative impact of fish, are the most probable reason for this decline.2. Small species of charophytes (shoot diameter 0.5–1.0 mm), which are able to form dense, low mats, still occur in eutrophic lakes with high phosphorus concentrations, but are restricted to areas of shallow water. In contrast, large species (shoot diameter1–4 mm) have totally disappeared from the most turbid lakes. I suggest that these species are unable to grow in very shallow water because of damage by ice and wave action.3. Maximum depth distribution (ze) and Secchi depth (D) were measured in Scanian lakes for both charophytes and angiosperms and combined with data obtained from Chambers & Kalff (1985). According to the combined data, zc and D are closely correlated with each other for both angiosperms and charophytes.4. The zc of charophytes is higher than zc of angiosperms in clear lakes but lower in turbid lakes. Higher zc of angiosperms in the most turbid lakes is explained by special adaptations of these species to poor light availability (shoot elongation, canopy formation, rapid growth during spring).
The reproductive success of the dipper Cinclus cinclus in relation to the acidity of streams in south‐west Scotland
Authors: VICKERY JULIET 
Published: May 2006

SUMMARY1. The breeding success of dippers Cinclus cinclus was assessed in south‐west Scotland over 3 years and related to the acidity of the streams along which they bred.2. At sites of high acidity, clutch and brood sizes were significantly smaller than those at sites of lower acidity.3. Egg weight and the incidence of second clutches increased significantly with pH, but there was no evidence to suggest an effect of acidity on hatching success.4. The rate at which food was delivered to individual nestlings was significantly lower at acidic than non‐acidic sites. Nestling weights and survival were lower at more acidic sites.5. Reduced brood sizes, low nestling survival and the low incidence of second brooding attempts resulted in a significant reduction in total productivity (number of fledglings produced, per pair, per year) at acidic compared with non‐acidic streams.6. It is suggested that pH‐related differences in the invertebrate fauna of streams result in low prey availability for dippers on acidic streams, leading to reduced productivity.
Clarification of the criteria used to identify near‐bed flow regimes
Authors: YOUNG W.J. 
Published: May 2006

SUMMARY1. Extensive measurements of near‐bed flow velocity were made over a reconstructed section of a cobble‐bed stream using a laser‐Doppler velocimeter. Based on these measurements descriptions of the near‐bed flow structure and flow conditions within benthic habitats are made.2. The near‐bed flow classification system of Davis & Barmuta (1989) is discussed, and the threshold criteria of the system are shown to be incorrect. The correct criteria are stated and discussed in the context of two‐dimensional uniform bed roughness.3. The improved classification system is used to classify the laboratory near‐bed flow regime, and this classification is compared to the flow types depicted in near‐bed flow structure diagrams. This comparison highlights the importance of accurately assessing stream‐bed roughness parameters to obtain accurate and useful near‐bed flow classifications.4. The potential limnological applications of near‐bed flow regime classifications are discussed, with improved benthic invertebrate sampling procedures being given as the likely major benefit.
The behavioural responses of juvenile signal crayfish Pacifastacus leniusculus to stimuli from perch and eels
Authors: BLAKE M.A. , HART P.J.B. 
Published: May 2006

SUMMARY

Experiments were designed to determine the relative importance of chemical and visual stimuli in eliciting predator avoidance behaviour in juvenile freshwater crayfish Pacifastacus leniusculus (Dana).
Crayfish placed in visual and/or chemical contact with one of two predators exhibited marked avoidance behaviour, spending less time walking and climbing and more time within shelters.
The combined effects of both visual and chemical stimuli increased crayfish shelter use and reduced walking and climbing activity to a greater degree than either stimulus when presented alone.
Crayfish exhibited avoidance behaviour in response to chemical stimuli during periods of light and darkness. Visual detection of predators elicited avoidance behaviour during the day.
It is suggested that the behavioural response of P. leniusculus to chemical stimuli reduces the likelihood of being detected by visual predators, and that chemical stimuli lower the response threshold for avoidance behaviour in crayfish reacting to visual stimuli. The adaptiviry of using chemical cues to detect predators is emphasized.
The changing ecosystem of a shallow, brackish lake, Hickling Broad, Norfolk, U.K. II. Long‐term trends in water chemistry and ecology and their implications for restoration of the lake
Authors: BALES MICHAEL , MOSS BRIAN , PHILLIPS GEOFFREY , IRVINE KENNETH , STANSFIELD JULIA 
Published: May 2006

SUMMARY

Hickling Broad underwent major changes from a clear water, charophyte‐dominated state in the decades previous to 1970 to a turbid, phytoplankton‐dominated state by the mid 1970s. These changes were complexly linked with increasing eutrophication by black‐headed gulls and increased salinity due to agricultural changes in the catchment.
At the turn of the 1970s, the lake began to change again and during the 1980s a submerged plant community, of tall, vigorously growing species (e.g. Myriophyllum spicatum, Patamogeton pectinatus) had recovered, despite a major reduction in the roosting gull population, no change in salinity, and only small reductions in phytoplankton biomass and total phosphorus concentration.
Recovery of the plants may be linked to grazing of periphyton on them by an increased population of a mysid Neomysis integer which had been suppressed by toxicity from an alga, Prymnesium parvum formerly stimulated by the ingress of gull guano.
A cladoceran community present in the clear‐water phase has not recovered and may be suppressed by continued high salinities. Further restoration of the lake requires displacement of the large phytoplankton biomass and this might best be contemplated by land use changes leading to lowered salinity and predicted recovery of grazing Cladocera.
Models are given which summarize the likely workings of the system in the early twentieth century, the mid‐twentieth century, the 1970s and the late 1980s.
Biofilm development and extracellular enzyme activities on wood in billabongs of south‐eastern Australia
Authors: SCHOLZ OLIVER , BOON PAUL I. 
Published: May 2006

SUMMARY

The accrual of organic matter, chlorophyll a and bacteria, and the activities of various extracellular enzymes were studied during biofilm formation on River Red Gum (Eucalyptus camaldulensis) wood submerged in two temperate Australian billabongs for 24 weeks over summer and winter of 1989–90.
Peak organic matter content of the biofilm ranged from 0.7 to 3.3mg AFDW cm−2, chlorophyll a content from 1.3 to 4. 2μg cm−2 and bacterial abundance from 18 × 106 to 94 × 106 cells cm−2. Most variation in organic matter content, chlorophyll a content and bacterial abundance in the biofilms couid be attributed to the duration of immersion (28–48% of variation) and to the interaction between site and submergence period (11–12%). Differences between sites and between seasons were less important in explaining total variation.
Alkaline phosphatase, aminopeptidase and [3‐D‐glucosidase activities, determined per unit substratum surface area, were up to 138 ± 26 nmol cm−2h−1, 113 ± 1 nmol cm−2h−1 and 9.3 ± 2.2 nmol cm−2h−1, respectively. Activities of these three enzymes determined per unit organic biomass were up to 203 ± 25, 157 ± 13, and 16 ± 2.1 nmol mg1 AFDW h−1 respectively. Enzyme activities expressed on an area‐ or biomass‐specific basis responded differently to the effects of season, site and duration of substratum exposure.
Few consistent relationships could be established between the activity of a given enzyme system and the activity of other enzymes, nor with the various biomass parameters, such as total organic matter content, chlorophyll a content or bacterial abundance.
We suggest that submerged wood of the River Red Gum is an important site for biofilm development in lentic systems in south‐eastern Australia, and thus as a food resource for grazing invertebrates and for transformations of various nutrients and organic matter.
Decomposition and macroinvertebrate colonization of aquatic and terrestrial leaf material in alkaline and acid still water
Authors: KOK C.J. , VAN DER VELDE G. 
Published: May 2006

SUMMARY

Decomposition of the leaves of Nymphaea alba L. and Betula pubescens Ehrh. was studied in two ponds of contrasting pH, buffering capacity and trophic level. Rates of carbon loss, concentrations of nitrogen, protein and phenolics and colonization of the leaf material by macroinvertebrates were studied.
Decomposition of B. pubescens leaves was slower than that of N. alba in both ponds. Protein and phenolic concentrations were higher in the decomposing N. alba material, whereas no significant difference was found for nitrogen concentrations.
Decomposition of both species was slower in the acid water. The effect of acid water on decomposition rate was similar for both species. Both nitrogen and protein concentrations of N. alba remained higher under acid conditions, whereas no effect of study site was observed on the protein and nitrogen concentrations in B. pubescens litter. The concentration of phenolic compounds was higher in N. alba litter from the acid pond; no such difference was observed for B. pubescens litter. The high concentrations of phenolic compounds in N. alba litter from the acid pond probably induced chemical immobilization (tanning reaction), yielding high concentrations of nitrogen and protein in the litter.
Diversity of the detritivorous macroinvertebrate fauna on the litter of both species was extremely low in the acid pond, while a relatively high diversity occurred in the alkaline water. Exclusion of large macrofauna inhibited decomposition in the alkaline water, while there was no comparable influence in the acid water.
The effects of low pH on the decomposition of both terrestrial and aquatic macrophyte litter appeared to be caused by interactive effects of low pH on the microbial decomposition, on the detritivorous macroinvertebrates and, in the case of N. alba, on the resource quality of the detritus.
Gastric evacuation rates of adult and larval alpine newts (Triturus alpestris) under laboratory and field conditions
Authors: SCHABETSBERGER R. 
Published: May 2006

SUMMARY1. The fits of exponential, square root, surface‐dependent and power exponential polynomials to gastric evacuation curves in alpine newts were compared. Both the more complex power exponential function and the exponential model provided good descriptions of gastric evacuation in adult and larval alpine newts.2. Gastric evacuation rates of adult female and male alpine newts did not differ significantly. Temperature‐dependent gastric evacuation rates were strongly affected by the composition of the meals eaten in the natural habitat. The time for total gastric evacuation in adults was generally longer than reported for teleost fishes and was within the range reported for some elasmobranchs.3. Gastric evacuation rates of newt larvae were low compared to fish larvae. Time for total emptying of the stomach increased exponentially with increasing body dry weight of larvae.
Light‐limited growth and photosynthetic characteristics of two planktonic desmid species
Authors: COESEL PETER F.M. , WARDENAAR KLAASJAN 
Published: May 2006

SUMMARY1.Staurastrum chaetoceras, originating from a eutrophic environment, andCosmarium abbreviatumvar.planctonicum, from an oligo‐mesotrophic one, were grown at 20°C in continuous‐flow culture under varied light conditions.2. Maximum growth rate inS. chaetoceraswas approximately 50% higher than inC. abbreviatum, corresponding to a higher photosynthetic capacity.3. Higher dry weight values and dark respiration rates inC. abbreviatum(compared withS. chaetoceras) support the suggestion from growth‐irradiance curves thatC. abbreviatumhas to invest a greater part of its photosynthetic energy in the construction and maintenance of specific cell components.4. The differences in growth and photosynthetic parameters might be related to the presence of a copious mucilaginous cell envelope inC. abbreviatum; such an envelope is lacking inS. chaetoceras.5. The possible ecological significance of these species‐specific differences is discussed.
A comparison of Acroneuria lycorias (Plecoptera) production and growth in northern Michigan hard‐ and soft‐water streams
Authors: EGGERT SUSAN L. , BURTON THOMAS M. 
Published: May 2006

SUMMARY1. Density, biomass, production and growth of a predaceous stonefly, Acroneuria lycorias, were compared between fourth‐order hard‐ and soft‐water streams in Michigan's upper peninsula, U.S.A.2. Mean densities, estimated from Hess samples, were higher (100 ± 17 individuals m−2) at the hard‐water site than at the soft‐water site (40 ± 9 ind. m−2). Mean dry weight biomass was 4.9 times greater at the hard‐water site.3. Mean annual production, calculated using the size frequency method, was 5.0 times greater at the hard‐water site (2.18 ± 0.44 g dry weight m−2yr−1) than at the soft‐water site (0.43 ± 0.02g dry weight m−2yr−1). Annual production/mean biomass ratios were similar between sites.4. Monthly growth rates of naturally occurring nymphs of paired cohorts were similar in both streams. Individual growth rates were similar for nymphs reared in artificial streams at high and low water hardnesses with unlimited food and space.5. Stonefly production and growth rates were influenced more by indirect physical, biological, or habitat factors than by streamwater cation concentrations.