bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biofilm development on leaf and wood surfaces in a boreal river
Authors: GOLLADAY S. W. , SINSABAUGH R. L. 
Published: May 2006

SUMMARY 1. Biofilms are organic layers that develop on submerged surfaces. They are composed of micro‐organisms, exoenzymes, and detritus particles enclosed within a gelatinous matrix. While much is known about mineral surface biofilms, those developing on organic surfaces have not been extensively studied. We examined the influences of current velocity and substratum composition on biofilm development in a fourth‐order North American boreal river.2. Arrays of white birch ice‐cream sticks and sugar maple leaves were placed at fast and slow current sites. Samples were collected periodically, analysed for mass loss, and assayed for microbial biomass (ATP, ergosterol, chlorophyll a) and exoenzyme activity associated with lignocellulose degradation (exo‐ and endocellulase, β‐glucosidase, phenol oxidase, peroxidase).3. Biofilms developed rapidly on both surfaces. On leaves, biomass peaked within 30 days of exposure. On wood, ATP and chlorophyll a concentrations peaked within 30–70 days, whereas ergosterol increased throughout the study (161 days). On leaves, current velocity had little influence on biofilm development, although breakdown rates were greater at the fast flow site. On wood, ATP and chlorophyll a concentrations were greater at the fast flow site, whereas ergosterol concentrations and breakdown rates were similar at both sites. Microbial biomass was consistently greater on wood than leaves, Exoenzyme activity developed rapidly on both surfaces; current velocity had little influence on activity. Except for β‐glucosidase, activities were greater on wood than leaves.4. Our results suggest that fungi are an important structuring element of organic surface biofilms and the physical stability of the substratum strongly influences biofilm development. Leaf surfaces are susceptible to softening and fragmentation, truncating biofilm development. In contrast, abrasion of wood surfaces removes senescent material exposing fresh substratum for colonization. Thus, wood surfaces with their greater physical stability, permit the development of more extensive biofilms. Wood surfaces may represent an overlooked but important site of metabolic activity in streams.
Continuous drift samples of macroinvertebrates in a large river, the Danube in Austria
Authors: ANDERWALD P. H. , KONAR M. , HUMPESCH U. H. 
Published: May 2006

SUMMARY 1. A new method is described for sampling the drift in large rivers continuously and automatically, using equipment based on the marine, continuous plankton sampler of Hardy (1936).2. Between April and November 1989, about 790 h were sampled continuously, equivalent to a water volume of 2937m3 and the total catch was 527 drifting macroinvertebrates, in forty‐nine taxa. Twenty‐five of these taxa are recorded in the drift for the first time and twenty‐eight of the drifting taxa were present in benthos samples from the Danube.3. Total drift density varied between 12 and 31 animals per 100m3 of water sampled throughout the year, with a maximum of 31 animals in May, The composition of major faunal groups showed a significant seasonal pattern, with Oligochaeta and Diptera predominant in spring, Crustacea and Insecta in summer and only Crustacea in autumn. The overall density of the macrozoobenthos from October 1986 to December 1987 was about 19360 animals m−2 and the proportion of total benthos animals, drifting at any instant in time, ranged from 0.0026 to 0.0064%.4. The relationship between drift density day−1 and mean daily discharge was described by a power‐function. Total mean drift rate of macroinvertebrates in the Danube was estimated to be 13 600 000 animals per 24 h and the mean drift distance was estimated to vary between about 4 and 31 m, dependent on the animal group and the water velocity.5. No obvious consistent diel pattern could be established from the continuous samples, and no marked diel rhythm could be detected for Oligochaeta, Diptera larvae and Crustacea.
Contribution of grazing in phytoplankton overall losses in a shallow French lake
Authors: GARNIER JOSETTE , MOURELATOS SPIROS 
Published: May 2006

SUMMARY 1. Based on data for 14C‐primary production and biomass changes in a small and shallow lake (Créteil Lake, France), overall phytoplankton losses were calculated through an annual cycle (November 1985‐October 1986). The summer period in 1986 is compared with two other summer periods in 1985 and 1980, these two years corresponding to extreme levels of algal biomass.2. Independent from the trophic state of the lake, phytoplankton populations were dominated by small‐sized species (<20 μm); their high growth rate (maximal in May and June: 0–8 day−1) was characteristic of nanoplanktonic natural populations.3. The positive correlation between phytoplankton losses and production indicates a close coupling between growth and loss processes.4. With a high filtering rate (0.22 day−1 as an annual average), zoo‐plankton impact is considerable at any time of the year but especially in late summer, when grazing losses exceeded primary production.5. Despite the uncertainty concerning the meaning of 14C‐primary production, the persistence of small algae throughout the year implies that a great part of the phytoplankton production was harvested by grazers which led to a recycling of organic matter within the water column.
Analysis, purification and quantification of extracellular DNA from aquatic environments
Authors: BEEBEE TREVOR J. C. 
Published: May 2006

SUMMARY 1. The presence of extracellular DNA, but not RNA, at μg 1−1 concentrations was demonstrated in seawater, river water and in a series of eutrophic lowland ponds.2. Extracellular DNA in natural waters invariably comprised two major components: one of high molecular weight (>20 kb) derived from viruses, and another of low molecular weight (1–500 bp) and apparently free in solution. Similar species of DNA molecules were produced within 2 weeks in simple laboratory modules.3. A purification procedure was developed which separated extracellular DNA from other components of dissolved organic matter, and which also separated viral from soluble DNA. Both types of DNA were purified sufficiently to constitute active templates for enzymes used in DNA manipulation.
The structure of a natural population of the medicinal leech, Hirudo medicinalis, at Dungeness, Kent
Authors: WILKIN P. J. , SCOFIELD A. M. 
Published: May 2006

SUMMARY 1. A hot branding method was used to mark medicinal leeches (Hirudo medicinalis L.) from five samples (four in 1984, one in 1985) at agravel pit at Dungeness in Kent. Analysis of capture‐recapture data by the Fisher‐Ford and Jolly methods gave similar results and indicated a population in excess of 10000 (0.112 leeches per m2) in 1984 and 1985. Successive estimates were each higher than the last suggesting a thriving community.2. The population structure was skewed towards the lower weight classes. This may indicate good recruitment of hatchlings, as also indicated by the presence of cocoons, or the failure to capture heavier satiated or gravid leeches because of their relative unresponsiveness to the sampling method involving water disturbance, or their complete absence from the water during cocoon laying. Gravid leeches were always above 2 g in weight. Recaptured marked leeches revealed that they migrated throughout the site, indicating active foraging for hosts.
Major ion chemistry of the lower Boro River, Okavango Delta, Botswana
Authors: SAWULA G. , MARTINS E. 
Published: May 2006

SUMMARY.
1. The composition of surface waters of the Boro River, Okavango Delta, Botswana, was determined on five occasions during 1989–1990. The waters could be characterized as caicium—sodium—bicarbonate, with moderate alkalinity, and moderate to high amounts of silica. Mean values of the major ions, in mg1‐−1, were: Ca2+ 4.8, Mg2+ 1.3, Na+ 3.9, K+ 2.7, HCO3− 27, Cl− 1.0 and SiO2 38; pH c. 7.2. The relative ionic composition of the waters changed gradually from the inlet in Seronga to the outlet at Boro/Thamalakane junction. There was a gradient of increasing concentrations of solutes resulting from the evaporative concentration of the waters in this semi‐arid region with an almost permanent water deficit, and the total dissolved solutes increased from c. 30 to 95 mg 1‐−13. There were seasonal differences in solute concentrations, connected with the rainfall pattern and climatic cycle and an ill‐defined relation with discharge. The chemical spectrum of the Boro, and the freshness of its waters, can be attributed to the major influence of precipitation within the basin and selective removal of solutes.4. Chemical equilibrium models indicate that amorphous silica and sepiolite are likely to precipitate from the Boro waters. Carbonate and silicate systems are responsible for the selective removal of solutes in the swamps, islands, or flood plains, as proposed by others in recent studies, but not in the Boro River waters.
Diurnal variation in light and carbon limitation of photosynthesis by two species of submerged freshwater macrophyte with a differential ability to use bicarbonate
Authors: MADSEN TOM V. , MABERLY STEPHEN C. 
Published: May 2006

SUMMARY.
Rates of photosynthetic oxygen evolution by Callitriche cophocarpa and Ranunculus peltatus in stream were measured on live occasions during the light period on 2 days at ambient light and ambient inorganic carbon, ambient light and saturating inorganic carbon, saturating light and ambient inorganic carbon, saturating light and saturating inorganic carbon and air‐equilibrium inorganic carbon and ambient light.
Despite an ambient CO2 concentration of about 220 μm, which is about ten times air‐equilibrium, the concentration of inorganic carbon was more limiting than light on all the occasions that rates were measured. On average, rates of photosynthesis at ambient concentrations of CO2 were about 130 and 425 μmol O2 g−1 DW h−1 for C. cophocarpa and R. peltatus, respectively. These rates as a percentage of carbon saturated rates were only about 35% for C. cophocarpa and about 60% for R. peltatus. Ambient rates as a percentage of light saturated rates were about 80% for C. cophocarpa and about 95% for R. peltatus. Only in early morning and late evening where the photon irradiance was below 160 μmol m−2 s−1 was there evidence for slight light limitation.
Based on results from pH‐drift experiments and from rates of photosynthesis as a function of CO2 concentration in the presence and absence of HCO3−, C. cophocarpa was unable, but R. peltatus able to use HCO3− at an ambient HCO3− concentration of about 0·84 mm. The greater rates of photosynthesis at ambient CO2 concentration and the lesser limitation by inorganic carbon shown by R. peltatus compared to C. cophocarpa was the result of HCO3−‐use as laboratory experiments showed that R. peltatus performed similarly to C. cophocarpa if the HCO3− concentration was reduced to 60 μm.
Distributions of Ephemeroptera, Plecoptera, and Trichoptera of three maritime catchments differing in pH
Authors: PETERSON R.H. , VAN EECKHAUTE L. 
Published: May 2006

SUMMARY1. Two broad‐scale environmental influences affecting species of Ephemeroptera, Trichoptera and Plecoptera inhabiting riffle habitat of three study catchments in New Brunswick and Nova Scotia were stream size‐temperature‐related variables and acidity‐related variables.2. Species richness was most affected by acidity in tributaries of intermediate size <0.001<0.1m3s−1).3. Of the three insect orders investigated, mayfly species richness was affected most by acidity, and stonefly species richness affected least by this factor.4. Zoogeographical isolation of the Nova Scotian catchments resulted in absence of some species of low general abundance, but these species had little influence on the site classification by TWINSPAN analysis.5. Predaceous stoneflies were collected in greater numbers from circumneutral sites and predaceous caddisflies in greater numbers from the Nova Scotian sites.6. Although the Nova Scotian catchments have probably been historically acidic, due to high concentrations of organic acids, pH currently limits the distributions of many indigenous invertebrate species. These species may be vulnerable to the more recent, additional, anthropogenic acidification of these catchments.
Feeding by blackfly larvae (Diptera: Simuliidae) forming dense aggregations at lake outlets
Authors: WOTTON R.S. 
Published: May 2006

SUMMARY1. Larvae of Simulium noelleri formed dense aggregations (>60 larvae cm−2) at a lake outlet where water passed in a very thin film vertically over wooden planks. Despite the high densities there was sufficient space between larvae to allow water to flow within an aggregation as well as over its surface.2. Small larvae, occluded within an aggregation, had a faster midgut throughput rate than larger larvae. Both had rates that were similar to those recorded in the literature for a range of habitats and species. The same relationship of throughput rate and larval size was maintained from upstream to downstream across 20cm of an aggregation.3. Material passed through the midgut of larvae of a given size at a constant rate, indicating that assimilation efficiency of the whole gut contents was low.4. By colour‐banding larval gut contents with fluorescent dye it was possible to demonstrate that faecal pellets are a component of the larval diet in the dense aggregations, especially of small larvae.5. The abundance of four easily identifiable components of the lake seston were measured from water samples above, and below, a larval aggregation. Particles with a mean diameter of 40 μm, or greater, showed significant reductions in numbers over a stream length of 6cm. Particles of smaller size showed reductions but these were not significant.
The effects of stream acidity on benthic invertebrate communities in the south‐eastern United States
Authors: ROSEMOND A.D. , REICE S.R. , ELWOOD J.W. , MULHOLLAND P.J. 
Published: May 2006

SUMMARY1. Patterns in invertebrate community structure were determined from analysis of benthic samples taken quarterly for 1 year from four sites in the Great Smoky Mountains National Park (GSMNP). Sites ranged in baseflow pH from 4.5 to 6.8, with a corresponding range in inorganic monomeric aluminium concentrations from 3 to 197 μgl−1.2. Total invertebrate density (excluding Chironomidae) was correlated with pH (R2= 0.90, P<0.05). Density of Ephemeroptera was more highly correlated with pH than density of invertebrates in other taxonomic orders. Invertebrate density (total and density of different orders) was generally more strongly correlated with pH than to inorganic monomeric aluminium concentrations.3. Species richness declined from sixty‐nine species at the highest pH site to thirty‐three species at the lowest pH site. Richness of Ephemeroptera and Trichoptera was positively correlated with pH (R2= 0.96 in both cases). Trichopteran richness was also negatively correlated with inorganic monomeric Al concentrations (R2= 0.96, P< 0.05). Plecopteran richness was not related to stream acidity.4. Not all species of Ephemeroptera were negatively affected by low stream water pH. At low pH sites, Ameletus lineatus Traver (Family: Siphonoluridae) was relatively more abundant compared to other species of Ephemeroptera, and had greater biomass and greater weight per individual length than at higher pH sites.5. Differences in invertebrate community parameters among sites were not based on changes in food abundance. Although grazer densities were positively correlated with pH (R2= 0.93, P < 0.05), differences in density were not related to differences in food. To the contrary, lower grazer densities occurred at the lowest pH site where measured food abundance (algae) was highest. Likewise, shredder density increased with increasing pH but was correlated with standing stocks of benthic organic matter (BOM), which had generally higher standing stocks at lower pH sites.6. Transplants of two species of Ephemeroptera between sites differing in pH (6.4 v 5.0) resulted in increased mortality of organisms placed at lower pH sites. In another transplant experiment, differences in mortality were not observed, although surviving invertebrates at low pH sites had ×10 higher body burdens of aluminium following the transplant than invertebrates from the reference site.7. These results indicate that direct effects of pH and Al (affecting survival) were more important than indirect effects of food availability in determining changes in invertebrate community structure between the study sites.
The relationship between pH and community structure of invertebrates in streams of the Shenandoah National Park, Virginia, U.S.A.
Authors: FELDMAN RICHARD S. , CONNOR EDWARD F. 
Published: May 2006

SUMMARY1. A replicated natural experiment was used to assess the influence of pH and low alkalinity on abundance and richness of invertebrate families in streams draining catchments that receive acid deposition. Individual streams were used as the unit of replication, allowing conclusions to refer to a class of streams rather than to particular streams.2. We also controlled for several factors other than pH and alkalinity, including flow and temperature, that are recognized as determinants of invertebrate distribution. Samples were from indigenous rocks, standardized for size, surface area, and geology.3. Repeated measures analyses of variance (ANOVA) revealed that invertebrate abundance and richness were significantly lower at pH 5.8 than at pH 7.1 for the total community. Thirty per cent of the forty‐seven families exhibited significantly lower abundance at pH 5.8; thirteen families were absent at pH 5.8. Differences were greatest for Ephemeroptera: species richness was significantly lower at pH 5.8, and 71% of the twenty‐four species were either absent (seven) or found in reduced abundance (ten) in the acidic streams.4. Stream alkalinity is projected to continue to decrease with continued acid deposition in the Shenandoah National Park. Concurrent decreases in pH may lead to the absence or continued numerical decline of certain Ephemeroptera species in streams that acidify to less than pH 6.0 and/or 50μEql−1 alkalinity.
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. Processing of five species of terrestrial leaves was compared in two summers and two winters at forest and pasture sites in each of two south‐eastern Australian streams, using leaf packs fastened with plastic buttoneers and anchored to capping bricks.2. Soluble carbohydrate and polyphenolics were rapidly lost from the leaves, mostly within 2 days. Total phosphorus and lipid contents remained constant, and nitrogen increased by about 50% over the period to 50% of leaf weight lost.3. Processing rates, expressed in terms of the negative exponential decay coefficient varied widely for each leaf species, but the rank ordering was consistent withPomaderris asperaandEucalyptus; viminalisprocessed at similar, rapid rates followed byCorrect lawrentiana, Acacia melanoxylonandBlechnum nudum. Abscissed leaves were processed more slowly than fresh leaves.4. Processing rates were significantly (P < 0.05) different between the two streams, and between leaf species, but there were no consistent differences between processing rates in winter and summer or between forest and pasture sites.5. When decay coefficients were calculated on a degree day basis,Eucalyptus viminalisleaves were processed significantly faster (P<0.05) in summer than in winter, whereasPomaderris asperaleaves were processed significantly more rapidly in winter than summer (P<0.05); processing rates ofAcacia melanoxylonphyllodes were not significantly different between the two seasons
The drifting of invertebrates and particulate organic matter in an Austrian mountain brook
Authors: WARINGER J.A. 
Published: May 2006

SUMMARY1. The drift of organisms and particulate organic matter in a calcareous mountain brook near Lunz, Lower Austria, was investigated for 1 year. Five sets of three drift nets (sampling at different water depths) were distributed along a cross‐section of the brook.2. From February to March 1989, samples were taken at intervals of 2–7 days over 24‐h periods, at the end of which the drift nets were emptied. From April 1989 to March 1990, sampling was carried out at monthly intervals and the nets emptied every 3h for 1 full day.3. Of 71 810 organisms caught, the most abundant taxa were Diptera (46.6%; mainly Chironomidae and Simuliidae), Ephemeroptera (24.0%; dominated by Baetis spp.) and Plecoptera (16.1%).4. The drift density (mean ± 95% CL) was significantly higher (P<0.05) in spring and summer (2.50 ± 0.32 specimens m−3) than in autumn and winter (2.01 ± 0,22 specimens m−3). In terms of biomass (wet weight), drift density was also significantly higher (P < 0.001) in spring and summer (2.50 ± 0.48 mgm−3) than during the rest of the year (1.04±0.12mgm −3).5. Total drift rates through a cross‐section of the brook ranged from 17366 organisms per day at low discharge (water depth = 10cm) to 955152 individuals per day at a water depth of 50cm in autumn and winter; in spring and summer the corresponding values were 21600 and 1188000 specimens per day.6. Ephemeroptera, Plecoptera, Coleoptera and Simuliidae were most abundant in night samples, whereas Hydracarina, Trichoptera and Chironomidae drifted mainly during daylight hours.7. Drift density (dry weight) of particulate organic matter was positively correlated with discharge and ranged from 2.16mgm−3 at a water depth of 10cm to 17.39mgm−3 at 50cm.
Invertebrate drift in a large, braided New Zealand river
Authors: SAGAR P.M. , GLOVA G.J. 
Published: May 2006

SUMMARY1. The spatio‐temporal patterns of drifting macroinvertebrates in a large, braided New Zealand river were determined by sampling with drift nets, seasonally, for 1 year.2. Drift densities were greatest in autumn, and at night in all seasons except winter. A greater proportion of larger animals drifted at night than during the day in all seasons. Mean annual drift densities were ninety‐six animals 100m−3 and 47 mg dry weight 100 m−3.3. There were relatively few taxa in the drift, and the mayfly Deleatidium spp. comprised more than 85% of the drifting aquatic invertebrates in all seasons except autumn. Chironomidae and terrestrial forms were the only other groups to occur at densities of more than one animal 100 m−3 in all seasons.4. Drift density was positively correlated with benthic density, which in turn was adversely affected by floods, particularly during spring and summer.
Population responses of the freshwater amphipod crustacean Gammarus pulex (L.) to copper
Authors: MAUND S.J. , TAYLOR E.J. , PASCOE D. 
Published: May 2006

SUMMARY1. Populations of Gammarus pulex (density 4000m−2) were exposed, over a 100‐day period in a continuous‐flow dosing system, to concentrations of copper below the 240 h median lethal concentration (LC50) for juveniles.2. There was a significant effect of copper on the resulting population density. In the control and lowest treatment (11.0μg1‐−1) it was double the initial density, but with increasing copper concentration there was a decrease in density until at the highest treatment (23.1 μg1‐−1), it was less than that of the initial population. The lowest observed effect concentration (LOEC) for population density was 14.6 μg 1‐−1.3. Copper significantly affected the age composition of the final populations. In the control and lowest treatment concentration, the population was composed mainly of juvenile animals. With increasing copper concentration, however, there was a decrease in the number of juveniles, the LOEC being 14.6 μg1‐−1. The number of adults in the final population was also significantly reduced by copper, with an LOEC of 18.2 μg1‐−1.4. The relationship between the body length and number of antennal segments of animals in the populations at each treatment concentration showed that growth was impaired by increased copper concentrations.