bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microbial growth and detritus transformations during decomposition of leaf litter in a stream
Authors: FINDLAY STUART E. G. , ARSUFFI THOMAS L. 
Published: May 2006

SUMMARY. 1. Despite the widely accepted importance of bacteria and fungi in degrading detritus in aquatic ecosystems there is still very little quantitative information on the abundance and dynamics of these microorganisms. Using epifluorescent microscopy, we measured the biomass of bacteria and fungi during decomposition of three types of leaf detritus. Bacterial production was determined from the rate of incorporation of 3H‐thymidine into DNA.2. The transformation of leaf carbon into dissolved organic carbon and fine particulate organic carbon was followed in order to compare the amounts of leaf material that were converted into these ‘end‐products’ of decomposition versus the amount converted into microbial biomass.3. The amount of microbial carbon in the leaf‐detritus complex never exceeded 5.2% of the total carbon, and fungal biomass was always much greater than bacterial biomass. Despite the greater standing stock of fungi, the rapid turnover of bacteria (doubling about once per day) implies that their role in degrading leaf litter or as a food source for detritivores might be as great as for fungi.4. Removal of microbial biomass from leaf litter may occur as release of fungal spores and consumption or shedding of bacterial biomass. Fungal spores can be a significant part of the fine particulate organic carbon released from leaf detritus and potentially represent an important food resource for filter‐feeding organisms.
The need for long‐term investigations in ecology and the contribution of the Freshwater Biological Association
Authors: ELLIOTT J. M. 
Published: May 2006

SUMMARY1. Long‐term investigations have provided critical data on a number of practical issues that are of concern to society, and have made important contributions to the development and testing of ecological theory.2. Some of the questions answered by long‐term investigations are briefly reviewed. The major objectives of such investigations are usually to provide reliable estimates of base‐line variation, to detect long‐term trends in the mean level of the base‐line, to detect rare events and to provide information for meaningful, testable hypotheses.3. The contributions of the Freshwater Biological Association are listed in a summary table that covers all projects lasting for 20 years or longer with at least one sample per year. Most projects are in the Windermere catchment and it is proposed that the latter should become the first U.K. Long Term Reference Site for the freshwater environment.
Contrasting responses of two cladocerans to changes in the nutritional value of nannoplankton
Authors: MATVEEV VLADIMIR F. , BALSEIRO ESTEBAN G. 
Published: May 2006

SUMMARY. 1. The potential tor competition in the zooplankton of small Araucana Lake (Andes, Argentina) was tested experimentally.2. Laboratory enrichment of lake water with nutrients resulted in an increased abundance of nannoplankton with the cyanobacteria Gloeocapsa minor predominating.3. The dominant species of zooplankton showed contrasting responses to enrichment: the abundance of Bosmina longirostris increased, whereas that of Ceriodaphnia dubia decreased relative to the corresponding controls.4. The clearance rates for various nannoplankton by these cladocerans were similar, resulting in high niche overlap as estimated by the Pianka index.5. Life table experiments showed that when fed on a pure suspension of lake flagellates (103 cells ml−1) Ceriodaphnia had a significantly higher average intrinsic rate of natural increase (r) than on a suspension of Gloeocapsa (0.28v. 0.146); in the case of Bosmina no significant differences for the two foods were found (0.182 and 0.141, respectively).6. The contrasting responses of the animals to enrichment are explained by the differing suitability of particular nannoplankton species as food for different cladoceran species. The seasonal succession in the species composition and food quality of nannoplankton may be important for the coexistence of competing zooplankters in lakes.
Experimental evidence quantifying the role of benthic invertebrates in organic matter dynamics of headwater streams
Authors: CUFFNEY THOMAS F. , WALLACE J. BRUCE , LUGTHART G. JOHN 
Published: May 2006

SUMMARY. 1. The insecticide methoxychlor was applied seasonally to one of three small headwater streams in the southern Appalachian Mountains in North Carolina, U.S.A. The initial application caused massive invertebrate drift (>1,000,000 organisms/week) and resulted in a community with few shredders and reduced abundances of most insect taxa.2. Bacterial densities and microbial respiration rates were not affected by treatment.3. Disruption of the invertebrate community resulted in significant reductions in leaf litter processing rates (50–74% reduction depending on leaf species) and in the amount of leaf litter processed annually (reduction of 25–28%).4. Reductions in leaf litter processing rates resulted in significant reductions in fine particulate organic matter (FPOM) export. Declines in both concentration and total export were detectable within 1 week of treatment. Annual FPOM export was reduced to 33% of pretreatment levels. Alteration to the invertebrate community had a much greater effect on FPOM export than a severe (50–200 year) drought.6. Course particulate organic matter (CPOM) export was not significantly influenced by treatment but was influenced by hydrologic differences among years.
Intra‐ and inter‐specific variations in egg survival and brood development time for Austrian populations of Gammarus fossarum and G. roeseli (Crustacea: Amphipoda)
Authors: PÖCKL M. , HUMPESCH U. H. 
Published: May 2006

SUMMARY. 1. Egg survival (ES, percentage of eggs hatched in vitro), reproductive success (RS, percentage of live young released from the brood pouch) and brood development lime (d, days) in four populations of Gammarus fossarum and two populations of Gammarus roeseli were studied, in the laboratory at water temperatures of 2.0–26.1°C. Intraspecific differences between populations were not significant, but interspecific differences were found between the two species.2. In natural stream populations, the reproductive period of G. fossarum lasted from December to September, that of G. roeseli from March to September.3. In the experimental temperature range 2–26°C, 73% of the total number (771) of G. fossarum females and 69% of 469 G. roeseli females were ovigerous. Of these, 45% of G. fossarum and 43% of G. roeseli females successfully released live young from their brood pouches.4. For G. fossarum, the optimum temperatures were 11.4°C for ES, where 76% of the eggs hatched, and 11.8°C for RS, where 77% of the females released live young from their brood pouches. For G. roseli, the optimum temperatures were 13.5°C for ES (51% hatched) and 14.0°C for RS (76% released). Over 50% of eggs hatched at temperatures of 3.6–19.2°C in G. fossarum and at 1 1.9–15.1°C in G. roeseli. Development time increased from 12 days at 21.9°C to 251 days at 2.0°C in G. fossarum, and from 10 days at 24.1°C to 212 days at 4.1°C in G. roeseli.5. interspecific differences between the effects of water temperature on ES, RS and d are used to explain the different distributional patterns of G. fossarum and G. roeseli in central European running water systems. assuming that other physico‐chemical variables are suitable for both species.
Competition and coexistence in submerged aquatic plant communities: the effects of species interactions versus abiotic factors
Authors: CHAMBERS P. A. , PREPAS E. E. 
Published: May 2006

SUMMARY. 1. Aquatic plant biomass and species composition were studied at three sites in Long Lake, Alberta, Canada, to examine the role of biotic and abiotic factors in determining species diversity.2. Results of controlled in situ experiments to test for interspecific competition showed that biomass of plants in four different mixed communities did not increase in response to selected species removals (P>0.1,n=16).3. In contrast, biomass of the dominant taxa (Myriophyllum exalbescens, Ceratophyllum demersum and Chara sp.) were correlated (P<0.05) with abiotic factors (i.e. distance from shore, water depth, sediment exchangeable phosphorus concentration and/or sediment organic content).4. These results suggest that interspecific competition between naturally coexisting species of submerged aquatic plants is slight and that spatial heterogeneity or differential utilization of abiotic resources promotes species diversity in submerged plant communities.
Responses of periphyton to changes in current velocity, suspended sediment and phosphorus concentration
Authors: HORNER RICHARD R. , WELCH EUGENE B. , SEELEY MARGUERITE R. , JACOBY JEAN M. 
Published: May 2006

SUMMARY.

Research was performed in laboratory streams to evaluate periphytic biomass accrual, export, and community composition over a range of limiting nutrient (phosphorus) concentrations with variable velocity, and suspended sediment addition, in comparison to constant velocity and no suspended sediment. In fixed‐velocity treatments, velocity increase to 60 cm s−1 significantly enhanced biomass accrual, but further increase resulted in substantial biomass reduction. Average biomass loss rates did not change significantly over a velocity range of 10–80 cm s−1. Diatoms were favoured at relatively high velocities and low phosphorus concentrations, whereas the blue‐green Phormidium tended to dominate at higher SRP concentrations and the green Mougeotia seemed to prefer lower velocities.
Sudden increases in velocity raised instantaneous loss rates by an order of magnitude or more, but these high rates persisted only briefly. As a result, marked biomass reductions were not apparent a day after the velocity change. Dominance change from filamentous green or blue‐green to diatoms immediately after the increase was reversed within 2 days. Loss rate increases due to solids addition were much smaller than those accompanying velocity increase, but simultaneous velocity elevation and solids addition produced instantaneous loss rates approximately double those with velocity increase alone.
The experiments demonstrated that an elevation in velocity, above that to which algae were accustomed, led to increased loss rates and temporarily reduced biomass. However, recolonization and growth after biomass reduction were apparently rapid. Substantial export of periphyton following solids addition required erosion of the protective boundary layer accompanied by a velocity increase. These results arc applicable to understanding the response of lotic periphytic algae to elevated, turbid storm discharges and similar runoff or high‐flow events.
Areal uptake rates of P by algae growing in the laboratory streams increased with soluble reactive phosphorus (SRP) concentration, up to approximately 15 μg I−1 in overlying water. They also increased above 35 cm s −1. Overall, uptake rate seemed to vary inversely with biomass. The ralio of areal uptake rate/biomass was significantly less where mean biomass was 411±6 mg chl a m−2 compared to 223±17 mg chl a m−2.
The results suggested that although nutrient uptake is primarily a surface phenomenon, diffusion to interior cells can also determine the responses of attached communities. Both diffusion and uptake rate were stimulated by increasing nutrient concentration and velocity up to certain levels, but became limited by biofilm thickness and scouring.
Microhabitat use by Blennius fluviatilis in the Río Matarraña, Spain
Authors: FREEMAN MARY C. , VIÑOLAS DOLORS , GROSSMAN GARY D. , DE SOSTOA ADOLFO 
Published: May 2006

SUMMARY.

Microhabitat use by Blennius fluviatilis in the Río Matarraña, Spain, varied significantly among dates during a 19‐month study. Most temporal variation, however, was attributable to changes in microhabitat availability.
B. fluviatilis demonstrated non‐random use of available microhabitats during each sampling period, and generally occupied deeper microhabitats with higher average current velocities dominated by rubblegravel substrates.
B. fluviatilis also demonstrated non‐random use of available nest sites; males generally nested under the largest available pieces of rubble, in areas with less gravel or sand. Water column depth influenced nest site use in two of four study areas.
We found few microhabitat differences between spawning and nonspawning periods, or between males and females. In addition, microhabitat use was similar among B. fluviatilis size‐groups.
Although B. fluviatilis often were over‐represented in deeper, erosional areas, blennies necessarily inhabited a wide range of microhabitats because average current velocities and water depths fluctuated greatly during the study. Tolerance of a broad range of environmental conditions may contribute to the species' persistence in habitats that exhibit extreme seasonal changes in discharge such as the Matarraña.
Fire and the dynamics of allochthonous detritus in a South African mountain stream
Authors: BRITTON D. L. 
Published: May 2006

SUMMARY.

Input of allochthonous material, standing stocks of benthic organic matter (BOM) and suspended paniculate organic matter (POM) were measured in a south‐western Cape mountain stream from March 1986 to February 1988. The surrounding fynbos‐dominated catch‐ment was subjected to a prescribed burn in March 1987.
Litter‐fall in the pre‐burn year exhibited a distinct seasonal pattern, with peak falls during the early summer. Although the riparian canopy was not directly affected by the fire, in that it did not burn, a heavy, aseasonal leaf‐fall occurred shortly afterwards. The following summer, litter‐fall was less than half that of the pre‐burn summer.
Standing stocks of BOM were significantly higher in autumn than in winter in the pre‐burn year and were inversely related to discharge. Despite the heavy post‐burn leaf‐fall and low litter‐fall during the post‐burn summer, there was no significant difference between pre‐ and post‐burn BOM standing stocks.
Proportions and quantities of fine benthic organic matter (FBOM) in the soft BOM fraction were significantly higher in the post‐burn spring, and monthly accumulation of ultra‐fine benthic organic matter (UBOM) was also significantly higher in the post‐burn spring and summer. These results may reflect accelerated decay rates of BOM in response to enhanced post‐burn nitrate concentrations in stream water.
Export of CPOM was low in comparison to FPOM and particularly to UPOM, and the stream appears to be highly retentive of CPOM.
The natural resilience of the riparian vegetation minimizes the potentially disturbing effects of fire on the stream environment. As a result, the prescribed burn had a less than expected effect on both standing stocks of BOM and the stream environment in general.
Bacterivory by deposit‐feeding mayfly larvae (Stenonema spp.)
Authors: EDWARDS RICK T. , MEYER JUDY L. 
Published: May 2006

SUMMARY.

The importance of bacteria in the diet of deposit‐feeding mayflies (Stenonema spp.) from the Ogeecnee River, a sixth order low‐gradient blackwater river in Georgia, U.S.A., was determined. Stenonema are abundant and productive on snags in biackwater rivers in the southeastern Coastal Plain of the U.S.A. Bacteria are abundant in the seston in this river, and are a potentially important food source.
Naturally occurring seston was fed to Stenonema larvae after bacterial DNA in the seston was labelled with methyl‐[3H]thymidine. Larval respiration measurements and growth rate estimations were used to compare the amount of bacterial carbon assimilated and retained in larval tissue to the carbon requirements of the larvae.
Stenonema larvae incorporated 8.7×107±1.3×107 bacteria larva−1 h−1 This was equivalent to 93±6% of their daily growth, and 47±3% of their total daily carbon needs. Larger larvae incorporated more bacterial biomass, but mass specific incorporation was not related to size. Ingestion of bacteria while eating seston accumulated on snags appears to be an important component of the diet of Stenonema larvae in these rivers.
Growth and development of larval northern cricket frogs (Acris crepitans) in relation to phytoplankton abundance
Authors: JOHNSON LAURA M. 
Published: May 2006

SUMMARY.
1. Tadpoles of Acris crepitans were collected from two ponds in central Illinois, Depth, water temperature, distance from shore and water samples were taken at each sample site. The potential for food limitation and non‐random habitat selection were examined.2. Algal densities from water samples averaged over 1.0× 106 cells ml−1 in Scott's pond hut only 4.6×103 cells ml−1 in Vic's pond.3. Guts of tadpoles from Scott's pond contained more algal cells than did guts of tadpoles from Vic's pond. Tadpoles from Scott's pond were consistently larger and more advanced in development than tadpoles collected from Vic's pond at the same lime. Therefore, tadpoles of Scott's pond were able to utilize the higher algal densities whereas tadpoles of Vic's pond may be food‐limited, causing reduced growth and development.4. Canonical discriminant analysis was used to test whether sites with different numbers of tadpoles could be distinguished based on environmental variables. Canonical function I was primarily a measure of water depth at a sample site. This function was significant in Scott's pond only. Sites containing one or more tadpoles were not easily distinguished from each other, but were found in consistently shallower water than sites where no tadpoles were found.
Phenology and the influence of meteorological parameters on the catching success of light‐trapping for Trichoptera
Authors: WARINGER J. A. 
Published: May 2006

SUMMARY.
1. Adult Trichoptera were caught for 1 year (February 1989‐March 1990) on the banks of the Danube at Bad Deutsch Altenburg, Lower Austria, using a Jermy‐type light trap. The blacklight tube of the trap was in operation all night, and the samples were taken at daily intervals. From a total of 33,465 specimens caught, the most abundant species were Psychomyia pusilla Fabr. (Psychomyidae), the three hydropsychids Hydropsyche pellucidula Curtis. Hydropsyche bulgaromanorum Mal. and Hydropsyche contubernalis McL., and the leptocerid Ceraclea dissimilis Steph.2. The total catch included fifty‐three of the 284 Austrian species from thirteen families. One female of the parthenogenetic Apatania muliebris McL. was the second specimen ever collected in Austria.3. The phenology of seventeen species was studied in detail, all of them summer species. Two types of flying seasons were observed: short flight periods of 3 months or less (seven species) and prolonged periods lasting 4–7 months (ten species).4. In nine species the sex ratio was significantly different from 1:1.5. The influence of precipitation, wind speed and night air temperature (maximum, mean and minimum) on catching success was tested. Only the effect of air temperature was significant with maximum night air temperature having a highly significant (P<0,001) correlation with flight activity. No specimens were caught at maximum temperatures below 6.8°C, and catching success was highest on warmest nights.
Suspended clay reduces Daphnia feeding rate
Authors: KIRK KEVIN L. 
Published: May 2006

SUMMARY.
1. Suspended sediments often reduce cladoceran abundance in the field, and reduce the algal feeding rates of cladocerans in the laboratory. This paper explores the behavioural mechanisms by which suspended clay reduces Daphnia feeding rates. Feeding experiments using radiolabelled Cryptomonas cells showed that 50–200 mg 1‐−1 coarse suspended clay (particle size<2 μm) reduced the algal ingestion rate of Daphnia ambigua by 29–87%, but fine suspended clay (<1 μm) had no effect. Suspended clay decreased feeding rate by 60–70% at low algal concentrations (≤5×103 cells ml−1), but by only 27% at high algal concentrations (20×103 cells ml−1). Thus, the inhibitory effects of suspended clay are greater at low algal concentrations. The sudden addition (or removal) of suspended clay caused immediate reductions (or increases) in algal ingestion rate.2. Observations of the feeding behaviour of tethered D.pulex showed that the frequency of postabdominal rejections increased greatly in the presence of suspended clay. The rejected boluses contained both algae and clay. Thoracic feeding appendage beat frequency decreased in the presence of suspended clay, decreasing the volume of water searched for food particles.3. These behavioural responses indicate that clay reduces cladoceran feeding rate by mechanically interfering with both the collection and ingestion of algal cells. Both inhibitory effects are caused because cladocerans collect and ingest suspended clay particles. The behavioural mechanisms by which cladocerans regulate their feeding rate in very high concentrations of algal cells (rejection of excess food and reduction in thoracic limb pumping movements) are the same mechanisms responsible for the inhibition of algal ingestion rate in the presence of high concentrations of suspended clay particles.
Effect of food concentration on the carbon balance of Bosmina longirostris (Crustacea: Cladocera)
Authors: URABE JOTARO 
Published: May 2006

SUMMARY.
1. The carbon balance of the small cladoceran, Bosmina longirostris, was examined at four food concentrations (0,05, 0.10, 0.25, 2.50mg C 1‐−1) based on long‐term growth experiments.2. At birth, B. longirostris allocated about 60% of assimilation to body growth at all food concentrations. However, allocation to body growth decreased with age and was less than 5% after the fourth instar at the lowest food concentration. The proportion allocated to reproduction increased with increasing food concentration, but was relatively constant among different adult instars.3. Assimilation rate increased with increasing food concentration and increasing body size: the mean rate from birth to 15 days was 6.6 times higher at the highest food concentration than at the lowest food concentration. However, with decreasing food concentration and increasing body size, a higher proportion of the assimilated carbon was lost as respiration. As a result, the net production rate reached a plateau at intermediate body size and was 9.1 times higher at the highest food concentration than at the lowest food concentration.4. Comparison with previous studies revealed that B. longirostris is more efficient than Daphnia with regard to carbon production, especially at low food conditions, if the death rate is negligible.