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  • 1
    Online-Ressource
    Online-Ressource
    Methods in Stream Ecology : Volume 2: Ecosystem Function. (2017)
    San Diego :Elsevier Science & Technology,
    Details
    Schlagwort(e): Stream ecology. ; Electronic books.
    Materialart: Online-Ressource
    Seiten: 1 online resource (374 pages)
    Ausgabe: 3rd ed.
    ISBN: 9780128132692
    URL: https://ebookcentral.proquest.com/lib/geomar/detail.action?docID=4860954
    DDC: 577.6/4
    Sprache: Englisch
    Anmerkung: Front Cover -- Methods in Stream Ecology -- Methods in Stream Ecology -- Copyright -- Contents -- List of Contributors -- Preface -- D - Organic Matter Dynamics -- 23 - Stable Isotopes in Stream Food Webs -- 23.1 INTRODUCTION -- 23.1.1 Hypothetical Food Web Using δ13C and δ15N -- 23.1.2 Overview of Basic and Advanced Methods -- 23.2 GENERAL DESIGN -- 23.2.1 General Site Selection Considerations -- 23.2.2 General Procedures -- 23.2.2.1 Influence of Urbanization on Food Webs -- 23.2.2.2 Gradients in δ13C and δ15N in Basal Resources -- 23.2.2.3 Use of δD in Stream Food Web Studies -- 23.2.2.4 Use of Mixing Models to Quantify Food Web Transfers -- 23.3 SPECIFIC METHODS -- 23.3.1 Basic Method: Comparison of Stream Food Webs Using Stable Isotopes of C and N -- 23.3.1.1 Site Selection -- 23.3.2 Advanced Method 1: Tracing Use of a Novel Terrestrial Particulate Organic Matter Source in a Stream Food Web -- 23.3.3 Advanced Method 2: Tracing Spatial Variation in Diet Sources for Food Webs -- 23.3.4 Advanced Method 3: Tracing Shifts in Basal Resources of Stream Food Webs Using δD -- 23.3.5 Data Analysis -- 23.4 QUESTIONS -- 23.5 MATERIALS AND SUPPLIES -- REFERENCES -- 24 - Dissolved Organic Matter -- 24.1 INTRODUCTION -- 24.2 GENERAL DESIGN -- 24.2.1 Site Selection and Study Design -- 24.2.2 Sample Collection and Analysis -- 24.3 SPECIFIC METHODS -- 24.3.1 Basic Method 1: A Stream and Its Multiple Sources of Dissolved Organic Matter -- 24.3.2 Advanced Method 1: Heterotrophic Activity of Dissolved Organic Matter -- 24.3.2.1 Dark Incubation to Assess Bioavailability -- 24.3.2.2 Data Analysis -- 24.3.3 Advanced Method 2: Enzymatic Characterization of the Dissolved Organic Matter Demand -- 24.3.3.1 Enzyme Collection -- 24.3.3.2 Enzyme Activity Measurement -- 24.3.3.3 Data Analysis. , 24.3.4 Advanced Method 3: Fluorescent Analysis of Dissolved Organic Matter Composition -- 24.3.4.1 Data Analysis -- 24.3.5 Advanced Method 4: Limitations to Degradation -- 24.3.5.1 Nutrients -- 24.3.5.2 Photolysis/Photobleaching -- 24.3.6 Advanced Method 5: Sorption of Dissolved Organic Matter in Soils -- 24.4 QUESTIONS -- 24.5 MATERIALS AND SUPPLIES -- REFERENCES -- APPENDIX 24.1 -- APPENDIX 24.2 -- 25 - Transport and Storage of Fine Particulate Organic Matter -- 25.1 INTRODUCTION -- 25.2 GENERAL DESIGN -- 25.2.1 Seston -- 25.2.2 Fine Benthic Organic Matter -- 25.2.3 Linkages -- 25.2.4 Site Selection -- 25.2.4.1 Seston -- 25.2.4.1 Fine Benthic Organic Matter -- 25.2.4.2 Linkages -- 25.3 SPECIFIC METHODS -- 25.3.1 Basic Method 1: Seston Concentration -- 25.3.1.1 Protocol for Seston Sampling in Streams and Small Rivers -- 25.3.1.2 Protocol for Seston Sampling in Large Rivers -- 25.3.1.3 Standard Processing Protocols -- 25.3.1.4 Particle Size Separation Protocols -- 25.3.1.5 Optional Experiment A: Seston Export -- 25.3.1.6 Optional Experiment B: Seston Sampling During Storms -- 25.3.2 Basic Method 2: Fine Benthic Organic Matter -- 25.3.2.1 Protocols for Field Collection of Fine Benthic Organic Matter -- 25.3.2.2 Fine Benthic Organic Matter Processing Protocols -- 25.3.3 Advanced Method 1: Linkages of Sestonic Fine Particulate Organic Matter to the Biota -- 25.3.3.1 Field Release and Larval Collection -- 25.3.3.2 Laboratory Analysis -- 25.4 QUESTIONS -- 25.4.1 Seston -- 25.4.2 Fine Benthic Organic Matter -- 25.4.3 Linkages of Sestonic Fine Particulate Organic Matter to the Biota -- 25.5 MATERIALS AND SUPPLIES -- REFERENCES -- 26 - Coarse Particulate Organic Matter: Storage, Transport, and Retention -- 26.1 INTRODUCTION -- 26.2 GENERAL DESIGN -- 26.2.1 Site Selection -- 26.2.2 Basic Methods -- 26.2.3 Advanced Methods -- 26.3 SPECIFIC METHODS. , 26.3.1 Basic Method 1: Coarse Particulate Organic Matter Storage and Measurement -- 26.3.1.1 Field Measurements -- 26.3.1.2 Laboratory Processing -- 26.3.1.3 Data Analysis -- 26.3.2 Basic Method 2: Coarse Particulate Organic Matter Transport and Retention -- 26.3.2.1 Laboratory Preparation -- 26.3.2.2 Field Physical Measurements -- 26.3.2.3 Field Coarse Particulate Organic Matter Releases -- 26.3.2.4 Data Analysis -- 26.3.2.5 Option to Basic Method 2: Single-Particle Releases -- 26.3.3 Advanced Method 1: Enhancement of Stream Retentive Capacity -- 26.3.3.1 Laboratory Preparation -- 26.3.3.2 Field Measurements-Deployment of Retention Devices -- 26.3.3.3 Field Measurements-Related Ecosystem Measurements -- 26.3.4 Advanced Method 2: Measurement of Organic Carbon Spiraling -- 26.3.4.1 Site Selection -- 26.3.4.2 Field Measurements-Transported Organic Carbon -- 26.3.4.3 Field Measurements-Benthic Organic Carbon -- 26.3.4.4 Field Measurements-Organic Carbon Turnover -- 26.3.4.5 Field Measurements-Physical Characteristics of the Stream -- 26.3.4.6 Laboratory Processing -- 26.3.4 7 Data Analysis -- 26.4 QUESTIONS -- 26.5 MATERIALS AND SUPPLIES -- ACKNOWLEDGMENTS -- REFERENCES -- 27 - Leaf-Litter Breakdown -- 27.1 INTRODUCTION -- 27.2 GENERAL DESIGN -- 27.2.1 Site Selection -- 27.3 SPECIFIC METHODS -- 27.3.1 General Protocol for Leaf-Litter Breakdown Experiments -- 27.3.2 Basic Method 1: Leaf Breakdown for One or More Leaf Species -- 27.3.3 Basic Method 2: Effects of Spatially Varying Stream Features on Leaf Breakdown Rates -- 27.3.4 Advanced Method 1: Effects of Anthropogenic Activities on Leaf Breakdown Rates -- 27.3.5 Advanced Method 2: Assessing Relationships Among Leaf Breakdown Rates and Shredders -- 27.3.6 Advanced Method 3: Assessing Microbial Activity During the Litter-Breakdown Process -- 27.3.7 Field Protocol -- 27.3.8 Data Analysis. , 27.4 QUESTIONS -- 27.5 MATERIALS AND SUPPLIES -- REFERENCES -- 28 - Riparian Processes and Interactions -- 28.1 INTRODUCTION -- 28.2 GENERAL DESIGN -- 28.2.1 Quantifying Riparian Vegetation Communities -- 28.2.2 Attenuation of Solar Radiation-Shading -- 28.2.3 Input and Decomposition of Coarse Organic Matter -- 28.2.4 Transfer of Dissolved Organic Matter and Nutrients -- 28.2.5 Remote Sensing of the Riparian Zone -- 28.3 SPECIFIC METHODS -- 28.3.1 Site Selection -- 28.3.2 Basic Method 1: Quantifying Riparian Vegetation Communities -- 28.3.2.1 Point-Centered Quarter Method -- 28.3.3 Basic Method 2: Attenuation of Solar Radiation-Shading -- 28.3.3.1 Pyranometer or Quantum Sensor -- 28.3.3.2 Spherical Densiometer Measurements -- 28.3.3.3 Hemispherical Photo Measurements -- 28.3.4 Basic Method 3: Input and Decomposition of Coarse Particulate Organic Matter -- 28.3.4.1 Leaf Litter Traps -- 28.3.4.2 Measurement of Coarse Particulate Organic Matter Decomposition Rates -- 28.3.4.3 Assessment of Detritivore Standing Crops -- 28.3.5 Advanced Method 1: Transfer of Dissolved Organic Matter and Nutrients from the Riparius to the Stream -- 28.3.5.1 General Measures of Dissolved Organic Matter and Nutrient Transfer -- 28.3.5.2 Nitrogen Mineralization Potential -- 28.3.5.3 Stable Isotope Analysis -- 28.3.6 Advanced Method 2: Remote Sensing of the Riparian Zone -- 28.3.6.1 Satellite Imagery -- 28.3.6.2 Airborne-Based Imagery -- 28.3.6.3 Light Detection and Ranging -- 28.3.6.4 Classification of Vegetation and Riparian Patches -- 28.4 QUESTIONS -- 28.5 MATERIALS AND SUPPLIES -- REFERENCES -- 29 - Dynamics of Wood -- 29.1 INTRODUCTION -- 29.1.1 Dynamics of Wood in Streams -- 29.1.1.1 Storage -- 29.1.1.2 Breakdown and Decomposition -- 29.1.1.3 Input -- 29.1.1.4 Transport -- 29.1.2 Models of Wood Dynamics -- 29.1.3 Humans and the Dynamics of Wood -- 29.2 GENERAL DESIGN. , 29.2.1 Site Selection -- 29.2.2 Marking Techniques for Repeated Surveys -- 29.3 SPECIFIC METHODS -- 29.3.1 Basic Method 1: Estimation of Standing Stocks of Wood -- 29.3.1.1 Data Analysis -- 29.3.2 Basic Method 2: Line-Intersect Estimation of Large Wood -- 29.3.3 Basic Method 3: Long-Term Wood Retention and Transport -- 29.3.4 Advanced Method 1: Modeling Wood Accumulation -- 29.3.5 Advanced Method 2: Modeling Effects of Timber Harvest on Wood Accumulation -- 29.3.6 Advanced Method 3: Modeling Wood Abundance in a River Network -- 29.4 QUESTIONS -- 29.5 MATERIALS AND SUPPLIES -- REFERENCES -- E - Ecosystem Processes -- 30 - Conservative and Reactive Solute Dynamics -- 30.1 INTRODUCTION -- 30.1.1 Conservative Solute Dynamics -- 30.1.2 Reactive Solute Dynamics -- 30.2 GENERAL DESIGN -- 30.2.1 Site Selection -- 30.2.2 Tracer Selection -- 30.2.3 Release Techniques -- 30.2.4 Data Analyses -- 30.3 SPECIFIC METHODS -- 30.3.1 Basic Method: Dynamics of Conservative Solutes -- 30.3.1.1 Laboratory Preparation -- 30.3.1.2 Field Preparation-Prerelease -- 30.3.1.3 Field Procedure-Pulse Release -- 30.3.1.4 Field Procedure-Constant-Rate Release -- 30.3.1.5 After the Release -- 30.3.1.6 Estimating Discharge -- 30.3.1.7 Estimating Other Hydraulic Parameters -- 30.3.1.8 Transient Storage -- 30.3.2 Advanced Method: Reactive (Nonconservative) Solute Dynamics -- 30.4 QUESTIONS -- 30.5 MATERIALS AND SUPPLIES -- ACKNOWLEDGMENTS -- REFERENCES -- 31 - Nutrient Limitation and Uptake -- 31.1 INTRODUCTION -- 31.1.1 Elevated Nutrient Loading to Streams -- 31.1.2 Capacity for Nutrient Retention in the Landscape -- 31.1.3 Overview of Chapter -- 31.2 GENERAL DESIGN -- 31.2.1 Index of Limitation: Nutrient Diffusing Substrata -- 31.2.2 Short-Term Nutrient Addition -- 31.2.3 Short-Term 15N Tracer Release -- 31.3 SPECIFIC METHODS -- 31.3.1 Basic Method: Nutrient Diffusing Substrata. , 31.3.1.1 Laboratory Procedures.
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  • 2
    Digitale Medien
    Digitale Medien
    Restoring Stream Ecosystems: Lessons from a Midwestern State (2004)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Restoration ecology 12 (2004), S. 0 
    Details
    ISSN: 1526-100X
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Reach-scale stream restorations are becoming a common approach to repair degraded streams, but the effectiveness of these projects is rarely evaluated or reported. We surveyed governmental, private, and nonprofit organizations in the state of Indiana to determine the frequency and nature of reach-scale stream restorations in this midwestern U.S. state. For 10 attempted restorations in Indiana, questionnaires and on-site assessments were used to better evaluate current designs for restoring stream ecosystems. At each restoration site, habitat and water quality were evaluated in restored and unrestored reaches. Our surveys identified commonalities across all restorations, including the type of restoration, project goals, structures installed, and level of monitoring conducted. In general, most restorations were described as stream-relocation projects that combined riparian and in-stream enhancements. Fewer than half of the restorations conducted pre- or post-restoration monitoring, and most monitoring involved evaluations of riparian vegetation rather than aquatic variables. On-site assessments revealed that restored reaches had significantly lower stream widths and greater depths than did upstream unrestored reaches, but riparian canopy cover often was lower in restored than in unrestored reaches. This study provides basic information on midwestern restoration strategies, which is needed to identify strengths and weaknesses in current practices and to better inform future stream restorations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1061-2971.2004.0340.x
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  • 3
    Digitale Medien
    Digitale Medien
    Temporal patterns of grazer-periphyton interactions in laboratory streams (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 23 (1990), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: SUMMARY. 1. The snail Juga silicuta (500 m−2) and the caddisfly Dicosmoecus gilvipes (50 m−2) were introduced into separate laboratory streams on days 1, 9, 16 and 28 of algal development. The mayfly Baetis spp. (500 m−2) was introduced on days 1 and 16, and two streams did not receive grazers. We assessed the interaction between succession in the pcriphyton, herbivore type and time of encounter in a 40-day experiment.2. In ungrazed streams, the chlorophyte Scenedesmus obliquus was the most abundant early colonizer. The relative abundance of diatoms increased after day 9, and at day 40 the algal assemblage consisted of a thick mat of diatoms and S. obliquus with an overstorey of filaments of the chlorophyte Stigeoclonium tenue. In general, introductions of grazers at any stage altered this pattern by removing biomass, accelerating the replacement of S. obliquus by diatoms, and suppressing the growth of filaments. Grazing also reduced the relative abundance of the larger diatom Nitzschia oregona but increased the relative abundance of the smaller adnate diatoms Nitzschia frustulum var. perpusilla and Navicula minima.3. Dicosmoecus decreased algal biomass and altered successional trajectories to a greater degree than either Juga or Baetis. Dicosmoecus rapidly grazed the entire substrate, whereas Juga and Baetis only cleared patches in the assemblages. Little alteration in algal development was observed in the Baetis streams after day 16, probably because (he periphyton assemblages attained a size and structure that prevented effective grazing by Baetis.4. The patchy grazing patterns of Juga and Baetis resulted in more diverse algal assemblages than either the Dicosmoecus grazed or ungrazed streams. In natural streams, the temporal and spatial pattern of grazing relative to the developmental stage of the periphyton may contribute to maintaining a mosaic of algal patches in different serai stages.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2427.1990.tb00289.x
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  • 4
    Digitale Medien
    Digitale Medien
    Subsurface hydrology and degree of burial affect mass loss and invertebrate colonisation of leaves in a woodland stream (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: SUMMARY 1. In deciduous forest streams, fallen leaves form a large component of the total organic matter budget, and many leaves become buried within stream sediments. We examined the processing of buried leaves as compared with those at the surface, and the influence of subsurface hydrology on processing rates.2. Leaf packs were secured on the streambed surface or buried 10 cm deep in upwelling and downwelling reaches of a second-order stream in Michigan, U.S.A. Mass loss and invertebrate colonisation were measured from October to February.3. Leaves buried in upwelling reaches lost mass more slowly (exponential decay coefficient, k=−0.0097) than did leaves from the other treatments (buried downwelling: −0.017; surface upwelling: −0.022; surface downwelling: −0.021).4. Initially, more invertebrates colonised surface leaf packs than buried packs. During the remainder of the study, however, hydrology had a greater effect on invertebrate abundance than did burial, as more invertebrates were found in packs in downwelling reaches than in upwelling reaches.5. Local subsurface hydrology and degree of burial, factors rarely considered in studies of detritus processing, can significantly influence mass loss and invertebrate colonisation of fallen leaves in streams. Furthermore, because of slower processing, subsurface zones may function as organic matter reservoirs that gradually ‘spiral’ carbon to downstream subsurface and surface habitats.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.00976.x
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  • 5
    Digitale Medien
    Digitale Medien
    Comparability of introduced tiles and natural substrates for sampling lotic bacteria, algae and macro invertebrates (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 15 (1985), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: SUMMARY. 〈list xml:id="l1" style="custom"〉1Benthic microflora (bacteria and algae) and macro invertebrates on two types of introduced substrates, unglazed clay tiles and sterilized rocks, were compared quantitatively with natural rocks in a third-order stream. Big Sulphur Creek, California, U.S.A.2Exposure periods ranging from 28 to 153 days for introduced substrates indicated that tiles accurately represented bacterial density, chlorophyll a, and macro invertebrate density and species composition of natural rocks within 28 days; phaeophytin and total organic material (as ash-free dry weight) were accurately represented within 63 days. In contrast. sterilized rocks required a 63 day exposure to simulate most of the above natural-rock features.3Tiles reduced sampling variability (i.e. increased precision) when compared with either natural or sterilized rocks, especially the variability associated with algal measurements. In benthic studies where a sufficiently long exposure period is possible (1-2 months), introduced substrates can reduce the effort and cost of benthic sampling while minimizing habitat disruption.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2427.1985.tb00693.x
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  • 6
    Digitale Medien
    Digitale Medien
    Grazer species effects on epilithon nutrient composition (2005)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 50 (2005), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 1. Field and laboratory experiments were conducted to investigate the excretion stoichiometry of nitrogen (N) and phosphorus (P) of two benthic macroinvertebrate grazers, the crayfish Orconectes propinquus and the snail Elimia livescens, that differ in body stoichiometry (mean body molar N : P 18 and 28, respectively). Crayfish excretion had a significantly higher ammonium : soluble reactive phosphorus (SRP) ratio in the laboratory and in three natural streams than did snails, as predicted by ecological stoichiometry theory.2. In greenhouse recirculating artificial streams, treatments consisting of crayfish, snails, or no grazers were used to examine responses in dissolved nutrient concentrations and epilithon nutrient composition and limitation. SRP concentrations depended upon the grazer species, with the snail treatment having a higher SRP concentration than other treatments (P 〈 0.05). Dissolved inorganic N was not affected by grazers, but appeared to be rapidly incorporated in epilithon.3. Epilithon N content was dependent upon the grazer species present, with the crayfish treatment having a significantly higher N content than other treatments (P = 0.001). No grazer species effects on epilithon P content were found. However, both grazer treatments had significantly lower epilithon P content than the no-grazer treatment.4. Traditionally, studies have focused on how grazer-induced structural changes to epilithon can alter epilithon nutrient dynamics, but this structural mechanism could not solely explain differences in epilithon nutrient contents and ratios in the present study. Our results rather suggest that benthic grazers can alter epilithon nutrient composition and limitation via nutrient excretion. Consequently, macroinvertebrate grazers may serve as ‘nutrient pumps’ that partly regulate the availability of nutrients to algae in stream ecosystems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2427.2005.01452.x
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  • 7
    Digitale Medien
    Digitale Medien
    Taxonomic and regional patterns in benthic macroinvertebrate elemental composition in streams (2005)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 50 (2005), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 1. Ecological stoichiometry has been used to better understand dynamics in consumer growth and the role of consumer-recycled nutrients because it focuses on more than one element. Most research has focused on pelagic rather than benthic consumers. Variation in elemental composition among benthic consumer taxa would suggest that taxa differ in their susceptibility to nutrient limitation or in their role in recycling nutrients.2. We collected benthic macroinvertebrates from streams in two regions (Indiana–Michigan and Wisconsin, U.S.A.) to examine taxonomic and regional variation in benthic macroinvertebrate body carbon (C), nitrogen (N), and phosphorus (P) concentrations and ratios.3. Elemental composition varied little within taxa common to both regions. In contrast, elemental composition differed greatly among taxa and appeared to be related to phylogeny. The elemental composition of macroinvertebrates clustered into three distinct groups: insects, mollusks, and crustaceans. To a lesser extent, insects and mollusks also differed in elemental composition among genera.4. Functional feeding groups (FFGs) differed in elemental composition, with predators having a higher N content than other groups. Substantial elemental imbalances between C and N were found between most primary consumers and their likely food sources, and the magnitude of the imbalance depended in part on the FFG.5. Our results support an assumption of most ecological stoichiometry models that, within a species, the elemental composition of aquatic invertebrates is relatively constant. Variation in elemental composition among taxa at various higher taxonomic levels suggests that susceptibility of stream invertebrates to nutrient limitation and their role in nutrient cycling will strongly depend on phylogeny.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2427.2005.01455.x
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  • 8
    Digitale Medien
    Digitale Medien
    Mortality of zebra mussel, Dreissena polymorpha, veligers during downstream transport (1999)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 42 (1999), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 1. Streams flowing from lakes which contain zebra mussels, Dreissena polymorpha, provide apparently suitable habitats for mussel colonization and downstream range expansion, yet most such streams contain few adult mussels. We postulated that mussel veligers experience high mortality during dispersal via downstream transport. They tested this hypothesis in Christiana Creek, a lake-outlet stream in south-western Michigan, U.S.A., in which adult mussel density declined exponentially with distance downstream.2. A staining technique using neutral red was developed and tested to distinguish quickly live and dead veligers. Live and dead veligers were distinguishable after an exposure of fresh samples to 13.3 mg L−−1 of neutral red for 3 h.3. Neutral red was used to determine the proportion of live veligers in samples taken longitudinally along Christiana Creek. The proportion of live veligers (mean ± SE) declined from 90 ± 3% at the lake outlet to 40 ± 8% 18 km downstream.4. Veligers appear to be highly susceptible to damage by physical forces (e.g. shear), and therefore, mortality in turbulent streams could be an important mechanism limiting zebra mussel dispersal to downstream reaches. Predictions of zebra mussel spread and population growth should consider lake-stream linkages and high mortality in running waters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2427.1999.00462.x
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  • 9
    Digitale Medien
    Digitale Medien
    Effect of dissolved organic carbon quality on microbial decomposition and nitrification rates in stream sediments (2002)
    Oxford UK : Blackwell Science Ltd
    Freshwater biology 47 (2002), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 1. Microbial decomposition of dissolved organic carbon (DOC) contributes to overall stream metabolism and can influence many processes in the nitrogen cycle, including nitrification. Little is known, however, about the relative decomposition rates of different DOC sources and their subsequent effect on nitrification.2. In this study, labile fraction and overall microbial decomposition of DOC were measured for leaf leachates from 18 temperate forest tree species. Between 61 and 82% (mean, 75%) of the DOC was metabolized in 24 days. Significant differences among leachates were found for labile fraction rates (P 〈 0.0001) but not for overall rates (P=0.088).3. Nitrification rates in stream sediments were determined after addition of 10 mg C L–1 of each leachate. Nitrification rates ranged from below detection to 0.49 μg N mL  sediment–1 day–1 and were significantly correlated with two independent measures of leachate DOC quality, overall microbial decomposition rate (r=–0.594, P=0.0093) and specific ultraviolet absorbance (r=0.469, P=0.0497). Both correlations suggest that nitrification rates were lower in the presence of higher quality carbon.4. Nitrification rates in sediments also were measured after additions of four leachates and glucose at three carbon concentrations (10, 30, and 50 mg C L–1). For all carbon sources, nitrification rates decreased as carbon concentration increased. Glucose and white pine leachate most strongly depressed nitrification. Glucose likely increased the metabolism of heterotrophic bacteria, which then out-competed nitrifying bacteria for NH4+. White pine leachate probably increased heterotrophic metabolism and directly inhibited nitrification by allelopathy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2427.2002.00776.x
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  • 10
    Digitale Medien
    Digitale Medien
    Distribution of benthic algae and macroinvertebrates along a thermal stream gradient (1985)
    Springer
    Hydrobiologia 128 (1985), S. 13-21 
    Details
    ISSN: 1573-5117
    Schlagwort(e): algae ; benthic ; geothermal ; macroinvertebrates ; stream ; thermal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The distribution and abundance of benthic algae and macroinvertebrates were examined along a natural thermal gradient formed by hot springs in Little Geysers Creek, Sonoma Co., California, USA. Maximum water temperatures ranged from 52 °C at the uppermost station to 23 °C at a station 400 m downstream. Benthic chlorophyll a decreased exponentially from 2.5 g m−2 at 52 °C to less than 0.1 g m−2 at 23 °C, a pattern of decline also exhibited by algal phaeophytin. Blue-green algae dominated at higher temperatures but were replaced by filamentous green algae and diatoms at lower temperatures. Macroinvertebrates were absent at temperatures ⩾45 °C; the highest density (〉 150 000 m−2, mainly Chironomidae) occurred at 34 °C, whereas biomass was highest (4.6 g m−2, as dry weight) at 23 °C and species richness (15 species) was highest at 27 °C. The two predominant macroinvertebrate populations (the midge Tanytarsus sp. and the caddisfly Helicopsyche borealis) occurred at sites that were several degrees below their lethal thermal threshold, suggesting that a temperature ‘buffer’ is maintained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00008935
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