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  • 1
    Electronic Resource
    Electronic Resource
    IMPACTS OF CLIMATE CHANGE ON AQUATIC ECOSYSTEM FUNCTIONING AND HEALTH (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 35 (1999), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : We review published analyses of the effects of climate change on goods and services provided by freshwater ecosystems in the United States. Climate-induced changes must be assessed in the context of massive anthropogenic changes in water quantity and quality resulting from altered patterns of land use, water withdrawal, and species invasions; these may dwarf or exacerbate climate-induced changes. Water to meet instream needs is competing with other uses of water, and that competition is likely to be increased by climate change. We review recent predictions of the impacts of climate change on aquatic ecosystems in eight regions of North America. Impacts include warmer temperatures that alter lake mixing regimes and availability of fish habitat; changed magnitude and seasonality of runoff regimes that alter nutrient loading and limit habitat availability at low flow; and loss of prairie pothole wetlands that reduces waterfowl populations. Many of the predicted changes in aquatic ecosystems are a consequence of climatic effects on terrestrial ecosystems; shifts in riparian vegetation and hydrology are particularly critical. We review models that could be used to explore potential effects of climate change on freshwater ecosystems; these include models of instream flow, bioenergetics models, nutrient spiraling models, and models relating riverine food webs to hydrologic regime. We discuss potential ecological risks, benefits, and costs of climate change and identify information needs and model improvements that are required to improve our ability to predict and identify climate change impacts and to evaluate management options.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1999.tb04222.x
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  • 2
    Electronic Resource
    Electronic Resource
    CHANGES IN PHYSICAL AND CHEMICAL VARIABLES IN A NEW RESERVOIR DUE TO PUMPED STORAGE OPERATIONS (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 18 (1982), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Information on biologically important physical and chemical variables is presented for Lake Oconee, a newly impounded pumped storage reservoir in Georgia. During its first summer, when no pumping occurred, temperature, oxygen, pH, inorganic nitrogen, and phosphorus were vertically stratified with severe hypolimnetic oxygen depletion. During the second summer, when pumped storage was in operation, more homogenous vertical profiles, generally higher oxygen, and lower dissolved nutrient concentrations were observed. These pumped storage effects were observed at all stations, rather than being confined to the immediate vicinity of the dam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1982.tb00045.x
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  • 3
    Electronic Resource
    Electronic Resource
    Rapid flow through the sediments of a headwater stream in the southern Appalachians (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 20 (1988), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The flow of water through the sediment layer (underflow) of streams can influence nutrient uptake dynamics and the supply of materials to microbes, meiofauna and macroinvertebrates living within stream sediments. We examined the extent of underflow in Hugh White Creek, a headwater stream in the southern Appalachian Mountains and compared underflow at different depths and at different sites within the stream.2. Initially rhodamine dye was used to trace the flow of water through the sediments; however, the dye was strongly absorbed by the sediments in Hugh White Creek. Thus rhodamine was not suitable as a tracer of water flow. Chloride reacted conservatively in laboratory experiments and was used as a tracer.3. The tracer infiltrated the sediments within 5 min to depths of 10 cm at all six sites. Chloride infiltration tended to decrease with depth of sediments at all sites although there was no consistent statistical pattern in chloride concentration with depth for the different sites. Equilibrium between the water column and sediments was reached rapidly, within minutes for the sites with coarse sediments and within a few hours for sites with finer sediments. Minimum rates of chloride infiltration into the sediments ranged between 1.0 cm min−1 for the sites with cobble substrate to 0.2 cm min−1 for sites with fine sand sediments associated with debris dams. These data suggest that underflow may be a major component in the functioning of Appalachian mountain streams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1988.tb00447.x
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of elevated nitrate concentration on rate of leaf decomposition in a stream (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 13 (1983), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 〈list xml:id="l1" style="custom"〉1Leaf decomposition was compared in two streams at the Coweeta Hydrologic Laboratory, North Carolina. U.S.A. One stream drains an undisturbed hardwood watershed, while the other drains a successional watershed subject to an insect outbreak. The successional watershed has elevated nitrate concentrations in the streamwater.2Both black locust (Robinia pseudo-acacia) and sweet birch (Betula lenta) leaf litter decomposed 2.8 times more rapidly in the stream with high nitrate concentrations.3The more rapid decay rates appeared to be partly due to accelerated microbial processing in response to nitrate enrichment, because microbial biomass (as ATP) was higher in the nitrate-enriched stream.4At each point in time, nitrogen and phosphorus content of the litter was lower in the high nitrate stream; however, there was no significant difference in nitrogen or phosphorus content at the same state of leaf decay in the two streams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1983.tb00669.x
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  • 5
    Electronic Resource
    Electronic Resource
    Factors affecting ammonium uptake in streams – an inter-biome perspective (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The Lotic Intersite Nitrogen eXperiment (LINX) was a coordinated study of the relationships between North American biomes and factors governing ammonium uptake in streams. Our objective was to relate inter-biome variability of ammonium uptake to physical, chemical and biological processes.2. Data were collected from 11 streams ranging from arctic to tropical and from desert to rainforest. Measurements at each site included physical, hydraulic and chemical characteristics, biological parameters, whole-stream metabolism and ammonium uptake. Ammonium uptake was measured by injection of 15N-ammonium and downstream measurements of 15N-ammonium concentration.3. We found no general, statistically significant relationships that explained the variability in ammonium uptake among sites. However, this approach does not account for the multiple mechanisms of ammonium uptake in streams. When we estimated biological demand for inorganic nitrogen based on our measurements of in-stream metabolism, we found good correspondence between calculated nitrogen demand and measured assimilative nitrogen uptake.4. Nitrogen uptake varied little among sites, reflecting metabolic compensation in streams in a variety of distinctly different biomes (autotrophic production is high where allochthonous inputs are relatively low and vice versa).5. Both autotrophic and heterotrophic metabolism require nitrogen and these biotic processes dominate inorganic nitrogen retention in streams. Factors that affect the relative balance of autotrophic and heterotrophic metabolism indirectly control inorganic nitrogen uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01094.x
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  • 6
    Electronic Resource
    Electronic Resource
    Fluxes of bacteria and organic matter into a blackwater river from river sediments and floodplain soils (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 28 (1992), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The Ogeechee River, in south-eastern Georgia, U.S.A, is a blackwater river with an extensive floodplain that is inundated regularly during winter months. Previous studies have shown that low to moderate bacterial production rates cannot support the relatively high suspended bacteria concentrations observed (107−-108 cells ml−1), suggesting an allochthonous source of bacteria. We report the results of a combination of field and flume experiments which demonstrate that river sediments and floodplain soils are significant sources of suspended bacteria during seasonal flooding. Benthic bacteria are also entrained by normal discharges. There are sizeable fluxes of POC and DOC from river sediments and floodplain soils.2. Bacterial, POC and DOC fluxes (14, 250, and 790 mg Cm−2 h−1, respectively) were substantial when water was percolated upward through floodplain soils.3. Simulation of overland flow using a flume demonstrated further fluxes of bacteria and POC from floodplain soils (up to 61 and 10700 mg Cm−2h−1, respectively) and river sediments, but did not yield additional DOC from floodplain soils.4. These laboratory results are supported by experiments in which we measured significant increases in concentrations of bacteria and DOC in a downstream direction in (i) the main river channel during a winter flood in 1986, and (ii) a floodplain slough (channel side-arm) which re-entered the main channel 800m from its initial divergence. Inputs of bacteria and DOC from the surrounding floodplain were estimated to be up to 3500 kg DOC h−1, and 4000 kg bacteria Ch−1 over a 50-km reach.5. These previously unmeasured fluxes of organic carbon help to explain the high concentrations of suspended bacteria in the Ogeechee River.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1992.tb00560.x
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of land cover on sediment regime and fish assemblage structure in four southern Appalachian streams (2002)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 47 (2002), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY 1. We examined the relationship between catchment land cover, sediment regime and fish assemblage structure in four small streams in the upper Little Tennessee River basin of North Carolina. Study streams drained similar sized catchments (17–31 km2) with different fractions of non-forested land cover. Non-forested land cover was 〈3% in two ‘reference’ streams, whereas it was 13 and 22% in two ‘disturbed’ streams. Land cover data were compared with sediment transport data (suspended and bedload), benthic habitat data (embeddedness, substratum composition and coverage of fines) and fishes collected in autumn 1997.2. Suspended sediment concentration was significantly higher in disturbed streams during both baseflow and stormflow. During baseflow disturbed streams nearly always exceeded 10 nephelometric turbidity units (NTU), whereas reference streams never exceeded this threshold. The difference in suspended sediment concentration between reference and disturbed streams was more consistent at baseflow than at stormflow. Therefore, baseflow turbidity may be a useful indicator of potential stream degradation.3. Disturbed sites had five- to nine-fold more bedload transport than reference sites. Both embeddedness and streambed instability increased with increasing non-forested land cover.4. Relative abundance of fishes requiring clean cobble/gravel substratum for spawning was lower in disturbed streams, whereas relative abundance of mound-building cyprinids, their nest associates and fishes that excavate nests in soft sediments (centrarchids) was higher. Relative abundance of fishes spawning in benthic crevices and gravel (BC + G) declined as the proportion of non-forested land cover increased. This study supports growing evidence that human-induced sedimentation alters stream fish assemblages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2002.00927.x
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  • 8
    Electronic Resource
    Electronic Resource
    Contribution of fungal biomass to the diet of a freshwater isopod (Lirceus sp.) (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 16 (1986), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The direct contribution of fungal biomass to the carbon needs of a freshwater isopod (Lirceus sp.) was measured using 14C-labelled fungi on leaf material. 14C-glucose was added to fungus-inoculated leaf discs periodically throughout the growth of the fungus. Amount of label incorporated into fungal biomass, radioactivity appearing in Lirceus after feeding on labeled fungus and the standing stock of fungus were used to calculate incorporation of fungal C by the consumer.2. Incorporation rates ranged from 0.06 to 70 ng fungal C mg wet wt isopod-1h-1. These rates of incorporation represent from 0.05 to 57% of C respired by the isopod.3. Fungal C does not meet the carbon needs of this consumer and the role of fungi as modifiers of the leaf substrate may be more significant than their role as a food source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1986.tb00978.x
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  • 9
    Electronic Resource
    Electronic Resource
    Development and composition of the epixylic biofilm in a blackwater river (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 27 (1992), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Comparisons of chlorophyll a, bacterial density, frequencies of dividing cells, ash-free dry mass (AFDM) and extracellular polysaccharide content were made for biofilm developing on wood (Salix) submerged in replicated stream-side flumes exposed to either ambient light (light treatment) or covered to exclude light (dark treatment). Biofilm was sampled on days 3, 6, 9 and 14 during experimental periods occurring irrMay, September, November and December.2. There were no significant differences in bacterial cell densities, frequencies of dividing cells, AFDM or extracellular poiysaccharide content between light and dark treatments. Ash content and bacterial biomass was similar to seston, suggesting the importance of seston as a source of material accumulating in the biofilm.3. Of total epixylic organic carbon 7.2% was estimated to be extracellular polysaccharide, and 0.8% was bacterial carbon. At least nine times more carbon was contained in extracellular polysaccharide than in bacterial biomass.4. In the epixylon of the Ogeechee River, bacterial dynamics appear to be controlled by factors other than the availability of algal substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1992.tb00521.x
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  • 10
    Electronic Resource
    Electronic Resource
    Bacterivory by deposit-feeding mayfly larvae (Stenonema spp.) (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 24 (1990), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 〈list xml:id="l1" style="custom"〉1 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.2 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.3 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1990.tb00724.x
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