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  • 1
    Electronic Resource
    Electronic Resource
    Biological Control of Eutrophication in Lakes (1995)
    s.l. : American Chemical Society
    Environmental science & technology 29 (1995), S. 784-786 
    Details
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/es00003a028
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  • 2
    Electronic Resource
    Electronic Resource
    Whole-lake carbon-13 additions reveal terrestrial support of aquatic food webs (2004)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 427 (2004), S. 240-243 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ecosystems are supported by organic carbon from two distinct sources. Endogenous carbon is produced by photosynthesis within an ecosystem by autotrophic organisms. Exogenous carbon is produced elsewhere and transported into ecosystems. Consumers may use exogenous carbon with consequent ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02227
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  • 3
    Electronic Resource
    Electronic Resource
    Ecosystem size determines food-chain length in lakes (2000)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 405 (2000), S. 1047-1049 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Food-chain length is an important characteristic of ecological communities: it influences community structure, ecosystem functions and contaminant concentrations in top predators. Since Elton first noted that food-chain length was variable among natural systems, ecologists have considered ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35016565
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  • 4
    Electronic Resource
    Electronic Resource
    Comparative and Experimental Approaches to the Study of Microbial Food Webs (1991)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 38 (1991), S. 0 
    Details
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The study of microbial food webs is dominated by field measurements of microbial standing stocks and rate processes and to a lesser extent by laboratory studies. These approaches reflect the concerns of microbial ecologists to assess accurately the capabilities of microorganisms and to compare microbial processes to other ecosystem parameters. These approaches have led to enormous advances in understanding microbial food webs. Reconciling our expanding knowledge with general questions about the significance and representation of microbial food webs in ecosystem studies requires additional approaches including comparative studies and field experiments. Comparative studies, analyses of microbial stocks or rates across a wide range of ecosystems, lead to quantitative models of microbial processes. These models facilitate testing of hypotheses at a very general level, allow the comparison of different stocks or rate processes across a gradient of systems, and detect unusual situations or outlier systems. Field experimental manipulations offer the advantages of working with intact natural communities, of direct evaluation of results with statistical methods, and of testing important qualitative hypotheses. Both comparative and field manipulation studies have led to important advances in the study of microbial food webs and should be expanded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1550-7408.1991.tb04807.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of an invasive bivalve on the zooplankton community of the Hudson River (1998)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 39 (1998), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Previous studies documented that zebra mussels became abundant in the Hudson River during 1992 causing an 80–90% reduction in phytoplankton biomass. This study used intervention time series analysis of abundance, biomass and reproduction over the period 1987–95 to assess changes in zooplankton in response to the invasion.2. Zebra mussels caused a size-dependent decline in zooplankton. Microzooplankton, including tintinnid ciliates, rotifers and copepod nauplii all declined in 1992 and were scarce thereafter. Mean abundances of post-naupliar copepods and of cladocerans were also lower following the invasion but these changes were not statistically significant (P 〉 0.05). Egg ratios and clutch sizes for the dominant cladoceran, Bosmina freyi, were not significantly related to zebra mussels, even though relatively low egg ratios were observed after the invasion.3. The strong declines in microzooplankton were probably caused by direct zebra mussel predation. Estimated consumption rates by mussels were roughly equivalent to maximum microzooplankton growth rates.4. The total biomass of zooplankton in the Hudson River declined by more than 70% following the invasion. Annual average zooplankton biomass was correlated with chlorophyll, but biomass per unit chlorophyll in the Hudson River was much lower than in lakes. The present study hypothesizes that this lower biomass reflects limitations by riverine flow and by predation during summer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.1998.00266.x
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  • 6
    Electronic Resource
    Electronic Resource
    Successes, Limitations, and Frontiers in Ecosystem Science: Reflections on the Seventh Cary Conference (1998)
    Springer
    Ecosystems 1 (1998), S. 137-142 
    Details
    ISSN: 1435-0629
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100219900010
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  • 7
    Electronic Resource
    Electronic Resource
    Hydrologic Variability of Small, Northern Michigan Lakes Measured by the Addition of Tracers (1998)
    Springer
    Ecosystems 1 (1998), S. 310-320 
    Details
    ISSN: 1435-0629
    Keywords: Key words: hydraulic residence time; hydrologic variability; lakes; Michigan; tracers; watershed.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT The hydraulic residence time (or flushing rate of water) is a key variable for any aquatic ecosystem and is used in many types of models and calculations. Rather than being measured directly, the hydraulic residence time is usually inferred from estimates of watershed size, precipitation, and water yield. Such estimates can be problematic in any environment but are especially so in environments in which flat or complex topography makes delineations of mapped watershed boundaries difficult to discern. We added lithium bromide, (LiBr) to three small seepage lakes in the flat topography of the Upper Peninsula of Michigan to provide an independent estimate of the water residence time. Water residence time [volume/(outflow + evaporation)] averaged 921 ± 381 (SD) days among lakes and years and ranged from 400 to 1661 days at the extremes. This variation was not clearly related to year-to-year variation in precipitation, which was relatively constant [0.26 ± 0.06 (SD) cm day (d)− 1]. The addition of the tracer (along with measurements of lake volume) enabled us to estimate, independent from other hydrologic information, the flow of water leaving the lakes in seepage plus surface outflow. This value, in conjunction with measurement of precipitation and evaporation, enabled us to calculate complete water budgets for these lakes. Among lakes and years, the groundwater input averaged 0.48 ± 0.36 cm d− 1 and accounted for 57%± 19% of total water input. This estimate was larger by 150% than that obtained by multiplying precipitation (minus estimated evapotranspiration) times a mapped value of the watershed areas. Our analysis enables us to calculate the relative significance of groundwater and precipitation for solutes such as phosphorus, hydrogen ion, and dissolved organic carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100219900024
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  • 8
    Electronic Resource
    Electronic Resource
    Evaluating Alternative Explanations in Ecosystem Experiments (1998)
    Springer
    Ecosystems 1 (1998), S. 335-344 
    Details
    ISSN: 1435-0629
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT Unreplicated ecosystem experiments can be analyzed by diverse statistical methods. Most of these methods focus on the null hypothesis that there is no response of a given ecosystem to a manipulation. We suggest that it is often more productive to compare diverse alternative explanations (models) for the observations. An example is presented using whole-lake experiments. When a single experimental lake was examined, we could not detect effects of phosphorus (P) input rate, dissolved organic carbon (DOC), and grazing on chlorophyll. When three experimental lakes with contrasting DOC and food webs were subjected to the same schedule of P input manipulations, all three impacts and their interactions were measurable. Focus on multiple alternatives has important implications for design of ecosystem experiments. If a limited number of experimental ecosystems are available, it may be more informative to manipulate each ecosystem differently to test alternatives, rather than attempt to replicate the experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100219900025
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  • 9
    Electronic Resource
    Electronic Resource
    Modeled Effects of Dissolved Organic Carbon and Solar Spectra on Photobleaching in Lake Ecosystems (2000)
    Springer
    Ecosystems 3 (2000), S. 419-432 
    Details
    ISSN: 1435-0629
    Keywords: Key words: CDOM photobleaching; solar wavebands; ultraviolet radiation; lake ecosystems; dissolved organic carbon.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dissolved organic matter (DOM) contains molecules that absorb light at various wavelengths. This chromophoric DOM (CDOM) influences the transmission of both visible and ultraviolet energy through water. The absorption of light by CDOM often causes structural changes that reduce its capacity to further absorb light, a process termed ‘photobleaching‘. A model was designed to assess photobleaching through the entire water column of lake ecosystems. The model uses lake morphometry and dissolved organic carbon (DOC) concentration in conjunction with a defined solar spectrum and experimentally measured photobleaching rates to compute the total water columm photobleaching. The model was initially applied to a theoretical ‘average‘ lake using solar spectra for both the north (N) and south (S) temperate western hemispheres and variable DOC from 0.3 to 30 mg L−1. The consequences of varying waveband-specific photobleaching coefficients and lake morphometry were explored in a second set of simulations. Finally, the model was also applied to four temperate northern lakes for which we had prior measurements of CDOM photobleaching rates. The model demonstrates that all three wavebands of solar radiation (UVB, UVA, and PAR) contribute significantly to total water column photobleaching, with UVA being most important. The relative contributions of the three wavebands were invariant for DOC more than 3 mg L−1. Total water column photobleaching at 440 nm was three to five times faster under the UV-enriched solar spectrum of the southern hemisphere. Increasing the lake’s mean depth (from 0.37 to 9.39 m) resulted in five- or 15-fold slower rates of total water column photobleaching for DOC concentrations of 1 or 10 mg L−1, respectively. Varying the waveband-specific photobleaching coefficients by 10-fold resulted in a similar change in total water column photobleaching rates. Applying the model to four specific lakes revealed that photobleaching for the entire water column would reduce CDOM light absorption by 50% in 18–44 days under summer conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100210000038
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  • 10
    Electronic Resource
    Electronic Resource
    Primary production, new production and vertical flux in the eastern Pacific Ocean (1987)
    [s.l.] : Nature Publishing Group
    Nature 325 (1987), S. 803-804 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The vertical flux of POC and PON in the upper 2,000 m of the water column was measured using free floating particle traps11 at nine sites in the Pacific Ocean12'13. While traps were deployed, PP was measured at each site, using the heavy-metal-free I4C method (ref. 14). Trapped materials were ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/325803a0
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