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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
    Predator-prey dynamics in an ecosystem context (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 45 (1994), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Evaluating the role of fishes at the food web and ecosystem scales profits from an iterative process. At the community and population scales, prey selection by predators alters habitat selection behaviours of prey species as well as their abundance, size distributions, life histories and the consequent effects on their own prey. At the whole system scale, predation by fishes alters community structure and nutrient cycling. Thus, both direct and indirect predation effects are expressed in population structure, community composition and production processes at all trophic levels. These are the central tenets of the trophic cascade argument.Examples are abundant and diverse. We know that predators are size selective, that resource partitioning occurs, that functional responses link the density dependence of predator and prey populations, and that predator avoidance behaviours are common. A more significant challenge exists when attempting to use this knowledge.This presentation attempts to link theory and empiricism in forecasts of what will happen next in response to a management action or a planned experiment. Examples are drawn from whole system experiments conducted in small lakes and from large-scale manipulations of predator populations in North America's Laurentian Great Lakes. Rapid and discontinuous or non-linear responses are common. Extrapolating the lessons of mechanistic process studies proves insufficient because the context is dynamic. Inferences built from the whole ecosystem scale yield equally misleading results because the scale is too general, Resolving these problems will require a clever mix of selective applications of predator-prey theory and astute empiricism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1994.tb01094.x
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  • 3
    Electronic Resource
    Electronic Resource
    An annual fossil record of production, planktivory and piscivory during whole-lake manipulations (1994)
    Springer
    Journal of paleolimnology 11 (1994), S. 133-149 
    Details
    ISSN: 1573-0417
    Keywords: piscivore ; planktivore ; zooplankton ; pigment ; invertebrate ; predation ; Cladocera ; carotenoid ; food web ; manipulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Annual and subannual paleolimnological records of pigments and zooplankton were used to analyze three whole-lake manipulations. The relative abundance of cladoceran remains in recent seasonal laminae was significantly correlated with the relative abundance of species in the plankton (r 2=0.59,P〈0.001). Comparison of food-web structure after piscivore introduction showed that there are multiple outcomes of predation and that final food-web structure depended on the strength of interaction between piscivorous and planktivorous fish. Intense predation on cyprinids (Phoxinus eos, P. neogaeus, Umbra limi) by largemouth bass (Micropterus salmoides) allowed large herbivores (Daphnia pulex) and invertebrate predators (Chaoborus punctipennis) to dominate. Analysis of fossil invertebrate morphology suggested that small grazers (Bosmina longirostris, Diaphanosoma birgei) were eliminated by invertebrate predators. Under moderate predation by rainbow trout (Oncorhynchus mykiss), cyprinids remained, only intermediate-size herbivores (D. rosea) increased in abundance, andBosmina persisted. In contrast to food-web manipulations, increased algal abundance resulting from watershed disturbance (road construction) did not alter the species composition or size-structure of fossil Cladocera.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00686862
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  • 4
    Electronic Resource
    Electronic Resource
    Effects on lower trophic levels of massive fish mortality (1990)
    [s.l.] : Nature Publishing Group
    Nature 344 (1990), S. 333-335 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/344333a0
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Density-dependent changes in individual foraging specialization of largemouth bass (1997)
    Springer
    Oecologia 110 (1997), S. 592-600 
    Details
    ISSN: 1432-1939
    Keywords: Key words Density dependence ; Diet consistency ; Intraspecific variability ; Keystone predator ; Largemouth bass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Individual foraging specializations are an important source of intraspecific variability in feeding strategies, but little is known about what ecological factors affect their intensity or development. We evaluated stomach contents in marked individual largemouth bass (Micropterus salmoides) and tested the hypothesis that diet specialization is most pronounced during periods with high conspecific densities. We collected diet data over 10 years from an unexploited population of largemouth bass that displayed a greater than threefold variation in density. Although diet composition of the aggregate bass population did not change during the study, bass body condition was inversely correlated with population size. Individual marked bass exhibited high diet consistency (diet overlap between successive captures) during years with high population densities. Diet overlap between randomly assigned pairs of bass was not correlated with population size. We did not detect the expected positive relationship between diet breadth and population size. Our analyses demonstrate that population responses to density changes may represent the sum of many unique individual foraging responses and would be obscured by pooled sampling programs. Behavioral flexibility of individuals may contribute to the ability of largemouth bass to function as a keystone predator in many aquatic communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050200
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  • 7
    Electronic Resource
    Electronic Resource
    Crab: snail size-structured interactions and salt marsh predation gradients (1994)
    Springer
    Oecologia 97 (1994), S. 49-61 
    Details
    ISSN: 1432-1939
    Keywords: Size-structure ; Predation ; Callinectes ; Littoraria ; Salt marsh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied size-structured predator-prey interactions between blue crabs (Callinectes sapidus) and marsh periwinkles (Littoraria irrorata) with a combination of field studies, laboratory experiments and individual-based modeling. Size distributions of Littoraria differed among years at the same sites in a salt marsh and could largely be explained by dominance of strong cohorts in the population. At a given site, abundance increased with elevation above tidal datum. Size-selective predation by blue crabs does not appear to be an important regulator of snail size distributions but may have a major effect on local abundance. Laboratory studies indicated that predator-prey interactions between Callinectes and Littoraria are strongly size-dependent. Crabs were generally effective at feeding on periwinkles at size ratios greater than approximately 6 (crab width: snail length). At lower size ratios crabs were far less effective at manipulating the snails, which often survived but with damaged shells. An individual-based model which incorporated information about incidence of snail shell scarring (resulting from non-lethal interactions) and snail density, predicted reduced predation rates and smaller average crab size with distance from the low tide refugium for crabs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317908
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  • 8
    Electronic Resource
    Electronic Resource
    Predation at a snail's pace: what's time to a gastropod? (1984)
    Springer
    Oecologia 62 (1984), S. 13-17 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Predation by naticid gastropods shows evidence of adaptation to maximize the rate of energy intake. The predation rate of Polinices duplicatus feeding on artificially altered, thin-shelled Mercenaria mercenaria was faster than the predation rate on normal Mercenaria. The rate of energy intake was limited by handling time. The time saved by predation on thin-shelled prey was used to forage. Thus time was shown to be valuable to P. duplicatus, and cost-benefit functions using time and energy as currencies are appropriate for estimating dietary efficiency and predicting prey choice. Despite the clear superiority of thin-shelled prey, P. duplicatus did not learn to prefer this novel prey type, suggesting that predator choices are sterotyped, reflecting optima selected over evolutionary time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377366
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Representing Density Dependent Consequences of Life History Strategies in Aquatic Ecosystems: EcoSim II (2000)
    Springer
    Ecosystems 3 (2000), S. 70-83 
    Details
    ISSN: 1435-0629
    Keywords: Key words: trophic interactions; cascades; risk-sensitive foraging; ecosystem management.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT EcoSim II uses results from the Ecopath procedure for trophic mass-balance analysis to define biomass dynamics models for predicting temporal change in exploited ecosystems. Key populations can be represented in further detail by using delay-difference models to account for both biomass and numbers dynamics. A major problem revealed by linking the population and biomass dynamics models is in representation of population responses to changes in food supply; simple proportional growth and reproductive responses lead to unrealistic predictions of changes in mean body size with changes in fishing mortality. EcoSim II allows users to specify life history mechanisms to avoid such unrealistic predictions: animals may translate changes in feeding rate into changes in reproductive rather than growth rates, or they may translate changes in food availability into changes in foraging time that in turn affects predation risk. These options, along with model relationships for limits on prey availability caused by predation avoidance tactics, tend to cause strong compensatory responses in modeled populations. It is likely that such compensatory responses are responsible for our inability to find obvious correlations between interacting trophic components in fisheries time-series data. But Ecosim II does not just predict strong compensatory responses: it also suggests that large piscivores may be vulnerable to delayed recruitment collapses caused by increases in prey species that are in turn competitors/predators of juvenile piscivores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100210000011
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