23 results in The Trophic Cascade in Lakes
14 - Heterotrophic microbial processes
-
- By M. L. Pace
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 252-277
-
- Chapter
- Export citation
-
Summary
Introduction
Heterotrophic microorganisms, here defined as bacteria and protozoa, account for a major portion of secondary production and nutrient remineralization in aquatic ecosystems (Stockner & Porter, 1988; Sherr & Sherr, 1991). These organisms are potentially regulated by both their predators and by the supply of organic carbon and inorganic nutrients. In general, prior studies of the trophic cascade have not considered heterotrophic microbial processes (e.g. Carpenter et al., 1987; McQueen et al., 1989; Benndorf, 1990; but see Riemann & Søndergaard, 1986). In previous chapters of this volume, the significance of cascading trophic interactions in determining the structure of zooplankton communities and in explaining shifts in phytoplankton biomass and primary production has been demonstrated. In this chapter, I consider the question, are heterotrophic microbes and the biogeochemical processes mediated by them strongly influenced by these same top-down controls?
One difficulty in answering this question arises from uncertainty about the trophic interactions and recycling processes connecting heterotrophic microbes with phytoplankton, zooplankton and fish. It is an oversimplification to consider the heterotrophic microbial food web as a separate ‘loop’ wherein bacteria utilize dissolved organic matter and are consumed by protozoa, with energy and nutrients there by returned to the phytoplankton–zooplankton–fish food chain (Azam et al., 1983). Rather, a more current view of microbial food webs is one of a complex interacting community including phytoplankton, bacteria and protozoans that collectively accounts for primary carbon fixation, nutrient regeneration and production to support metazoans (Sherr & Sherr, 1991).
4 - The fish populations
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 43-68
-
- Chapter
- Export citation
-
Summary
Introduction
Fundamental to the cascade hypothesis are the effects that fish populations can exert on species composition, biomass and productivity at other trophic levels. These may be direct or indirect (nonlethal) effects. Direct effects such as prey consumption, and indirect effects such as those influencing behavior (avoidance of predators) have been widely documented at the population level (e.g. Stroud & Clepper, 1979; Werner et al., 1983) and the indirect effects expressed at the community and ecosystem levels such as those reviewed in Kerfoot & Sih (1987) & Northcote (1988). Indirect effects pertinent in the case of our studies would include behavioral responses, such as migration from or selection of specific refugia from predation (e.g. diel vertical migration of zooplankton and onshore–offshore migration of small fishes), that result in changes in foraging patterns of prey species (Carpenter et al., 1987; He & Kitchell, 1990; He & Wright, 1992; Chapter 5). Another category of effects includes changes in nutrient flux due to shifts in the behavioral or structural properties of the fish populations (Carpenter et al., 1992b).
Fish in our study lakes (Fig. 4.1) are common to the Great Lakes region, but some are near the limits of their geographic distributions. Largemouth bass and golden shiner are at the northern limits, while finescale and northern redbelly dace are near the southern limits (Scott & Crossman, 1973; Becker, 1983). Adult largemouth bass and rainbow trout can be keystone piscivores (Keast, 1985; Carpenter et al., 1985, 1987) with an ability to limit the abundance of forage fish.
8 - Zooplankton community dynamics
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 116-152
-
- Chapter
- Export citation
-
Summary
Introduction
Whole-lake manipulations of the fish assemblages in Peter and Tuesday Lakes provided an excellent opportunity to ask how vertebrate and invertebrate predators affect zooplankton communities. A central element of the cascade hypothesis is the regulation of large herbivores by visually feeding planktivores. In the light of the prominent position that large herbivores can occupy in zooplankton communities, repercussions in populations of less conspicuous taxa are expected (Lewis, 1979; Zaret, 1980; Kerfoot & Sih, 1987). These include compensatory shifts in the dominant species and increases in previously rare species.
Planktivory by fishes and invertebrates (such as Chaoborus) has both direct and indirect effects on zooplankton populations (Zaret, 1980; Neill, 1981; Vanni, 1986). Fish predation can constrain the maximum adult body size of prey, while invertebrate predation can restrict the minimum size. Either can interact with effects of food limitation to alter zooplankton populations (Hall et al., 1976). At the community level, however, the significance of predation is less clear. Changes in density alone may not be sufficient to alter competitive exclusion, diversity, or their consequences for the community (Thorp, 1986). Interpretations of zooplankton community structure must consider competitive interactions among species, especially among the dominant herbivores (Lynch, 1979).
In this chapter, we focus on the changes in the zooplankton communities of Peter and Tuesday Lakes as a result of fish manipulations and contrast them to the natural variation exhibited by Paul Lake.
3 - Statistical analysis of the ecosystem experiments
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 26-42
-
- Chapter
- Export citation
-
Summary
Introduction
Experimentation at the ecosystem scale has made important contributions to ecology in general, and limnology in particular, over the past several decades (Likens, 1985; Schindler, 1987). Unlike some alternative approaches, large experiments are appropriately scaled for direct, strong inference about ecosystem dynamics and responses to perturbation (Chapter 1). The main disadvantage of ecosystem experiments is that replication is difficult or impossible (Matson & Carpenter, 1990).
By emphasizing whole lake experiments, we attain the appropriate scale but sacrifice replication. We have compensated for this shortcoming in several ways.
First, some of our manipulations have been strong and sustained ones, in the sense that changes in the independent variates (the fishes) were near the extremes of the natural range, and maintained for many generations of the zooplankton and phytoplankton populations that were the dependent variates (Carpenter, 1989). Such manipulations attempt to cause changes that are large enough to be evident without resorting to statistics, and would be viewed as ecologically significant by most practitioners. Strong sustained manipulations have been used in most ecosystem experiments, with the consequence that subtle responses and interactions are usually not detected (Likens, 1985; Schindler, 1987). For a variety of views on the utility of such ‘sledgehammer’ experiments, see Hurlbert (1984), Schindler (1987), Crowder et al. (1988), Kitchell et al. (1988) and Carpenter (1989).
Second, in some cases we have used data from many reference lakes to test for responses using conventional statistics (Carpenter et al., 1989).
Frontmatter
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp i-vi
-
- Chapter
- Export citation
10 - Zooplankton biomass and body size
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 172-188
-
- Chapter
- Export citation
-
Summary
Introduction
Zooplankton affect lake ecosystem processes by grazing on phytoplankton, recycling nutrients through excretion, and serving as prey for both vertebrate and invertebrate planktivores (Brooks & Dodson, 1965; Peters, 1975; Neill, 1981). Consequently, the zooplankton can be analyzed from two points of view: as a dependent variable with respect to planktivores, and as an independent variable with respect to algal community dynamics and nutrient recycling. In this chapter, we focus primarily on the responses of zooplankton biomass and body size to manipulations of fish populations. Responses of the phytoplankton to changes in the zooplankton community are addressed in Chapters 11 and 13.
Planktivorous fish feed selectively on larger and more conspicuous zooplankton (Zaret, 1980; Neill, 1984; Vanni, 1986). Zooplankton community changes associated with fish manipulations were discussed in Chapter 8. Here, we examine the implications for the total biomass and the size structure of the zooplankton, which are associated with rates of key ecosystem processes. Rates of grazing or nutrient excretion per unit biomass are proportional to the body mass of individual zooplankters (Peters, 1983). The range of particle sizes consumed by filter-feeding cladocerans is also proportional to body size (Burns, 1968).
Total rates of grazing or nutrient excretion scale directly with zooplankton biomass. Therefore, zooplankton body size and biomass indicate the potential rates of ecosystem processes, such as grazing and nutrient excretion, that are performed by the herbivorous zooplankton.
11 - Phytoplankton community dynamics
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 189-209
-
- Chapter
- Export citation
-
Summary
Introduction
Limnologists have long appreciated the potential importance of grazing to phytoplankton community composition (Reynolds, 1984a). At certain times during seasonal succession, grazers have clear-cut effects on algal assemblages (Lampert et al., 1986; Sommer et al., 1986; Vanni & Temte, 1990). Grazers affect phytoplankton communities through several mechanisms, including direct suppression of edible algae, enhancement of inedible algae via nutrients excreted by grazers, and shifts in the outcome of competition caused by grazer effects on nutrient supply ratios (Sterner, 1989). The complexity of the mechanisms may explain the multifarious and individualistic outcomes of field experiments on zooplankton–phytoplankton interactions (Lehman & Sandgren, 1985; Bergquist & Carpenter, 1986; Elser et al., 1986a; Vanni & Temte, 1990).
Organism size may provide important organizing principles for understanding zooplankton–phytoplankton interactions (Peters & Downing, 1984). With the exception of calanoid copepods capable of feeding selectively on certain algae, the size of the herbivore largely determines the range of algal sizes upon which it can feed (Burns, 1968; Reynolds, 1984a). Feeding rates also depend on herbivore size (Peters & Downing, 1984). Size-selective predation by fishes strongly influences size structure of the herbivore community (Brooks & Dodson, 1965; Chapter 8). Therefore, size-structured interactions of zooplankton and phytoplankton have important implications for the trophic cascade (Bergquist et al., 1985).
We developed a simulation model to determine the potential effects of herbivore size on phytoplankton size structure, biomass, and primary production (Carpenter & Kitchell, 1984; Chapter 17).
Preface
-
- By Stephen R. Carpenter, James F. Kitchell, Madison, Wisconsin
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp xi-xii
-
- Chapter
- Export citation
-
Summary
This book attempts a bridge between ecosystem and population ecology. These fields have gradually separated in recent decades as ecosystem science has focused on production and biogeochemical processes at large scales, while population biology has emphasized biotic interactions, often at small scales and typically excluding feedbacks with the physical–chemical environment. The trophic cascade concept has elements of both. It emphasizes the consequences of population interactions for production processes. Population dynamics influence nutrient cycles and must therefore be considered in an ecosystem context. These questions entail concerted work at several different scales, using theoretical principles and practical tools derived from several of the subdisciplines of ecology.
Our approach focused intensive effort on three experimental lakes for seven years. A coordinated, multidisciplinary team is mandatory for this kind of research. We are fortunate to have worked with a remarkable group of collaborators, postdocs, graduate students, technicians, and undergraduates in the course of this project. Their contributions include participation as coauthors of this volume. We also wanted to produce an integrated synthesis of the ecosystem experiments, while minimizing gaps and redundancies that sometimes arise in multiauthored collections. In an attempt to avoid these difficulties, one or both of us is among the authors of most chapters. Our job was made easier by the efforts of Xi He on chapters about fishes and Pat Soranno on chapters about zooplankton.
Individual chapters acknowledge the helpful contributions of reviewers.
16 - Simulation models of the trophic cascade: predictions and evaluations
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 310-331
-
- Chapter
- Export citation
-
Summary
Introduction
Previous chapters have detailed the responses of Peter and Tuesday Lakes to fish manipulations. Some of the changes were anticipated, while others were surprises. Our research was guided by models of the trophic cascade in lakes. To what extent did these models forecast the experimental results? The purpose of this chapter is to assess how our predictions fared, and how our view of the trophic cascade has been modified by the experimental outcome. First, we must explain why we developed simulation models of the trophic cascade, how the models were structured, and the predictions that derived from the models.
The trophic cascade is, in essence, a simple idea. In the complexity of real lakes, however, it involves the collective outcome of life history, predator–prey, and physical–chemical processes that cannot be adequately represented by simple verbal, graphical or mathematical models. Computer simulations are one way of integrating these complex interactions. They elaborate the conceptual framework and develop specific, testable predictions. We began simulation studies of the trophic cascade in 1981, three years before initiating the ecosystem experiments. Many of the predictions of those models can now be evaluated.
This chapter has four parts. First, we review three simulation models that produced the hypotheses we tested in the field. Second, we address predictions specific to the outcome of our ecosystem experiments. Third, we turn to more general expectations that should apply to trophic cascades in many lakes.
13 - Primary production and its interactions with nutrients and light transmission
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 225-251
-
- Chapter
- Export citation
-
Summary
Introduction
The trophic cascade from fish to ecosystem processes is the central theme of this book. Previous chapters have documented the changes in piscivore, planktivore and herbivore trophic levels in our experimental lakes. Effects of changes in herbivory on phytoplankton communities have been discussed (Chapter 11) and we have compared the distinctive habitats for algae provided by the epilimnion and metalimnion (Chapter 12). This chapter turns to the central ecosystem variates of our study: biomass and metabolism of primary producers.
In lakes, dynamics of herbivores, primary producers nutrients, and light have strong feedbacks. Excretion by herbivores is a major source of nutrients for phytoplankton. Limnetic grazers affect their prey negatively, through grazing, and positively, through nutrient recycling. The phytoplankton also respond to inputs of nutrients from outside the lake, and to mixing of nutrients upward from the hypolimnion. Light drives photosynthesis, and phytoplankton attenuate light as it passes down-ward through the water column. In lakes where substantial aggregations of algae exist in deep, low-light habitats, feedbacks between algal biomass and light extinction may strongly influence primary production (Chapter 12).
These strong feedbacks imply that primary production cannot be addressed without considering physical–chemical factors such as mixing depth, irradiance, and nutrient limitation. This chapter focuses on dynamics of algal biomass (measured as chlorophyll) and production, in the context of selected physical and chemical characteristics of the water column. These include indicators of nutrient deficiency, light penetration, and mixing depth.
Index
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 381-385
-
- Chapter
- Export citation
12 - Metalimnetic phytoplankton dynamics
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 210-224
-
- Chapter
- Export citation
-
Summary
Introduction
Temperature, light and oxygen change markedly with depth, thereby altering the habitats of phytoplankton. Often, the upper waters are the most favorable habitat for algae, so maximum algal biomass occurs in the epilimnion. Where there is adequate light penetration to near or below the thermocline, however, the maximum algal biomass may occur deep in the water column. Algal maxima in the metalimnion and hypolimnion are known from many lakes (Moll & Stoermer, 1982). This chapter is especially concerned with metalimnetic communities of algae found near the thermocline. Although metalimnetic algae can attain high biomass and can contribute substantially to whole-lake primary productivity (Moll & Stoermer, 1982), little is known about the mechanisms which control their dynamics.
Epilimnetic phytoplankton communities benefit from relatively favorable light and temperature, but can suffer great losses through sedimentation. In addition, cells are constantly mixed throughout the epilimnion and must cope with changing light conditions (Reynolds, 1984a). Nutrients are depleted as the summer progresses with little opportunity for regeneration from below before fall turnover. Also, migrating zooplankton and zooplankton feces can transport phosphorus into the hypolimnion, further depleting the nutrient pool (Dini et al., 1987). On the other hand, grazing losses may be low for many hours each day if zooplankton migrate in and out of the epilimnion (Lampert & Taylor, 1985; Dorazio et al., 1987; Chapter 9).
In contrast, metalimnetic phytoplankton communities must contend with lower light levels and temperatures, which can reduce growth rates (Healey, 1983; Raven & Geider, 1988; Reynolds, 1984a).
15 - Annual fossil records of food-web manipulation
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 278-309
-
- Chapter
- Export citation
-
Summary
Introduction
Limnologists are interested in why lakes vary from year to year. Studies of temporal variability under baseline conditions are needed to quantify the relative importance of mechanisms regulating production, to interpret ecosystem experiments and to help solve lake management problems (McQueen et al., 1986; Benndorf, 1987; Carpenter, 1988a).
Long-term studies, ecosystem experiments and paleolimnology provide information on interannual variation in lakes. Long-term studies potentially span many short and intermediate-length processes (10−4−101 y) (Edmondson & Litt, 1982; Goldman, Jassby & Powell, 1989; Schindler et al., 1990) but are rare and sometimes purely descriptive or site-specific. Results of ecosystem experiments may apply more broadly (Carpenter, 1991), but are also costly and rare. Further, many are too brief (<10−1 y) to detect the long-term responses of lakes to perturbation. Paleolimnology is relatively inexpensive and can yield records that are otherwise unobtainable.
Paleolimnology is the study of lake ecosystem structure and function using the historical record in sediments. Lake sediments accumulate through time and integrate material from the lake, its basin and catchment, and atmospheric sources (Frey, 1969; Binford, Deevey & Crisman, 1983; Battarbee et al., 1990). Development of high resolution sampling techniques (Glew, 1988; Davidson, 1988; Leavitt et al., 1989), well-defined taxonomy and autecology (e.g. Walker, 1987; Kingston & Birks, 1990) and automated analysis of some fossils (Mantoura & Llewellyn, 1983) allows paleoecological analysis on time scales relevant to population interactions in lakes and watersheds (10−1−104 y).
9 - Effects of predators and food supply on diel vertical migration of Daphnia
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 153-171
-
- Chapter
- Export citation
-
Summary
Introduction
The Cascade Project provided a perfect opportunity to study one of the great puzzles of limnology, a puzzle which has occupied numerous aquatic biologists over the past century-and-three-quarters. Hardy (1956) called it ‘the planktonic problem No. 1’ and more recent research has still not succeeded in providing an ultimate explanation that satisfies all cases. The adaptive significance of nocturnal diel vertical migration (DVM), a phenomenon whereby organisms throughout 15 aquatic phyla (Kerfoot, 1985) ascend through the water column around dusk and descend before dawn on a daily basis, is one of limnology's longest-standing enigmas.
Initial research on DVM was not published until almost sixty years after Baron Cuvier (1817) first documented its existence among fresh-water crustaceans. The phenomenon received attention from many of the crowned heads of nineteenth century European biology. August Weismann (1874, 1877), one of Darwin's strongest supporters on the Continent, and Forel (1876) both speculated on the causes of the behavior, as did Thienemann in the next century (1919). Most explanations from the nineteenth century, as well as from the first half of the twentieth, focused on the proximal causes of the behavior. Many abiotic factors were proposed as cues for the initiation of migratory behavior, including diel changes in temperature, pH, light intensity and density (Kikuchi, 1930). It eventually became apparent that no single factor could explain the many behavioral variations exhibited by migrators, including differences in the same species' migratory behavior in lakes near each other, and even substantial differences in migration by the same species in the same body of water (Juday, 1904; Kikuchi, 1930).
Contents
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp vii-viii
-
- Chapter
- Export citation
1 - Cascading trophic interactions
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 1-14
-
- Chapter
- Export citation
-
Summary
Introduction
The extent to which physical–chemical or biotic factors influence community structure and ecosystem function continues as one of the fundamental issues of ecology. The action and interaction of abiotic and biotic factors was recognized in early concepts of plant succession (McIntosh, 1985) and continues in the most contemporary reviews of plant-animal interaction (Strong, 1992). In animal community ecology, there have been several recent syntheses of the effects of multiple controlling factors (Menge & Sutherland, 1976, 1987; Fretwell, 1977; Oksanene et al., 1981; Power, 1992; Strong, 1983, 1992). Vigorous debate has surrounded the relative roles of predation and competition (Hairston, Smith & Slobodkin, 1960; Murdoch, 1966). Predation has been viewed from the standpoints of predator control of prey communities (Oksanen, 1983, 1990) and of prey constraints on predator communities (Price et al., 1980; Kareiva & Sahakian, 1990; Hunter & Price, 1992).
Like the other branches of ecology, limnology has evolved through debates about the roles of abiotic and biotic factors (Edmondson, 1991). In some respects, lakes are ideal systems for the study of multifactor interactions at the ecosystem scale (Carpenter, 1988a, pp. 4–5). Boundaries are clear and the difficulties of system definition that plague some areas of ecology (McIntosh, 1985) are lessened. Lakes are amenable to experimentation on a variety of scales, including whole-lake manipulations (Frost et al., 1988). At a global scale, insolation and climate have dominant effects on lake ecosystems (Brylinsky & Mann, 1973).
References
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 351-380
-
- Chapter
- Export citation
17 - Synthesis and new directions
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 332-350
-
- Chapter
- Export citation
-
Summary
Introduction
Preceding chapters provide the theoretical, analytical and empirical background for food-web interactions in an ecosystem context. In this chapter, we summarize what we consider to be the major accomplishments of our work and our interpretation of certain important, unexpected results. We also provide our view of the next generation of research issues involving the interactions of food-web structure and nutrient status in lakes, and speculate about the generality of trophic cascades in terrestrial and aquatic ecosystems.
Our primary goal in designing these experiments was to evaluate the role of food-web interactions in regulating primary production rates of planktonic algae. Regressions based on data from many lakes revealed that nutrient loading rates could account for only about half of the observed variance in primary production; roughly an order of magnitude of variability among lakes remained unexplained (Carpenter & Kitchell, 1984; Carpenter et al., 1985). We reasoned that a substantial share of that was due to differences in trophic interactions and developed a set of experiments designed to test that idea. Manipulations of fish populations in Peter and Tuesday Lakes were intended to yield maximum contrast in food web structure while the reference system, Paul Lake, remained as a monitor of interannual variance due to other sources.
We found that piscivores had rapid, massive effects on planktivores (Chapters 4–6). Predator avoidance behavior exhibited by small fishes caused planktivory in the pelagic zone to decrease much more rapidly than it would have done through piscivory alone (Chapter 5).
6 - Roles of fish predation: piscivory and planktivory
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 85-102
-
- Chapter
- Export citation
-
Summary
Introduction
Understanding the impacts of fish predation on lower trophic levels is a generally important goal (Wootton, 1990). In the special case of our studies, fishes are the reagents of whole-lake experiments. Because many fishes are opportunistic predators capable of complex behavior (Chapters 4 and 5; Hodgson & Kitchell, 1987), manipulation of fish populations may change predation pressure on lower trophic levels in unexpected ways. Therefore, it was essential to measure rates of predation on key food web components during the course of our experiments.
In piscivore-dominated systems, some species of planktivorous fishes may not persist or may be maintained at very low population densities (Tonn & Magnuson, 1982). Juvenile fishes are typically planktivorous and may be very abundant after hatching. Although a cohort of juveniles may be dramatically reduced owing to intense, continuous predation by adult piscivores, their effect as predators of zooplankton may be intense for very short periods. The prospect for a pulse of zooplanktivory followed by a pulse of piscivory heightened our interest in providing quantitative measures of intensity and duration of such short-term dynamics in predator–prey interactions revolving around fishes.
Habitat heterogeneity and habitat selection also influence predator–prey interactions (Werner & Gilliam, 1984). The relatively simple habitats in our study lakes provide only a modest amount of refuge where prey fishes may escape piscivores. Lack of refugia in Peter Lake explains the quick disappearance of the minnows introduced in 1985 and the rapid decline of rainbow trout in 1989 (Chapter 4).
Contributors
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
-
- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp ix-x
-
- Chapter
- Export citation