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15 - Annual fossil records of food-web manipulation
- Edited by Stephen R. Carpenter, University of Wisconsin, Madison, James F. Kitchell, University of Wisconsin, Madison
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- Book:
- The Trophic Cascade in Lakes
- Published online:
- 06 August 2010
- Print publication:
- 19 August 1993, pp 278-309
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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).
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
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- Chapter
- Export citation
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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).