CHAPTER SEVEN
Body size and trophic cascades in lakes
J.IWAN JONES
Centre for Ecology and Hydrology, UK
ERIK JEPPESEN
National Environmental Research Institute,
University of Aarhus, DenmarkIntroduction
Since its first appearance (Hairston, Smith & Slobodkin,1960), the hypothesis
that predation can structure communities has courted controversy (Shapiro,
Lamarra & Lynch, 1975 ; Strong, 1992 ; McCann, Hastings & Strong, 1998 ). Nearly
50 years later there is still ongoing debate over the importance of predation
relative to other factors limiting the growth of populations (Paceet al., 1999;
Holt,2000; Poliset al., 2000; Power,2000), and the conditions that cause the
effect of predation to cascade through the community (Polis & Strong,1996;
Schmitz, Krivan & Ovadia,2004; Boreret al., 2005; Vander Zanden, Essington &
Vadeboncoeur, 2005 ). With the discovery of predator impacts on the structure
and dynamics of a diversity of real communities (Paine, 1980 ; Power, Matthews
& Stewart,1985; Carpenter & Kitchell,1993), it became apparent that higher
trophic levels could affect the biomass and dynamics of not only their prey,
but of their prey’s prey and, hence, the whole community. Earlier it was
assumed that communities were typically pyramidal in structure, with declining
biomass in each successive trophic level, and the dynamics of each trophic level
dependent upon those of their prey and ultimately the primary producers/basal
resources (Whittaker,1961 ). It isnow clear from habitats as diverse as Californian
islands (Roemer, Donlan & Courchamp,2002 ), the forests of Yellowstone Park
(Ripple & Beschta,2004 ) and the cod banks of the North Atlantic (Worm & Myers,
2003 ; Franket al., 2005 ) that this assumption is not correct, such that nowadays
the predictions of the trophic cascade influence how we manage our natural
environment (Scheffer, 1998 ). Nevertheless, despite numerous thoughtful
arguments, and theoretical and empirical analyses, the subject still remains
controversial.
The trophic cascade is defined as the propagation of indirect mutualism
between non-adjacent levels in a food chain, and manifests itself as a change
in the biomass of primary producers in response to changes in the biomass of
consumers separated by at least one trophic level. Hence, in the cascade
described for lakes, increased biomass of planktivorous fish leads to decreased
Body Size: The Structure and Function of Aquatic Ecosystems, eds. Alan G. Hildrew, David G. Raffaelli and Ronni
Edmonds-Brown. Published by Cambridge University Press.#British Ecological Society 2007.