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CHAPTER SEVENTEEN

Body size in aquatic ecology: important,

but not the whole story

ALAN G. HILDREW

School of Biological and Chemical Sciences, Queen Mary, University of London

DAVI D G. RAFFAELLI

Environment Department, University of York

RONNI EDMONDS - BROWN

Division of Geography and Environmental Sciences, University of Hertfordshire

Introduction
Ecologists have long been aware of regularities and patterns in the body size of
organisms in populations and communities, observations that go back at
least to Alfred Wallace and continue through the works of Elton, Thienemann,
Hutchinson, MacArthur and many others. The classical contribution of
R. H. Peters (1983 ) codified such patterns through the concept of body-size
allometry, of metabolic rate and other features, and led on to many of the
phenomena now included under macroecology (Blackburn & Gaston, 2003 ).
Brown and colleagues (Brown et al., 2004; Brown, Allen & Gillooly, this volume),
in particular, added new advances in scaling theory and, incorporating the
exponential effect of temperature on metabolic rate, sought to explain a wide
variety of patterns and processes in ecology at levels of organization from
individuals to ecosystems.
The focus on aquatic systems at the Hatfield symposium, and in this resultant
volume, is justified because body-size patterns may be more important, or at
least more obvious, in aquatic ecosystems. Woodward and Warren (this volume)
offer three possible reasons. First, the most important primary producers in
water are small and, along with small heterotrophic micro-organisms and small
detritus particles, are gathered from suspension by larger consumers. Second,
they point out that conventional predators, larger in turn than their prey, seem
particularly prominent in aquatic systems where there may be fewer parasite
food chains (see Cohen, this volume). A third, methodological reason for a
particular emphasis on body size by aquatic ecologists, may be the relative
ease of automated counting of particles and organisms in suspension across a
wide range of scales. Perhaps with particular reference to methodology, it is
noteworthy that terrestrial and aquatic ecologists have also generally taken
different perspectives on body size. Thus, in describing assemblages, aquatic

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.