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).