Lindeman (1942) made early distinctions between aquatic food webs and Elton's (1927) terrestrial biomass pyramids that firmly established the study of lakes and rivers as fertile ecosystems for examining the relative roles of resources and consumers in controlling energy flow and biomass. Building on these early observations, ecologists have established that energy transfers more efficiently through freshwater food webs than terrestrial food webs as a result of higher consumer-producer size ratios, higher producer growth rates and population turnover, and lower consumer-resource elemental imbalances, as compared to terrestrial systems (Shurin et al., 2006). Freshwater ecologists have confirmed the importance of nutrients in limiting primary production and the rapid transfer of energy to herbivores, thereby establishing the important role of bottom-up processes in regulating freshwater food webs (McQueen et al., 1986; Power, 1992). Freshwater ecologists have also recognized the role of top-down processes in freshwater ecosystems, and contributed substantially to demonstrating that higher trophic levels can influence primary producer biomass through trophic cascades (Carpenter et al., 1985; Power, 1992; Pace et al., 1999).
Clearly, both “top-down” (TD) and “bottom-up” (BU) regulation are pervasive in freshwater food webs (Shurin et al., 2006; Gruner et al., 2008), and these two processes do not act independently. For example, increasing nutrients can intensify consumer control and the effects of trophic cascades on producer communities (Carpenter et al., 2001; Jeppesen et al., 2003), and increase overall contribution of animal-mediated nutrient recycling to ecosystem demand (Vanni et al., 2006; Wilson and Xenopoulos, 2011). Understanding mechanisms that facilitate interactions between resource and consumer control of food web structure is an important avenue of research. Moreover, the importance of BU and TD interactions also pervades applied aspects of ecology, including water quality management and biodiversity conservation. For example, BU and TD interactions are beginning to help conservationists predict consequences of changing species composition on ecosystem function (Eby et al., 2006; McIntyre et al., 2007; Vaughn, 2010).