Nutrient Transport and Recycling by Consumers in Lake Food Webs: Implications for Algal Communities

Abstract

Ecologists have recently focused much attention on quantifying the strengths and relative importance of resource-based (bottom-up) and predator-based (top-down) forces in food webs (e.g., Hunter and Price (1992), Power (1992), and Strong (1992)). Resource abundance and quality can have strong effects on the composition and dynamics of food webs, particularly primary producer assemblages (Tilman, 1982). Predators also have strong influences on lower trophic levels. Top predators in food webs may regulate the abundance of species at lower trophic levels; when the effects of top predators extend through the food web all the way to the primary producers the result is called a trophic cascade effect (Paine, 1980; Carpenter et al., 1985, 1987; {McQueen} et al., 1986; Power, 1990; Vanni et al., 1990).