Trophic Cascades, Nutrients, and Lake Productivity: Whole-Lake Experiments

• DOI: 10.2307/2657215
• Publication Date: 2006-04-26T14:18:33Z
• Authors: Stephen R. Carpenter; Jonathan J. Cole; James R. Hodgson; James F. Kitchell; Michael L. Pace; Darren Bade; Kathryn L. Cottin...; Timothy E. Essington; Jeffrey N. Houser; Daniel E. Schindler

Responses of zooplankton, pelagic primary producers, planktonic bacteria, and CO2 exchange with the atmosphere were measured in four lakes with contrasting food webs under a range of nutrient enrichments during a seven-year period. Prior to enrichment, food webs were manipulated to create contrasts between piscivore dominance and planktivore dominance. Nutrient enrichments of inorganic nitrogen and phosphorus exhibited ratios of N:P > 17:1, by atoms, to maintain P limitation. An unmanipulated reference lake, Paul Lake, revealed baseline variability but showed no trends that could confound the interpretation of changes in the nearby manipulated lakes. Herbivorous zooplankton of West Long Lake (piscivorous fishes) were large-bodied Daphnia spp., in contrast to the small-bodied grazers that predominated in Peter Lake (planktivorous fishes). At comparable levels of nutrient enrichment, Peter Lake's areal chlorophyll and areal primary production rates exceeded those of West Long Lake by factors of approximatel...