Synthesis of a 33‐yr series of whole‐lake experiments: Effects of nutrients, grazers, and precipitation‐driven water color on chlorophyll

Abstract

AbstractWe conducted a 33‐yr series of whole‐lake experiments to measure ecosystem responses to food web structure and nutrient load, compare aquatic and terrestrial carbon flows to consumers, and evaluate indicators of ecosystem resilience. These manipulations showed that chlorophyll responded to nutrient loading and to grazing controlled by a trophic cascade. In this article, we synthesized experimental results using a new analysis of heretofore unrecognized variation in water color, measured as light absorbance at 440 nm. Long‐term data revealed fluctuations in precipitation that drive water color variation. We compared effects of nutrient loading, zooplankton biomass, zooplankton body size, and water color on chlorophyll. Water color was an important factor in the chlorophyll response. This driver of the chlorophyll response to manipulation was not resolved until decades of data were available. A long‐term context enriched insights from ecosystem experiments and exemplified the complementarity of experimental and long‐term approaches in limnology.