OPUS: Collaborative Research: Analysis of Cross-Boundary Fluxes, Trophic Cascades and Ecosystem Stability Based on 32 Years of Whole-Lake Experiments

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

Large-bodied, long-lived fishes sometimes dominate aquatic food webs. Their rise to dominance causes declines in abundance of small-bodied fishes, rise in abundance of invertebrates, and high concentrations of algae, including noxious species that form toxic blooms in nutrient-rich lakes. These modifications are accompanied by changes in lake productivity and availability of nutrients that limit the productivity in many lakes. Often the populations of top predators and the food web structure that they enforce appear to be stable, persisting for many years. However, the factors that stabilize dominant populations of top predators are not well understood. The researchers will investigate if material transported from land, including dissolved as well as large particles such as leaves, help to support the production of top predators and thereby stabilize their dominance in lake food webs. The investigators will archive data collected from the study lakes since 1984 and make them available to the public. Multiple students will be trained during the course of this project and the findings from this study will be communicated to the public through blog postings. The investigators in a series of experiments from 1984-2015 in a suite of lakes investigated stability and change in food webs in response to predator harvest and stocking as well as nutrient enrichment. Other experiments studied the contributions of terrestrial organic matter to production of many consumers including large-bodied long-lived fishes. So far, however, the individual experiments have been analyzed separately. A comprehensive evaluation of the full set of experiments is needed to determine the role of terrestrial organic matter in food web patterns and the response of food webs to harvest, stocking and nutrient enrichment. More specifically, existing data from whole lake experiments will be used to investigate: (1) the interactive effects of nutrients, terrestrial dissolved organic matter (DOM), and consumer assimilation of terrestrial organic matter (allochthony) on the biomass of herbivorous zooplankton and the capacity of large-bodied grazers to withstand predation, (2) the effects of terrestrial prey on the stability and resilience of lake food webs and the strength of trophic cascades, and (3) the regulation of whole-ecosystem respiration by nutrients, terrestrial DOM, and food web structure. Beyond this contribution to basic science, the project will create an online, publicly-available database of data from the 32 years of whole lake experiments, train students in the use of large-scale experimental data, and create blog posts that present results of the research for a general audience.