Combined impacts of temperature and trophic cascades in mountain lakes

University Of California-San Diego, La Jolla CA

Investigators

Abstract

The supply of energy and nutrients and the numbers of predatory or herbivorous animals play important roles in ecosystems that may be magnified or dampened by changes in temperature or precipitation due to climate change. Such interactions between climate and ecological processes are challenging to disentangle because of gradual, long-term responses of organisms through evolution or migration. Future climate change that alters the roles of nutrients and predators may compromise the capacity of ecosystems to provide valuable services to society. Uncertainty about how climate change alters ecological interactions presents a great challenge to forecasting the future state of the earth's ecosystems. This project examines how freshwater organisms and ecosystems in California mountain lakes change with temperature and the presence of trout that have been stocked for fishing. Fish strongly affect their prey and alter the flow of materials between lakes, the land and the atmosphere. Using mesocosm experiments and whole lake surveys, this project will study the interactive effects of fish and temperature on lake biogeochemical processes. In addition, the researchers will study how evolutionary responses by lake organisms to environmental changes might buffer populations, allowing them to persist in a changing environment. Results from this project will aid in understanding how lake ecosystems respond to changing climate and predator abundance, and whether lake ecosystems can continue to function in ways that are important in the environment and for society in the future. Effects of climate and predation on lake ecosystems have so far been studied in isolation. This project examines the impact of non-native predatory fish (trout) on the structure of lake ecosystems along an elevational (1200m to 3300m) thermal cline in the Sierra Nevada mountains. Interspecific and intraspecific morphological trait variation of important zooplankton taxa will also be studied to determine the cumulative impacts of predators and warming along a natural cline. In addition, the researchers will test the interactive effects of trophic cascades and temperature on system metabolism, processing of organic matter and carbon flux between lakes and the atmosphere. A field mesocosm transplant experiments will test the hypothesis that a history of selection by fish and high temperatures buffers communities against warming and trophic cascades through a combination of ecological and evolutionary processes. Undergraduate and graduate students and a postdoctoral researcher will be trained through this grant. Results from this project have direct applications to water resource management in a changing climate, and the researchers will share project findings with a variety of agencies, including the National Park Service.