Aquatic ecosystems are ecological hot-spots in the landscape. Our research group studies how physical, chemical, and biological processes interact to regulate the structure and function of aquatic ecosystems, with an emphasis on understanding and predicting how these systems are responding to anthropogenic change. We use observational, comparative, and experimental approaches to understand and model ecological processes in habitats ranging from coastal streams and estuaries to arctic and alpine lakes. Much of our research is done in the Sierra Nevada of California, where we use steep landscape gradients and heterogeneity in space and time as a natural laboratory to test ecological questions, explore landscape limnological patterns, and develop a predictive understanding of ecosystem responses to environmental change.