Institute of Ecosystem Studies

2008 BES Annual Meeting Presentation and Poster Abstracts

Land use, climate variability, and transformation of nutrients across an urban river continuum
Kaushal, Sujay
Co-Authors: Peter M. Groffman, Lawrence E. Band, Kenneth T. Belt, Stuart E.G. Findlay, Catherine A. Shields, Emily M. Elliott, Andrew J. Elmore, Claire Welty
Abstract: The River Continuum Concept is a widely used conceptual framework that describes and predicts changes in ecosystem structure and function along river systems. We investigate how the River Continuum Concept can be applied as a predictive framework to understand changes in transport and transformation of nutrients along urbanizing landscapes from headwaters to coastal ecosystems. We hypothesize that changes in headwater stream network structure are related to downstream changes in stream ecosystem function and decreased resilience to climatic events. We illustrate scaling relationships between stream size and network structure, shifts in chemical forms and bioavailability of nutrients across across stream order, and analysis in changes in ecosystem stability and nutrient retention/transport from headwaters to coastal waters in response to increasing climate variability. Results show that there is a large increase in stream “burial” rates with decreasing stream size leading to a general impairment of headwater streams in drainage networks. Increased subsidies of inorganic nutrients are converted to bioreactive organic forms as stream size increases indicating the shifting role of mid-order streams from “transporters” to “transformers” of nutrients and an emerging class of organic pollutants linked to eutrophication and harmful algal blooms. In addition, the interaction between between climate variability and urbanization amplifies nutrient transport from headwaters to rivers with drainage network structure strongly related to ecosystem retention. Our work suggests that massive alteration of headwater areas can be linked to important downstream effects on nutrient transport and transformation along urban river networks and highlights strategies for restoration as ecosystem experiments.