NSF Award
9013883
This research will investigate the response of stream ecosystems to nutrient limitation and the response of nutrient-limited stream ecosystems to different types of environmental disturbances. Specific objectives are to (1) determine the role of in-place recycling of a limiting nutrient within the benthic boundary region of natural stream reaches, (2) determine the spatial variation in recycling both among streams and longitudinally within a stream, and whether recycling varies in a predictable way, and (3) test some theoretical predictions about the relationship between ecosystem resilience/resistance and in-place nutrient recycling in natural streams, including the effect of longitudinal nonuniformities in nutrient availability and recycling due to spatial heterogeneity in nutrient input and within-stream nutrient uptake. The overall goal is to better understand the factors regulating the structure and productivity of benthic communities in lotic ecosystems, including their resistance and resistance to disturbances that include scouring, toxicant pulses, and changes in nutrient input. The proposed work will be achieved by combining theoretical analyses using mathematical models with empirical studies using both natural and laboratory streams that can be experimentally manipulated and to which releases of radiotracers can be made to quantify nutrient cycling processes under ambient conditions. The network of large-scale laboratory streams and the ability to use radiotracers in natural streams are unique capabilities for conducting stream ecosystem research at Oak Ridge National Laboratory.
