Integrating aquatic ecology into a channel evolution model

Channel evolution, or the predictable trajectory of change in stream geometry in response to disturbance, is a fundamental concept in stream geomorphology and restoration. Currently, there is no accompanying conceptual model of aquatic ecology during channel evolution.  Specifically, how do periphyton communities, ecosystem respiration, and carbon stores respond to changes in substrate, geometry, shear stress and light? And, how does the ecosystem function when the channel reaches a “quasi-equilibrium” morphology? We developed a conceptual model of ecological response during the stages of channel evolution. Using a combination of empirical and modeled geomorphic and ecological conditions from Morgan Creek, NC, we conducted simulations of channel and ecosystem change through time in response to geomorphic disturbance. We hypothesize that the main controls of ecological adjustment will be type of disturbance (chronic versus temporary) and the relative erodibility of bank and bed materials. Results suggest that ecosystem respiration and gross primary productivity are insensitive metrics for examining ecosystem response to channel change. Periphyton growth is only sensitive in systems with frequent storms. Carbon stores are significantly different between degrading and aggrading channels, with increased benthic storage in aggrading channels. Currently, this is a heuristic exercise, designed to generate questions and direct future research.