Application of a Sediment Model to Estimate Light Attenuation in Estuarine Environments

Jesse Lopez, Oregon Health and Science University

Estimates of light attenuation due to the turbidity of water are of great interest for biological and ecological studies in estuarine environments. Suspended sediment concentrations frequently are a dominant source of turbidity and therefore strongly affect estuarine biogeochemical processes, ecosystem structure, and prey-predator relationships for federally protected fish species. To develop estuary-wide estimates of light attenuation we have developed an approach that combines an empirical model of the light attenuation coefficient, Kd, with predictions of suspended sediment concentrations from a three-dimensional numerical model. The empirical model providing estimates of Kd is parameterized using observations of PAR, turbidity and CDOM. Estuary-wide predictions of Kd are then estimated from modeled suspended sediment concentrations and temporally and spatially representative values of CDOM. Here we describe the formulation of the model, assess predicative skill, explore model sensitivity to input parameters, and present preliminary results of estuary-wide characterizations of Kd in the Columbia River estuary.

Abstract Author(s): Jesse E. López, António M. Baptista