Includes bibliographical references (leaves 111-116). Chair of Advisory Committee, Dr. Leo Bodensteiner. Online resource; title from PDF title page (Western CEDAR, viewed December 13, 2024). Print reproduction. Online version record

Surface water chemistry can vary in a basin on various spatial and temporal scales due to differing geology, land use, seasons, and groundwater contribution. Trace elements from ambient water can be assimilated into calcified structures of fish which have been widely used to understand their life history. Understanding the spatial distribution and temporal stability of elements in the water is first required for this application. I investigated the spatiotemporal signatures of trace elements in the Skagit River Basin for the potential application to otolith-based determination of fish life habits by analyzing trace element concentrations in surface waters collected from 27 unique sites, each season, over two years. Variations in concentrations of strontium and magnesium to calcium showed potential for spatial discrimination at a subbasin level, however, the temporal overlap of signatures limits the ability to differentiate between individual sites. Site separation without temporal consideration could be achieved for the South Fork Sauk River and Nookachamps Creek due to their unique arsenic, sodium, potassium, magnesium, and barium concentrations. Higher resolution site separation may be achieved by combining multiple elemental signatures. Summer Year 1 samples provided the clearest spatial groupings of sites by subbasin while all other seasons showed no geographically significant groupings. Intra-year variation was heavily influenced by glacial melt in the Sauk subbasin during summers, and proximity to urbanized areas in the Lower Skagit subbasin. The least variability of elemental concentrations between seasons was observed in Upper Skagit subbasin sites.