MULTIVARIATE ANALYSIS OF LABORATORY AND IN SITU OPTICAL MEASUREMENTS TO INVESTIGATE DOM DYNAMICS IN A TIDAL WETLAND

Abstract:

The Sacramento-San Joaquin Delta (Delta) is a source of drinking water for over 30 million people in California and is an important source of carbon and nutrients for aquatic habitats in the San Francisco Estuary (SFE). The pool of dissolved organic matter (DOM) in the Delta and SFE represents a mixture of river-derived material — the integration of watershed catchment processes — and locally derived wetland DOM. Physical, biological, and chemical transformation and removal processes influence the composition of this DOM pool on timescales ranging from seconds to hours. Measuring DOM composition and concentration in estuarine environments on scales at which they are forced is impractical using traditional grab sampling and laboratory-based analysis. To better accomplish this, we deployed in-situ instrumentation to provide high frequency measurement of velocity and optically based biogeochemical proxies (absorbance, fluorescence) to investigate DOM dynamics over spring neap tidal cycles in the main slough of Brown’s Island, a natural tidal wetland in the Delta. Descriptive statistics and multivariate classification of both the laboratory and in situ optical measurements (absorbance and EEMs) were obtained using parallel factor analysis (PARAFAC), principle component analysis (PCA) and linear discriminant analysis (LDA) to obtain useful high frequency optical parameters that describe DOM dynamics qualitatively and quantitatively. In this presentation we report findings from this study designed to derive and use optical indicators to continuously measure cumulative fluxes and chemical composition of wetland-derived DOM.