| This study explores changes in organic biogeochemistry characteristics possibly associated with the abundance of Didymosphenia geminata in Boulder Creek, CO. This diatom, once believed to be native to cool, oligotrophic waters in North America and Europe, has demonstrated nuisance behavior beyond its range over the last decade. From May through August 2008, one-liter whole water samples were collected weekly at four hydraulically variable sites along Boulder Creek in Colorado, USA. Additionally, periphyton samples, analyzed for their D. geminata content, and other water quality samples were collected weekly.;Chromatographic separation of the whole water samples was completed to isolate the hydrophobic organic acid components, which were primarily fulvic acid. Once separated, the whole water and fulvic action fractions were analyzed for dissolved organic carbon (DOC) concentration. The characterization process using fluorescence spectroscopy involved collecting excitation emission matrixes (EEMs) for the dissolved organic matter (DOM) fractions, modeling with parallel factor analysis (PARAFAC), and identifying the quinone-like fluorophores. The Fluorescence Index (FI) and Specific UV absorbance (SUVA254), were calculated to understand the source, either terrestrial or microbial, and the aromaticity of the DOM.;Few relationships were found between D. geminata abundance and the measured organic biogeochemistry characteristics. D. geminata abundance estimated by a Didymo Rating Index generally was not significantly associated with DOC concentration, SUVA254, fluorescence index, redox index, or component analysis values, with one exception. At two of the four sites a significant relationship was seen between whole water fluorescence index values and flow, indicating a possible link between presence of D. geminata and microbially-derived dissolved organic matter. This comparison demonstrated that assuming constant abundance of D. geminata , the fluorescence index tended to be higher under low flow conditions. |
