Dissolved Organic Matter (DOM) is a dynamic carbon source that plays many roles in aquatic systems. It can provide nutrients for microorganisms and act as organic ultraviolet protection for everything under the water’s surface. Thus, understanding DOM’s variation is meaningful since the quality can indicate its source and/or processing dynamics in freshwater ecosystems.Over nine months, we collected biweekly water samples from the hyporheic, riparian, and stream surface water (n=215 unique water samples) from an Ozark forested intermittent stream. We analyzed the samples for DOM properties using spectrophotometry optical techniques and calculated SUVA 254, E2:E3 ratio, E4:E6 ratio, and Spectral Slope Ratio metrics. Results showed that during the retweeting season, specifically in November, DOM had UV-shifted, smaller molecular weight signals than during other seasons. E2:E3 ratios were similar in the hyporheic, riparian, and surface samples, until the end of February coinciding with increased hydrologic connectivity between the three compartments. The ratios then diverged as time progressed but converged again during June (the drier period). This first year of study suggests significant impacts of discharge and precipitation events on DOM properties. We will also present DOC:DON ratios, which reflect compositional changes in incorporated nitrogen in DOM. This study is a model for DOM chemical dynamics in intermittent forested streams in the Midwestern region of the United States. The observed trends can inform our understanding of carbon cycling in the intermittent streams in the Anthropocene.

Dissolved organic matter (DOM) optical properties change over space and time in an intermittent Ozark forest stream

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