Diatom communities and correlative water quality variables in agricultural streams

Diatom assemblages from tributaries of Wisconsin’s Green Lake agricultural watershed were studied in relation to in-stream water quality in effort to expand local monitoring methodologies. Seven stream sites were classified by stream quality (impairment status, habitat, nutrient thresholds, and restoration status) and were sampled once during summer 2021 and 2022. At each site, diatoms were collected alongside water samples for diatom community composition, and analysis of total phosphorus, total nitrogen, pH, and total solids. A total of 147 diatom taxa (> 1% abundance) were identified across sites. Non-metric multidimensional scaling indicates associations between the twelve most abundant taxa and stream quality (impairment and nutrient thresholds). These findings demonstrate that diatom communities in the Green Lake agricultural watershed tributaries may be useful indicators of stream quality, expanding the monitoring tools for local stakeholders.