12S metafish amplification product data used for DNase comparison

The potential for false positive detections caused by co-extracted environmental DNA (eDNA) remains largely underexplored. Distinguishing true signals from false positives caused by residual eDNA is a technical challenge in eRNA-based metabarcoding. To address this issue, we employed a freshwater river receiving treated effluent from a wastewater treatment plant as a model system. In such settings, eDNA in the treated effluent can lead to the detection of non-local species (e.g., marine taxa). Treated effluent typically contains minimal or no eRNA, making it well-suited for evaluating the influence of eDNA carryover. By comparing DNase-treated and untreated eRNA samples, we assessed the impact of residual eDNA on fish species richness and community composition.