# Environmental insights from non-target detections in urban eDNA metabarcoding

## TL;DR

The study explores non-target DNA detections in urban water systems, revealing ecological and human-related signals that can improve biodiversity monitoring.

## Contribution

The paper introduces a new perspective on interpreting non-target eDNA detections as meaningful ecological and anthropogenic signals in urban ecosystems.

## Key findings

- Non-target taxa included 30 species from 21 families and 35 marine fish species in urban freshwater samples.
- Marine fish detections were linked to wastewater facilities, indicating human activity influences.
- Non-target signals revealed invasive species, waterbirds, and bats, suggesting ecological relevance.

## Abstract

Metabarcoding amplifies environmental DNA (eDNA) but often yields non-target taxa and false positives. Urban ecosystems are particularly prone to such detections due to inflows of external genetic material, yet their interpretation in urban eDNA studies remains unclear. This study examined non-target occurrences from fish-targeted metabarcoding in inland urban freshwater systems and proposes a perspective on interpreting such detections as ecologically meaningful signals rather than analytical noise. From 32 samples, 27.8% of total reads were non-targets, including 30 species from 21 families of non-target taxa and 35 species from 20 families of marine fish. Non-target taxa were most common in rivers, whereas marine fish appeared near wastewater facilities, reflecting human-derived inputs. These findings highlight that unexpected eDNA detections may reveal overlooked ecological and anthropogenic signals, offering insights for more reliable biodiversity assessment and management in urban ecosystems.

•Detected 30 non-target taxa and 35 marine species in urban freshwater systems•Non-target signals revealed invasive species, waterbirds, and bats•Marine fish detections were confined to sites near waste-processing facilities•Seafood-related marine taxa indicate human activity signals in urban eDNA studies

Detected 30 non-target taxa and 35 marine species in urban freshwater systems

Non-target signals revealed invasive species, waterbirds, and bats

Marine fish detections were confined to sites near waste-processing facilities

Seafood-related marine taxa indicate human activity signals in urban eDNA studies

Environmental science; environmental monitoring; environmental biotechnology; urban planning