Quantifying impacts of an environmental intervention using environmental DNA

Area of Science:

• Ecology
• Environmental Science
• Molecular Biology

Background:

• Environmental impact assessments are legally mandated for development projects, often requiring biological assessments.
• Environmental DNA (eDNA) metabarcoding offers a powerful tool for analyzing species presence in ecosystems.
• Culvert replacements are a significant infrastructure undertaking with potential ecological consequences.

Purpose of the Study:

• To assess the impact of culvert removals on salmonid populations in a freshwater stream using eDNA.
• To establish a quantitative baseline for eDNA concentrations in control streams for comparison.
• To evaluate the efficacy of eDNA metabarcoding for environmental impact monitoring.

Main Methods:

• Collected an 18-month time series of water samples before, during, and after culvert removals.
• Utilized eDNA metabarcoding of the 12s MiFish mtDNA locus and quantitative PCR (qPCR).
• Employed linear mixed effects models to analyze eDNA concentration patterns and culvert impact.

Main Results:

• One of two culvert removals significantly impacted fish passage; the other had no discernible effect.
• Construction activities associated with culvert removal had only transient effects on salmonid species.
• eDNA data provided multispecies estimates of absolute eDNA concentrations, revealing temporal and spatial patterns.

Conclusions:

• Culvert replacement can be performed with minimal disruption to key salmonid species.
• eDNA methods provide an efficient approach for monitoring numerous culverts and prioritizing replacements.
• A rigorous, quantitative eDNA-based method for environmental impact reporting is demonstrated, applicable globally.