Guelph (LabNews Media LLC) – Environmental DNA (eDNA) metabarcoding is significantly superior to conventional morphological identification of aquatic organisms and reveals previously hidden losses of biodiversity in flowing waters. This is shown in a study from the University of Guelph in Ontario, Canada, published in the journal Molecular Ecology .
Scientists led by Dr. Mehrdad Hajibabaei analyzed 18 streams in the South Nation River basin, an area heavily impacted by agriculture. Using eDNA metabarcoding, they detected 282 species – including 261 species that were completely missed by conventional methods. The median species richness per sampling site was 59 species (eDNA) compared to only 15 species in conventional surveys.
The DNA-based method also enabled a significantly clearer distinction between agricultural, forestry, and mixed-use water bodies. Streams impacted by agriculture showed significantly higher conductivity, turbidity, and altered pH values, while forest waters exhibited higher oxygen levels and greater biodiversity.
The study underscores that traditional monitoring methods underestimate a large proportion of actual biodiversity due to the difficulty of morphologically identifying larvae and microorganisms. eDNA, on the other hand, offers a fast, scalable, and high-resolution alternative that makes even minor ecological changes detectable at an early stage.
The authors advocate for a combined use of eDNA screening and targeted conventional surveys to obtain a more accurate and timely picture of water quality – especially in times of increasing anthropogenic pollution from agriculture and urbanization.
Original publication:
Silva et al. (2026): Fine-scale ecological biomonitoring in a large, complex agriculturally impacted watershed via eDNA metabarcoding. Molecular Ecology.
DOI: 10.1111/mec.70377
Credits
Hajibabaei lab
