Unlocking rivers' hidden diversity and ecological status using DNA metabarcoding in Northwest Spain

Area of Science:

• Ecology
• Molecular Biology
• Environmental Science

Background:

• Rivers are vital ecosystems facing global degradation, necessitating improved biomonitoring.
• Traditional methods using macroinvertebrate morphology have limitations in taxonomic resolution and scalability.
• DNA metabarcoding presents a novel molecular approach for ecological assessment.

Purpose of the Study:

• To evaluate DNA metabarcoding using bulk and environmental DNA (eDNA) for river macrozoobenthos assessment.
• To detect invasive and endangered species in river ecosystems.
• To compare molecular results with traditional methods for ecological status evaluation.

Main Methods:

• DNA metabarcoding was applied to homogenized bulk sediment samples and water eDNA samples.
• Macrozoobenthic biodiversity, species composition, and taxonomic resolution were analyzed.
• Detection of exotic and endangered species was performed using molecular tools.
• Ecological Quality Ratio (EQR) values from the IBMWP index were correlated with molecular data.

Main Results:

• DNA metabarcoding revealed high species richness in both bulk (100 species) and eDNA (87 species) samples, with distinct community compositions.
• Taxonomic resolution varied, with higher species-level identification in eDNA (49.4%) compared to bulk samples (17.43%).
• Eleven exotic species, including new regional records, and one endangered species were identified.
• Molecular methods correlated with morphological data for EQR, though bulk samples suggested higher ecological status.

Conclusions:

• DNA metabarcoding is a promising, scalable tool for comprehensive river biomonitoring, offering multi-faceted insights.
• It effectively assesses biodiversity, detects invasive/endangered species, and evaluates ecological status.
• Further optimization and intercalibration are crucial for integrating DNA metabarcoding into routine monitoring programs.