Maximising environmental pressure-response relationship signals from diatom-based metabarcoding in rivers

Area of Science:

• Ecology
• Molecular Biology
• Environmental Science

Background:

• River phytobenthos are crucial ecological indicators.
• DNA metabarcoding offers a powerful tool for biodiversity assessment.
• Current methods using rbcL primers are optimized for diatoms.

Purpose of the Study:

• To assess non-diatom diversity in river phytobenthos using DNA metabarcoding.
• To evaluate the impact of including non-diatom data in nutrient gradient models.
• To explore the potential of metabarcoding for expanding aquatic biodiversity knowledge.

Main Methods:

• DNA metabarcoding of river phytobenthos samples from the UK.
• Utilized rbcL primers optimized for diatoms.
• Analyzed non-diatom sequence reads and their contribution to ecological models.

Main Results:

• Detected non-diatom diversity, though often incomplete compared to expectations.
• Identified significant diversity in Eustigmatophyceae and wider distribution of freshwater Phaeophyceae.
• Models including non-diatoms showed similar predictive strength to diatom-only models for nutrient gradients.

Conclusions:

• Diatoms provide a strong signal for nutrient gradients, with non-diatoms adding little unique information.
• Limitations in primers and reference databases hinder comprehensive non-diatom assessment.
• Future research requires improved reference databases and ASV-based metrics for accurate taxonomic identification.