Unlocking Rivers Hidden Diversity and Ecological Status using DNA
Metabarcoding in Northwest Spain.
Abstract
1. Rivers are crucial ecosystems supporting biodiversity and human
well-being, yet they face increasing degradation globally. Traditional
river biomonitoring methods based on morphological identification of
macroinvertebrates present challenges in terms of taxonomic resolution
and scalability. 2. This study explores the application of DNA
metabarcoding analysis in both bulk and environmental DNA (eDNA) samples
for comprehensive assessment of macrozoobenthic biodiversity, detection
of invasive and endangered species, and evaluation of river ecological
status in northwestern Spain. 3. DNA metabarcoding of homogenised bulk
samples and water eDNA revealed a mean of 100 and 87 macrozoobenthos
species per sample respectively. However, it was a significantly
different specific composition with only 27.3% of the total species
shared. It was not possible to identify all the OTUs to species level,
only 17.43% and 49.4% of the OTUs generated could be identified to
species level In the Bulk and eDNA samples respectively. However, a
total of 11 exotic species (2 first records for the Iberian Peninsula
and another 3 first records for Asturias region) and 1 endangered
species were detected by molecular tools. Molecular methods showed
significant correlations with morphological identification for EQR
values (Ecological quality ratio) of IBMWP index, yet differences in
inferred river ecological status were noted, with bulk samples tending
to indicate higher status. 4. Overall, DNA metabarcoding offers a
promising approach for river biomonitoring, providing insights into
biodiversity, invasive species, and ecological status within a single
analysis. Further optimization and intercalibration are needed for its
implementation in routine biomonitoring programs, but its scalability
and multi-tasking capabilities position it as a valuable tool for
integrated monitoring of river ecosystems.