Environmental DNA (eDNA) metabarcoding of sediments expands the utility of biological indicators in temporary rivers to hitherto neglected taxa

Le résumé fourni par la source

Biological indicators constitute an essential part of the ecological assessment under the European Water Framework Directive. However, in temporary rivers (TRs), high hydrological variability decreases richness and drives rapid community turnover, limiting the ability of biological communities to respond to anthropogenic impacts. To overcome these limitations, molecular methods such as environmental DNA (eDNA) metabarcoding may offer a more sensitive and minimally invasive approach to detect community-level responses because of a higher number of indicator taxa assessed. We aimed to evaluate the effectiveness of sediment eDNA metabarcoding for characterizing invertebrate communities and assessing the ecological status of disconnected pools in TRs. We collected sediment samples from 52 pools in Catalonia (NE Spain) and analyzed them using COI eDNA metabarcoding. Morphology-based indices and metrics did not detect significant differences between natural and impacted categories. In contrast, multiple invertebrate Operational Taxonomic Units (OTUs) showed strong and consistent associations with anthropogenic impact affecting sampled TRs. These taxa primarily belonged to groups typically determined at higher taxonomic levels (e.g., Class, Order) in routine river biomonitoring but also included members of the Chironomidae, Oligochaeta, Cladocera, Copepoda, and Ostracoda. The broader taxonomic coverage and the fine-scale OTU-level resolution provided by sediment eDNA metabarcoding revealed ecological responses masked by conventional invertebrate-based family-level metrics. We demonstrated that this approach can infer anthropogenic pressures in TRs by using a wider range of macro- and meiofaunal invertebrate taxa. This represents a significant methodological advance for deriving biological metrics in TR monitoring and assessment.

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