Preprint compares environmental DNA and RNA metabarcoding for tropical marine biodiversity assessment

A preprint posted to bioRxiv reports a paired environmental DNA (eDNA) and environmental RNA (eRNA) metabarcoding comparison at 19 co-sampled marine sites near San Andres Island, Colombia, spanning coral reefs, seagrass beds, and other tropical marine habitats. The study addresses a methodological challenge in biodiversity monitoring: eDNA recovers genetic material irrespective of whether source organisms are alive or recently dead, potentially conflating signals from living communities with historical or degraded material.

Environmental RNA, derived from the less chemically stable ribonucleic acid, is hypothesised to be preferentially associated with metabolically active organisms, thereby providing a more temporally resolved view of which species are currently present and active. The researchers used both approaches on the same water samples to assess how much the community pictures they generate diverge and whether eRNA recovers a detectably different or more contemporaneous biodiversity signal.

The work is relevant to the growing application of genomic tools in ecology and conservation biology, including assessments of reef health. It also illustrates methodological considerations in the design of environmental genomics surveys — particularly the trade-offs between sensitivity, temporal resolution, and practical field logistics. As a preprint, the findings have not yet been peer-reviewed.