CCZ Meiofauna; Bulk vs Sediment DNA

This study evaluates how different DNA extraction methods influence biodiversity assessments of deep-sea meiofaunal communities in the Clarion-Clipperton Fracture Zone (CCZ), a region of high interest for future polymetallic nodule mining. By comparing Bulk DNA extractions from isolated meiofauna with sedimentary DNA (SeDNA) extractions using the 18S V1-V2 marker, the researchers examined differences in OTU richness, taxonomic composition, and community patterns. Bulk DNA yielded far higher metazoan diversity than SeDNA, with very little overlap in detected OTUs, indicating strong method-specific biases. Modeling suggested that much larger sediment volumes would be needed for SeDNA to match Bulk-derived richness, but also demonstrated its potential if optimized for large-scale monitoring. The study's goal was to determine the most effective approach for biodiversity monitoring in deep-sea mining areas, and its relevance lies in providing methodological guidance for standardized, scalable, and reliable DNA-based impact assessments in fragile and understudied ecosystems.