Vertical stratification of environmental DNA in the open ocean captures ecological patterns and behavior of deep-sea fishes

The deep-sea provides global vital functions such as sequestration of carbon from the atmosphere. The increased anthropogenic pressures and interest in expanding deep-sea fisheries makes this pristine ecosystem particularly vulnerable, whose conservation largely depends on rapid knowledge acquisition. In view of the limitations of traditional methods to explore the biodiversity of this vast ecosystem, the analysis of traces of macroorganismal DNA released into the water column arises as a cost-effective, non-invasive alternative. Yet, the success of this approach requires understanding of the stratification of DNA traces in the ocean. This study provides evidence that fish DNA traces can be used to establish depth-specific fish diversity and abundance throughout the water column, opening a promising avenue for gathering knowledge about the deep-sea ecosystem.