Biodiversity in seagrass meadows in contrast to adjacent bare sand habitats of Foros Bay (Bulgarian Black Sea coast) assessed using environmental DNA (eDNA) metabarcoding

The present study presents an initial eDNA-based assessment of metazoan biodiversity associated with Zostera seagrass meadows and neighbouring bare sand habitats in Foros Bay, located along the Bulgarian Black Sea coast. Environmental DNA metabarcoding targeting the 12S and 18S rRNA regions revealed species-specific habitat associations, the presence of economically important fish species and increased detection frequencies of benthic metazoans in seagrass habitats relative to bare sand. On the contrary, data analyses conducted at the community level revealed that the degrees of compositional heterogeneity, total fish detection and eDNA signals were comparable amongst habitats. This indicates that mobile taxa are not closely associated with particular habitat and that habitat effects depend on the ecological characteristics of the organisms and the spatial scale of the research. These results highlight that Zostera meadows can enhance species richness and diversity; however, they do not consistently stabilise community composition. Our findings, demonstrate that eDNA metabarcoding is an effective instrument for evaluating the ecological and management significance of coastal habitat mosaics.