| Summary: | Progress Code: completed Statement: Only a small proportion of DNA sequences were assigned to the target taxa (multicellular animals, or metazoa). Samples that yielded less than 1000 metazoan DNA sequence reads are unlikely to provide sufficient DNA sequence depth to properly characterise metazoan diversity in those samples, and were excluded. Non-invasive, “capture-free” approaches like eDNA also raise the question: how do we know an organism detected with eDNA is really there? The issue is discussed in the final paragraph of the article. Purpose To explore the potential of environmental DNA (eDNA) as a metazoan biodiversity monitoring tool for Antarctic benthic ecosystems. Specifically: (1) Are there differences between sediment and water eDNA samples in terms of (a) number of reads assigned to metazoans, non-metazoans, and unclassified, (b) the number of metazoan species detected, (c) metazoan community composition? (2) Does eDNA-based species richness decrease with sediment depth, similar to trends observed in morphology-based studies? (3) Do environmental parameters (e.g., depth, distance to open ocean) influence community composition in water eDNA? Our aim was to compare water and sediment as sources of environmental DNA (eDNA) to better characterise Antarctic benthic communities and further develop practical approaches for DNA-based biodiversity assessment in remote environments. We used a cytochrome c oxidase subunit I (COI) metabarcoding approach to characterise metazoan communities in 26 nearshore sites across 12 locations (including Ellis Fjord, Warriner Channel, Hawker Channel, Abatus Bay, Powell Point, Shirokaya Bay, and Weddell Arm) in the Vestfold Hills (East Antarctica) based on DNA extracted from either sediment cores or filtered seawater. We detected a total of 99 metazoan species from 12 phyla (including nematodes, cnidaria, echinoderms, chordates, arthropods, annelids, rotifers and molluscs) across 26 sites, with similar numbers of species detected in sediment and water eDNA samples. ...
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