Meiobenthic community composition and biodiversity along a 5500 km transect of Western Antarctica: A metabarcoding analysis

Meiobenthic organisms, consisting of meiofauna and benthic microeukaryotes, are key components of marine ecosystems and facilitate bentho-pelagic coupling. However, their bio-geographic ranges and dispersal abilities are poorly known, especially in Antarctic waters where knowledge is extremely limited. Many Antarctic marine invertebrates are reported to have circumpolar distributions despite lecithotrophy and brooding development being common. Similarly, most meiofauna have developmental stages that are often assumed to have limited dispersal capabilities. To assess Antarctic meiobenthic community distribution patterns and diversity, the hypervariable V9 region of the 18S small subunit ribosomal RNA (SSU rRNA) gene was used to metabarcode shelf sediment samples (water depth 223 to 820 m) across a 5500 km region of the Western Antarctic. We found that some taxa had broad geographic distributions given that 28 operational taxonomic units (OTUs) were present in every core processed, 74 OTUs were found at every sampling event, and 722 OTUs were present in all of the major water basins sampled. Among these broadly distributed OTUs, metazoan taxa from 4 phyla (annelids, arthropods, kinorhynchs, and nematodes) were dominant members. As many of these OTUs relate to taxa expected to have limited dispersal capabilities based on current life history information, these results highlight our limited understanding of how small organisms move around in the sea. We also noted that the Antarctic Peninsula hosts a strikingly different and less diverse community than higher latitude regions, in contrast to benthic macrofauna.