Sediment eDNA metabarcoding reveals the endemism in benthic foraminifera from Arctic methane cold seepages

Benthic foraminifera are one of the major groups of eukaryotes living at cold seeps on the Arctic seafloor. However, their distribution and endemicity in these habitats have been largely debated. It is still unclear whether foraminiferal species commonly found in cold seeps differ genetically from those in deep-sea environments, and to what extent the seep community is distinct. To address these questions, we analyzed sediment DNA metabarcoding data specifically targeting foraminifera in different deep-water cold seep microhabitats (microbial mats, siboglinid tubeworms field) and reference sites within and outside the seep. Our results revealed microhabitat specificity among benthic foraminifera species. Microbial mats were dominated by a unique type of rDNA sequences assigned to a new lineage of monothalamid (single-chambered) foraminifera not previously reported from any other Arctic location. Other foraminiferal species were found across both seeps and reference stations. This study shows the presence of an endemic benthic foraminiferal species at cold seeps and confirms the existence of many common opportunistic species.