Environmental selection and advective transport shape the distribution of two cyst-forming Acantharia clades in the Canadian Arctic.

Anthropogenic induced climate perturbations are seen in changes in oceanic circulation patterns, and Arctic water masses defined by salinity are vulnerable to change. Biogeography of marine microbial eukaryotes is expected to be impacted by changes in local environmental conditions and advective processes, but tracking the extent of plankton distribution requires understanding routes for both active and passive tracers. To identify such tracers, we focused on samples collected in the western (Canada Basin) and eastern (Nares Strait); extremes of the Canadian High Arctic that are connected by an east flowing current north of Canada. Sequencing of the V4 region of 18S rRNA revealed that Acantharia, a taxonomically and functionally diverse group of large planktonic protists, were particularly common. Arctic acantharians in our study were dominated by two clades belonging to cyst-forming groups. The distribution of one clade suggested successful advective transport from the Pacific sourced water in the Beaufort Gyre to southern Nares Strait, with cells transported along the northern shelf of the Canadian Arctic. A second clade appeared to be a resident taxon of the Canada Basin whose distribution correlated to local environmental conditions, and detection in deeper samples would be consistent with swarmer formation enabling reestablishment the following year.