Wind-driven distribution of bacteria in coastal Antarctica: evidence from the Ross Sea region

Abstract

Wind is a major transporter of biotic and abiotic material in coastal Antarctica. Sulfate-depleted sea salts delivered by wind to the Antarctic interior are thought to derive from sea ice, signifying a connection between Antarctic coastal environments and the interior. We hypothesized that bacteria, known to concentrate in salt-rich environments on the surface of sea ice, may also be subject to wind-driven transport. To test this hypothesis, we undertook a comparative evaluation of the composition and structure of bacterial communities, determined by deep sequencing of the V4 region of the 16S rRNA gene, in samples of frost flowers, young sea ice, and seawater from two coastal sites north of Ross Island, Antarctica, and in fresh snow over land and in surface ice of the Wilson Piedmont and Taylor Glaciers. Contrary to expectation, sequence reads that were consistently found in frost flowers, presumed to be the most mobile element of the sea ice environment, were rarely found in the terrestrial samples. Instead, cyanobacterial reads associated with the genus Pseudanabaena and found in abundance in the glacial ice and snow samples comprised up to 14.1 % of frost flower communities at one of our sites. Although this clade had not previously been reported in the Ross Sea region, wind patterns and other published data suggest that a likely source may be terrestrial aquatic environments on nearby Ross Island, including Mt. Erebus. One member of a sulfur-oxidizing, halophilic clade of the Gammaproteobacteria previously associated with hydrothermal sites was more abundant in frost flowers than in any other sample type. We hypothesize that these bacteria originated from hydrothermally influenced environments on Mt. Erebus. Overall, these findings suggest that wind is an important mechanism of microbial transport between the terrestrial and marine environments in coastal Antarctica, and may facilitate the exchange of taxa and genetic material between isolated habitats.