Patterns of marine bacterioplankton biodiversity in the surface waters of the Scotia Arc, Southern Ocean

Spatial patchiness in marine surface bacterioplankton populations was investigated in the Southern Ocean, where the Antarctic Circumpolar Current meets the islands of the Scotia Arc and is subjected to terrestrial input, upwelling of nutrients and seasonal phytoplankton blooms. Total bacterioplankton population density, group-specific taxonomic distribution and six of eight dominant members of the bacterioplankton community were found to be consistent across 18 nearshore sites at eight locations around the Scotia Arc. Results from seven independent 16S rRNA gene clone libraries (1223 sequences in total) and fluorescent in situ hybridization suggested that microbial assemblages were predominantly homogeneous between Scotia Arc sites, where the Alphaproteobacteria,Gammaproteobacteria and the Cytophaga–Flavobacterium–Bacteroidetes cluster were the dominant bacterial groups. Of the 1223 useable sequences generated, 1087 (89%) shared ≥ 97% similarity with marine microorganisms and 331 (27%) matched published sequences previously detected in permanently cold Arctic and Antarctic marine environments. Taken together, results suggest that the dominant bacterioplankton groups are consistent between locations, but significant differences may be detected across the rare biodiversity.