Vertical distribution and temporal variation of marine planktonic archaea in the Gerlache Strait, Antarctica, during early spring

A station located in the Gerlache Strait (Antarctic Peninsula) was sampled during early spring to determine the vertical distribution of marine planktonic archaea and to further describe the dynamic environment where they live. Chlorophyll concentration indicated that sampling occurred during the early stages of austral spring algal development. As expected, prokaryote abundance was higher at surface than at depth, and prokaryotic activity estimated by leucine incorporation was low at the surface and extremely low at 500 m. The relative abundance of planktonic archaeal, eucaryal, and bacterial ribosomal RNA was determined by quantitative rRNA hybridization, and the performance of two different universal probes used to normalize group-specific probe hybridization response was compared. Archaeal rRNA was detected in all samples analyzed, and was more abundant at depth (up to 25% of total rRNA) than at the surface. In both years, the archaeal signal decreased during the sampling period, particularly at surface. Most of the archaeal signal was attributable to group I archaea, affiliated with the kingdom Crenarchaeota. Planktonic euryarchaeotes (group II archaea) showed a larger contribution to the archaeal assemblage in surface waters than at depth. In total, our results verify that planktonic archaea are dynamic and abundant components in marine picoplankton assemblages of the Antarctic Peninsula.