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 sam pled during early spring to determine the vertical distribution of mar ine planktonic archaea and to further describe the dynamic environment where they live. Chlorophyll concentration indicated that sampling oc curred during the early stages of austral spring algal development. As expected, prokaryote abundance was higher at surface than at depth, a nd prokaryotic activity estimated by leucine incorporation was low at the surface and extremely low at 500 m. The relative abundance of plan ktonic archaeal, eucaryal, and bacterial ribosomal RNA was determined by quantitative rRNA hybridization, and the performance of two differe nt universal probes used to normalize group-specific probe hybridizati on response was compared. Archaeal rRNA was detected in all samples an alyzed, and was more abundant at depth (up to 25% of total rRNA) than at the surface. In both years, the archaeal signal decreased during th e sampling period, particularly at surface. Most of the archaeal signa l was attributable to group I archaea, affiliated with the kingdom Cre narchaeota. Planktonic euryarchaeotes (group II archaea) showed a larg er contribution to the archaeal assemblage in surface waters than at d epth. In total, our results verify that planktonic archaea are dynamic and abundant components in marine picoplankton assemblages of the Ant arctic Peninsula.