Response of bacteria and phytoplankton from a subtropical front location Southern Ocean to micronutrient amendments ex-situ.

The effects of micronutrient amendments such as cobalt (Co), copper (Cu), iron (Fe) and their mixture (CoþCuþFe) on bacterial abundance, phytoplankton, bacterial community (BC) composition were examined at a subtropical front (STF) location in the Indian Sector of the Southern Ocean (ISSO) during the austral summer of 2012. From the 15-day on-board experiment it became evident that there was no significant increase in total chlorophyll a concentration or phytoplankton cell numbers in micronutrient enriched microcosms (MEM) compared to the control microcosms (CM) with no added micronutrients. Highest bacterial abundance was observed in the Fe-enriched microcosm within 5 days of incubation unlike in other microcosms. Interestingly, significant differences in the BC composition were observed between MEM and CM. In that an increase of � 10 unique phylotypes affiliated with Psychrobacter sp,