Abstract (eng)
Marine microbial communities are essential contributors to global biomass, nutrient cycling, and biodiversity since the early history of Earth and their stability is influencing biogeochemical processes. In the present study, the temperature response (in situ temperature vs. 20°C) of the meso- and bathypelagic prokaryotic community of the North Atlantic and the Ross Sea in terms of dissolved inorganic carbon (DIC) fixation and community composition was determined. The prokaryotic community composition was assessed by 16S rRNA fingerprinting and 454 Tag sequencing. At a temperature of 20°C, DIC fixation was up to 230-times higher than at in situ temperature. This response was observed for the North Atlantic, in the Ross Sea, however, the increase in DIC fixation at 20°C remained insignificant. Although significant differences in prokaryotic community composition were observed between the in situ temperature and the 20°C incubations, the selective pressure applied as temperature increase, did not lead to a convergence of the prokaryotic communities of the different water masses incubated at 20°C. Sequencing revealed a high contribution of the gammaproteobacterial order Oceanospirillales to the total sequence abundance in the 20°C incubations. Our results indicate a high metabolic plasticity among members of this order and the potential of autotrophic DIC fixation indicated by the presence of genes for sulphur oxidation and carbon fixation, present in some Oceanospirillales (Swan et al. 2011). The temperature response is apparently not ubiquitously present in all the world’s oceans albeit widely distributed. The energy sources for this inorganic carbon fixation of the deep-sea microbial community remain enigmatic.