Distribution and Activity of Chemoautotrophs Across Environmental Gradients in the Southern Ocean

Stefan Sievert, Biology


2015 OEI Funded Project


The Southern Ocean is currently subject of intense investigations, mainly related to its importance for global biogeochemical cycles and its alarming rate of warming in response to climate change. The Southern Ocean is a large and heterogeneous biogeochemical system, comprising both highly productive coastal and ice-edge waters that contrast with open ocean waters where primary production is to a large extent limited by the availability of the micronutrient iron. Microbes play an essential role in ecosystem functioning and are the main drives of the biogeochemical cycling of elements. Yet, the diversity, activity, and abundance of microorganisms in this system remains poorly studied, in particular with regard to changes along environmental gradients, i.e., with depth and from shore to the open ocean. An increased understanding of the factors that drive the diversity and activity of microbes is paramount to predict responses of this important biome to future changes. Chemoautotrophic production, i.e., the assimilation of inorganic carbon into biomass using inorganic energy sources, has been identified as a potentially important process sustaining the ecosystem and contributing to the biogeochemical cycling of carbon and other elements in the Southern Ocean, in particular during winter and in the aphotic zone, yet no study has performed a systematic survey assessing the distribution, activity, and production of chemoautotrophs in this region.
Here, I propose to study the distribution and activity of chemoautrophic bacteria and archaea in the Southern Ocean using molecular- and cultivation-based techniques to examine their impact on the cycling of carbon, nitrogen, and sulfur. This study will be enabled by a funded cruise to the Southern Ocean funded by the Brazilian Antarctic Program (PROANTAR), and will build on a collaboration I started with Dr. Camila Negrão Signori, who spent part of her PhD studies in my lab as a Mary Sears Visitor in 2013. The results of the proposed research will be an invaluable contribution to understanding the distribution and contribution of chemoautotrophs to carbon cycling and biogeochemical fluxes in the Southern Ocean, and help to assess how the dynamic seascape of the Southern Ocean shapes microbial community composition and activity. This is important in elucidating the factors controlling microbial processes, and to evaluate how the system might respond to future changes.