Welcome to the Sievert Lab - Studying the Microbial Ecology & Physiology of Dark Life
Overall Research Goals
Focus on Autotrophic Microbes in Subseafloor at Deep-Sea Vents
For example, we are currently utilizing molecular biological tools with concomitant analysis of lipids and their stable isotopic compositions as well as microscopic identification of environmental samples and activity measurements to provide a comprehensive assessment of the importance of sulfur oxidation in the subsurface at deep-sea vents. We are attempting to assess the potential importance of carbon fixation pathways other than the Calvin-Benson-Bassham (CBB) cycle for the productivity of this ecosystem. Our present knowledge of organisms responsible for inorganic carbon fixation at hydrothermal vents is inadequate, despite the fact that these organisms form the basis of these ecosystems. Given the prevalence of Campylobacteria (formerly known as Epsilonproteobacteria) at hydrothermal systems, and the fact that cultivated representatives are autotrophic, it is likely that these organisms contribute significantly to primary organic matter production at hydrothermal vents. These and other autotrophic microbes at vents are using the reductive tricarboxylic acid (TCA) cycle for autotrophic carbon fixation, suggesting that this cycle might be more significant for carbon production at hydrothermal vents than previously thought. Thus, a picture begins to emerge questioning the paradigm of the CBB cycle being at the base of the food web of deep-sea hydrothermal vents.
Quantifying subseafloor productivity at deep-sea hot springs
The discovery of deep-sea hot springs at the Galapagos Spreading Center in 1977 forever changed our perception of life on Earth. It was the first ecosystem to be identified where chemoautotophy is the predominant form of organic carbon production, triggering a series of groundbreaking discoveries over the last forty years. Yet, up to this point we still lack a quantitative assessment of the amount of carbon being produced at deep-sea hot springs, in particular in the sub-seafloor portion of these systems. In a paper published at Proceedings of the National Academy of Sciences of the USA, we describe the results of innovative experiments, which have allowed us to address questions that have so far remained unanswered by directly quantifying the efficiency of natural chemosynthetic microbial communities and to derive empirical constrains on the primary productivity, standing stock, and turnover time of the sub-seafloor biosphere at deep-sea hot-springs. Please read the WHOI news release here.
Expeditions to Study Subseafloor Life at Deep-Sea Vents
In April/May 2017, we went on the Dark Life II expedition to study life on and below the seafloor at the deep-sea hydrothermal vents at 9oN on the East Pacific Rise using the deep-sea submersible Alvin on R/V Atlantis. The focus was on using a newly developed seafloor micro-laboratory, named the Vent-SID, to measure chemoautotrophic production at deep-sea vents directly at the seafloor under in situ conditions. The research is funded by the National Science Foundation, and it represents a collaboration among scientists from different research institutions around the world. Please feel free to check out also our previous expeditions in 2014, Dark Life I, and WHOI's Dive & Discover Expedition 15.