Diffuse-flow deep-sea vent site ‘Crab Spa’
From April 24 – May 14, 2017, a team of scientists, technicians, and engineers from different research institutions will use the deep-sea submersible Alvin to obtain new insights into the functioning of deep-sea hydrothermal vent ecosystems.
The discovery of deep-sea hydrothermal vents in 1977 has forever changed our perception of life on Earth. Deep-sea vents were the first ecosystems discovered where chemosynthesis, i.e., the production of living cells from carbon dioxide (CO2) by using chemical energy rather than light as in photosynthesis, plays an important role in producing the food for the higher trophic levels. However, despite 40 years of research, knowledge about identifying the chemosynthetically active microbes and measuring their rates of primary production at deep-sea vents is still very limited, which is a measurement ultimately needed to constrain production in these ecosystems, and to assess their role for the global ocean.
Vent-SID was deployed atop a vent site on the seafloor called Crab Spa. The Vent-SID collects fluid from the vent and incubates it in the white chambers near the top. Then it measures the rates at which microbes in the vent fluids perform chemosynthesis. (Courtesy of Stefan Sievert, Woods Hole Oceanographic Institution)
We have recently developed a robotic micro-laboratory, the Vent-Submersible Incubation Device (Vent-SID), to make these measurements directly at the seafloor. The Vent-SID represents the latest version of the SID instruments developed by Craig Taylor and engineers at WHOI, making it possible for the first time to determine rates of chemosynthesis at both seafloor pressure and vent temperatures at deep-sea hydrothermal vents. We successfully tested this instrument during the previous Dark Life cruise to the deep-sea vents at 9ºN on the East Pacific Rise in 2014. Read more about Vent-SID in Oceanus Magazine.
During Dark Life II, we will continue this work to learn more about the processes underlining and controlling chemosynthetic production at deep-sea vents. We will perform seafloor incubations using the Vent-SID under various conditions and at two vent sites (Crab Spa and Teddy Bear) that differ in temperature and chemistry. Comparing the microbial communities of these two sites and how they respond to the different incubation conditions will provide important insights into the factors controlling chemosynthesis. In particular, we will assess the relative importance of oxygen and nitrate in driving chemosynthesis. These two chemicals are being used by microbes to oxidize hydrogen sulfide and other reduced chemicals, which provides the energy allowing the microbes to convert CO2 into their own food (‘autotrophy’).
Specifically, we will address the following currently unresolved objectives:
- Obtain rates of chemoautotrophic carbon fixation (chemosynthesis) at a deep-sea hydrothermal vent site by measuring directly in the environment (in situ)
- Obtain in situ oxygen consumption rates coupled to carbon fixation.
- Obtain in situ nitrate reduction rate measurements at a deep-sea hydrothermal vent site.
- Directly correlate the in situ measurement of these processes with the expression of key genes involved in carbon and energy metabolism.
Besides studying free-living microorganisms and their activities, the research team will further perform investigations of microbes living in symbioses with invertebrates, most importantly the giant tubeworm Riftia pachyptila, study hydrothermal vent crabs, investigate the microbial degradation of the produced organic matter, and look at microbial colonization of various surfaces. So, please come along on our adventure to study life as you don’t know it.
