Interdisciplinary Investigation of a New Hydrothermal Vent Field

Strange New Vents
The new vent field was discovered sitting atop a fault scarp at more than 3,600 meter depth in the Southern Pescadero Basin (SPB), the southernmost sediment-covered pull-apart basin in the Gulf of California. The limits of this vent field have yet to be defined and many features have yet to be explored, but what is clear is that these vents are unusual physically, chemically, and biologically.

The more commonly observed hydrothermal vents are polymetallic sulfide chimneys, also known as “white and black smokers.” This is because they release hydrothermal fluids that resemble smoke plumes rising from chimneys. The vents at SPB are uniquely comprised of hydrothermal carbonates and are venting clear, shimmering water around 290 degrees Celsius. These fluids have a higher pH and produce different mineral deposits than most commonly observed vents. Hot water reacting with sediment forms organic gases and hydrothermal petroleum, a process that usually requires deep burial of organic-rich sediment and millions of years. These organic compounds provide an alternative source of energy for microbial life in addition to the hydrogen and hydrogen sulfide gases dissolved in the hydrothermal fluid.

Using new technology, scientists will be able to explore the sediments and their associated microbes to possibly validate the presence of subsurface metal and the critical community of life surrounding this habitat.

Interdisciplinary Exploration of SPB
The vents at SPB offer a unique opportunity to compare microbial and animal community compositions between vents with different chemistries and mineral deposits. To fully investigate both the geochemical and biological sides of the story, this 21-day cruise will be split into two legs with an interdisciplinary team of geologists, chemists, microbiologists and biologists on board the R/V Falkor.

First a “big picture” will be formed with R/V Falkor’s shipboard multibeam mapping and magnetic instruments to determine the regional tectonic setting. Then, an Autonomous Underwater Vehicle (AUV) equipped with sonar and seismic sensors will fill in areas of interest with high resolution bathymetry data on a meter scale while collecting data on water temperature and salinity. This finer-scale mapping will identify targets for later dives with the Remotely Operated Vehicle (ROV) SuBastian. The most detailed mapping will be done in the known vent field using a low attitude survey system mounted onto the ROV for centimeter-scale mapping using a new Lidar system. This will be tested down to 3,800 meters for the first time. Mapping at this scale will provide an unprecedented view of the geological and geochemical controls on vent faunal communities.

Once the entire vent field has been mapped, the team will use the new AUV maps to explore for new hydrothermal fields using the ROV to collect chimneys, vent fluids, sediment, and rock samples. The geological and chemical insights from these data will allow the team to compare the composition and inner workings of vents within the SPB field and establish a tectonic context for the site. These dives will also retrieve and live-stream high definition 4K video of never-before-seen areas of the SPB field providing potential targets for the biological team on leg two.

On the second leg, the team will focus on biological research questions aimed at investigating the density, distribution, diversity, and metabolism of organisms on and around the vents. They will use a heat flow probe to quantify the thermal setting in and around the animal communities. This will allow the scientists to compare between vents at SPB and with other known hydrothermal vent sites. ROV SuBastian will sample extensively along a series of transects from low activity areas into the main vent field exploring unusual assemblages of tubeworms, polychaetes, and of course the microbes. In an environment where there is no sunlight to provide energy to plants, the food chain is reliant on these tiny but important chemosynthetic microbes. Connecting the type, diversity, and lifestyle of microbes associated with different mineral deposits, chemical components dissolve in the vent fluids, and associated hydrothermal hydrocarbons will reveal new, exciting insights into the alien world of hydrothermal vents.

Linking the Deep Sea to Space
This cruise promises to be filled with discovery as diverse researchers come together to collect and analyze data at multiple scales, from multiple disciplines. Technology will be key: for example, one-centimeter-scale topographic mapping will be created using a specialized Lidar mounted on ROV SuBastian. Combined with seismic measurements, water samples, and 4K imaging of animals in their habitats, this research will allow for an unprecedented integration of geological, chemical, and biological data.

This research will have important implications for the deep sea research community, and for conservation of the hydrothermal vent habitats. There is still so little that we know about the microbial community and these vent systems, and what kind of impact they may have on the rest of the oceans. The discovery of chemosynthetic communities associated with hydrothermal vents has changed the way we think of life, both on Earth and in our search for life on other planets. We know that hydrogen, hydrogen sulfide, and methane are present on other planets, and the moon Titan has oceans of hydrocarbon. If there is a source of available electrons, such as oxygen gas, then there are potential energy sources which could support life. Do the microbial communities in the Pescadero Basin hold clues to life elsewhere? We do not know, but we are certainly looking forward to trying to answer questions such as these while aboard Falkor!

Permit Information:
• Permiso de Pesca de Fomento a Extrajeros No. PPFE/DGOPA-200/18
• Authorization EG00122018 granted by Direccion General de Geografia y Medio Ambiente del Instituto Nacional de Estadistica y Geografia (INEGI)
General Geographical Direction and Environment of the National Institute of Statistics and Geography