A Hydrothermal Vent Biosampler for Filtration and Concentration of Hydrothermal Vent Fluids

Christina Stam, Moogega Cooper, Alberto Behar, Kasthuri Venkateswaran

As unexplored areas of the world slowly decline, precise and efficient instruments are needed to retrieve accurate data from remote subterranean aquatic habitats. Understanding the geothermal habitat of deep-sea environments can have strong implications of the upper boundary of life on Earth as well as in extraterrestrial locations. Since these habitats are poorly understood, the possibility of discovering new and rare species of microbes is a distinct possibility. The best ways to discover if life can exist in the harshest areas on Earth is by visiting and collecting data from these locations. By using, testing and perfecting the proper instruments, these tools can be then be utilized on other planets to challenge the understood/accepted notions of life.

The discovery of lush animal communities at deep-sea hydrothermal vents fundamentally changed the way we viewed life on Earth. Reduced hydrothermal fluids supply inorganic electron donors and acceptors to diverse microbial communities that span large gradients in temperature, energy availability, and physical parameters. Microbial habitats at deep-sea hydrothermal vents include animal symbioses, sulfide chimneys, microbial mats, sediments, the subseafloor, and vent fluids. There is little data regarding the microbial composition of high temperature fluids, mainly due to challenges in sample collection and processing. In-situ colonization devices used on high temperature vent orifices have successfully detected microbial cells at temperatures up to 180°C, and DNA has been extracted and quantified from high temperature vent fluids. However collection of pristine high temperature fluids from these locations cannot be guaranteed.

A novel hydrothermal vent biosampler (HVB) sampler was developed by the JPL Robotic Vehicles Group with input from the Biotechnology and Planetary Protection Group and experts from the Monterey Bay Aquatic Research Institute (MBARI), Scripps Institute of Oceanography (SIO) and Woods Hole Oceanographic Institute (WHOI). The HVB has been designed to collect large-volume samples of hydrothermal vent fluid untainted by the surrounding waters. The HVB performs in-situ filtering of hydrothermal vent fluids to concentrate a large volume of vent fluid to a smaller volume more suitable for transport. The unique aspect of the HVB is its lightweight, compact but efficient design. Standing at two feet tall with a mass of ~23kg, the HVB can withstand extreme temperatures (~400°C) and pressure (depths of 6500m). Using the unique bypass valve, the key mechanism to preventing contamination from surrounding water, the HVB can collect pure samples in excess of 10L of fluid which eventually is concentrated to a final volume of 200mL. The bypass pipe is used to flush the system to eliminate cross-contamination between samplings. By pumping fluid through the bypass valve before actual sampling, fluid from the previous sampling left in the intake nozzle through the four-way valve will be flushed. The four-way valve is then rotated to one of the three filter assemblies to begin sample collection. While the four-way valve acts to close off the front end of each filter assembly before and after sampling, a check-valve on the end of each filter assembly accomplishes the same on the back end. Each of the check valves is opened only when the four-way valve is aligned to its filter assembly and the pump is turned on. In-situ sensing devices have been positioned throughout the system to monitor real-time temperature and flow rates during sampling, ensuring that samples are collected from specific areas of interest (i.e. they are ‘pristine’).

The HVB has been deployed in various field locations that have included the hydrothermal vents in Iceland, Suiyo Seamount and Myojin Knoll vents in Japan, Rio Tinto in Spain, Hermosa Beach and cold seeps off of the Monterey Bay coast.