ROV investigation of hydrothermal fluids issuing from vents on the floor of Yellowstone lake revealed temperatures in excess of 170 °C — the highest temperature yet reported for vent fluids within Yellowstone National Park (YNP). The study site is east of Stevenson Island at depth of approximately 100–125 m. In-situ pH and redox measurements of vent fluids were made using solid state sensors designed to sustain the elevated temperatures and pressures. YSZ membrane electrode with Ag/Ag2O internal element and internal pressure balanced Ag/AgCl reference electrode were used to measure pH, while a platinum electrode provided redox constraints. Lab verification of the pH sensor confirmed excellent agreement with Nernst law predictions, especially at temperatures in excess of 120 °C. In-situ pH values of between 4.2 and 4.5 were measured for the vent fluids at temperatures of 120 to 150 °C. The slightly acidic vent fluids are likely caused by CO2 enrichment in association with magmatic degassing effects that occur throughout YNP. This is consistent with results of simple model calculations and direct observation of CO2 bubbles in the immediate vicinity of the lake floor vents. Simultaneous redox measurements indicated moderate to highly reducing conditions (− 0.2 to − 0.3 V). As typical of measurements of this kind, internal and external redox disequilibria likely preclude unambiguous determination of redox controlling reactions. Redox disequilibria, however, can be expected to drive microbial metabolism and diversity in the near vent environment. Thus, the combination of in-situ pH and redox sensor deployments may ultimately provide the requisite framework to better understand the microbiology of the newly discovered hot vents on Yellowstone lake floor.
Bibliographical noteFunding Information:
The authors want to thank Dave Lavalvo and his colleagues with Global Foundation for Ocean Exploration without whose efforts this project could not have been undertaken. We would also like to thank Dr. Rob Sohn and others involved in the HD-YLAKE research team for constructive advice throughout the study and for providing high resolution bathymetric maps, which facilitated lake floor exploration. Funding for the project was provided by the National Science Foundation (EAR 1515377 and OCE 1434798). The paper benefitted tremendously from the insightful reviews provide by Jacob Loewenstern and Shaul Hurwitz.
© 2017 Elsevier B.V.
- Dissolved CO
- Hydrothermal vent fluids
- In-situ sensor
- Yellowstone Lake
- pH and redox