A Stealth Mode of Energy Transfer and a New Way to Measure It

The flow of energy from Earth to Ocean creates life-sustaining habitats in the deep sea that likely hosted some of the earliest life forms on the planet. Finding hydrothermal ecosystems often relies on identifiable plumes from "black smoker" vents that occur in close proximity to biological communities and produce a torrential flow of scalding hot, particle-rich fluid. In contrast, the Lost City hydrothermal system, located 15 km away from the nearest high temperature venting, represents a new paradigm of energy transfer: the slow leak of low temperature, chemically heated, gas-rich fluids that are invisible to most methods of real-time detection.

Lost City fluids are warmed by a process known as serpentinization: a heat-generating chemical reaction between water and rock that produces large quantities of hydrogen gas. Hydrogen (H2) is the chemical equivalent of sunshine for organisms that thrive in a world without light. One of the most remarkable findings of this study is that the plume richest in hydrogen (with concentrations as high as plumes from 380°C black smokers) appears to come directly from the seafloor at a spot where there are no visible vent structures and where the temperature is barely above background seawater.

Discovery of additional serpentinization-driven venting could have profound implications for our understanding of how energy makes its way from the Earth’s interior to deep-ocean ecosystems. Because of the "invisible" nature of the Lost City plume, it will be challenging to find new examples. On this point, the Larson et al. study yielded a promising innovation: a data processing technique—adapted from a method used to enhance satellite imagery—that improves the ability of the electrochemical sensor to quantify the gas-rich plumes given off by Lost City-style venting. This new technique and the recent findings discussed in this article offer fresh opportunities for exploration.