Hydrothermal Vents of the Western Galápagos

“The 13-Frame Discovery”
In February 1977, aboard the R/V Knorr, Dr. Robert Ballard and a team of scientists pored over some 3,000 photographs taken by a deep-sea sensor sled towed across the Eastern Galálapagos Spreading Center (EGSC). The team were exploring the region after Dr. Kathleen Crane had detected a temperature anomaly on a previous expedition, providing strong evidence to support the hypothesis of hydrothermal venting. Nearly all the images featured a mostly barren seafloor at 2,500 meters, except in thirteen frames—hundreds of unknown clams and mussels crowded near warm water shimmering out of vents. Up until this moment, photosynthesis was thought to be the only driver of life on Earth. Yet here, well beyond the sun’s reach, these creatures weren’t merely existing. They were thriving.

Over the last forty-five years, hydrothermal vents have been uncovered in all five Ocean basins. Much progress has been made in understanding their inner workings, yet they remain one of Earth’s most mysterious and understudied ecosystems. Scientists believe there are hundreds more active sites yet to be uncovered—with each discovery an opportunity to characterize a distinct ecosystem and understand how these vents vary from one another. Answering this question compels Beinart and her team to explore the Western Galápagos Spreading Center (WGSC), just a few hundred kilometers from the original discovery sites. 

At the WGSC, the science team will study two known vent sites,  “Iguanas-Pinguinos” and “Navidad,” and search for more undetected hydrothermal vents. Confirmed in 2005, the two known sites feature 40 black smoker vents—unlike the white smokers discovered in 1977. The Navidad site remains unexplored, and three inferred sites flanking it are unconfirmed. These sites, and any unexpected vent discoveries, brim with possibilities for the team to explore, and connect these ecosystems.

Unique Vents, Unique Ecosystems
Examining vents on either side of the Galápagos Spreading Center is like comparing an acoustic and electric guitar—they’re similar, but very distinct. First, magma in the mantle percolates seawater that has seeped into the Earth’s crust. The seawater leaches minerals from the crust before discharging up through the seafloor in a distinctive plume. At the EGSC, there is a warm (2–23° C) calcium-rich plume, while the WGSC ejects metal-laden fluids up to 400° C at high velocity. In both cases, the vent fluid contains hydrogen sulfide that chemosynthetic bacteria convert into energy—kick-starting a food chain that supports one of the most diverse and abundant ecosystems in the Ocean. The bacteria provide energy to some creatures symbiotically by living in their tissues. To others, it serves as free-floating food particles. But just as the vents differ, so do their biological communities. While EGSC vents are dominated by tube worms, giant clams, and white crabs, WGSC vents may feature different chemosynthetic microbes and invertebrates. 

A Compact Laboratory of Oceanic Connectivity
Hunting for hydrothermal vents almost three kilometers below the surface requires a double-dose of surveying—using multibeam sonar and CTD hydrocasts—before sending in ROV SuBastian. Once the vents are located and confirmed, Beinart and her multidisciplinary team will target the vents’ mineral composition, vent fluid geochemistry, and the animal and microbe populations for sampling and study. Moving beyond simply identifying and characterizing these intertwined components, they will also examine how variations in one impacts the others. For example, since crust thickness varies across locations, they will determine how these fluctuations alter the sites’ specific geochemistry and biological characteristics. Their strategy turns each vent site into a living laboratory to examine environmental cause-and-effect.

The team will also use genetic data from biological samples to drive their understanding of hydrothermal vent “biogeography,” the study of species distribution across geologic time and space. Examining genetic divergences and species dispersal across vent sites will reveal the animals’ movements and adaptations. The next step is to combine this information with the team’s mineralogy and geochemistry data to determine how and why these environmental factors impact the evolution and migration of organisms. Understanding subtle but significant impacts on the ecosystem creates an outwardly expanding circle of knowledge. The data will ultimately aid in creating a big-picture view of how life on vents functions across time and space, reacting to an ever-changing Earth.