Hydrothermal Vents Reveal Unexpected Oases of Life

Life in the deep ocean has an almost unyielding quality. Organisms have discovered a way to survive kilometers below the surface, where sunlight cannot reach and pressures would instantly crush an unprotected human body. They congregate near hydrothermal vents, which are fissures in the seafloor where mineral-rich, superheated fluid rushes upward from the Earth’s interior. They seem unaffected by the harshness of their surroundings. Since a historic discovery on the Galápagos Rift in 1977, scientists have been aware of these communities, but the ocean continues to surprise us. The most recent one, which was discovered off the coast of Papua New Guinea, is the kind that causes scientists to reevaluate their preconceived notions.

The location, now called Karambusel (a Tok Pisin word meaning “mussel”), is located on the western Pacific slope of Conical Seamount at a depth of roughly 1,300 meters. It was discovered during the 2023 SONNE expedition when the ROV Kiel 6000, a remotely operated vehicle, descended into the darkness and delivered something that no one had anticipated. A few centimeters away, cold methane-rich gas was escaping from one patch of seafloor while hot hydrothermal fluids were rising from another. It had never been observed that these two processes could coexist. Dozens of similar hybrid sites might exist elsewhere on the ocean floor and have gone unnoticed because no one had looked in the proper location.

When describing the expedition, GEOMAR marine geologist Dr. Philipp Brandl sounded genuinely taken aback. “We essentially have a hot vent bubbling right next to a cool gas seep,” he stated, “a combination that has never been described before.” It says something that a researcher who has conducted numerous surveys of this same underwater volcanic chain would exercise such restraint. Not only was what they discovered geologically unique, but it was also brimming with life. Mussels covered the rocks, amphipods and shrimp swam through the water, tube worms coiled upward, and bright purple sea cucumbers lay on the bottom. It was so dense that, in some areas, the organisms layered over the bare rock made it impossible to see it at all.

Conical Seamount’s unique geology is what enables this. Beneath the volcanic structure are thick layers of organic-rich sediment, which are heated by rising magma to produce methane and other hydrocarbons. Chemically rich fluid is also propelled upward by the same magma heat until it emerges as a traditional hot vent through the seafloor. The pathways used by the two processes are identical. In the end, the same holes in the rock produce both hot water and cold gas. The end product is a habitat that has never been described before, a sort of unintentional greenhouse for biodiversity that is powered solely by chemical energy and located far below the reach of sunlight.

It’s difficult to ignore how the more we learn about these vents, the more intricate their story becomes. According to early theories, a hydrothermal vent’s supporting community simply collapses when the magma beneath it cools and the flow stops. However, scientists examining long-extinct vents close to the East Pacific Rise discovered something different: up to 2,000 different types of microbes were still present in rock that had been chilled for hundreds of years. The species mix had completely changed, replacing the heat-loving organisms with a completely new population that included aerobic and anaerobic microbes living within centimeters of one another. Scientists described this cohabitation arrangement as unusual even by deep-sea standards. It appears that life at the bottom of the ocean is more interested in creating rules than it is in following them.

Beneath its biological diversity, Karambusel also carries something unfamiliar. In addition to arsenic, antimony, and mercury, which were deposited during earlier times of intense hydrothermal activity, the rocks shimmer with traces of gold and silver. In essence, the site is sitting on geological memory. A precious metal record of previous heat. That particular detail is likely to draw the wrong kind of attention for some people. The Ladolam gold mine on Lihir Island, where waste is dumped into the ocean, is one of the nearby mining operations. There are more exploration licenses in the area. Karambusel seems to have been discovered just in time, or perhaps not in time enough.

Before commercial interests can access the site, Brandl’s team has demanded that it be formally protected. “We have discovered an unexpected treasure trove of biodiversity,” he stated, “that needs to be protected before economic interests destroy it.” It remains to be seen if that protection comes to pass. The deep sea has always been viewed as being far enough away to be ignored, out of sight in a way that makes it simple to undervalue. However, the vastness of the ocean floor and the processes that take place there, such as the slow accumulation of biomass, the cycling of minerals, and the processing of carbon, shape the planet’s systems in ways that scientists are still figuring out. Beyond the immediate wonder of its methane-breathing mussels and purple sea cucumbers, Karambusel serves as a reminder that the inventory of life on Earth is still far from complete. In a significant way, we are still in the early stages of comprehending what resides down there and what we risk losing before our search is complete.