Researchers made this astonishing discovery during a 30-day expedition aboard the “Falkor” research vessel from the Schmidt Ocean Institute, exploring an underwater volcano off the coast of Central America in the Pacific Ocean.
Along the active volcanic range are hydrothermal vents (fissures on the ocean floor), where hot water and magma from beneath the Earth’s crust combine to form a type of underwater hot spring.
These hydrothermal vents release elements that help bacteria, clams, tube worms, and other species gather around them at extreme ocean depths. This ecosystem has been studied extensively, but much of the underlying areas remain largely unexplored.
A sea eel swims past a tube worm tower at Tica Vent, a hydrothermal vent site on the Eastern Pacific Rise. (Photo: Schmidt Ocean Institute ROV SuBastian).
The “Subterranean World” Beneath the Ocean Floor
Using the remotely operated vehicle SuBastian, researchers made a surprising discovery: caves connected to hydrothermal vents filled with giant tube worms, some measuring up to 0.5 meters in length, along with other animal species.
This finding indicates a connection between the deep-sea ecosystem and the ocean floor, allowing life to thrive in unexpected places above and below the ocean bed.
Dr. Sabine Gollner, co-author of the study and marine biologist at the Royal Netherlands Institute for Sea Research, stated: “We wanted to understand how animals move and how they disperse, so we explored beneath the surface. Animals can live beneath hydrothermal vents, and to me, that’s incredible.”
The research team used the SuBastian exploration robot to drill small holes into the seabed and raise them, revealing cavities beneath the hydrothermal vents, as well as tube worms in both larval and adult forms, mobile animals like snails, and chemosynthetic bacteria.
Sunlight cannot penetrate the depths of the ocean to assist organisms in photosynthesis. Instead of sunlight, bacteria use chemical reactions to produce sugars, which other animals gather around to survive.
A large cluster of fixed tube worms residing in the outskirts of Fava Flow, a site on the Eastern Pacific Rise. (Photo: Schmidt Ocean Institute).
Protecting the Subterranean World
Next, the research team aims to determine whether life exists beneath all deep-sea hydrothermal vents and how far these caves extend horizontally and vertically.
However, caution is necessary when studying these fragile ecosystems. In the study, researchers only lifted six small squares of the seabed measuring approximately 50 x 50 cm to cause minimal disturbance.
The research team is concerned that raising larger blocks or any form of large drilling, such as deep-sea mining, could alter the pathways of hydrothermal vents and redirect them to other locations, potentially leading to the extinction of life forms that gather around these openings.
