Hidden marine life: Scientists uncover secret world beneath ocean floor

An international team led by Monika Bright from the University of Vienna made a remarkable discovery involving a hidden world of marine animals beneath the Pacific Ocean floor.

At a depth of approximately 2,500 metres, in the hydrothermal field of the East Pacific Rise, previously unknown subterranean cavities were found, serving as habitats for various organisms. The discovery suggests that hydrothermal marine ecosystems are more complex than previously thought, given the harsh conditions there—such as high pressure, intense cold, and darkness.

The discovery of these cavities surprised scientists. While geologists had previously described such cavities, according to Monika Bright, biologists were unaware of their existence. During research conducted with the remotely-operated vehicle SuB-astian, from the research vessel Falkor, scientists were examining life around underwater hot vents.

Their attention was drawn to the mentioned cavities, found about 10 centimetres below the surface. Monika Bright described this extraordinary moment in an interview with ScienceAlert: "When we tried to collect rocks to look for tube worm larvae on their surfaces, we broke into the caves and discovered animals."

Inside the hidden cavities, where the water temperature reached about 25 degrees Celsius due to heat from volcanic activity, scientists identified at least ten species of animals. These included polychaetes, sea snails, and giant tube worms such as Riftia pachyptila. Interestingly, some species were also visible on the ocean floor, hinting at potential connections between the underground and above-ground environments.

Research published in the journal Nature Communications suggests that larvae may colonise the surface of hydrothermal vents from hidden cavities beneath the sea floor.

"The fact that large, living tube worms were found confirms the hypothesis that larvae can colonise the openings from below," added Bright. Scientists suggest that underground animal communities may play a crucial role in quickly colonising the surface after volcanic eruptions.

So far, it is unclear how extensive these hidden cavities are, how often they occur, or their significance for the entire hydrothermal ecosystem. Their discovery presents a significant challenge to scientists in exploring their extent. Researchers also highlight the need to protect these ecosystems from human activities, such as deep-sea mining.