Researchers have discovered animal life beneath the seafloor at hydrothermal vents in the eastern Pacific, near the Galápagos Islands. Scientists found enormous tubeworms and other vent animals thriving, challenging the previous belief that only microbes and viruses can inhibit inhospitable subseafloor crust.
The East Pacific Rise is a volcanically active region boasting numerous hydrothermal vent fields. Recent eruptions have uncovered megafauna colonization patterns at new vent sites, mainly tubeworms and bathymodiolin mussels. Hydrothermal vents in volcanically active regions erupt as boiling mineral-rich fluid, attracting animal life.
While the scientists knew that life existed in and around the hydrothermal vents, they are unclear about how these larvae arrive to settle at a vent.
As larvae cannot swim against the currents, their efficient dispersal by the ocean current seems more likely. Therefore, researchers hypothesized that larvae get entrained with seawater into the ocean crust. Since the shallow Earth’s crust is a porous volcanic rock, these creatures finally settle at vents.
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“Rapid colonization by these animals suggests efficient larval dispersal, with larvae assumed to be transported through the bottom, ridge, and ocean currents before they settle at vents through downwards swimming or sinking,” says the study.
To test their hypothesis, the group utilized the Remotely Operated Vehicle (ROV) SuBastian to a vent site 8,250 feet (2,515 meters) beneath the ocean surface. ROV drilled smaller holes at the sampling site (nicknamed Fava Flow Suburbs) and uplifted the lava slab.
ROV discovered caves of approximately 10 cm height below a 10-15 cm thick lava shelf, revealing hydrothermal fluid-filled pockets. They studied six caves inhabited by macroscopically visible animals, and the results showcased the shallow subseafloor as a suitable habitat for vent animals.
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“Here we report, to our knowledge for the first time, the discovery of animals excavated from fluid-filled, shallow cavities in the subseafloor of deep-sea hydrothermal vents,” says the study.
These small vents appeared to be populated with tubeworms. One of the caves even demonstrated males’ testes filled with sperm and female species with egg-filled gonads. This hinted at the reproduction occurring in the subseafloor cavities.
“We note that even when mussels were present at the seafloor surface above four of these cavities, they were not visible in the subseafloor cavities. The most abundant tubeworm species, growing from the roof of all five caves and often wrapped around lava drips, was O. alvinae with record sizes of 20 cm tube length, exceeding the ones described from the surface, indicating that these large specimens were adult,” describes the study.
The study pointed out that the subseafloor could be a transient or a permanent habitat, depending on the location. A few larvae could disperse in cavities to potentially colonize other lava cracks or settle at the existing site as permanent fauna.
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Journal Reference
- Bright, M., Gollner, S., De Oliveira, A. L., Fulford, A., Hughes, I. V., Hourdez, S., Karthäuser, C., Kolar, I., Krause, N., Le Layec, V., Makovec, T., Messora, A., Mitchell, J., Pröts, P., Sieler, F., Sievert, S. M., Steger, J., Tinta, T., Winter, T. R., . . . Paris, A. (2024). Animal life in the shallow subseafloor crust at deep-sea hydrothermal vents. Nature Communications, 15(1), 1-9. DOI: 10.1038/s41467-024-52631-9
