A team of researchers has discovered macroscopic life beneath the ocean floor in the deep ocean, one of Earth’s most extreme environments.
The discovery both complicates scientists’ understanding of the living communities around hydrothermal vents in the deep sea and provides a tantalizing glimpse into what life might look like beyond Earth. Although the scientists knew that life existed in and around the hydrothermal vents, it was not clear whether living things made use of the sediments beneath the actual miles of seawater.
In its latest work – published today in Nature Communications – the team used the remotely operated vehicle Subastian on the research vessel Falkor (also) to identify animals typically associated with the ocean’s deep-sea hydrothermal vents—which literally means beneath the ocean floor. The team conducted their study about 8,250 feet (2,515 meters) below sea level on a stretch of ocean floor they nicknamed the Fava Flow Suburbs in the eastern Pacific.
“Our discovery shows us that marine wildlife is not limited to what we see on the surface of the ocean floor, but that wildlife extends into the shallow ocean crust,” said study co-author Sabine Gollner, a researcher at the Royal Netherlands Institute. for Sea Research, in an email to Gizmodo. “The extent of undersea cavities — horizontally and how deep they reach — is not known yet,” Gollner added. “Submarine habitat can also be very important to the succession at hydrothermal vents, as the seafloor and submarine habitat are connected.”
The team found that animals such as tube worms twist through cavities in the undersea floor to move from point A to point B. Specifically, the team identified the tube worms R. pachyptila and O. alvinae and the clams B. thermophilusas well as polychaete worms and limpets, among the species that live in underwater cavities.
To get a sense of the conditions under the seabed, the team used Subastian‘s tool kit for drilling small holes in exposed chunks of igneous rock on the sea floor. The submarine also lifted up sections of lava shelves to see what lived beneath. Before lifting the shelf, the team sampled the vent fluid through the holes they drilled and measured the temperature inside the cavities (which averaged about 64° Fahrenheit or 18° Celsius).
Beneath the 4- to 6-inch-thick (10 to 15 centimeters) lava shelf, the team identified 4-inch-high (10 cm) cavities where macroscopic tubeworms and clams resided. Some of these underwater inhabitants were clearly adults; at least one of the tube worms was over 16 inches (41 cm) long, indicating that the burrows were not simply a nursery. As adults, the snake worms lose their mouths and intestines and are dependent on the bacteria Candidate Endoriftia persephone for nutrition, which lives inside the worms. With livable temperatures inside the underwater cavities and their source of nutrition in the worms themselves, the macroscopic animals were able to survive in the extreme environment without issue.
There are a few necessary necessities for life as we know it. Water, carbon, nitrogen, luck — there are a handful of factors that appear to be necessary for living things, and which guide the search for life beyond Earth, a field of science called astrobiology. By probing some of Earth’s most extreme environments, scientists hope to better understand the kinds of conditions that can host life everywhere from distant exoplanets to the subsurface oceans of Jupiter’s icy moons.
“The study of the underwater biosphere for wildlife is just beginning,” the team wrote in the paper. “These efforts will lead to a better understanding of the biogeochemistry, ecology and evolution of hydrothermal vents and its impact on global biodiversity and connectivity, potentially leading to better management of seafloor surface and terrestrial hydrothermal vents.”
Last year, a team using the same vessel found new hydrothermal vents teeming with life on the sea floor. The Schmidt Ocean Institute coordinated this effort, which highlighted the need to protect such parts of the mineral-rich seabed that may be affected by deep-sea mining. the same year, Falkor (also) was used to locate an octopus nursery deep off the coast of Costa Rica.
“The uniqueness of active hydrothermal vents is well known, and safeguards against potential future anthropogenic impacts such as deep-sea mining have been proposed or are in place,” the team added. “The discovery of animal habitats in the Earth’s crust, the extent of which is currently unknown, increases the need for such protections.”
The vessel Falkor—Falkor (also)s predecessor – shed light on the almost alien life forms that eke out an existence on the seabed. In 2021, a team aboard the vessel found microbes in the deep sea that are invisible to the human immune system, indicating that our bodies’ ability to recognize foreign microbes is not so all-encompassing. In addition to being alien to our conventional life sensibilities, these life forms are so alien to us that our bodies cannot even recognize them as living things.
The recent discovery could lend itself to the search for alien life. If creatures can make happy homes in the sediments beneath the sea, it expands the kind of horizons that life can have in deep space. Sure, we may still be alone in the galaxy, but the universe is a big place, full of possibilities.
Take, for example, a study published in PNAS Nexus back in April that found an ecosystem teeming with life beneath Chile’s Atacama Desert. The Atacama is an arid region in northern Chile that is one of the least hospitable places on Earth. Still, the team leading this research found several classes of bacteria that eke out existence underground. The bacteria are protected from the ultraviolet radiation above the ground underground, but remain close enough to the surface that they can obtain energy to undergo photosynthesis.
It is not yet clear how deep below the ocean floor life can continue, but it is clear that several macroscopic species make it work. The team wrote that “due to the increase in temperature, it has been predicted that life should be limited to several meters below the ocean floor.” Future studies could clarify exactly how far below the conditions become unsuitable for life.
The findings could hold water (no pun intended) as scientists look deeper below the surface of Jupiter’s icy moons Europa and Ganymede, which are believed to harbor subsurface oceans. Even if alien life isn’t floating around in the water column, recent findings may suggest it’s worth digging—or diving—deeper to find it.