The hot springs of the subantarctic islands host bacteria, archaea and viruses adapted to extreme environments. Devoid of oxygen, the chemistry of geothermal springs is comparable to certain extraterrestrial environments.
100 kilometers from the base of Port-aux-Français in the Kerguelen Islands, the Fumerolles plateau is very difficult to access, even for scientists. The geothermal springs in this area are nevertheless teeming with tiny life forms of interest to biologists at the Paul-Émile Victor Institute. No “district chief” – person in charge of the scientific base – would give permission to go there by foot for security reasons. Because in case of an accident, to help them would be hazardous. However, an expedition was able to collect the sometimes boiling water from the springs of the Fumerolles plateau and discovered 13 new species of microorganisms, some of which belong to new genera. The renowned journal Nature published these results in its December issue.
« La vie qui prolifère dans l’eau et la vapeur de cet écosystème pourrait directement descendre des premiers êtres vivants qui ont habité la Terre, et seraient aussi rustiques que les éventuelles formes de vie qu’on pourrait trouver dans l’espace. »Marc Le Romancer, microbiologist at the University of Western Brittany (France)
“We have been there three times since 2005, dropped off by the helicopter of the Marion Dufresne II (French oceanographic and supply ship, an unfailing companion of the French Southern and Antarctic Lands). We then set up camp in these windy areas for short stays of 48 to 72 hours. ” Marc Le Romancer, microbiologist, tells us.
The island sits on a sunken continental shelf that it shares with Heard-and-MacDonald, a volcanic archipelago that lies 500 kilometers to the southeast. At depth, a hot spot surrounds sheets of water that rise through the rocks, up to 300 meters above the surface of the sea. On the peninsula of Rallier du Batty the last volcanic activity of the island goes back to twenty-six thousand years. Remnants of the eruptions of yesteryear, there remain today only fumaroles, mud pools and hot springs.
Bacteria live in baths varying from 35 to 100°C, sometimes acidic, sometimes basic. Deprived of oxygen, they use dissolved minerals such as sulfur or iron to make their cells work. These primordial soups are considered to be remnants of the beginning of evolution or the cradle of life.
“In the island’s Saint Paul crater exists a hot water virus that is found in springs of southeast India. Does it come from the time when all the land masses were together and Antarctica and India were very close? This is a hypothesis,” wonders Marc Le Romancer. Some species of bacteria discovered in Kerguelen are common to those of Deception Island (near the Antarctic Peninsula), Yellowstone and Kamchatka.
Between the rocks, thermophilic bacteria are abundant hundreds of meters below the earth’s crust. “We have a set of hypotheses, technically difficult to verify, according to which underground water tables would connect certain hot spots between them and microorganisms would circulate in them,” says the researcher. According to these postulates, the thermal springs of the Antarctic regions would be only the submerged part of the iceberg.
Camille Lin, Polar Journal
Link to the study: Maxime Allioux, Stéven Yvenou, Alexander Merkel, Marc Cozannet, Johanne Aubé, Jolann Pommellec, Marc Le Romancer, Véronique Lavastre, Damien Guillaume and Karine Alain, Nature, 2022, A metagenomic insight into the microbiomes of geothermal springs in the Subantarctic Kerguelen Islands, https://doi.org/10.1038/s41598-022-26299-4.