When a new island emerged in the South Pacific in 2015, it created an unprecedented opportunity not only for geologists and volcanologists, but also for biologists and ecologists. The emergence of a new island provides an opportunity to learn about how ecosystems began, from microbial precursors colonizing new land like this one to the emergence of plants or animals.

The island of Hunga Tonga-Hunga Ha’apai (Hunga Tonga) was short-lived – after being formed by a volcanic eruption in 2015, it was destroyed by another eruption in early 2022.

However, during the seven years of its existence, the island has revealed many interesting secrets. In a new study, researchers report evidence of an unexpected community of microbes metabolizing sulfur and atmospheric gases on the island; this is similar to organisms occupying very different habitats: hot springs or deep-sea hydrothermal vents.

“We didn’t see what we expected,” says microbial ecologist Nick Dragon of the University of Colorado.

“We thought we’d see the organisms you’d find when a glacier retreated, or the more typical early colonial species, cyanobacteria, but instead we found a unique group of bacteria that metabolize sulfur and atmospheric gases.”

Dragon and his fellow researchers collected 32 soil samples on surfaces ranging from the island to the top of a crater about 120 meters (394 feet) above sea level. They then extracted DNA from the samples and sequenced them.

Plants colonized the island fairly quickly after its formation, possibly thanks to seeds in bird droppings, but the researchers focused their efforts on collecting the vegetation-free surfaces.

They found bacteria and archaea in all the samples they took from the volcano cone, but these microbes were less diverse and very different from those from nearby plant areas.

It would make sense for the first microbes on the new island to come from ocean water or bird droppings, but these strange bacteria and archaea don’t seem to have come from there. Rather, the researchers suspect that these microbes may have gone deep into the ground.

“One of the reasons we think we’re seeing these unique microbes is because of features associated with volcanic eruptions: most likely lots of sulfur and hydrogen sulfide feeding the unique taxa we found,” Dragon says.

“The microbes were most similar to the microbes found in hydrothermal vents, hot springs like Yellowstone, and other volcanic systems. Our best guess is that the microbes came from such sources.”

It is rare to have the opportunity to explore such a system. Big bangs are one thing; Watching a pristine ecosystem flourish on a newly formed volcanic island is another.

The researchers say Hunga Tonga is only the third such landmass of its kind to emerge over the past 150 years and lasts more than a year, and the first in the tropics.

The scientists focused more on plants and animals than on microbes, although they will also study the emergence of life on the newly formed islands before.

“These types of volcanic eruptions happen all over the world, but they don’t usually form islands,” says Dragon. “We had an incredibly unique opportunity. No one had studied the microorganisms of this type of island system at such an early stage before.”

And no one will have the opportunity, at least directly, to study the inhabitants of the island. Hunga-Tonga spectacularly disappeared seven years after leaving the Pacific Ocean. When the volcano erupted again in January 2022, it produced the largest explosive eruption of the 21st century, with the largest cloud of steam and ash in recorded history. Hunga Tonga was destroyed, but not before scientists learned some intriguing details about its short lifespan.

“Of course we were disappointed that there were no islands, but now we have a lot of guesses as to what will happen when the islands are formed,” says Dragon. “So if something happens again, we’d like to go out there and collect more data. We would have a game plan to find out.”