Scientists studying recent volcanic eruptions in Iceland have discovered that microbes begin colonizing new lava flows far faster—and more predictably—than previously thought.
In a testament to the hardiness of Earth’s extremophiles, University of Arizona researchers have identified microbes colonizing fresh volcanic lava they studied almost as soon as it hardens.
The new work, published in Nature Communications Biology, highlights how quickly life can recover from devastating events to colonize new habitats. Research for the paper was conducted around the Fagradalsfjall volcano in southwestern Iceland, during a period of three eruptions between 2021 and 2023.
“The lava coming out of the ground is over 2,000 degrees Fahrenheit, so obviously it is completely sterile,” said lead author Nathan Hadland, a doctoral student in the U of A Lunar and Planetary Laboratory, in a statement. “It’s a clean slate that essentially provides a natural laboratory to understand how microbes are colonizing it.”
The extreme heat of lava sterilizes the landscape before it cools, leaving behind rock that is nearly devoid of water and nutrients—conditions that make it an exceptionally inhospitable habitat. One of the central questions facing the researchers was where the materials needed to support new life were coming from.
To investigate, the team collected samples from freshly solidified lava and potential microbial sources, including rainwater and aerosols, and compared them with microbial communities in surrounding rocks.
“These lava flows are among the lowest biomass environments on Earth,” said co-author Solange Duhamel, associate professor at the U of A’s Department of Molecular and Cellular Biology, in the College of Science, as well as LPL. “They are comparable to Antarctica or the Atacama Desert in Chile, which is not that surprising considering they start out as a blank slate.”
However, as Duhamel notes, “our samples revealed that single-celled organisms are colonizing them pretty quickly.”
From Heat to Cold
“It appears that the first colonizers are these ‘badass’ microbes, for lack of a better term, the ones that can survive these initial conditions,” Hadland said, “because there’s not a lot of water and there’s very little nutrients. Even when it rains, these rocks dry out really fast.”
The researchers observed a dynamic pattern of microbial colonization that gradually trended toward stability. Initially, diversity increased as more species began inhabiting the newly formed rocks. That early growth, however, was later challenged by another extreme environmental filter: Iceland’s harsh winters. The dramatic shift from intense heat to prolonged cold tested microbial survival, ultimately favoring species capable of enduring both nutrient-poor volcanic rock and freezing seasonal conditions.
“Early on, it appears colonizers are mostly coming from soil that is blown onto the lava surface, as well as aerosols being deposited,” Hadland said. “But later, after that winter shift in diversity we observed, we see most of the microbes are coming from rainwater, and that’s a pretty interesting result.”
The team found that rainwater played a major role in shaping microbial communities. Microbes are not confined to land or ocean environments; they can also persist in rainwater, where they may influence weather and climate. These organisms can exist as free-floating cells, attach to dust particles, or even act as nuclei for cloud formation.
“Seeing this huge shift after the winter was pretty amazing,” Duhamel said, “and the fact that it was so replicable and consistent over the three different eruptions – we were not expecting that.”
Extremophiles in New Habits on Earth and Beyond
While previous work has examined organisms reclaiming habitats after major disruptions, this is the first to focus on a new habitat created in the wake of volcanic eruptions.
“The fact that we were able to do this three times – following each eruption in the same area – is what sets our project apart,” Hadland said. “In science, we want to measure things three times – what we call a ‘triplicate,’ if possible, and that is very rare in a natural environment. For this study, nature essentially is giving us a triplicate.”
“For the first time, we are beginning to gain a mechanistic understanding of how a biological community [is] established over time, from the very beginning,” Duhamel said, adding that one implication of the work is its relevance to questions of habitability beyond Earth.
While volcanic activity is currently minimal on Mars, it has in the past shaped the Red Planet’s surface. Its ability to melt water may have produced habitable periods in harsh environments. This earthbound work may offer essential clues to understanding life elsewhere in the universe, revealing how life takes its first steps toward colonizing new worlds.
“We can begin to tackle questions like, ‘How does volcanism influence habitability?’ ‘How do microbes take advantage of those types of environments?’ and apply the answers to similar types of systems that we have observed on Mars.” Duhamel said.
“Understanding how life could establish itself on a new lava flow on the surface of Mars, or at least how it could have done so in the past and knowing what kinds of biosignature we should look for and could potentially retrieve is a crucial step in that direction,” she concludes.
The paper, “Three Eruptions at the Fagradalsfjall Volcano in Iceland Show Rapid and Predictable Microbial Community Establishment,” appeared in Nature Communications Biology on November 24, 2025.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.