New research reveals that lurking in some of the most inhospitable parts of the ocean depths, a blue volcanic mud contains evidence of extremophiles that push our ideas of survivability to the limit.
The goo in which the microbes reside has a pH value of 12, one of the highest ever recorded in a functional ecosystem. Using lipid biomarker analyses, a University of Bremen team traced how life finds a way in one of Earth’s harshest habitats, as revealed in their new paper in Communications Earth & Environment.
Exploring the Mariana Trench
Since 2014, the German Research Vessel Sonne has supported scientific operations primarily in the Pacific and Indian Oceans. The sediment core samples for the study were collected in 2022 during Sonne’s Expedition SO 292/2. Scientists aboard the expedition conducted a variety of research, including measuring geodynamic processes and geochemical cycles, and collecting atmospheric data.
The expedition explored the Mariana Forearc, discovering previously unknown mud volcanoes and collecting samples. Mud volcanoes erupt material from subduction zones, where surface material is carried into the mantle to mix with subsurface liquids. The actions that occur here drive earthquakes and tsunamis, yet are too deep to observe directly. Therefore, sampling the material that spews back to the surface through mud volcanoes provides essential information about what is occurring at such depths.
Additionally, the rare lifeforms that make their homes in such regions provide scientists with information about how life can evolve and persist under such desolate conditions. It was in one of these volcanoes that the team found the high pH blue volcanic mud at the center of the research.
Extremophiles in a Base Environment
The high pH meant only the most robust extremophiles could survive in this ecosystem. Therefore, there were few living cells to locate, requiring special trace analysis methods to find.
“But we were able to detect fats,” says first author Palash Kumawat, who is presently a PhD candidate in the Geosciences Department. “With the help of these biomarkers we were able to obtain insights into the survival strategies of methane- and sulfate-metabolizing microbes in this extreme environment.”
From analyzing the lipids, researchers can determine the microbe’s age. A living or only recently deceased microorganism will show intact cellular biomolecules. On the other end of the spectrum, if they are not intact, they have become a type of fossil called a geomolecule. After a careful investigation of the habitat, the team determined that, despite its extreme inhospitality, multiple microbial communities have made a home there, both now and in the past.
“This distinction helps us when working in areas with extremely low biomass and nutrient deficiency,” Kumawat said.
An Isolated Ecosystem
The life found in this volcanic sludge behaved differently from typical deep-sea microbes, which metabolize carbon to play an essential role in the global carbon cycle. Instead, the microbes derived their energy from minerals in the rocks, while taking in carbon dioxide and hydrogen to produce methane, leaving their ecosystem relatively separate from the ocean above them.
“What is fascinating about these findings is that life under these extreme conditions, such as high pH and low organic carbon concentrations, is even possible,” said co-author Dr. Florence Schubotz, organic geochemist at MARUM – Center for Marine Environmental Sciences at the University of Bremen. “Until now, the presence of methane-producing microorganisms in this system has been presumed, but could not be directly confirmed.”
“Furthermore, it is simply exciting to obtain insights into such a microbial habitat because we suspect that primordial life could have originated at precisely such sites,” Schubotz added.
To follow up, the team plans to incubate the microbes to learn more about their survival secrets. They will study cultivated microbes more closely, understand their nutrient preferences under such extreme conditions, and determine the edges of survivability at the planet’s extremes.
The paper, “Biomarker Evidence of a serpentinite Chemosynthetic Biosphere at the Mariana Forearc,” appeared in the Communications Earth & Environment on August 13, 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.