About 20 miles inland from Antarctica’s frigid coast, within the continent’s arid polar desert, blood‑red water surges from the stark white cliffs of Taylor Glacier. Rich in iron, the water gives the cascade its crimson appearance, creating the striking feature known as Blood Falls.
Blood Falls is exceptional because its flow is a blend of salty seawater and occasional fresh meltwater. “It is extremely osmotically challenging,” said Angela Zoumplis, a postdoctoral researcher at Yale University. “You wouldn’t expect much life in such a harsh environment.”
During her Ph.D. at the University of California, San Diego, Angela Zoumplis and her colleagues made a surprising discovery. The team identified a diverse community of eukaryotic microbes in the red ice and mud surrounding Blood Falls, and surprisingly, these organisms are marine in origin. Their findings, reported in Nature Geoscience, illuminate how microbes adapt to extreme conditions and provide new clues about Antarctica’s past and present climate dynamics.
As a graduate student, Angela Zoumplis collected samples of the red ice, mud, and sediment around Antarctica’s Blood Falls and discovered the presence of marine eukaryotic microbes there.
Anne Beaulaurier
“It’s a truly fascinating and remarkable place on Earth,” said Andrew Alverson, a diatom researcher at the University of Arkansas who was not involved in the study. “You can learn a lot about evolution and how life finds a way…They approached the system in a way that has never been done before, using extensive DNA sequencing.”
Exploring Eukaryotic Microbial Communities in Antarctica’s Dry Valleys and Blood Falls
Mixed with salty seawater and fresh meltwater, the red ice at Blood Falls is an osmotically challenging environment for microbes.
Angela Zoumplis
When Zoumplis and her team arrived in the McMurdo Dry Valleys in November, it was the Antarctic summer. Their objective was to collect water, wind, and soil samples throughout the valley to identify the eukaryotic microbes present.
For roughly six to eight months, the organisms experience a complete lack of water and become highly dehydrated, Zoumplis explained. “However, for about six weeks each year, meltwater streams flow from the glaciers, re‑hydrating the stream beds.”
The researchers gathered samples by hiking across the polar valleys and, when necessary, using a helicopter to access remote locations. Although the fieldwork occurred during the summer, the expedition was far from comfortable.
“We spent four months essentially confined to a tent in the middle of a freezing desert,” Zoumplis recounted. “I study cold‑adapted life forms, but I’m not one of them,” she laughed. “Even so, I would do it all again. The landscape is absolutely stunning, and while it’s incredibly fun, it’s also extremely challenging.”
During one sampling excursion, Zoumplis realized they were near Blood Falls. “Blood Falls wasn’t originally on our radar,” she noted. “We happened to have permits, so I ran over and quickly collected a few samples without expecting anything remarkable.”
Marine Diatoms Establish a Colony at Blood Falls
Located 20 miles from the nearest ocean, the red sediment around Blood Falls is home to eukaryotic marine microbes.
Angela Zoumplis
To focus on living organisms, the researchers extracted RNA rather than DNA from the samples. DNA can persist after cell death, whereas RNA indicates active metabolism, so “RNA is currently the more reliable indicator of life,” Zoumplis explained.
The team extracted total RNA from each sample and amplified the 18S rRNA gene to identify eukaryotes. Surprisingly, the community in the red mud and sediment at Blood Falls consisted almost entirely of marine microbes.
Surviving Away From the Sea: Adaptations of Marine Microbes at Blood Falls
The ocean is a very different environment than the iron-rich mud around Blood Falls, so the marine microbes living there must have adapted significantly to survive, researchers hypothesize.
Angela Zoumplis
Metatranscriptomic analyses revealed that the Blood Falls community is functionally distinct from microbes in dry‑valley waters and from those in the adjacent McMurdo Sound. Genes associated with active photosynthesis, ion transport, and sulfur assimilation were highly expressed, and many taxa displayed mechanisms for coping with fluctuating salinity—conditions typical of Blood Falls.
The ocean is a very different environment than the iron-rich mud around Blood Falls, so the marine microbes living there must have adapted significantly to survive, researchers hypothesize.
Angela Zoumplis
Future work aims to elucidate the specific adaptations these microbes employ to endure such a stressful setting. “Being separated from the ocean is extremely challenging for marine life, and we suspect dormancy is a key factor,” Zoumplis noted. Indeed, many of the identified taxa can form cysts or spores, enabling survival in harsh conditions.
The ocean is a very different environment than the iron-rich mud around Blood Falls, so the marine microbes living there must have adapted significantly to survive, researchers hypothesize.
Angela Zoumplis
Alverson is keen to explore how these microbes have physiologically reorganized themselves after leaving the ocean. “They appear to have escaped limitations of iron or silica and now thrive in nutrient‑rich conditions,” he observed. Growing the organisms in the laboratory and subjecting them to stress would be invaluable. He suggested comparative experiments that pair Blood Falls microbes with their closest marine relatives under various stress regimes.
Both researchers anticipate that deeper genomic sequencing would allow phylogenetic and molecular‑clock analyses, helping to estimate when these marine taxa diverged from their Blood Falls counterparts and to date the underlying geological event. Such data could refine models of past sea‑level changes and the timing of marine flooding that likely feeds Blood Falls.
Alverson emphasized that locations such as Blood Falls are ideal for probing climate and evolutionary processes. “They resemble deep‑sea hydrothermal vents in their potential to reveal how life adapts and evolves,” he noted. Zoumplis recalled, “I wrote a report on Blood Falls in high school…Never did I imagine I’d work there. It’s been an absolute dream.”
- Zoumplis A, et al. Molecular evidence for a relict marine community in an Antarctic Dry Valleys subglacial brine‑fed system. Nat Geosci. 2026;19:1105-1114.
- Mikucki JA, Priscu JC. Bacterial diversity associated with Blood Falls, a subglacial outflow from the Taylor Glacier, Antarctica. Appl Environ Microbiol. 2007;73:4029-4039.
- Lyons WB, et al. The geochemistry of englacial brine from Taylor Glacier, Antarctica. J Geophys Res Biogeosci. 2019;124:633-648.
- Schulte NO, et al. Blowin’ in the wind: Dispersal, structure, and metacommunity dynamics of aeolian diatoms in the McMurdo Sound region, Antarctica. J Phycol. 2021;58:36-54.