Ancient marine microbes found near Antarctica’s Blood Falls

A Nature Geoscience study found molecular evidence of an active, marine-derived microscopic community near Blood Falls at Taylor Glacier in Antarctica’s McMurdo Dry Valleys. The findings suggest the red outflow may preserve traces of ancient seawater and help explain how life survives in one of Earth’s harshest environments.

Why it matters: - The finding could help scientists reconstruct how Antarctica’s coastline, ice sheets and inland valleys changed over time. - The study also shows how life can persist in extreme, salty, cold and isolated environments. - Blood Falls may be preserving biological traces of older ocean connections rather than only modern contamination.

What happened: - Researchers reported molecular evidence of an active, marine-derived community of microscopic eukaryotes near the Taylor Glacier terminus in Antarctica’s McMurdo Dry Valleys. - The study was published in Nature Geoscience as “Molecular evidence for a relict marine community in an Antarctic Dry Valleys subglacial brine-fed system.” - Angela Zoumplis, formerly a joint PhD student between the J. Craig Venter Institute and Scripps Institution of Oceanography at UC San Diego, led the work. - Andrew E. Allen, a professor at JCVI and Scripps Oceanography, was the senior author. - The team examined 167 samples from the Taylor Glacier terminus, other Dry Valley habitats, wind-deposited material and marine reference sites in McMurdo Sound.

The details: - Blood Falls is a red-stained outflow from Taylor Glacier fed by iron-rich brine trapped beneath the glacier. - The red mud and sediment around Blood Falls showed the strongest marine signal. - Marine-associated diatoms made up more than 60% of the diatom community in those samples, and in some analyses about 80%. - Most nearby freshwater sites were dominated by diatoms tied to terrestrial or freshwater environments. - The team used molecular sequencing and metatranscriptomics, which examines RNA, to identify organisms and test whether they were active. - RNA data showed active phototrophic eukaryotes with gene activity tied to photosynthesis, stress responses, cellular repair and salt tolerance. - The study found evidence that the organisms were not just genetic leftovers. - Earlier work had already found bacteria in Blood Falls brine with similarities to marine microbes. - The new study extends that marine link to eukaryotes, including diatoms, dinoflagellates and ciliates. - Marine diatom fossils and fragments have also been found in other nonmarine Antarctic settings, fueling debate over whether they arrived by ancient marine incursions, wind transport or both. - Marine signatures were rare in wind-collected samples, while the Taylor Glacier terminus community showed marine affinity and genetic differences from modern McMurdo Sound communities. - Blood Falls brine is rich in salts, iron, silica and other materials and periodically mixes with glacial meltwater. - Some detected organisms form resting cells, cysts or spores that can help them survive long periods of harsh conditions. - The authors said the modern community likely reflects a mix of past marine introduction, redistribution within the valley, limited modern transport and strong selection at the glacier terminus. - Collaborating institutions included the University of Colorado Boulder, Lund University and the University of Tennessee, Knoxville. - Support came from multiple National Science Foundation awards and Gordon and Betty Moore Foundation Grant GBMF3828.

Between the lines: - The results point to persistence, not just delivery, which means Blood Falls may be a biological archive of environmental change. - The pattern argues against wind alone as the main explanation for the marine material near Blood Falls. - The unusual chemistry of the brine appears to create a niche that can preserve or favor marine-linked microbes. - Antarctic polar deserts may hold specialized ecosystems that retain clues about past climates and ice behavior.

What’s next: - Researchers are likely to keep studying how marine material entered the Dry Valleys and how long these communities have persisted. - The findings may guide future work on Antarctic climate history and on microbial survival in cold, salty habitats. - Blood Falls remains a target for understanding ocean-ice-land connections in Antarctica.

The bottom line: - Blood Falls may be more than a geological oddity: It could be a living record of Antarctica’s marine past.