MICROBES IN ANTARCTICA'S BLOOD FALLS LINKED TO ANCIENT SEAWATER

A red waterfall in East Antarctica's Taylor Valley contains microorganisms that suggest the brine originates from ancient seawater trapped beneath Taylor Glacier millions of years ago, according to research published in Nature Geoscience on 3 August. The study, led by microbiologist Angela Zoumplis of the University of California, San Diego, analysed 167 samples of water, sediment and air from Blood Falls and the surrounding McMurdo Dry Valleys. Researchers found that the crimson brine and associated red-tinted sediments shared a higher proportion of eukaryotic microorganisms with nearby oceanic samples than other sites in the Dry Valleys did. The waterfall's vivid red colour results from iron dissolved in the salty brine oxidising when exposed to air, not from algae as initially suspected.

The brine is believed to have been trapped beneath the glacier when ocean levels fell and the glacier advanced, though researchers noted the exact timing remains unclear. Previous studies had proposed a seawater origin based on chemical signatures and bacteria, but the new findings add molecular and genetic evidence. The study identified a dominance of marine eukaryotic lineages at Blood Falls compared with the broader McMurdo Dry Valleys region, with a marine signal remaining detectable in prokaryotic structures. Some researchers contend that marine bacteria and chemical signatures pointing to seawater may have reached the falls from the ocean via intense winds common to the Dry Valleys rather than originating from trapped ancient seawater.

The brine has remained liquid beneath the glacier despite freezing temperatures because the freezing point of hypersaline water is lower than that of freshwater. The water has been isolated in this subglacial reservoir for at least 1.5 million years, according to the research. Blood Falls has captivated scientists since British-born Australian geologist Thomas Griffith Taylor first encountered it during an expedition in 1911. The findings suggest a distinct microbial community may have evolved in isolation within the ancient subglacial system.