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Red Sea brine pools contain microbial communities and metal-rich sediments that may preserve clues to how microbes obtained energy in ancient, oxygen-poor oceans. A 2026 study found manganese, iron, molybdenum, and copper enrichment in an active pool and a suspected extinct one, and identified manganese-oxidizing bacteria in the active pool. The evidence supports a possible model of early microbial metabolism; it does not prove how life began or establish that modern brine pools recreate the ancient ocean.
What is a brine pool?
A brine pool is a lake-like body of very salty, dense water resting on the seafloor. The Red Sea environments in this study are dark and oxygen-depleted. Their extreme chemistry can make them hostile to many organisms, but it does not mean they are lifeless: microbes can inhabit the brine and the sediments around it.
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The phrase “death pool” is a dramatic nickname, not a claim that nothing lives there. In this case, researchers found bacteria and archaea in the active pool and studied the chemistry of sediments beneath a microbial mat.
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Researchers analyzed sediment geochemistry and organic matter and used metagenomics and metatranscriptomics to characterize microbial communities. They compared an active brine pool with three non-brine seafloor sites, and also examined a location suspected to be an extinct pool. The active pool lies 1,770 meters below the sea surface; the suspected extinct pool is nearly 1,400 meters deep.
| Site | Status and evidence reported | Depth |
|---|---|---|
| Active Red Sea brine pool | Bacteria and archaea were found; sediments beneath a microbial mat were enriched in metals. Metagenomic analysis identified manganese oxidizers, including Nitrospira. | 1,770 meters |
| Suspected extinct brine pool | Similar metal-enrichment patterns were reported, including oxidized manganese and iron phases and molybdenum-enriched organic matter. | Nearly 1,400 meters |
| Three non-brine seafloor comparison sites | Used as counterparts for comparing sediment metal concentrations. |
Some metal concentrations in brine-pool sediments were reported as upward of 100 times those at non-brine comparison sites. That approximate figure applies to some areas, not every sample.
Why might metals matter to early life?
Microbes need energy to grow and carry out cellular processes. One proposed explanation is that early microbes could have gained energy through reactions involving metals such as manganese and iron, before oxygen became abundant in the atmosphere. The study’s observations—manganese-oxidizing microbes in the active pool and oxidized manganese and iron phases in sediments from both pools—are consistent with that possibility.
The researchers place this idea in the context of conditions before the Great Oxidation Event, which occurred around 2.4–2.2 billion years ago. That interval is geological background, not an age measured from the modern pools. The Red Sea findings do not directly establish what ancient seawater was like or which metabolic pathways the earliest organisms used.
What the sediment clues can—and cannot—show
Metal-rich sediments and organic matter can preserve chemical traces associated with microbial activity. If similar signatures are found in ancient rocks, they may help scientists assess whether microbes once used metal-based reactions for energy. The modern pools offer a setting in which to investigate how microbial communities and unusual seafloor chemistry interact.
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- What the study supports: Metal enrichment is associated with microbial communities in the active pool, and similar enrichment patterns occur at the suspected extinct site.
- What it suggests: Microbial oxidation of metals is a plausible energy source in environments with little oxygen.
- What it does not prove: That this pathway powered the origin of life, that early organisms definitely used it, or that modern brines are exact analogues of the early ocean.
The findings were reported by Rebecca Dzombak in an AGU Eos research spotlight on September 22, 2026, with corroborating details in an AGU-provided report published the same day. The study is Chakraborty et al., “Brine Pool Microbes Enrich Metalliferous Sediments in Salt Giant Basins,” AGU Advances (2026), DOI 10.1029/2026av002570. The reported interpretation remains tentative.
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