After 7,000 years at the bottom of the Baltic Sea without light or oxygen, dormant in the mud that makes up the seabed, prehistoric algae have been awakened and have regained all their functions, from the ability to grow to photosynthesis. They are microalgae of the species Skeletonema marinoi, making them among the oldest organisms to have been successfully revived. The result, published in The Isme Journal of the International Society for Microbial Ecology, is thanks to researchers led by the German Leibniz Institute for Baltic Sea Research – Warnemünde and will help reconstruct the past of the Baltic Sea to understand how it will adapt to future changes.
Many organisms, from bacteria to mammals, can enter a dormant mode to survive periods of unfavorable environmental conditions. Among these is Skeletonema marinoi, a very common algae in the Baltic Sea that is one of the most important lungs of the planet: it produces 25% of all the oxygen released into the atmosphere. “These deposits are like time capsules,” says Sarah Bolius, who led the study, “containing valuable information about past ecosystems and the biological communities that inhabited them, as well as the development of their populations and genetic changes.”
During a 2021 expedition, researchers collected sediment samples at a depth of 240 meters: from nine of these samples, algae were successfully brought back to life, the oldest of which dates back to approximately 7,000 years ago. “The fact that we were actually able to successfully reactivate these old algae from their dormant state,” comments Bolius, “is an important step in further developing ‘Ecology of Resurrection.’ This means that now, in the laboratory, it is possible to take leaps back in time to various stages of the history of the Baltic Sea.”
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