Algae reveal clues about climate changes over millions of years: Scientists identify and investigate algae which register sea water temperatures of the warmest months

Organisms adapt their cell walls to environmental conditions such as temperature. Some adaptations involve changes in lipids that can still be preserved long after the rest of the organisms have been degraded. Researchers at the University of Göttingen studied a specific group of lipids called long-chain diols that are found in sea sediments all over the world and that can be preserved for millions of years. The researchers discovered that these lipids are produced by a hitherto unknown group of marine eustigmatophyte algae that developed before the currently known species emerged.

This finding changes our understanding of the composition and evolution of these algae, as they were previously considered to consist of a relatively small group of mainly soil and freshwater species. In addition, the researchers show that a proportion of these distinct lipids, known as the Long chain Diol Index, can be used to reconstruct the summer sea surface temperatures from the past. The research was published in Proceedings of the National Academy of Sciences (PNAS).

For this study, which combines expertise from the University of Göttingen’s Geoscience Center (Geobiology) and the Experimental Phycology and Culture Collection of Algae, the researchers took samples of seawater from the Mediterranean every month between April and October 2019 and analyzed them for lipid and DNA. content. . DNA data revealed the presence of an early-developing group of marine eustigmatophyte algae that had not been previously identified. Similarities in the patterns of eustigmatophyte DNA and the specific lipid concentrations, combined with in-depth analyzes of previously published DNA and lipid data sets, show that these marine algae are the main producers of the long-chain diols. “These lipids have been found in sediments from all over the world, dating from millions of years ago until now. But so far no one has matched the unique lipid signature for these algae,” says first author Dr Sebastiaan Rampen, who conducted this research at Göttingen University.

“A variety of techniques can be used to derive ancient climates over the Earth’s history,” explains Rampen. “What is exciting about our discovery is that we have shown that the relationship between these unique lipids reveals temperatures during the warmest months. This explains why readings obtained with this method sometimes differ from other temperature reconstructions that give average temperatures over the year. Combine different methods now provides additional information to help us better understand the Earth’s climate, which goes back millions of years. “

This project was made possible thanks to funding from the German Research Foundation (DFG)

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