Scientists identify and study algae that record seawater temperatures in warmer months


Organisms adjust their cell walls based on environmental conditions such as temperature. Some adaptations involve changes in lipids that can still be retained long after the rest of the organisms have been broken down. Researchers at the University of Göttingen studied a specific group of lipids called long-chain diols that are found in marine sediments around the world and can be stored for millions of years. Researchers have found that these lipids are produced by a previously unknown group of eustigmatophyte marine algae that evolved before the currently known species arose.

This discovery changes our understanding of the composition and evolution of these algae, as they were previously thought to consist of a relatively small group of mostly soil and freshwater species. Additionally, the researchers show that a ratio of these distinctive lipids, known as the long-chain diol index, can be used to reconstruct past summer sea surface temperatures. The research was published in the Proceedings of the National Academy of Sciences (PNAS).

For this study, combining the expertise of the Geosciences Center of the University of Göttingen (Geobiology) and the Experimental Collection of Phycology and Algae Culture, the researchers collected seawater samples from the Mediterranean each months between April and October 2019 and analyzed them for their lipid and DNA content. . DNA data revealed the presence of an early-evolving group of marine eustigmatophyte algae that had not been previously identified. Similarities in eustigmatophyte DNA patterns and specific lipid concentrations, combined with extensive analyzes of previously published DNA and lipid datasets, show that these marine algae are major producers of long-lasting diols. chain. “These lipids have been found in sediments all over the world, dating from millions of years ago until now. But until now, no one matched the unique lipid signature of these particular algae,” says the first author, Dr. Sebastiaan Rampen, who conducted this research at the University of Göttingen.

“A wide variety of techniques can be used to infer ancient climates throughout Earth’s history,” says Rampen. “What is exciting about our discovery is that we have demonstrated that the ratio of these unique lipids reveals temperatures during the warmest months. This explains why readings obtained by this method sometimes differ from other temperature reconstructions that give average temperatures over the year. The combination of different now provides additional information to help us better understand the Earth’s climate over millions of years.”

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

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