Nitrates to blame in algae, flowers or even your neighbors? A team of geologists at Virginia Tech has found evidence that may suggest this. The team’s findings, published recently Science Advancesshows an increase in bioavailable nitrogen at a time when marine eukaryotes—organisms with a nucleus in their cells—became dominant. Complex eukaryotic cells evolved into multicellular organisms and are thought to have ushered in an entirely new era of life on Earth, including animals, plants and fungi.

“Where we are today with life on the planet is the sum total of all the events that have occurred in the past,” said Ben Gill, associate professor of sedimentary geochemistry and co-author of the paper. “And that’s a major event as we moved from predominantly prokaryotic ecosystems—cells that are much simpler than the cells in our body—to eukaryotic ecosystems. Without it, we wouldn’t be here today.”

Previous research has focused on the role of phosphorus in the emergence of eukaryotes, but Junyao Kang, a PhD student in the Department of Earth Sciences and lead author of the paper, wondered what role nitrogen played in this event.

“This data is unique because there is virtually no nitrogen isotope data from the early Neoproterozoic or one billion to 800 million years ago,” Kang said. Said.

Working with Nanjing University in Najing, China, Kang spent two years using nitrogen isotope analysis of rock samples from the North China Craton to understand what caused the eukaryotes to emerge. This region was once covered by an ocean with rocks dating back 3.8 billion years.

“We had some rough ideas of when eukaryotes were successful ecologically,” said Shuhai Xiao, professor of geobiology and co-author of the paper. “They were there for a long time in low-key status until they were abundant there, about 820 million years ago.”

Kahn decided to find out why. It took data from rock samples, imported it into a larger database, and analyzed it over a longer time scale covering different geographic locations.

“Once we did this integration and put it into the big picture, we saw an increase in nitrates over time that occurred around 800 million years ago,” Kang said.

solid collaboration

A common international approach was key to linking these new data to biological events, particularly the emergence of eukaryotes. Gill and Rachel Reid, also geochemists in the College of Science and co-authors of the paper, provided critical analysis with resources including a mass spectrometer at the Geoscience Stable Isotope Laboratory at Virginia Tech. An elemental analyzer attached to a mass spectrometer allowed the researchers to extract pure nitrogen from the samples for analysis.

Gill specializes in reconstructing current and past chemical cycles on our planet. She works with paleontologists to study the records of life preserved in the geological record and explore what potential environmental factors may have caused changes in life throughout history.

Typically focusing his research on recent Earth events, Reid had a unique opportunity to present his knowledge of nitrogen isotopes to these ancient fossils. Feifei Zhang, a geochemist at Nanjing University, was the paper’s fourth co-author. Zhang gave some insight into how much oxygen could be found in the oceans at a time when nitrates were on the rise. The Virginia Tech authors are all affiliated members of the Fralin Life Sciences Institute’s Center for Global Change, and Kang is a Ph.D. Member of the “Interfaces of Global Change” graduate program. The center brings together experts from various disciplines to solve these complex global problems and train the next generation of leaders.

Past, present and future

Xiao, who has helped excavate and study some of the oldest fossils from around the world, said such research gives him hope for future discoveries. Team members look forward to working with NASA on future grants, such as the exobiology program that supports their ongoing research. Also, thanks to University Libraries at Virginia Tech for supporting open access publications such as: Science Advances to provide a peer-reviewed selection of research that is freely accessible to readers.

“We can connect the dots from the isotopic composition of nitrogen in the ancient past, and then move on to the next step and figure out how much nitrate was available to organisms,” Xiao said. Said. “And then we correlate it with the fossil record to show that there is a connection.” While the ancient oceans are long gone, what happened in the ancient oceans is recorded in rocks, and the study of these rocks allows us to relate the history of our Earth to the present and the future.

“Geologists look at rocks for the same reason that stock traders look at the Dow Jones when deciding to buy or sell a stock. The geological history recorded in rocks gives us important context for future global changes,” he said.