The greater picture

What started as a Sycamore’s summer research project into phosphorus levels 93 million years ago could shed light on why fertilizer runoff creates “dead zones” around the world.




Lifting two vials from a tray packed with samples, Indiana State researcher Andrew Dryden twists open their numbered white caps. Tap, tap, tap — and fine sediments tumble onto waxed paper. The nickel-sized piles of black and tan grains look a little, well, ordinary — until you realize that they might be clues to a 93-million-year-old environmental mystery.

The sediments, taken from black shale deposits deep under the Indian Ocean, date back to the Cretaceous Period when dinosaurs roamed Earth and elevated levels of CO2 warmed the climate so much that sea levels were significantly higher than today. And back then, around 93 million years ago, a curious thing happened. Oxygen seemed to vanish from the bottom of the ocean, apparently causing almost 30 percent of marine invertebrates to go extinct.

A scientific debate surrounds the cause of the Cretaceous Ocean Anoxic Event II (OAE II). But these sediments, and a particular element they contain, might hold some answers. And that’s where Andrew Dryden comes in.

Andrew Dryden, a chemistry major from Seymour, Ind.

“We want to find the puzzle pieces to the greater picture. We’re gathering data that could help us look at how environmental conditions have changed through time, and how those conditions could be related to the anoxic event,” said Dryden, a senior chemistry major at State.

Working under Jennifer Latimer, associate professor of geology in the department of earth and environmental systems, Dryden’s work started after freshman year as a project for State’s Summer Undergraduate Research Experience (SURE). The unique program engages students in real research projects led by State professors — and their work even has the chance to get published. That’s just what Dryden aims to achieve with his work on the Cretaceous OAE II.

“To try to figure out what happened, I’m actually studying the burial of phosphorus,” Dryden said.

That important element is contained in Dryden’s sediments, once buried on the Kerguelen Plateau in the southern Indian Ocean. Phosphorus earns the label of “limiting nutrient” because the amount of the element caps the abundance of all living things — more phosphorus means more organisms and vice versa. Around the time of the Cretaceous OAE II, the geological record seems to show a sharp increase in the element. More phosphorus might have allowed so many organisms to flourish and die that increasing bacteria, working to decompose those organisms, used up oxygen on the seafloor — only to later suffocate bottom-dwellers. But how did that extra phosphorus get there in the first place?

Sediment samples are used for phosphorus analysis in Andrew Dryden’s research.

As he processes the sediment samples, Dryden searches for different types of buried phosphorus that result from particular environmental and biological conditions. In combination with other data, the concentrations of those types can indicate which conditions might have predominantly caused extra phosphorus to become available to organisms.

“Based on phosphorus, we might be able to better understand what things were happening in the ocean and on land,” Dryden said. “We can look at ocean circulation, which can cause nutrients like phosphorous to spread around. We can also look at the chemical weathering of rocks on land, which can release phosphorus that eventually enters the ocean. There are multiple areas that we can look at to get the broader picture.”

Dryden continues to gather more and more detailed phosphorus data to uncover the most accurate picture possible. Not only will his data shed some light on the Cretaceous OAE II, it could also help the scientific community better understand phosphorus in natural, undisturbed environments. That’s useful information to compare with modern times, when runoff from fertilizers is adding excessive phosphorus to water systems across the globe and creating “dead zones.”

Using techniques learned in his chemistry classes, Dryden has put in a good deal of work to generate data since he started the project with SURE. And along the way, he’s encountered the rather messy world of research. He’s had to navigate unforeseen obstacles like learning how to fix broken equipment. But overcoming those real-world challenges has only made him a better scientist.

“With research, not everything is going to go as planned,” Dryden said. “In the classroom, you can memorize an equation, and that will give you the answer on a test. But if you’re doing research that a lot of people aren’t working on, there is no clear answer yet. You are forming the answer. It’s forced me to think outside of what I know, and learn things that I probably never would have learned had I not been in SURE.”

Sediment samples are seen in an Indiana State lab.

That kind of experience is a hallmark of the program. Latimer, Dryden’s advisor for the project, said it’s incredible to watch undergraduates in SURE progress over just one summer.

“They give their first presentations, they’re nervous and really uncomfortable talking about science. They’re really unsure of themselves,” Latimer said. “And by the end, they’re like professionals. It’s just amazing. They have so much more self-confidence in their own abilities as scientists after this experience. Plus, it helps them make career decisions and become more competitive for jobs and grad school later on.”

“It definitely solidified my career goal of doing scientific research, and SURE has made me want to continue my education even into the doctorate level,” said Dryden, who hopes to get started by earning his master’s degree in geology from State. “And being able to actually participate in substantial research, something that could have an influence on the greater knowledge of the world, is the best part.”



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