Voyage to the Bottom of the Sea
Graduate student Lizette Leon Rodriguez had never been on a boat for more than a couple of hours before embarking on the voyage of a lifetime.
A paleontologist specializing in planktonic foraminifers, otherwise known as forams, she was one of 27 scientists among a crew of 120 that left Hawaii aboard the JOIDES Resolution, a research ship operated by the Integrated Ocean Drilling Program. As the vessel skirted the equator, the crew drilled hundreds of meters of core samples to give them a glimpse at what the planet looked like in the Eocene Epoch, approximately 55 to 34 million years ago — core samples that Leon Rodriguez analyzed for clues that may ultimately reveal something about the near- and long-term fate of Earth’s ocean–atmosphere dynamics.
Sinking to the sea floor in a constant shower over millions of years, forams and their calcium carbonate shells were buried in sediment, creating a fossil record that can reveal a lot about the Earth during times when atmospheric carbon dioxide peaked and the planet suffered bouts of global warming.
“What is interesting about the Eocene is there were periods very similar to what we’re experiencing now in terms of global warming,” said Leon Rodriguez, a native of Colombia who earned her master’s degree at Florida International University before coming to Rice. “There was a huge release of carbon into the oceans and the atmosphere that increased temperatures.”
Her adviser, Gerald Dickens, a professor of earth science, and his colleagues argued in a paper in Nature in late 2007 that a chain reaction of events in the Eocene that probably started with a period of intense volcanic activity led to the release of a massive amount of greenhouse gases that warmed the planet. The paper was based on Eocene sediments from what was then the ocean floor but is now New Jersey.
Leon Rodriguez believes more evidence exists in the gooey sediments beneath the Pacific in the chemical composition of plankton’s calcium carbonate shells. “We can look at isotopes and different chemical processes and know, for example, the temperature and the acidity of the oceans at the time. We can track periods from the beginning to the end and all of the processes that happened during that time. The equatorial Pacific is a very productive place to get these samples.”
“We can look at isotopes and different chemical processes and know, for example,
the temperature and the acidity of the oceans at the time.”
Collecting the core samples one after another from each of seven target locations was hard work, and Leon Rodriguez put in 12-hour shifts analyzing the samples, which one scientist on board described as “white ooze, like toothpaste, and brown ooze, like crumbly brown sugar.” Each 30-foot core was cut into manageable pieces, and samples were extracted from the eras the scientists wanted to analyze.
“We had to cut the pieces in the right places, wash the samples — sometimes a couple of times — and then go to the microscope and check the forams to determine their ages by comparing them to comprehensive fossil records,” Leon Rodriguez said. “It got stressful, because we could see them drilling, and samples were coming, and we had a bunch waiting for us to wash, and we were looking at the forams — we were racing all the time.”
Now that a huge box of samples has landed in her Rice office, Leon Rodriguez can begin detailed analysis to learn about ocean conditions eons ago.
“This is the real thing in terms of my research. On the ship, you have to know what you’re doing, but you’re more like a technician. Here, I can run my chemical analyses and play with the samples. We’re going to have different curves that will tell us how the temperature and carbon levels in the ocean fluctuated over time. It’s going to be fun.”