“Core on Deck!” LSU Graduate Student Digs Deep into Mediterranean Seabed Secrets

Early in her PhD program at LSU's Department of Geology and Geophysics, Danielle Noto found herself on an extraordinary 60-day adventure. Aboard the JOIDES Resolution, a scientific drilling vessel, she would be part of the NSF-funded International Ocean Discovery Program (IODP) Expedition 401, delving into Earth's climate history in the Mediterranean Sea.

"During my first meeting with my PhD advisor, Dr. Sophie Warny, we discussed potential projects," Noto recalls. "Dr. Warny had previously worked on the Mediterranean-Atlantic Gateway Exchange during her own PhD at the University of Montpellier in France, and mentioned an upcoming expedition." 

Despite the competitive selection process, Warny encouraged Noto to apply for a spot on the expedition’s science team. "She said I might not get in, but we should try. If successful, that was my PhD project right there." 

Including only 28 scientists from around the world, the expedition was part of the Investigate the Miocene Mediterranean–Atlantic Gateway Exchange (IMMAGE) project, which aims to recover sedimentary and fossil records of the ancient flow of water between the Mediterranean and the Atlantic Ocean, exploring its impact on global climate change. 

Millions of years ago, the landscape between Europe and Africa looked completely different. Two narrow seaways connected the Atlantic to the Mediterranean. However, around 6 million years ago, tectonic activity sealed off these connections, isolating the Mediterranean and disrupting global ocean currents. 

This isolation not only triggered a significant global cooling period but also cut off the Mediterranean's supply of Atlantic water. With reduced Atlantic input and high evaporation, the Mediterranean Sea became significantly saltier. This resulted in a massive salt deposit accumulating on the seabed, forming today's giant salt layer (more than 2 km thick deposits in the deepest parts of the basin). 

However, this drastic transformation wasn't permanent. Around 5 million years ago, a dramatic reflooding event called the Zanclean Flood reshaped the Mediterranean. Atlantic waters surged back into the basin, rapidly refilling it and carving its current configuration as we know it, including the Gibraltar Strait as its single connection to the Atlantic Ocean. This reflooding again influenced the local and global climate and fostered a new era of biodiversity in the reborn Mediterranean Sea. 

To understand these dramatic changes, scientists and technicians aboard the JOIDES Resolution used advanced drilling techniques to retrieve core sediment samples from the seafloor, each 10 meters long. These cores were then analyzed by onboard specialist teams, including sedimentologists, micropaleontologists, paleomagnetists, physical properties specialists, and geochemists. 

"My group was in charge of sedimentology," explains Noto. "We were the first ones to examine the cores as they were retrieved, and we had about an hour to describe them." 

The intensive schedule required 12-hour shifts with a rotating task system. Each day, Noto and her team members switched between four distinct roles. One team member meticulously described the core sample's color, grain size, and fossil content, while another person would input this data into a computer. The third team member prepared smear slides for microscopic analysis of minerals that are invisible to the naked eye. The fourth and final task of her team involved operating instruments to capture core images, measure magnetic susceptibility, and utilize an X-ray scanner. "That person would be running around the lab, getting like 20,000 steps a day," Noto adds with a laugh.

With no prior experience describing sediment cores, Noto had to learn everything from scratch. "I really liked the data entry job, specifically when working with one of the most experienced sedimentologists on board," she explained. "I liked sitting at the table and entering all the information they wrote down. I learned a lot." 

Despite the challenge of mastering a new sedimentology vocabulary, Noto's biggest hurdle was adjusting to the long night shifts, which ran from midnight to noon. To meet tight research deadlines, the JOIDES Resolution crew operated around the clock, collecting and analyzing samples from four drilling sites. Two complete research teams alternated shifts to ensure continuous work. Yet, Noto found a silver lining: "One really cool thing about the night shift was that we would all take a break in the middle of our shift to head out on deck and watch the sunrise together." 

Life onboard the JOIDES Resolution had its perks. Laundry magically appeared clean and folded, birthdays were always celebrated with a cake, and there was even someone willing to give a haircut in a pinch. "The crew put in a big effort to ensure everyone felt at home," recalled Noto. "We had chefs from the Philippines, and they went all out for Christmas and New Year's, and even made King Cake for Mardi Gras! The food was delicious. I definitely miss it." 

Although initial observations were made on the ship, most discoveries will come through the post-processing of the samples back at each researcher's home institution. Noto joined the expedition as a sedimentologist, but at LSU she specializes in palynology—the study of microscopic organic-walled fossils such as pollen, spores, and dinoflagellate cysts (collectively known as palynomorphs). These tiny time capsules hold the key to unlocking secrets about past vegetation and sea-surface conditions. 

To decipher these secrets hidden beneath the Mediterranean seabed, Noto collected 145 mud samples and shipped them to a lab in Canada for processing into microscope slides. By examining these slides for palynomorphs, she hopes to unveil the previously unknown history of plant and algal life preserved within the sediments. 

"We're all trying to understand how the changing patterns of oceanic gateways can affect global climate," Noto adds. "With my samples, I will identify the different pollen and algal species that will tell us what kind of trees or vegetation were growing in the area at the time, and what was the sea-surface salinity and sea-surface temperature of the water masses. From that, we will know the type of climate and environment and how it was impacted by the opening and closing of the Mediterranean-Atlantic Gateway."

Back at the lab, Noto began working alongside Dr. Warny to analyze palynomorphs from a specific drilling site. This site had an unclear age model, which needed refinement before a recent post-cruise editorial meeting at the International Ocean Discovery Program Building at Texas A&M in College Station. By studying the palynomorphs in the core samples, they aimed to improve the age estimates for that site and update the reports drafted during the expedition. 

"It’s always amazing to be able to meet with my Expedition 401 colleagues, especially in person, since we all live across the world from each other,” says Noto about attending the post-cruise editorial meeting last month. “We have monthly Zoom meetings to discuss our scientific results, but being able to work together again at the meeting – on land – was truly incredible."

Noto's initial analysis of sediment cores, though focused on a limited set so far, reveals compelling clues about the history of the Mediterranean-Atlantic gateway. Her findings show a dramatic increase in the abundance of tiny marine phytoplankton called dinoflagellate cysts during a specific period, which coincides with the reflooding of the Mediterranean Sea. "I am eager to see the story that will come from the remainder of my samples."

Looking ahead, Noto has a busy schedule. She just presented her initial findings with Dr. Warny at the AASP-The Palynological Society Conference in Montpellier, France, an international conference organized by Warny herself (who is the current president of that society). The fall semester will see her return to meticulous microscope work, followed by the acquisition of new samples for even higher-resolution analysis in the spring.