The Sacramento Deep Water Ship Channel was still and quiet as the boat cut through the morning fog. For Cristina La, then a graduate student at Southern Illinois University Carbondale, this was the moment she had been preparing for over months of planning and lab work. Somewhere below the boat swam the last remaining stronghold of California’s delta smelt — a tiny, silvery fish whose decline has become a warning signal for the entire Sacramento-San Joaquin Delta ecosystem.
“It’s surreal going into the actual field portion when coming from a different state,” La recalled. “All of these mythical locations we’d discussed for months just suddenly materialize in front of you. And then you realize — this is it. This is where you have to get it right.”
La’s master’s research was part of a collaborative project focused on the Sacramento Deep Water Ship Channel, one of the few remaining habitats for delta smelt and longfin smelt: small, sensitive fish often called a “canary in the coal mine” for the San Francisco Estuary. Their steep decline signals ecosystem disruption that threatens other native fish such as salmon, steelhead and sturgeon, making their survival a key measure of the delta’s overall health.
Working alongside researchers from the University of California, Davis and the California Department of Fish and Wildlife, she helped collect and analyze hundreds of samples of sediment, suspended solids and zooplankton in April 2023 and November 2024, plus a focused June 2023 study on ship traffic. La’s contributions were pivotal in coordinating sampling efforts and processing samples in SIU’s lab.
The results were striking: contaminants such as DDE, phenanthrene, fluoranthene, pyrene and chrysene turned up in every sample, with the highest concentrations in suspended solids. Many of these pollutants are known to harm wildlife and people, causing problems like cancer, reproductive issues and damage to organs. The research team’s findings suggest that fish like the delta smelt face their greatest exposure in the water column — the vertical section of water where they swim and feed — particularly when ship traffic or storms stir up bottom sediments and release contaminated particles into the water.
La’s work contributed to one of the most detailed contaminant profiles of the Sacramento Deep Water Ship Channel to date, providing data that will help guide management decisions aimed at protecting both wildlife and the millions of people who rely on the San Francisco Estuary for water. She has already published one paper from this research in the international, peer-reviewed journal “Environmental Pollution” and is preparing a second manuscript that will combine results from multiple sampling events, ensuring that her findings reach the broader scientific community.
Growing as a scientist
La was part of SIU’s Lydy Research Lab, which she joined in June 2022 as a research assistant while pursuing her master’s degree in zoology. Under the mentorship of her adviser, Michael Lydy, distinguished professor of zoology, she learned the fundamentals of environmental toxicology.
“The Lydy Lab was the perfect place to grow as a scientist,” La said. “I gained confidence in my skills — from designing projects and developing methods to running extractions — but I also learned how critical communication and collaboration are. I didn’t just learn techniques in isolation; I learned how to contribute to a bigger scientific effort.”
Housed within SIU’s Center for Fisheries, Aquaculture, and Aquatic Sciences, the Lydy Lab offers students access to expansive research ponds, wet-lab space, a closed-cabin research vessel and state-of-the-art toxicology facilities. La said those resources, paired with mentorship from faculty and senior scientists, gave her the tools and confidence to take on ambitious research questions.
Mapping contaminants in a critical habitat
La’s research became the foundation of her master’s thesis and was key to her earning her M.S. in zoology in May 2025.
The science was rigorous, but La says the fieldwork shaped her just as much. With her collaborators, she spent 12- to 15-hour days riding up and down the channel, coring sediments, pulling zooplankton nets and filtering water — often under shifting weather and tight time windows.
“Sampling days were always entertaining,” she said. “Whether it was a team of two or four, you have these long boat rides to get to know each other and keep morale up. By the time we finally met the UC Davis team in person, we already felt like a well-coordinated unit.”
La’s deep familiarity with the project design made her a key voice when decisions had to be made in the field — an experience that strengthened her confidence and leadership skills.
Representing SIU on a national stage
La’s success was more than personal — it was a reflection of the training she received at SIU.
“The experience taught me persistence, problem-solving and how to collaborate across institutions,” she said. “I felt a real responsibility to represent SIU well. The trust my collaborators put in me meant a lot — and showed me just how well SIU prepares its students to step into those roles.”
Mentorship was key to that preparation. In addition to Lydy, La credits SIU Senior Scientist Kara Huff Hartz and other members of the lab for helping her refine her research questions, troubleshoot problems and present her work with confidence.
After graduating in May 2025, she moved to Colorado, where she hopes to work in environmental analysis and risk assessment before eventually pursuing a Ph.D. in environmental toxicology.
“The lab, field and mentorship experiences I gained at SIU were all important,” she said. “I don’t think I could separate them in terms of what best prepared me for my next steps.”
Tim Crosby contributed to this report.
