Marine biologist’s NSF grants propel ocean, carbon research

The oceanic expedition, embarking on a ship based out of the Bermuda Institute of Ocean Sciences, will serve as the second of five explorations supported by a $200,000 National Science Foundation grant Trueblood secured in 2024. La Sierra University student Emma Arroyo will join Trueblood and assist in his research, supported by funding from La Sierra’s College of Arts & Sciences.

Trueblood’s research lab focuses on the “squishy” animals of the sea as he calls them––invertebrates such as octopuses, cuttlefish, squid, and particularly salps, a species of plankton. He has participated in four oceanic expeditions aboard research vessels since 2023 to study the soft, narrowly bulbous salps, creatures that can reproduce asexually, vertically migrate and create dense fecal pellets that resemble Captain Crunch cereal.

During his latest research voyage in May in the Gulf of California, Trueblood joined with researchers from the Arizona State University, the University of South Florida, Monterrey Bay Aquarium Research Institute and Evergreen College to study various plankton, their vertical migration patterns, and metabolic rates. The salps, which are important in studying where carbon goes after it gets drawn into the ocean from the atmosphere, are difficult to locate and track due to their quick appearances and disappearances in groups.

Trueblood’s research follows his innovative studies published in 2019, a first analysis of the effect of temperature change on salp metabolic rates during their daily vertical migration. His work showed a 27% reduction in fecal pellet production in the deeper, colder ocean waters, revealing that current carbon models are overestimating how much carbon is being fixed in the deep ocean by salps, by as much as 11% in the Sargasso Sea. “This may not seem like a lot, but when you consider the scale, we are talking about a difference of nearly 420,000 tons of carbon,” Trueblood said.

A major focus of Trueblood’s work is the so-called biological pump, where various marine organisms are involved in moving carbon both into and out of the ocean. He is studying salp metabolisms and fecal pellet production as these unique animals filter feed on algae and produce a dense fecal pellet that sinks quickly into the deep ocean. The same process occurs with salp carcasses. The process acts as a carbon sink, keeping carbon dioxide from the atmosphere and fixing it in the deep ocean. 

Trueblood is now attempting to expand on this work to include multiple species of salps. 

Trueblood used his research data from the 2023 voyage, a trip that was first aborted in 2020 due to the COVID-19 pandemic, to apply for the National Science Foundation grant. He used a portion of the capital to join a research vessel off the coast of Bermuda for a week and for a month in the Gulf of California last year. 

“It's all kind of part of that same project of trying to collect as many different species of salps as I can and get metabolic rate data on them, because that data doesn't exist in abundance. I look at how they deal with hypoxia when they're vertically migrating, and compare it to the same species from different ocean basins, which nobody's done yet,” Trueblood said in a June interview. “I was literally editing [a research article] this afternoon. One set is the same species I collected right here off the Channel Islands, and the other is the same species I collected in Bermuda. And even though the two environments are very different, my data shows their response to environmental changes, like temperature and oxygen, is the same, which is very interesting given how different the two locations are from each other.” 

The publication was submitted to the Journal of Plankton Research and is currently under review. 

Going forward, Trueblood hopes he and his student workers can continue to use the NSF grant funds to complete building a model that helps predict with precision when areas of the ocean are conducive to supporting a salp bloom.

“It would be super exciting if we can pull it off,” he said, “as there a lot of people working a predictive model , but an accurate model has not been produced yet.”

While in Bermuda, Trueblood made a visit to the Bermuda Institute, a Seventh-day Adventist academy. He shared some of his current research, how he became a marine biologist, and some of the opportunities for students in Bermuda to participate in marine and oceanographic research in collaboration with the Bermuda Institute of Ocean Sciences.