Microscopic Plankton Are Small Wonders to Biology Professor
By Brian Hiro
The smallest beings in the marine world are a source of enormous fascination to Darcy Taniguchi.
The plankton that she has devoted her career to researching consist of just a single cell, but the things that happen in that one cell enchant her. A particular species of plankton, for example, acquires its energy both like a human (through consumption) and a plant (through photosynthesis). Another type can devour a cell that’s photosynthesizing, steal its chloroplasts (essentially the machinery for energy production) and use it to photosynthesize itself.
Some plankton can, like a python, ingest things considerably larger in size. They do this either by inserting the single-celled equivalent of a straw into their prey and sucking out the insides, or by releasing a veil of sorts around the prey, digesting it outside the cell and then slurping it in.
And those are just feeding habits. It’s not to mention the brilliant blue glowing that plankton generate off the coast at certain times of year – otherwise known as bioluminescence.
“I'm just amazed at all the cool things that plankton do,” Taniguchi said. “It's fascinating to me how a single cell can do so much. And they have so many behaviors that we just are learning to appreciate now.”
Taniguchi has been a biology professor at Cal State San Marcos since 2018, but her deep personal and professional interest in plankton dates back much farther, to when she was an undergraduate student at UC San Diego almost two decades ago. It helped fuel her through a master’s and Ph.D. program in biological oceanography at UCSD, as well as three stints as a postdoctoral researcher, two at the Scripps Institution of Oceanography and one at MIT. It motivated her to embark on five different ocean expeditions to conduct intensive studies for weeks at a time with no land in sight.
It also drives her to keep advancing scientific understanding of what are easily the most abundant organisms of the sea, with an estimated population of over one billion in a single liter of seawater. Plankton serves as the base of the food web; without it, there would be no whales or dolphins or penguins.
“They're sort of like the grass of the ocean,” Taniguchi said. “That's why studying this biology that forms the foundation for all the sea creatures that the public knows about is important because anything that happens to plankton is going to have ramifications for all the bigger things that we tend to notice as humans. That’s why I really like studying them – not only because they do such cool stuff, but they are fundamentally important to life in the ocean, which as a biologist I'm very passionate about.”
As an undergrad at UCSD, Taniguchi actually earned bachelor’s degrees in biology and math (she graduated summa cum laude in both disciplines in 2006), and she relies heavily on this dual expertise in her plankton research. Taniguchi the biologist makes frequent treks to the coast to gather water samples, though she saves her most important collections for her sea voyages.
Her most recent one came during the pandemic, in the summer of 2020 (she had to quarantine in a hotel for a week beforehand), on a ship based out of Scripps Oceanography in La Jolla. For more than two weeks, she collected water at varying depths using special bottles ranging from 3 to 4 feet tall and 10 liters in volume. Then Taniguchi analyzed the specimens to determine what type of plankton were found where, how quickly they were growing and how quickly they were being eaten. The twist in her experiment was looking at how the results vary during the day versus the night, which meant even more hours of work on top of the normally grueling schedule at sea, and precious little sleep.
“If plankton are growing more during the day and then being eaten at night,” she said, “that’s going to have a really big effect on how their populations are changing just over a 24-hour period.”
One of Taniguchi’s students, Anissa Garcia (who’s in the biology master’s program at CSUSM after graduating from the university last year), carried on the experiment through her own ocean expedition in 2021, and the pair now is collaborating with CSUSM biology professor Elinne Beckett to examine the DNA of the collected plankton.
Then there’s Taniguchi the mathematician. She taught herself computer programming through a college internship with the National Oceanic and Atmospheric Administration, and before being hired at CSUSM, she took a brief detour into working as a software developer for a private company. That experience now proves invaluable. She has built a mathematical model that uses computer code to simulate interactions between plankton. The objective is to examine how predator and prey communities interact in an environmental setting, with the findings having significant repercussions.
“Dr. Taniguchi's ability with dynamic models allows us to look at complex processes in a realistic but simplified way,” said Susanne Menden-Deuer, a professor of oceanography at the University of Rhode Island and one of Taniguchi’s mentors. “We can turn things on and off and ask ‘what if’ questions: What if this predator eats only smaller prey. What if it eats only every other day? These questions are important, as the answers determine how much production of organic matter will result. Organic matter is the basis for fisheries but also how carbon cycles through the ecosystem.
“Dr. Taniguchi’s research is addressing crucial questions about how plankton dynamics in the ocean can be incorporated into predictive, global model simulations to understand the large-scale ramifications of the biogeochemical processes that are driven ultimately by individual, microscopic cells. Her work is essential to gain a predictive understanding of how organisms might respond to a changing planet and thus is at the heart of solving critical problems involving global biogeochemical cycles, fisheries production and the ocean’s response to and role in climate change.”
As vital as Taniguchi’s research is to oceanography, she’s more than just a scholar on a ship or in front of a computer. After studying and working at UCSD for more than a decade, she was drawn to CSUSM because of its strong commitment to teaching in addition to research. She’s dedicated to incorporating students in her studies and she’s determined to increase opportunities in science for historically and presently excluded students.
Taniguchi’s second postdoc project at Scripps Oceanography involved helping develop and run a marine science education program for middle school students in the City Heights neighborhood of San Diego – some of them had never seen the Pacific Ocean despite their proximity. She’s currently part of a project led by Scripps Oceanography and funded by the Office of Naval Research that aims to enhance participation by historically and presently excluded groups in oceanography.
Garcia, the student who went on the ocean trek three summers ago, has worked in Taniguchi’s lab since 2019, even to the point of volunteering for the spring 2022 semester between when she graduated and began her master’s program.
“When I first started, I was very, very intimidated,” Garcia said of Taniguchi’s research. “But she’s so accommodating and so good at explaining complex ideas. And she cares so much about her students. She’s like our lab mom.”
The daughter of parents who both were college professors, Taniguchi grew up in the Central Valley city of Merced, which doesn’t exactly suggest a future in oceanography. But her mother was an ocean lover, and even though it was a two-hour drive, she bought an annual membership to the famed Monterey Bay Aquarium.
Taniguchi recalls one trip when she went tide-pooling with her family after a visit to the aquarium. Her father pointed to a squishy creature about half the size of a football and asked Darcy what it was. She correctly identified it as a gumboot chiton, having retained the knowledge from her stop at the aquarium’s touch tank.
“Clearly I did absorb a lot,” Taniguchi said. “Those experiences of going to the ocean and having hands-on interactions with organisms was definitely what led me on my path.”
Her burgeoning zeal for the ocean attracted her to UCSD’s Scripps Oceanography, and she discovered plankton through her first course in biological oceanography. Twenty years later, Taniguchi’s childlike wonder and academic rigor toward these so-called “drifters of the sea” show no signs of abating.
“The oceans are so big and plankton are so small, and there’s so much we don’t know about both of them,” she said. “There’s lots of room for real exploration, which I think is really neat.”
Brian Hiro, Communications Specialist
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