Mysterious Little Creatures that Lurk in Plain Sight

By Jess Liu

Protist illustrations by Jess Liu.

Man-eating plants. Photosynthetic bears. Blobby beasts that can switch between sun-powered and meat-powered at a moment’s notice. No, this isn’t the premise of Stephen

King’s new science fiction novel or a safari tour of the Chernobyl Exclusion Zone. This is the very real world of microscopic protists living in oceans, lakes, streams, and even that dirty old puddle in your driveway. These strange oddities have been lurking under our toes for all of human history (and even before that, for that matter). But for the first time, we’re finally able to peer into their fascinatingly strange world.

For over a hundred years, scientists have sailed the high seas in the name of protist research, and we’ve learned crucial information as a result of their expeditions. These microscopic organisms form the base of nearly all aquatic food chains, fueling animals as small as newly-hatched fish and as large as baleen whales. They produce nearly 80% of the Earth’s oxygen. They’re the perpetrators of ecological phenomena like red tides and plankton blooms. But the more we uncover about these unicellular critters, the more questions we have. Critically: “What do they eat?”

Traditionally, we’ve understood and taught that any species of protist plankton occupy one of two sides of a trophic dichotomy. On one hand, we had the “plants of the sea”, green little phytoplankton that float under rays of sunshine, harnessing its energy through photosynthesis.

On the other hand, we had the “bugs of the sea”, tiny zooplankton that chase after the former and graze upon them as insects do on fields of grass.

After years of research, we’ve finally begun to understand that most species can actually do both, a phenomenon known as “mixotrophy”. Tiny aquatic critters can suddenly behave more like plants. Seemingly harmless little green algae can become voracious eaters when conditions are right. These new breakthroughs have extraordinary implications for understanding aquatic life, to the same extent that man-eating trees would have on terrestrial life. But all of these complex interactions are nearly impossible for scientists to consistently and accurately observe.

A tiny radiolarian, a type of protist, captured under the microscope by Senior Research Scientist John Burns.

Enter the lab of Dr. John Burns at Bigelow Laboratory for Ocean Sciences. Well, I would’ve loved to have entered the lab of Dr. John Burns this summer, but with the threat of another microscopic anomaly floating around, we’ve had to translate our research onto digital platforms. To our benefit, computational modeling answers the questions that wet lab research can’t quite explain. We aim to find a distinct collection of proteins required for mixotrophic processes by searching for common proteins present in all mixotrophic protists. With this data, we’ll be able to construct a model that would be able to predict the trophic capabilities of any unicellular organism given enough protein data.

While it sounds simple, protein models require a fair bit of computer science knowledge to be able to create. Knowledge I didn’t have coming in. Over the course of our research project, I’ve gone from fearing the dark abyss that is the computer terminal to writing scripts that could help answer these critical questions. I’ve gained a tremendous amount of respect for these mysterious little creatures that lurk in plain sight, as well as the computational biologists who spend their lives studying them.

Jess Liu is a Vassar College student in Bigelow Laboratory for Ocean Science’s Research Experience for Undergraduates program. This intensive experience provides an immersion in ocean research with an emphasis on state-of-the-art methods and technologies.

Mysterious Little Creatures that Lurk in Plain Sight