These Mesmerizing Anemones Have a Glowing Layer of Protection

Marine biologist Dimitri Deheyn walks over to an isolated aquarium in a room at the Scripps Institution of Oceanography. All around him, pumps churn in blue vats, rubber boots squeak against concrete floors, and the sweet smell of intertidal algae fills the air. Deheyn swings open the hinges to the experimental aquarium and examines rows and rows of anemones. Then he submerges his hand in the water, transfers one of the invertebrates into a petri dish and walks to the photobiology laboratory, a room where researchers study how living organisms interact with light.

Deheyn switches the lights off in the photobiology lab, and the anemone, which sits in an inch of water, is placed under an ultraviolet (UV) spotlight. The drab creature begins to glow a brilliant green. The transformation is the result of biofluorescence—the process in which unique proteins absorb specific wavelengths of light, namely UV light, and transform them back at different wavelengths. Depending on the type of protein in an organism, among other molecular factors, creatures can create colors including neon green, blue, yellow or orange.

Intertidal anemones, such as this one, are incredibly resilient. Twice a day, every day, the intertidal where many anemone species live changes entirely. The shift in the area exposed between high and low tide leaves the ecosystem’s residents with two choices: survive the change or perish. Intertidal anemones have evolved specialized adaptations to deal with this change, letting them thrive in these extremes, and scientists have just discovered more about one of these adaptations.

In a study published in March in the Proceedings of the National Academy of Sciences, researchers found that a protein in intertidal anemones boosts fluorescent output while enabling an antioxidant property. Antioxidants are compounds that detoxify free radicals, dangerous chemicals created through stressors to organisms. By offering a new source of biochemical defense against stressors, this protein could be the difference between life and death for anemones in a changing ocean. It could help the creatures deal with shifts—like greater temperature extremes—and improve the chances for anemones to survive and pass off their genes to a new generation. The brighter the anemone, the more readily it can process and handle climate-induced stressors.

For the study, led by biologist Nathaniel Clarke, then of Stanford University and now at MIT, and Deheyn, of the University of California San Diego, the researchers studied three species of anemones on the California coast and identified a unique protein called AnthoYFP that controls biofluorescence intensity. The three anemone species are similar in that they occupy similar environments and fluoresce a brilliant green under ultraviolet light, but their color under white light can vary. While exploring one species, sunburst anemones (Anthopleura sola), the researchers found a unique color morph that displayed a neon green when fluorescing under UV and under white light. (Other types of this anemone have an olive green or brown hue under white light.) Perplexed by this perpetually neon color morph, the authors investigated and identified a version of the AnthoYFP protein that makes the anemone brighter under white light as well as UV.

Even more remarkable than the photonic properties the protein produces is the biochemical defense it provides. This study demonstrates the antioxidant function of fluorescent proteins in a living organism for the first time, opening a door for more research.

The implications of this discovery could go beyond the intertidal in the future. Clarke imagines a future in which AnthoYFP is utilized to help other invertebrates deal with cellular stress. Deheyn suggests the protein could possibly be genetically engineered into other cnidarian species—including corals and anemones—to boost resilience in the face of increased temperature extremes, more severe storms and increased ocean acidity due to climate change. For example, Clarke says this protein could help create stress-resilient corals that could withstand the challenges of warmer oceans.

All intertidal stressors—from high to low tide—will increase as the coasts morph due to climate change, according to Deheyn. At high tide, more extreme waves will provide additional shearing stress on the anemones, threatening to rip them out to sea. At low tide, extreme heat and extended periods of being out of water could increase the chances the creatures dry out. Rising seas will also push their ecosystem farther up the beach and to the edges of their habitable zone. According to Deheyn, anemones with the newly identified protein would be best equipped to flourish under such incremental stressors.

Deheyn says thanks to citizen scientists he and his colleagues know where the color morph of the sunburst anemone lives and is spreading. The authors used observations from the digital platform iNaturalist to determine the range, population density and prevalence of this unique anemone.

In California, a strong community of intertidal enthusiasts regularly submits pictures and observations to databases like iNaturalist. For these citizen scientists, the rush of discovery and the ever-changing nature of tide pools draws them in. For this study, thousands of citizen scientists took pictures of and analyzed nearly 6,000 anemones from Oregon to Baja, Mexico, to help identify sunburst anemone populations.

Jami Feldman is one of those passionate citizen scientists. An avid diver, ScubaPro ambassador and TikTok creator with the username @UnderwaterPaparazzi, Feldman heads to the tide pools in La Jolla, California, equipped with neoprene waders, an underwater camera and a headlamp. She often arrives at her destination 30 minutes before low tide, enabling her to get to her favorite pools before the high tide washes them away. Feldman sometimes even visits the pools at 3:30 a.m., an arduous trek that rewards her with rare sightings of species that are active at night or at dawn and dusk.

Her love of the intertidal began because she wanted something to do when the ocean was too rough to scuba dive. Now, Feldman has become obsessed with the challenge of finding and photographing different species in the pools. As San Diego’s climate changes, she hopes to provide “a real-time view” of ecosystem shifts for scientists.

Citizen scientist and nudibranch lover Laura Simonato actively shares her intertidal findings to iNaturalist, too. She posts about the diversity and wonder of intertidal life @thetidepooler on Instagram. Simonato looks at iNaturalist when deciding which sites to visit to find certain species, including ones she’s never seen. To educate other intertidal explorers, Simonato has created a “Tidaldex,” an interactive poster of intertidal creatures, that she sells.

Finding and photographing small invertebrates took a lot of practice for Simonato. After years of visiting the tide pools, she became more aware of what was around her and what was out of place. Sharing these observations of out-of-place creatures helps scientists identify habitat shifts and species range expansions, which are possibly influenced by climate change.

By introducing the intertidal to others, Feldman and Simonato hope to encourage new voices to join them—and, with the help of scientists, create a brighter and more resilient future for the ocean.