Underwater views of Antarctic jellies are 'a magic portal to another world'

The gelatinous, transparent bodies of bizarre jellylike sea creatures — illuminated by the twinkling of an internal light, and some with a recent meal still visible in their bellies — tumble and drift in hypnotic footage that was captured below the Antarctic ice. Edited into a "trippy video composition," as filmmaker and scientist Emiliano Cimoli described the film in a statement, the footage presents close-up views of jellyfish, comb jellies and other soft-bodied, see-through ocean life in the Ross Sea, a deep body of water in the Southern Ocean at McMurdo Sound. The exceptional detail in the video enabled researchers to spot a dozen species of gelatinous animals, of which two species of jellyfish and three comb jelly species are as yet unknown to science, according to a new study. Cimoli, co-author of the study and a postgraduate researcher at the University of Tasmania in Hobart, Australia, shot the footage when he visited Antarctica to conduct research in 2018 and 2019. But he wasn't there to study jellyfish or comb jellies; rather, he was testing sensing equipment to monitor algae that live under sea ice, Cimoli wrote in a video description on YouTube. "Ice algae play a crucial role in polar marine food webs and ecosystems," Cimoli said. "The research theme of the expeditions was to investigate their abundance and physiology under changing light conditions," such as those caused by climate change, he explained on YouTube.

Inside the researchers' field tent, there was a sizable viewing hole cut into the sea ice. Cimoli, an amateur wildlife videographer and photographer, saw this as an opportunity to send cameras under the ice — some tethered to the surface, and some attached to diving robots — to seek out elusive marine life that's often difficult to observe in its natural habitat. This opened a window into a rarely-glimpsed ocean ecosystem, "kind of like a magic portal to another world," Cimoli said in the statement. In some of the footage, surface ice is visible overhead. Other clips show the sea bottom sprinkled liberally with pink starfish. But the most dramatic scenes are the ones in which jellies drift and undulate through inky water. In an astonishing shot, a Diplulmaris antarctica jellyfish's body gently pulses and ripples; a number of small orange globes — small parasitic crustaceans called hyperiid amphipods — cluster around its bell. And engulfed inside the jellyfish is a recent meal: a comb jelly in the Beroe genus. Cimoli edited the video during COVID-19 lockdown, and he posted it on YouTube and Vimeo in March 2020. Gerlien Verhaegen, a postdoctoral researcher at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in Kanagawa, Japan, and lead author of the study, recognized that the footage was a gold mine for biologists studying jellies. Delicate structures in jellyfishes' and comb jellies' squishy bodies are very hard to preserve when the animal is removed from the water, so the study authors identified species in the video by comparing them to naturalists' illustrations and descriptions, many of which date to the early 20th century, Verhaegen said in the statement.

"Our study constitutes the first optics-based survey of gelatinous zooplankton in the Ross Sea," the study authors reported. This is also the first study to use observations of living jellies in their Southern Ocean habitats to describe species and document some of the behaviors in jellyfish and comb jellies.