Rare phantom jellyfish seen in Argentina deep sea exploration

The sighting happened during an Argentinian‑led mission aboard Schmidt Ocean Institute’s research vessel Falkor (too), which spent weeks exploring deep‑sea habitats.

by · 5 NBCDFW

A rare giant phantom jellyfish spotted off Argentina’s coast has become one of the most striking discoveries from a new deep‑sea expedition.

The sighting occurred during an Argentinian‑led mission aboard Schmidt Ocean Institute’s research vessel Falkor (too), which spent several weeks examining deep‑water ecosystems along the country’s entire coastline.

While the jellyfish encounter stood out, it was only one part of a mission that revealed a surprisingly vibrant deep‑sea landscape. As the team moved from Buenos Aires toward Tierra del Fuego, they documented an enormous Bathelia candida coral reef, several additional reef complexes and 28 organisms that scientists believe may be new species.

Juvenile fish (Centrolophus sp.) swim around the bell of a Stygiomedusa gigantea, commonly known as the giant phantom jelly, which ROV pilots filmed at 250 meters. Their bell can grow up to 1 m (3.3 ft) in diameter, and their four arms can reach up to 10 m (33 ft) long. They do not have any stinging tentacles, but use their arms to catch prey, including plankton and small fish. CREDIT: ROV SuBastian / Schmidt Ocean Institute

“We were not expecting to see this level of biodiversity in the Argentine deep sea, and are so excited to see it teeming with life,” said the expedition’s chief scientist, Dr. María Emilia Bravo of the University of Buenos Aires and CONICET. “Seeing all the biodiversity, ecosystem functions, and connectivity unfolding together was incredible. We opened a window into our country’s biodiversity only to find there are so many more windows left to be opened.”

The newly mapped Bathelia reef spans an area comparable to Vatican City and supports a wide range of marine life, from octopuses to crustaceans. Its discovery far south of its previously known range suggests the species occupies a much broader stretch of the South Atlantic than scientists realized.

Deep-sea corals are slow-growing and long-lived. They are often classified as Vulnerable Marine Ecosystems, or VMEs, because they support high biodiversity and are threatened by human activities such as bottom trawling. In this image, red and pink basket stars (Gorgonocephalus chilensis) perch on top of white hard corals (primarily Bathelia candida and Solenosmilia sp.). The sea stars and corals actively feed by capturing particles and small organisms from the water. CREDIT: ROV SuBastian / Schmidt Ocean Institute

The expedition also recorded Argentina’s first deep‑water whale fall nearly four kilometers below the surface, and observed ancient bubblegum coral gardens growing among large sponges in the Malvinas Trough. The phantom jellyfish became one of the expedition’s standout sightings as its long arms drifted through the deep.

“We collected an unprecedented number of chemical, physical, and biological samples that will be used to understand connections in our waters for years to come,” said Dr. Melisa Fernández Severini of Instituto Argentino de Oceanografía and CONICET. “These samples represent a unique opportunity to understand not only how extraordinary these extreme ecosystems are, but also how vulnerable they can be.”

Deep-sea jellyfish prefer the darker depths, where their red hue helps keep them hidden (red is harder to see in the deep) and helps disguise bioluminescent prey in their bellies. ROV pilots filmed this Periphylla at 2,070 meters while exploring the Colorado-Rawson submarine canyon. CREDIT: ROV SuBastian / Schmidt Ocean Institute

A major focus of the mission was the search for cold seeps, places where methane and other chemicals leak from the seafloor and support specialized communities of clams, mussels and tube worms. The team located an active seep roughly one square kilometer in size, making it one of the most substantial features documented during the voyage.

Even in these remote depths, the researchers found traces of human activity, including fishing gear, plastic debris and a Korean‑labeled VHS tape preserved by the cold, high‑pressure environment.

“With every expedition to the deep sea, we find the Ocean is full of life—as much as we see on land, and perhaps more because the Ocean contains 98% of the living space on this planet,” said Schmidt Ocean Institute’s executive director, Dr. Jyotika Virmani. “We have been privileged to work with outstanding scientists across three expeditions in Argentinian waters, and look forward to seeing their research continue to unfold, unlocking new understanding and inspiration.”

R/V Falkor (too) crew recover ROV SuBastian following operations in the South Atlantic Ocean. Each ROV dive produces about a billion bytes of video data, along with sensor data and samples for further study. CREDIT: Misha Vallejo Prut / Schmidt Ocean Institute

Schmidt Ocean Institute, founded in 2009 by Eric and Wendy Schmidt, supports ocean exploration through advanced technology, open data practices and global scientific collaboration.

The expedition brought together researchers from the University of Buenos Aires, one of Latin America’s leading public universities, and CONICET, Argentina’s national science agency known for its high‑impact research across scientific fields.