• A deep-sea expedition has recorded 30 previously unknown species from one of the planet’s most inaccessible regions, at depths of up to 700 meters, or 2,300 feet, in the Southern Ocean.
• The astonishing array of deep-sea life included a carnivorous “death-ball” sponge, unknown sea stars spanning multiple families, and new crustaceans.
• Researchers gathered nearly 2,000 specimens representing 14 major animal groups while documenting new hydrothermal vents, vibrant coral gardens, and evidence of explosive undersea volcanism.
• Scientists estimate up to 2 million marine species exist, yet only 240,000 have been formally identified, meaning roughly 10% of ocean life has been cataloged.

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In the darkness of the deep ocean, where pressure crushes and light fails, an expedition has found an astonishing array of life, including a carnivorous “death-ball” sponge (from the genus Chondrocladia) covered in tiny prey-catching hooks; “zombie worms” (genus Osedax) lacking mouths but harboring symbiotic bacteria that digest whale bones; armored scale worms of iridescent colors (genus Eulagisca); and rare mollusks adapted to the volcanic seafloor.

The footage, recorded in March 2025, confirms 30 previously unknown deep-sea species from one of the planet’s most inaccessible regions in the South Atlantic Ocean.

Researchers found new sea stars spanning multiple families (Brisingidae, Benthopectinidae and Paxillosidae), novel crustaceans, and candidate species such as black corals and a potential sea pen genus still under expert review.

New iridescent scale worm found by the ROV SuBastian at 2859 metres at the South Trench dive site, northwest of Zavodovski Island. Photo courtesy of Jialing Cai/The Nippon Foundation-Nekton Ocean Census/Schmidt Ocean Institute © 2025
New In-situ sea pen found by the ROV SuBastian at 805 metres at the Mystery Ridge dive site. />Photo courtesy of  The Nippon Foundation-Nekton Ocean Census/Schmidt Ocean Institute © 2025

“The Southern Ocean remains profoundly under-sampled. To date, we have only assessed under 30% of the samples collected from this expedition, so confirming 30 new species already shows how much biodiversity is still undocumented,” Michelle Taylor, head of science at The Nippon Foundation–Nekton Ocean Census, said in a statement.

Researchers also glimpsed one of Earth’s most mysterious giants deep below. For the first time, they filmed a live colossal squid (Mesonychoteuthis hamiltoni) in its natural environment. A translucent juvenile measuring just 30 centimeters (12 inches) was captured gliding through frigid waters 600 meters (nearly 2,000 feet) below the surface near the South Sandwich Islands.

This is the first confirmed live observation of the colossal squid, Mesonychoteuthis hamiltoni, in its natural habitat. The 30-centimeter-long squid (nearly one foot)  was seen  in the remote South Sandwich Islands in the South Atlantic Ocean. This year (2025) is the 100-year anniversary of the identification of the colossal squid. Photo courtesy of Schmidt Ocean Institute © 2025

“For 100 years, we have mainly encountered them as prey remains in whale and seabird stomachs, and as predators of harvested toothfish,” said Kat Bolstad of the Auckland University of Technology in New Zealand, an independent expert who verified the colossal squid footage. “It’s exciting to see the first in situ footage of a juvenile colossal and humbling to think that they have no idea that humans exist.”

Adult colossal squid can reach 7 m (23 ft) in length and weigh up to 500 kilograms (1,100 pounds), making them Earth’s heaviest invertebrate. Yet their biology, behavior and ecological roles, like those of many other ocean species, remain largely unknown.

During the expedition, researchers gathered nearly 2,000 specimens across 14 major animal groups. They documented new hydrothermal vents 700 m (2,300 ft) deep, where chemosynthetic bacteria, rather than photosynthesis, fuel entire ecosystems. The team also recorded vibrant coral gardens and found evidence of explosive undersea volcanism.

Newly discovered hydrothermal vents teem with life, revealing the ocean’s hidden geothermal diversity. Photo courtesy of The Nippon Foundation-Nekton Ocean Census/Schmidt Ocean Institute © 2025.

The discoveries emerged from a 35-day voyage aboard the Schmidt Ocean Institute’s research vessel Falkor (too), during which the remotely operated vehicle SuBastian explored volcanic calderas, the South Sandwich Trench, and seafloor ecosystems around Montagu and Saunders islands.

The expedition included members from The Nippon Foundation–Nekton Ocean Census, Schmidt Ocean Institute, the GoSouth consortium (University of Plymouth, British Antarctic Survey, and GEOMAR), and the government of the U.K.-administered South Georgia and the South Sandwich Islands.

Scmidt Ocean Institute’s research Vessel RV Falkor (too), at the South Sandwich Islands, during the 2025 expedition. Photo courtesy of Paul Satchell/The Nippon Foundation-Nekton Ocean Census/Schmidt Ocean Institute © 2025

The expedition serves as an example of Ocean Census’s goal to shorten the time it takes to describe new species. This is done through collaborative workshops, advanced imaging and DNA analysis.

Following fieldwork, researchers transported specimens to the Southern Ocean Species Discovery Workshop hosted by the University of Magallanes in Punta Arenas, Chile, where international taxonomists rapidly verified species through on-site examination and targeted genetic barcoding.

“By coupling expeditions with species discovery workshops, we compress what often takes more than a decade into a faster pathway while maintaining scientific rigour by having world experts involved,” Bolstad said.

The urgency is real. Scientists estimate that 1 million to 2 million marine species exist, yet only 240,000 have been formally identified. That’s only about 10% of ocean life cataloged.

New seastar found by the ROV SuBastian at 1107 metres at the Mystery Ridge dive site. Photo courtesy of The Nippon Foundation-Nekton Ocean Census/Schmidt Ocean Institute © 2025
New Carnivorous death ball sponge found by the ROV SuBastian at 3601 metres at the Trench North dive site, east of Montagu Island. Photo courtesy of The Nippon Foundation-Nekton Ocean Census/Schmidt Ocean Institute © 2025

The Southern Ocean, encompassing the vast expanse of waters around Antarctica, remains particularly understudied despite its critical functions in global ocean circulation, carbon storage and nutrient distribution.

Since launching in April 2023, Ocean Census has confirmed more than 800 new species through 13 expeditions and a network of more than 1,000 scientists across 500-plus institutions worldwide. All discoveries are uploaded to the open-access Ocean Census Biodiversity Data Platform, ensuring global access for researchers, conservationists and policymakers.

“Accelerating species discovery is not a scientific luxury, it is essential for public good,” said Mitsuyuki Unno, executive director of The Nippon Foundation, which co-founded Ocean Census with the Nekton Foundation. “Ocean Census is a program with the goal to reveal the unknowns of our world. Through its expeditions, we have seen another groundbreaking species discovery that benefits the world’s scientists, policymakers and communities.”

A newly-discovered deep-sea coral garden flourishes in the dark depths, showcasing stunning biodiversity. Credit: The Nippon Foundation-Nekton Ocean Census/Schmidt Ocean Institute © 2025.

Scientists are rushing to document ocean biodiversity before climate change, overfishing and other threats erase species we don’t even know about yet.

The discoveries provide essential baseline data as nations implement the Agreement on Marine Biodiversity of Areas Beyond National Jurisdiction, adopted by U.N. member states in 2023. The treaty establishes frameworks for creating marine protected areas in international waters and mandating environmental assessments for activities on the high seas.

“This is exactly why the Ocean Census exists, accelerating the discovery of ocean life and making it openly available,” said Taylor, a senior lecturer at the University of Essex, U.K., who specializes in deep-sea corals. “Each confirmed species is a building block for conservation, biodiversity studies, and untold future scientific endeavours.”

Banner image of carnivorous death ball sponge found by the ROV SuBastian at 3601 metres at the Trench North dive site, east of Montagu Island. Photo courtesy of The Nippon Foundation-Nekton Ocean Census/Schmidt Ocean Institute © 2025

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Liz Kimbrough is a staff writer for Mongabay and holds a Ph.D. in ecology and evolutionary biology from Tulane University, where she studied the microbiomes of trees. View more of her reporting here.

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