For 35 days, a research vessel pushed deep into one of the most isolated stretches of ocean on Earth — the South Sandwich Islands, where active volcanoes smolder beneath the seafloor and the nearest humans were sometimes astronauts orbiting overhead on the International Space Station.
Scientists aboard Schmidt Ocean Institute’s Falkor (too) had come to explore a place few have ever studied up close: frigid, geologically restless, and largely unmapped. What they found in those icy depths is still being counted.
A mission to the edge of the known ocean
The 35-day expedition was part of the Nippon Foundation–Nekton Ocean Census programme, the world’s largest initiative to accelerate marine species discovery. Its goal is straightforward in ambition, daunting in scale: close the gap between what science has catalogued and what the ocean actually holds. Only about 240,000 marine species have been formally documented, while millions more are estimated to remain unknown.
Alongside the Ocean Census scientists, the GoSouth team — a collaboration between the University of Plymouth, GEOMAR, and the British Antarctic Survey — pursued a parallel mission. Their focus was geohazards: the underwater volcanism, tsunamis, and earthquakes that make the South Sandwich Islands as geologically dangerous as they are biologically rich.
How the hydrothermal vents were tracked down
Co-Chief Scientist Dr. Jenny Gales and the GoSouth team identified two pockmarks while analyzing seafloor mapping data inside an underwater caldera — a bowl-shaped depression formed after a volcanic eruption. Pockmarks of this kind can signal hydrothermal activity beneath the seafloor. The team used a nested mapping approach, progressively zooming in before deploying ROV SuBastian to confirm their hypothesis.
The confirmation came quickly. The larger pockmark contained three hydrothermal vents; the smaller held one. All four sat at roughly 700 metres depth — placing them among the shallowest vents ever recorded near the South Sandwich Islands, and the only ones ever examined with a remotely operated vehicle. The tallest chimney stood four metres high, roughly the height of a basketball hoop, and had never been explored before. “Discovering these hydrothermal vents was a magical moment,” Gales said. “Making such a discovery is rare.”
Life thriving where it shouldn’t: coral beside the vents
Each vent was covered in organisms that require no sunlight. Sea snails and barnacles clustered around the chimneys, sustained by chemosynthesis — a process by which life extracts energy from chemical reactions rather than solar radiation. This type of ecosystem is well documented at deep-sea vents around the world.
What caught scientists off guard was what sat nearby. Thriving coral gardens and large sponges were found in close proximity to the vents, a combination researchers described as unusual. Dr. Michelle Taylor, head of science at the Ocean Census, noted that the co-existence of coral gardens and hydrothermal vents is a rare and scientifically significant observation. A separate coral garden, dense and visually striking, was also discovered west of Saunders Island at just 120 metres depth — adding another layer to an already complex picture of life in these waters.
A catalog of suspected new species — and a few surprises
The species list spans a broad range of marine life: potentially new corals, sponges, snails, sea urchins, benthic ctenophores, and sea stars. In the trench itself, snailfish eggs were found laid on black coral — a vivid image from one of the ocean’s coldest environments — and a potential new sea cucumber species was recorded. Large pumice blocks on the seafloor provided geological evidence of explosive volcanism, reinforcing the GoSouth team’s findings about the region’s tectonic instability.
The expedition also produced two notable firsts on film. Researchers captured the first footage of Akarotaxis aff. gouldae, a dragonfish species discovered only two years ago. Separately, the team filmed the first confirmed sighting of a juvenile colossal squid — footage that drew widespread attention when released.
Why exploring the deep ocean still matters
The exact species count won’t be confirmed until later this year, when taxonomic experts convene at a formal Ocean Census workshop to assess and catalogue all findings. That process takes time. But the early scope of what was observed suggests the total will be significant.
Dr. Taylor has been direct about the urgency behind this work. These ecosystems exist in environments that climate change and habitat loss could alter before science has had a chance to fully understand them. The findings from this expedition are expected to inform marine conservation and management decisions for years ahead.
What this mission ultimately illustrates is how much of the deep polar ocean remains unexplored — and how much can be found when international teams commit to going there. Future expeditions to similarly remote environments will likely keep revising what scientists believed they knew about life at the ocean’s edge.