In one of the most isolated corners of the planet, the nearest humans to the research vessel Falkor (too) were often astronauts orbiting aboard the International Space Station. That is how remote the South Sandwich Islands are.
Yet it was here, across 35 days at sea, that an international team of scientists descended into frigid, largely uncharted waters — and found things no one had documented before.
A voyage to the edge of the known ocean
The expedition — a 35-day Ocean Census Flagship mission aboard Schmidt Ocean Institute’s research vessel Falkor (too) — brought scientists to one of the most forbidding marine environments on Earth. The South Sandwich Islands sit at the convergence of extreme cold, geological instability, and near-total isolation, anchored by one of the coldest and most isolated submarine trenches on the planet.
The GoSouth team — a partnership between the University of Plymouth, GEOMAR in Germany, and the British Antarctic Survey — focused on geological hazards including volcanic activity, tsunamis, and earthquakes. Ocean Census scientists, operating under the Nippon Foundation–Nekton programme, led the biological discovery work.
The voyage’s significance was already established before the hydrothermal vents were found. This was the same expedition that captured the first confirmed footage of a juvenile colossal squid. What came next only deepened the record.
How the hydrothermal vents were found
Discovery often begins with an anomaly in the data. For the GoSouth team, led by Co-Chief Scientist Dr. Jenny Gales, it was two pockmarks spotted in seafloor mapping data inside an underwater caldera — a bowl-shaped depression left behind after a volcanic eruption. Pockmarks can indicate hydrothermal activity beneath the seafloor.
To confirm what they were seeing, the team deployed Schmidt Ocean Institute’s remotely operated vehicle SuBastian, using a “nested” approach to map the pockmarks at higher resolution and verify the presence of active vents.
The results were unambiguous. The larger pockmark contained three hydrothermal vents; the smaller held one. All four sat at roughly 700 metres depth — among the shallowest vents ever found near the South Sandwich Islands, and the only ones explored by ROV. The tallest chimney reached about four metres, roughly the height of a basketball hoop.
“Discovering these hydrothermal vents was a magical moment, as they have never been seen here before,” said Gales. “Making such a discovery is rare. It highlights the importance of ocean exploration and seafloor mapping.”
Life thriving where it shouldn’t
Each vent was covered with communities of organisms that do not depend on sunlight — drawing energy instead from the chemicals the vents release, a process called chemosynthesis. Sea snails and barnacles were among the invertebrates observed blanketing the vent structures.
What surprised scientists most was what they found nearby. Thriving coral gardens and large sponges were growing in close proximity to the hydrothermal vents, an observation researchers described as unusual. Corals and sponges typically favor stable, nutrient-rich conditions, so finding them adjacent to active vents is not what anyone would expect.
A separate coral garden was found west of Saunders Island at a depth of 120 metres. Intact and visibly healthy, it added another layer to a growing picture of unexpected biological richness across the region.
A catalog of suspected new species
The biological inventory extends well beyond the vents. Ocean Census scientists observed potentially new marine life including corals, sponges, snails, sea urchins, benthic ctenophores, and sea stars — each requiring formal taxonomic assessment before any new species designations can be confirmed.
Some individual finds stand out sharply. In the trench, scientists discovered snailfish eggs laid on black coral — an unusual placement — along with what may be a new sea cucumber species. The expedition also captured the first known footage of Akarotaxis aff. gouldae, a dragonfish species only described two years ago. A final species count will follow a formal Ocean Census taxonomic workshop later this year.
What these findings mean for ocean science
The South Sandwich Islands expedition sits within a much larger knowledge gap. Ocean Census notes that only around 240,000 marine species have been documented, while millions more are thought to remain unknown. Closing that gap is the programme’s central mission.
Large pumice blocks observed during the expedition suggest the South Sandwich Islands are capable of explosive volcanism. The newly discovered vents also offer fresh data on the region’s tectonic activity — information with value well beyond pure science.
“This expedition has given us a glimpse into one of the most remote and biologically rich parts of our ocean,” said Dr. Michelle Taylor, head of science and expedition principal investigator at Ocean Census. “The implications of which will be felt for many years to come as discoveries filter into management action.”
As taxonomists work through specimens and data in the months ahead, findings from this expedition are expected to inform both conservation priorities and broader ocean management decisions — shaping how the deep ocean is understood and protected for years to come.