Deep-sea scientists make "incredible discovery" on 35-day expedition in South Atlantic

A team of scientists has returned from a dramatic 35-day deep-sea mission to the South Sandwich Islands – one of the most remote and extreme places on Earth – with a host of remarkable discoveries.

Exploring the icy South Atlantic Ocean aboard Schmidt Ocean Institute’s research vessel Falkor (too), the team uncovered stunning coral gardens, rare hydrothermal vents and many marine species likely to be new to science – including corals, sponges, snails, sea urchins, benthic ctenophores and sea stars.

Researchers discovered hydrothermal vents at 700 meters depth — Researchers discovered hydrothermal vents 700 metres down on the north-east side of Quest Caldera, off the South Sandwich Islands. The tallest vent chimney was four metres (13 feet), and they were was covered with an array of life, including sea snails and barnacles. Credit: ROV SuBastian / Schmidt Ocean Institute

The South Sandwich Islands – a volcanic island chain in the South Atlantic – are rarely visited, let alone studied. Surrounded by hadal trenches, underwater volcanoes and deep-sea ridges, the region is a hotspot for both marine life and geological drama.

“This expedition has given us a glimpse into one of the most remote and biologically rich parts of our ocean," says Dr. Michelle Taylor, head of science and expedition principal investigator at the Ocean Census, who led the species discovery efforts.

"This is exactly why the Ocean Census exists – to accelerate our understanding of ocean life before it’s too late."

“The 35 days at sea were an exciting rollercoaster of scientific discovery; the implications of which will be felt for many years to come as discoveries filter into management action.”

ROV SuBastian is recovered at night after dive — Remotely Operated Vehicle SuBastian is recovered to the Research Vessel Falkor (too) after a dive. Credit: Alex Ingle / Schmidt Ocean Institute

The team braved eight-metre waves, iceberg-strewn waters and even a subsea earthquake. But their efforts paid off with remarkable finds.

Scientists discovered four hydrothermal vents – underwater openings where heated, mineral-rich water gushes out from the seabed. Found at a depth of 700 metres, these are among the shallowest vents recorded in the region.

The largest chimney stood as tall as a basketball hoop and was teeming with life, including sea snails and barnacles that rely on chemicals, not sunlight, for survival.

Nearby, colourful coral gardens and large sponges flourished – a rare sight so close to vents.

A vibrant grouping of coral, documented on on Humpback Seamount — A vibrant grouping of coral, documented on Humpback Seamount. Credit: ROV SuBastian / Schmidt Ocean Institute

“Discovering these hydrothermal vents was a magical moment, as they have never been seen here before,” says co-chief scientist Dr Jenny Gales.

"It’s an incredible discovery that provides valuable insights into the area’s tectonic activity. Making such a discovery is rare. It highlights the importance of ocean exploration and seafloor mapping.”

Green deep-sea sponge — The science team observed this green deep-sea sponge at 974 metres; these animals are very slow-growing, sometimes less than two centimetres a year. Credit: ROV SuBastian / Schmidt Ocean Institute

Other fascinating finds included snailfish eggs laid on black coral in one of the world’s deepest trenches, a possible new species of sea cucumber, giant floating pumice stones (hinting at past volcanic eruptions), and a rarely seen dragonfish species.

A snailfish (Careproctus sp.) rests atop a king crab (Lithodidae sp.) in a possible parasitic interaction. Some species within the genus Careproctus are known to lay their eggs inside the gill cavities of king crabs, using the oxygen-rich space as a protected environment for their clutch. Credit: ROV SuBastian / Schmidt Ocean Institute

The species identification process is ongoing, with marine taxonomists expected to confirm the new finds later this year.

“The challenging ocean and weather conditions and the isolated location of the South Sandwich Islands capture the imagination of the boldest explorers — often the closest humans to the vessel were on the International Space Station,” says Schmidt Ocean Institute’s Executive Director, Dr. Jyotika Virmani.

“We are proud to have collaborated with Ocean Census in their mission to advance the discovery of marine life and GoSouth (who were also involved in the expedition) in their quest to better understand the geological nature of this dynamic corner of the world.”