New coral gardens and hydrothermal vents – all thriving with biodiversity, including many suspected new species – have been observed for the first time on a recent 35-day deep-sea expedition to one of the most remote island chains in the world.

The Ocean Census Flagship expedition aboard Schmidt Ocean Institute’s research vessel, Falkor (too) explored the South Sandwich Islands, including one of the coldest and most isolated submarine trenches on the planet.

Also found during the expedition was evidence of explosive volcanism.

The research expedition was part of the Nippon Foundation-Nekton Ocean Census programme, the world’s largest initiative to accelerate the discovery of ocean life. The Ocean Census scientists led the species discovery efforts, uncovering a wide range of potentially new marine life – including corals, sponges, snails, sea urchins, benthic ctenophores, and sea stars.

The exact number of new species will be announced later this year following an Ocean Census workshop, where taxonomic experts will formally assess and catalogue the findings. The GoSouth team – a collaboration between the University of Plymouth in the UK, GEOMAR in Germany, and the British Antarctic Survey – investigated the effects of geohazards, including tsunamis, volcanoes, and earthquakes.

“This expedition has given us a glimpse into one of the most remote and biologically rich parts of our ocean. This is exactly why the Ocean Census exists – to accelerate our understanding of ocean life before it’s too late,” said Dr Michelle Taylor, head of science and expedition principal investigator at the Ocean Census, and senior lecturer at the University of Essex.

“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.”

Along the way, the team were faced with a multitude of events, including a subsea earthquake, tropical storm force winds with hurricane-level gusts, eight-metre waves, and icebergs to navigate. 

Located in the South Atlantic, the South Sandwich Islands are part of a rich mosaic of geologic features such as hadal zone trenches, underwater volcanoes, and spreading centres – features created by tectonic forces that have supported the evolution of species found nowhere else on the planet. It took eight days for the research vessel to travel to the islands from the port of Punta Arenas in Chile.

The GoSouth team, led by Co-Chief Scientist Dr. Jenny Gales, discovered two pockmarks in the mapping data of an underwater caldera — a bowl-shaped depression in the seafloor, left after a volcano erupts. Pockmarks can indicate hydrothermal activity. Using a “nested” approach, the team deployed Schmidt Ocean Institute’s remotely operated vehicle, SuBastian to map the pockmarks at a higher resolution and confirm the presence of vents.

The larger pockmark contained three hydrothermal vents, and the smaller contained one. Located at 700 meters depth (nearly 2300 feet), they are one of the shallowest hydrothermal vents to have been discovered near the South Sandwich Islands, and the only ones to be explored using a remotely operated vehicle. 

The tallest vent chimney was four meters (13 feet), making it about as tall as a basketball hoop. Each vent was covered with an array of life dependent on chemosynthesis, including sea snails and barnacles. Thriving coral gardens and large sponges were found in close proximity to the vents — an unusual observation, said Taylor.

“Discovering these hydrothermal vents was a magical moment, as they have never been seen here before,” said Gales, an associate professor in Ocean Exploration at the University of Plymouth (UK). “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.”

In the trench, scientists found snailfish eggs that had been laid on a black coral, as well as a potential new sea cucumber species; large pumice blocks, indicating that the South Sandwich Islands were capable of explosive volcanism; a vibrant coral garden located west of Saunders Island; and a species of dragonfish that was discovered two years ago.

Click here for more from the Oceanographic Newsroom.