Creatures from the deep: exploring the seas around remote South Atlantic islands

In October 2022, the RRS Discovery set sail from Southampton on a 9,000-mile expedition to survey some of the remotest marine environments on the planet.

On board were a team of scientists equipped to sample and map the sea floor, test water quality, measure temperature and plastic particles, and identify the species living in the remote waters of the South Atlantic.

The expedition is part of the UK government's Blue Belt Programme, which works closely with UK Overseas Territories to assist them in managing and maintaining healthy and productive marine environments.

The programme works closely with eight UK Overseas Territories, which include Ascension Island, St Helena, Tristan da Cunha, South Georgia & the South Sandwich Islands, British Antarctic Territory, Pitcairn Islands, British Indian Ocean Territory and the Turks & Caicos. Combined, their Marine Protected Areas span 4.3 million square kilometres of ocean. 

Museum scientists Chris Fletcher and James Maclaine joined the expedition providing their expertise in collecting and identifying specimens while taking tissue samples of fish and invertebrates for molecular analysis.

The expedition was initially scheduled for the end of 2021. But even after two-weeks isolation on board the ship, some crew, including the captain, caught COVID-19 and the trip was postponed for a year.

It initially set out from Southampton, stopping in Cape Verde to pick up some of the research team including Chris and James, before setting a course for the South Atlantic.

Discoveries from the deep 

The team aboard the ship worked 24 hours a day throughout most of the sampling periods.  

During the day, teams would analyse the seabed, including sampling the sea floor thousands of metres below the surface, but during the night, Chris and James would get to work.

James, Senior Curator of fish at the Museum, says, 'My job was to help with the pelagic trawls, which sample the midwater region between 200-1000m'

'Most of the really interesting animals go deeper in the day and then move up when it gets dark to avoid predators, so we had to work through the night.'

'Chris and I were there for when the nets came in, going through the samples, sorting them and trying to identify as much as we could to get an idea of the biodiversity. It was great to see specimens that were fresh out of the sea.'

'We used a UV pen to see if any of the animal's photophores lit up, and this jewel squid just lit up beautifully with red,' explains Chris. 'Usually, deep sea photophores glow blue, which is better for communication because red light gets absorbed easily by water.'

'It's really bizarre, but I don't think there's any function to it because these animals wouldn’t want their lights to glow red,' James adds.

'I think it's just to do with the chemicals in the light organs, but it's really spectacular.'

When asked if they may have found anything new to science, James says, 'It's totally possible, but will take a bit of investigation. The problem is that it's hard to say if something is new or if it's just a baby version of something else because quite often things change quite dramatically as they develop.'

'But one of the most exciting fish we found was a juvenile anglerfish which has strange filaments on the stem of its lure. And that means it's either a new species or a species only previously known from six specimens. So that's really exciting.'

Expeditions such as RRS Discovery provide the equipment and expertise to help support these islands and survey the surrounding areas to help better protect them.

'It’s so that the waters around these British Overseas Territories can be managed better,' says James.

'There's the nice example of Tristan da Cunha, which now has a huge protected area around the islands. So, if you want to fish or sample there, it's a lot more regulated, and that was a direct result of the kind of work we are doing.'

'It's all evidence to say an area is important and fragile and needs to be regulated and managed properly. You can't properly manage an area if you know nothing about it.'

The expedition has made some new and exciting discoveries, including two previously unknown mountain ranges under the sea, known as seamounts.

Shallow underwater cameras unearthed huge populations of Galapagos sharks, which is a good indicator of a healthy marine ecosystem. Deep-water cameras also found large cold-water coral reefs at a depth of 1,000 metres. These reefs contained species like black coral which can live for up to 4000 years, making it one of the oldest living animals on Earth.

When the boat reached each island, Chris and James got the chance to explore these isolated lands. On Ascension, they spoke to local schools about the importance of the work they were doing and hiked up a mountain to see land crabs. 

On St Helena, they got to meet Jonathan the Seychelles giant tortoise as he turned the ripe old age of 190, making him the oldest known living land animal.

Reflecting on the trip, Chris says, 'It's a lot of hard work and a lot of night shifts. You're tired most of the time and forget what it is to be fully awake, but you survive it because everything is just so interesting.'

'That excitement of seeing what the nets have brought up is my absolute favourite moment,' James adds.

'These experiences don't come around very often, so it's such a privilege, and I'm very grateful for being invited. To be there collecting these samples and seeing things for the first time alongside people making all these new discoveries. It's one of the best parts of my job.'