How deep sea sludge is inspiring leadership for a greener future

It’s not every day that you get the call to go to the other side of the world.

While many people might leap at the chance of an adventure, deep sea scientist Dr María Belén Arias Mella was on holiday and initially concerned when she saw the name of her team leader, Dr Adrian Glover, flash up on her phone. No one wants to receive an unexpected phone call from their manager, especially when they’re relaxing during leave.

“When I saw the boss was calling, I was a bit worried at first,” admits Belén. “I could only think that something had gone wrong, and I was going to need to cut my break short.”

“As it turned out, he was calling me about an expedition. A nine-day-long cruise to investigate the unexplored deep sea around the Cook Islands in the south Pacific.”

The cruise was much more than a scientific venture, however. It was a dedicated Women in Science Expedition (WISE), aiming to champion female and Pacific islander participation in science while acting as a proof-of-concept for similar expeditions in the future.

Belén’s role, if she chose to accept it, was to help train budding scientists in how to take samples from some of the deepest waters in the world. While she was hesitant about going at first, Belén soon realised it was an opportunity she couldn’t miss.

“I’d already spent 45 days at sea in 2024, so I didn’t want to rush back out there,” she recalls. “But I found myself talking it over a lot with my husband, and realised that I’d already made my decision.”

“So, a short while later, I found myself making a 40-hour trip out to investigate a patch of unexplored deep sea on the far side of the world. I didn’t have any idea what I was getting myself into.”

There was one catch: the expedition was leaving in less than three months.

Ship shape

Being used to these cruises taking years to organise, Belén suddenly found herself contending with a flurry of paperwork and last-minute details as she got up to speed with the expedition.

“I’m from Chile originally, and having moved to the UK I’m used to working in various conditions with different budgets and equipment,” Belén says. “But I must admit that I was a little surprised that an expedition of this complexity was being mounted at such short notice. There are a lot of challenges to consider, but the Cook Island team worked very hard to make it work.”

An added complication was that not everyone going on the expedition had a scientific background. While many of the 20 experts selected were scientists, the cohort also included lawyers, activists, charity workers and even an MP from French Polynesia.

With the potential for so many conflicting views on the sometimes contentious issue of the deep sea, Belén might have just signed up to lock herself in a pressure cooker of a cruise. As it turned out, she needn’t have worried.

“I really shouldn’t have doubted them,” Belén says. “The cruise came together as planned, and when I got to meet the cohort for the first time I realised they were able to put their differences aside.”

“We were united in our concern about the oceans, and what the future holds for the deep sea. Everyone on the expedition knew how important it was to get out there and find out about the deep sea, so they could go home and be able to explain exactly why it’s important.”

“That really put the pressure on me and the other advisors to live up to their expectations.”

Setting sail

After a few last-minute checks, and a blessing from the Cook Islands’ Prime Minister, the expedition set sail into the Pacific Ocean.

Belén is used to voyages taking days to reach the first site, but the areas being investigated this time were all relatively close together. The first stop was just five hours out, meaning a hectic few hours of giving the expedition’s members a crash course in box corers.

These devices are bit like deep-sea cookie cutters. The corers are lowered down to the seabed into which they sink, capturing a block of sediment that is then brought up to the surface along with any animals, microbes or other objects caught within it.

In the Pacific, this can include potato-sized lumps of metal known as polymetallic nodules.

These nodules have received global interest in recent years as a potential source of manganese, cobalt, nickel and copper – all metals that are important for the production of green technologies. Around the world, there are numerous regions of the deep-sea floor that is littered with these nodules. However, the prospect of mining for them is controversial.

One of the largest deep-sea polymetallic nodule fields is found within the Cook Islands’ exclusive economic zone. This means that if the island nation wanted to, they would be able to fully exploit these minerals.

“Pacific island nations are heavily dependent on fishing and tourism, but deep-sea mining could offer a new opportunity,” Belén says. “It’s really important for them to know about their resources, and the potential impacts it could have on their ecosystems, economies and people.”

By sampling from across the region, scientists can then calculate a baseline for what the area is currently like. This can then provide vital evidence to feed into any decisions made about the future of these polymetallic nodules.

But this is only possible if the box cores work: the first sample brought up by the expedition failed.

“It’s strange to be happy that sampling failed, but it was actually a really good learning opportunity for the team,” Belén explains. “It meant they could all touch the sediment and understand what the animals look like, and get a better understanding of what they were working on.”

“I also learned a lot about how best to share my knowledge with them, so we could start speeding up the process. We started getting into the rhythm of it, learning from each other while getting important new data.”

This wasn’t all that went wrong. One expedition member was put into isolation after coming down with a fever, while others not used to living on a boat for long periods of time suffered from seasickness. A plan to explore the seabed was also scuppered when the remotely operated vehicle broke down, with the team forced to lower an underwater camera instead.

Nonetheless, the expedition was able to collect six samples from an area of the deep sea that had never been explored before, an outcome Belén describes as “very successful”. Their initial research shows that far from being a uniform and almost endless flat plain the undersea environment is a diverse landscape.

“The cores collected closer to the Cook Islands’ exclusive economic zone were absolutely full of nodules,” Belén recalls. “It was really eye-opening to see just how much was down there, and also a bit worrying because I thought we’d never finish counting them!”

“But as we got closer to the exclusive economic zone of French Polynesia, the samples changed completely. The nodules looked very different, and there were much fewer of them. It was a good opportunity to show just how little we know about these environments, and how important high-resolution maps are to understand what’s happening in the deep sea.”

Looking to the future

After nine exhausting days, the expedition returned to the Cook Islands. They’d explored a little-known area, carried out groundbreaking science and perhaps most importantly, proven their skills as custodians of the Pacific.

“I think women already know that they can be leaders, but they definitely need role models to show that it is actually achievable,” Belén says. “I’m so glad that I was able to provide that experience and show exactly what they can achieve.”

“Women can be part of, and even be leaders of, this type of research in any country. Hopefully, following this experience, the team have realised that there’s no limit to the opportunities out there for them.”

In an ideal world one of the team members would have joined Belén back at the Natural History Museum to process the samples themselves. Unfortunately, as scientists are all too aware, money was the ultimate stumbling block.

“In the end, there wasn’t anyone willing and able to fund one of the team to come to the Museum,” Belén says. “It’s a real shame, as collaborating with communities is critical to giving them an insight into research that affects them.”

Despite this setback, the Cook Islands will continue to be involved in the expedition’s research. An intern from the nation’s Ministry of Marine Resources is already working with the deep sea team and will help to process the samples.

“We’re hoping this research will provide the evidence that this work is necessary, so we can get the money to bring more Pacific island researchers here in the future,” Belén says. “In the long term, we hope the experience they gain would allow them to head back home to establish their own labs and investigate their own resources.”

As for Belén, she’s looking forward to keeping her feet on solid ground for the foreseeable future. Although time will tell for how long.

“It’s good to be home, but at the same time I would love to head out there again,” she says. “Being an advisor was outside my comfort zone, but being able to inspire this group was an absolute privilege.”

“If just one of them now has the confidence to become a decision-maker and take the lead, then I’ve done exactly what I wanted.”