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New ocean layer discovered

A Nekton submarine descends into the Abyss A Nekton submarine descends into the Abyss Nekton 2018
11 May
2018
A deep-sea mission in the ocean around Bermuda confirms the existence of a new oceanic zone 

‘You almost pinch yourself and think you’re on some distant planet,’ explains Professor Alex Rogers as he reminisces about his dives into the deep ocean around Bermuda. For him, every trip in the Triton submarine, whose clear dome provides an unprecedented view of the ocean’s inhabitants, is magical. ‘There’s always something novel to see and the landscapes are fantastical. It’s a very humbling experience,’ he adds.

Rogers is a co-founder of Nekton, an organisation exploring the depths of the ocean for the benefit of humankind. In July 2016, Rogers and a team of marine scientists launched Nekton’s ‘Mission I’ to investigate the ocean around Bermuda, the Sargasso Sea and the northwest Atlantic. During the mission, dive teams, manned submarines and remote-controlled vehicles collected thousands of samples from the ocean’s surface down to 1,500 metres. Now, nearly two years later, the results of the mission have been processed and the team has announced some striking finds.

There was a great deal beneath the waves to excite the Nekton team, but the most important discovery of all was the existence of a new zone in the ocean, dubbed the ‘rariphotic’ (or ‘rare light’) zone. First mentioned by Dr Carole Baldwin from the Smithsonian Institute in March 2018, and now confirmed by the Nekton mission, the rariphotic zone extends from 130m to 300m and is the fourth zone confirmed in the top 3,000m of the ocean.

The rariphotic zone was identified by examining the unique biological communities that congregate at those depths. Each of the four ocean zones – altiphotic (0m to 40m), mesophotic (40m to 130m), rariphotic (130m to 300m) and bathyal (300m to 3,000m) – are characterised by these distinct groups of sea-life. For the Nekton researchers, understanding the zones and their different inhabitants is vital for improving understanding of ocean biodiversity and patterns of life.

At the moment, that understanding is limited. One impact of the mission’s results was to reveal just how much we still don’t know. Rogers and his team were amazed to discover over 100 new species around Bermuda, mostly in the rariphotic zone, including more than 40 new species of algae, a new black coral and at least 13 new crustaceans.

‘Given that Bermuda is such a well-studied area in general terms, we really weren’t expecting to find as many new species,’ says Rogers. ‘We found a new species of black coral. They looked like big forests of coiled bed springs. Discovering an animal that large and learning that it makes up a community that was not known to be around the islands of Bermuda was a really nice thing to find.’

Each discovery made bears its own wider significance and Nekton is currently preparing policy recommendations for the Bermudan government in light of the research. One of the most significant finds was a number of lionfish, an invasive species, as far down as 300 metres, the deepest recorded evidence of their troubling presence. Lionfish are capable of reducing populations of smaller fish on a reef by nearly 90 per cent in just five weeks. While policies to control them in shallow waters have had some success, their discovery in deeper water requires further action.

edit lionfishLionfish are an invasive species in Bermuda and can have devastating effects on the reef

Also important was the team’s exploration of the Plantagenet Seamount (locally known as Argus). There are more than 100,000 seamounts – or underwater mountains – globally, but less than 50 have been biologically sampled. Argus sits 15 miles off the coast of Bermuda and researchers noticed a different community of plants and animals there, compared to other areas around the island. The slopes of the seamount played host to gardens of wire corals and sea fans, communities of sea urchins, green moray eels, yellow hermit crabs, fish and other mobile fauna feeding off zooplankton and algae drifting off the summit and settling on the seabed. ‘We think there is a reason to consider specific management measures for that seamount,’ says Rogers. ‘Whether that’s a marine protected area is up to the government, but it would seem to require some special management measures.’

SVSleft 30023 SPT01 D8 1 wire corals and sea fan c Nekton and XL Catlin Deep Ocean SurveyWire corals and sea fan (Image: Nekton and XL Catlin Deep Ocean Survey)

More generally, Rogers believes the rariphotic zone probably extends throughout the Caribbean and he is particularly excited about taking the research forward into the Indian Ocean. Nekton’s next mission is planned for 2018-2021 and will focus on six distinct regions of the Indian Ocean, from the Mozambique Channel in the west to Sumatra in the east.

‘There’s still a huge amount of work to be done on the mesophotic zone and we’ve only just discovered the rariphotic zone,’ says Rogers. ‘We are very keen to see if there’s a similarly distinct community at those depths in the Indian Ocean because that will mean that the rariphotic zone goes through the Indopacific.’

The team is also aware of the importance of analysing human impact on the ocean. In Bermuda, where there is no trawling of the ocean floor, it found relatively little human debris, but it knows this will not be the case everywhere it goes.

Mission I was just the beginning for Nekton. By embracing new technology, artificial intelligence and improved camera technology it hopes to spread the word about its findings and continue to explore the ocean’s depths. For Rogers it means more trips into the unknown and more memories he’ll never forget.

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