Marine expedition discovers ‘oasis of ocean life’ in unexplored depths

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Scientists on the Nekton Maldives Mission have discovered evidence of a previously unknown deepwater ecosystem at a depth of 500 metres.

The new ecosystem was dubbed ‘The Trapping Zone’ as marine life are prevented from diving deeper when the sun rises. This is due to the steep vertical cliffs and shelving terraces that were created by volcanic subsea strata and fossilised carbonate reefs that form the base of Maldivian atolls.      

The trapped animals are targeted by large pelagic predators, including schools of tuna and sharks, along with large deep-water fish including the spiky oreo (named after the biscuit) and alfonsino.

“Image data, combined with the biological samples we have collected from our submersibles and extensive sonar mapping all point to megafauna predators such as sharks and other large fish feeding on swarms of micro-nekton – small swimming creatures that are trapped against the subsea landscape at that depth,” explained Professor Lucy Woodall, Nekton Principal Scientist.

“We’ve observed sharks in shallower waters quite extensively in the Maldives before, but for the first time we’ve have been able to document an immense diversity of sharks in the deep sea,” explained Shafiya Naeem, Director General of the Maldives Marine Research Institute, which has partnered with Nekton on the expedition. 

Tiger sharks, six gill sharks, sand tiger sharks, dog fish, gulper sharks, scalloped hammerhead sharks, silky sharks and the very rare bramble shark have all been documented.

Marine ecosystems are defined by both the topography and ocean life. “This has all the hallmarks of a distinct new ecosystem,” explained Professor Alex Rogers, who has spent over 30 hours underwater in the mission’s submersibles observing ‘The Trapping Zone’ during the expedition. “The Trapping Zone is creating an oasis of life in the Maldives and it is highly likely to exist in other oceanic islands and also on the slopes of continents,” he added.

Whilst a trapping effect has been associated with the biodiversity hotspots on subsea mountains or seamounts, it has not previously been linked to the different geomorphology and biological parameters of oceanic islands, like the Maldives.

“Maldives, a coral atoll archipelagic nation is facing existential threat caused by human impacts and climate change. For our very survival as a nation, we ought to look for science-based solutions that help us to mitigate and adapt to the disastrous effects of climate change,” remarked Dr. Hussain Rasheed Hassan, Minister of Fisheries, Marine Resources and Agriculture. 

“The evolutionary history of this beautiful coral atoll nation is written as a record on the bedrock, deposits and the fauna of the deep. This Mission is shedding light on how we may use the science to survive as a nation.”

Analysis of the video and biological data is ongoing in the Maldives as well as in Nekton’s UK headquarters in Oxford and partner laboratories. The discovery could have important implications for other oceanic islands and the slopes of continents, sustainable fisheries management, the burial and storage of carbon and, ultimately, climate change mitigation.

“The discovery of ‘The Trapping Zone’ and the oasis of life in the depths surrounding the Maldives provides us with critical new knowledge that further supports our conservation commitments and sustainable ocean management, and almost certainly support fisheries and tourism,” said President Ibrahim Mohamed Solih.

Previous Nekton missions have led to major scientific breakthroughs. Its expedition to Bermuda in 2016 confirmed the discovery of the Rariphotic Zone, or rare light zone, a new ecosystem found at depths between 120 metres and 300 metres.

The Nekton Maldives Mission set sail on September 4 and was at sea for 34 days. The mission successfully undertook the first systematic survey and sampling of Maldivian waters from the surface to 1000 metre depths. Almost nothing was previously known about what lay below 30 metres.

The Mission by numbers

34 Days At sea

850 Nautical miles

294 Sq Km mapped (*Equivalent to total Maldives land mass)

25 Scientists

10 Nationalities

352 Deployments

186 Fish species recorded

201 Other organisms

554 Samples

Other discoveries from the Nekton Maldives Mission

The old beach line: Terracing and wave erosion at depths of 122m, 101m, 94m, 84m and 55m revealed evidence of different beach lines from sea level rise over the last 20,000 years since the end of the last glacial maximum.

Coral Reefs: The mission systematically mapped, surveyed, determined location, health, and resilience of coral reefs in six major locations to inform the Maldives Government’s conservation and management policies. The reefs are essential to life in the Maldives and help reduce the impacts from sea level rise and the increasing frequency and intensity of storms caused by climate change. Whilst the atolls are sinking due to subsidence of the seamounts, they are also growing because of the reef growing corals and other organisms. The ocean is literally growing these atolls, albeit slowly. But, in the face of an ever-warming planet, that is no guarantee of self regeneration.  

Deep-sea refuge: At depths from 120 metres to 300 metres, the team systematically surveyed the Rariphotic Zone for the first time in Maldives — home to corals, reefs and organisms, some of which are highly likely to be species new to science. These depths provide refuge to species such as the Indian Butterfly Fish that are caught in sunlit reefs for the aquarium trade as well as other species fleeing warmer, shallower water.

Images courtesy of Nekton