Life at the Romanche Fracture Zone

The Romanche Fracture Zone 
The Romanche Fracture Zone is a massive area in the equatorial Atlantic that bisects the Mid-Atlantic Ridge. It contains the deepest part of the Mid-Atlantic Ridge: Vema Deep, at a depth of 7,856 meters. 

The fracture zone includes a transform fault, a place where two tectonic plates move in opposite directions and grind against each other rather than collide or diverge. Whereas most deep water is constrained by the underwater mountains of the Mid-Atlantic Ridge, this 950-km-long rift is a conduit for deep-sea currents, facilitating mixing between the eastern and western Atlantic basins. Its varied topography includes valleys, ridges, and scarps that could host a range of deep-sea ecosystems such as coral and sponge gardens and hydrothermal vents. 

Beyond its topography, the region’s physical oceanography sustains deep-ocean dwellers. Each spring, eastern equatorial upwelling occurs in the Atlantic. During this time, the trade winds push surface waters away from the equator, which are then replaced by deeper, nutrient-rich waters rising to the surface. These waters fuel phytoplankton blooms, which feed complex oceanic food webs including fish, jellies, and cetaceans. Organic matter — created by animals living and dying in the water column — sinks, providing food to the deep sea. 

Little research has examined life at the Romanche Fracture Zone, and while the region has prime conditions for supporting biodiversity, previous sampling let scientists to believe that few ecosystems exist here. 

Biodiversity Sampling Gaps 
In the Romanche Fracture Zone, net sampling has revealed little, leading scientists to believe that almost no life existed there. And yet, the topography, currents, and equatorial upwelling along the Romanche Fracture Zone make it an ideal environment for deep-sea life and vulnerable marine ecosystems (VMEs), which are classified based on specific criteria that identify areas as extremely fragile and unlikely to recover from human activities. 

The deep sea is the largest ecosystem on our planet, comprising 66% of the globe. And yet, it is also the least studied and observed. Only 28.7% of the seafloor has been mapped, and scientists estimate that millions of marine animals remain undiscovered. 

Scientists estimate that less than 3,000 square kilometers of the deep sea have been visually studied; that’s roughly the size of the island State of Samoa in Polynesia. Many of the places that have been visualized exist within the waters of a handful of countries. For the Mid-Atlantic Ridge, most visual data comes from the North Atlantic, and little to no data exists in the Romanche Fracture Zone, creating a massive sampling gap. 

Biodiversity Beyond National Jurisdiction 
Biodiversity Beyond National Jurisdiction, also known as the High Seas Treaty, was ratified on 17 January 2026. The treaty expands the United Nations Convention on the Law of the Sea, which established guidelines for regulating ocean use beyond national boundaries. 

The 1982 Law of the Sea established international regulations for activities on the high seas; however, it provided no mechanism to establish marine protected areas, conduct environmental impact assessments, or determine who controls genetic resources in areas beyond national boundaries. The Biodiversity Beyond National Jurisdiction agreement closes these missing gaps and establishes protocols for all three areas, as well as guidelines for sharing marine technology and exploration opportunities with developing nations. 

The Romanche Fracture Zone lies in the high seas, and no single country controls the territory. The data collected during this expedition will help inform management of the ecosystems examined in the Romanche Fracture Zone under BBNJ. 

The expedition is endorsed by the Brazilian Deep Sea Program, launched by the National Institute for Ocean Research, and it is part of the UN Ocean Decade-endorsed Challenger 150 Program.