World’s largest deep-sea coral reef system discovered in Atlantic ocean (2024)

A collaborative effort between organisations has resulted in the discovery of an expanse of deep, cold-water coral similar in size to the US State of Vermont

By Mark 'Crowley' Russell

The most expansive cold-water coral reef habitat so far known to science has been discovered off the southeastern United States, the result of a coordinated collaboration between scientific organisations to map an area known as the Blake Plateau.

The coral ‘mounds’ were first discovered in the 1960s, located approximately 100 miles (161km) offshore, and have been researched in the intervening years to determine their importance as habitats and implement protections for the area.

In a new study documenting the mapping of the Blake Plateau, teams of scientists from a variety of institutions, conducted operations across an area stretching from Miami in Florida, to Charleston in South Carolina. A total of 31 sonar mapping surveys conducted between 2003 and 2021 – the largest areas of which were carried out by NOAA Ocean Exploration onboard the Okeanos Explorer research vessel – were spliced together to create one giant map of an area some 310 miles (500km) in length, and up to 68 miles (110km) wide, ranging from between 500m to 1000m of depth.

Further data from 23 submersible dives undertaken across the Blake Plateau was used to supplement the sonar scans, with the final result containing a tally of 83,908 individual ‘coral mound peak features’, providing an estimate into the approximate number of reef mounds contained within the plateau’s boundaries.

One area, nicknamed the ‘Million Mounds’ for the density of the coral it contains, covers an area 158 miles (254km) long by 26 miles (42km) all by itself, although the study’s author jokes that the name is something of a misnomer, as there are ‘only’ 35,789 possible coral mounds contained within it.

The deep, cold-water coral species contained within the reef system have been identified as Desmophyllum pertusum(previously namedLophelia pertusa) – the most common reef-building coral in the north Atlantic – and other species from the Enallopsammia,Madrepora,Oculina, andSolenosmilia genera. All are scleractinian (stony), branching corals, and all are slow to grow, with samples of Desmophyllum calculated to have a growth rate of between 3.2mm to 33mm per year.

The coral is very old, with dead fragments dated between 5,000 and 44,000 years old, meaning it has survived through a great deal of geological and climatic change – including the last glacial maximum – but such a slow growth rate implies that its recovery would be very slow, were it to be damaged by industrial activity impacting the sea floor.

As deep, cold-water coral does not contain the symbiotic, photosynthetic zooxanthellae dinoflagellates which provide shallow-water coral with nutrients and colour, it is much less affected by temperature changes and requires no sunlight for survival, instead feeding on organic matter drifting through the water.

The scientists believe that this process is driven by the Gulf Stream, the deep-water current that flows from the Gulf of Mexico across the Atlantic, and provides an insight into how similar currents across the globe may affect other deep-water environments, previously thought to be barren and relatively lifeless.

‘For years we thought much of the Blake Plateau was sparsely inhabited, soft sediment, but after more than 10 years of systematic mapping and exploration, we have revealed one of the largest deep-sea coral reef habitats found to date anywhere in the world,’ said Kasey Cantwell, operations chief for NOAA Ocean Exploration.

‘Past studies have highlighted some coral in the region, particularly closer to the coast and in shallower waters, but until we had a complete map of the region, we didn’t know how extensive this habitat was, nor how many of these coral mounds were connected. This discovery highlights the importance of exploring our deepwater backyard and the power of interagency collaboration and public-private partnerships.’

With at least ten different organisations involved – albeit four of them part of NOAA – the mapping project highlights not only how little is known about the deep ocean environment – which will be of critical importance to the discussion surrounding future mining of the sea floor – but how scientific collaboration can work to greatly enhance our understanding of an environment that is very close by, but extremely challenging to explore.

“This strategic multiyear and multi-agency effort to systematically map and characterize the stunning coral ecosystem right on the doorstep of the U.S. East Coast is a perfect example of what we can accomplish when we pool resources and focus on exploring the approximately 50 per cent of US marine waters that are still unmapped,’ said Derek Sowers, PhD, Mapping Operations Manager for theOcean Exploration Trustand lead author of the study.

‘Approximately 75 per cent of the global ocean is still unmapped in any kind of detail, but many organizations are working to change that. This study provides a methodology aimed at interpreting mapping data over large ocean regions for insights into seafloor habitats and advancing standardized approaches to classifying them to support ecosystem-based management and conservation efforts.’

The study, ‘Mapping and Geomorphic Characterization of the Vast Cold-Water Coral Mounds of the Blake Plateau’ by Derek Sowers, et al, is published in the open-access journal Geomatics.