New discovery of deep-water coral reefs in UK waters

Spectacular white glass sponge forming part of a newly discovered reef on Anton Dohrn Seamount. © JNCC

A BGS team has led an offshore survey to East Rockall Bank and Anton Dohrn Seamount in the north-east Atlantic Ocean discovering previously unknown deep-water cold-water coral reefs.

Five new coral reefs

A total of five new cold-water coral reefs were found using multibeam echosounder, high resolution video and digital photography. These particular biological communities seem to prefer clinging to the exposed geological rock formations of the flanks of the seamount and bank and the parasitic volcanic cones in deeper water adjacent to the larger features.

The team of eight scientists from the BGS, the Marine Institute, University of Plymouth and the Joint Nature Conservation Committee (JNCC) explored the sea floor of East Rockall Bank and Anton Dohrn Seamount using state of the art technology onboard the survey vessel MV Franklin. The survey was commissioned by the JNCC.

For more information and pictures see the JNCC 2009 survey BLOG .

Pristine condition

The majority of the reefs were pristine, appearing completely untouched by human activity. Following these discoveries, JNCC will consider recommending them for protection, in order to ensure that these rare and fragile habitats can be preserved into the future.

Ken Hitchen, of the BGS and Chief Scientist onboard the vessel, said, 'The dark, near-vertical volcanic cliff rocks of Rockall Bank and Anton Dohrn are the Scottish equivalent of the White Cliffs of Dover. We observed a mixture of sedimentary and volcanic rocks and hope to determine the relationship between rock types and the modern biological communities such as the thriving coral reefs.'

Neil Golding, JNCC’s Offshore Survey Manager said, 'At the beginning, when we were planning the survey, we really hoped that we would find evidence of these habitats. We’re delighted that we discovered such pristine examples, and I think the images we’ve captured show some of the amazing habitats that we have in our deep seas.'

Why conduct the survey?

We have some of the most amazing habitats in our deep seas. © JNCC

The main aim of the 2009 survey was to acquire high quality geological and biological data so the JNCC can assess the distribution and extent of EC Habitats Directive Annex I reef within both areas.

The JNCC commissioned the BGS to lead the survey and data interpretation working with deep-sea marine biologists from the University of Plymouth.

We contracted the Swedish survey vessel MV Franklin, owned by Marin Mätteknik AB, to acquire the offshore data.

Rockall Bank — summary of the geology

Colourful corals of one of the newly discovered reefs. © JNCC

Rockall Bank is the bathymetric expression of the underlying structural Rockall High. It’s only expression above sea level is the granitic Rockall Island which is 18m high and approximately 25m in diameter. The granite has been dated as being about 55 million years old.

The bulk of Rockall High comprises Early Proterozoic granite and high-grade metamorphic gneiss and granulite which crop out at the sea bed on the crest of the Bank.

Extensive volcanic rocks overlie the basement rocks on Rockall High. These are mainly Late Paleocene (57 million years old) to Early Eocene (53 million years old) basaltic lavas but less basic lavas and tuffs have also been recovered by sea-bed sampling and drilling. A composite, latest Paleocene to mid Eocene (57–53 million years old), eastward-prograding sediment wedge, drilled by BGS borehole 94/3 is present on the eastern margin the High.

A major latest Eocene unconformity is prominent on, and adjacent to, the eastern flank of Rockall High and is onlapped by fine-grained Oligocene to Recent sediments which blanket most of the Rockall Basin.

On the eastern flank of the Bank in water depths of between 140 and 500m a number of linear scarps/ridges have been identified which are wave cut terraces formed when sea level was lower. Some local erosion and the development of ‘moats’, adjacent to the eastern margin of the Bank, suggest strong bottom currents are active. The eastern flank of Rockall Bank descends into the Rockall Trough, which is a broad deep-water sea way between Rockall Bank and the shallow water shelves adjacent to the UK and Ireland.

Anton Dohrn — summary of the geology

Possible vesicular basalt at sea bed on the Anton Dohrn Seamount with encrusting biogenic organisms. © JNCC

Anton Dohrn Seamount is a former volcano centrally situated in the Rockall Trough and is roughly circular in shape. The slopes of the seamount are relatively steep and a moat-like depression surrounds the seamount, being slightly deeper around the northwest flank. The upper plateau surface has a diameter of approximately 40km and the highest point confirmed to date is about 650m below sea level.

Previous BGS research shows that the Anton Dohrn seamount comprises basalts at or near the sea bed on its crest with Eocene and post-Eocene sediments onlapping its flanks. A wedge of Eocene sediments is also present on the summit of the seamount. Evidence suggests that at least part of the volcanic activity at this location initiated about 70 million years ago and may have been episodic for some time afterwards.

Other projects and collaboration

Further Information

Contact David Long or Heather Stewart for further information about BGS habitat mapping work.