Cold-water corals in the canyons off south west England

3m Vibrocorer first launch.

Location map of the areas visited during this research campaign.

Multibeam bathymetry of the Explorer and Dangeard Canyons.

A team of scientists, including Heather Stewart of the BGS marine geology and operations team, have returned from a ten day research cruise in the Bay of Biscay to study the mini-mounds of the Dangeard-Explorer Canyons. Led by Prof David Van Rooij of the University of Ghent, Belgium, and working with scientists from the universities of Plymouth and Vigo (Spain) the group aims to understand:

  1. how old the mini-mounds are
  2. how the oceans have changed since the time they started to form to the present day
  3. how the mounds are formed
  4. the biology and ecology of the mound systems

The survey follows on from work in 2007 during which hundreds of mini-mound features were observed on the canyon interfluves (the area between the canyon heads) between the Dangeard and Explorer Canyons in the UK's South West Approaches.

Cold-water coral mounds

In 2007, the team only had time to run video cameras over three of these mound features, but were able to confirm that they were cold-water coral (CWC) mounds. The CWC mounds (also known as coral carbonate mounds) are structures found in the deep sea and formed from the progressive growth and decay of reef forming hard coral species. The mounds discovered in 2007 at the heads of Dangeard and Explorer are relatively small (hence the term 'mini-mounds') at only 50–150 m wide at their base, and up to 3 m in height, and occur in water depths between 260–410 m.

Since their discovery in 2007, the team have learned that four mini-mound provinces have been documented in this region, on the Porcupine Seabight upper slope (Irish margin), near the Dangeard-Explorer Canyon (Celtic margin), the Guilvinec Canyon (Armorican margin) and between the Ferrol and A Coruña Canyon (Cantabrian margin). All occur within a depth range of 200–550 m and all are of similar size. How these mini-mounds relate to the better known larger and deeper CWC mounds is currently unknown, but the working hypothesis is that the mini-mounds represent a start-up phase in larger mound formation.

June 2014 survey

The recent survey started on 13 June 2014 when the team left Porto in Portugal on board the Belgian research vessel R/V Belgica. Also on board were BGS engineers Iain Pheasant and Dave Wallis of BGS marine operations and engineering, who were responsible for developing the new, autonomous, BGS battery-operated vibrocorer used on this research cruise.

During the course of this research cruise, 34.96 m of core from 20 vibrocore sites were collected, the new video system was deployed 14 times and acquired nearly 10 hours of on-bottom footage, and additional seismic profiles were acquired to complement the data collected in 2007. That is a lot of data collected in only 10 days! The campaign ended on the 23 June 2014 when the R/V Belgica docked in its home port of Zeebrugge.

References

Davies, J S, Howell, K L, Stewart, H A, Guinan, J, and Golding, N.  2014.  Defining biological assemblages (biotopes) of conservation interest in the submarine canyons of the South West Approaches (offshore United Kingdom) for use in marine habitat mapping.  Deep-Sea Research II, Topical Studies in Oceanography, vol. 104, 208–229.  doi: 10.1016/j.dsr2.2014.02.001

Stewart, H A, Davis, J S, Guinan, J C, and Howell, K L.  2014.  The Dangeard and Explorer Canyons, South Western Approaches UK: Geology, sedimentology and newly discovered cold-water coral mini-mounds. Deep-Sea Research II, Topical Studies in Oceanography, vol. 104, 230–244. doi: 10.1016/j.dsr2.2013.08.018

Contact

Contact Heather Stewart or Iain Pheasant for further information.