New technology explores UK deep-waters

 

Survey work underpins JNCC’s role in developing a network of Marine Protected Areas (MPAs) in UK waters. Working alongside colleagues from the National Oceanography Centre (NOC), JNCC staff surveyed the seabed at three locations recently - Darwin Mounds candidate Special Area of Conservation (cSAC), Hatton-Rockall Basin and North West Rockall Bank cSAC – as part of a five week study aboard the RRS James Cook.

 

Fionnuala McBreen and Sophie Elliott from JNCC’s Marine Protected Areas team were on board to collect data to support these significant sites....

 

The first survey area was located in the Darwin Mounds cSAC (2008) which has been closed to fisheries since August 2003. The area was designated as a cSAC to protect its unusual mounds supporting cold water coral reefs (e.g. Lophelia). The mounds were first discovered by scientists from NOC in 1998. Vessel Monitoring Systems (VMS) data show that the area was heavily fished before the fisheries closure was implemented.

 

The seabed was mapped using the ship’s Multibeam system and a Sub Bottom Profiler to identify areas for more detailed surveillance. Multibeam data is used to collect depth and backscatter information, giving an indication of the type of seabed – rocky, gravelly, sandy or muddy. The Sub Bottom Profilers indicate the depth of sediment, past and present geological processes or areas where fluid is currently escaping.

 

Autosub6000 © JNCCMore detailed seabed mapping involved the UK’s first deep-water scientific AUV (Autonomous Underwater Vehicle) Autosub6000 which can be sent on up to 24 hour missions to map the floor independently of the ship.

 

Samples were taken using a megacore, boxcore, piston core and a Remotely Operated Vehicle (ROV) - the longest piston core used on the survey was 13.5 metres long. The ROV provided video footage and detailed still images of the two areas studied within the Darwin Mounds (Eastern and Western Mounds).

 

Autosub6000 is fully equipped with: EM2000 multibeam; dual frequency sidescan sonar; Acoustic Doppler Current Profiler

 (ADCP); Conductivity Temperature and Depth Sensor (CTD); Eh (redox potential) sensor; stills camera; inertial navigation

system; and a GPS for positioning when at the surface.

 

Hatton Rockall Basin has polygonal faults, a similar shape to mud cracks that develop at the bottom of a dried-out pool. Several different species of glass sponges (Hexactinelids) were seen, including aggregations of Pheronema carpenteri found close to an unusual rocky outcrop holding a host of deep sea creatures, such as the wolfish and numerous octopuses.

 

The next stop was Rockall Bank where it was planned to survey inside and outside of two fishery closure areas: Rockall

Fish species in the water column © Seafish

Haddock Box and NW Rockall Bank cSAC (2010) which is also a demersal fisheries1 closure (2005) . The Autosub6000 and ROV dives in the Haddock Box were successful but as the seabed was too hard to obtain Megacore, piston core or box core samples we moved to the NW Rockall Bank cSAC earlier than planned. Within the Haddock box some juvenile Haddock (Melanogrammus aeglefinus) were seen alongside many Urchins (Echinus). The areas inside and outside were mapped using both the ship’s multibeam and Autosub’s high resolution side scan data which provided clear images of iceberg ploughmarks. This data was supplemented with ROV dives which found bushes of cold water coral (Lopheilia and Madrepora reefs) teeming with squat lobsters, a variety of sponges, sea stars, juvenile and adult fish, urchins and anemones. Outside the fisheries closure boundary, fresh and older trawl tracks were identified with large expanses of decimated coral reefs.

 

 

1. Demersal fisheries target fish  such as cod, haddock or whiting, which live on or near the seabed

 

 

Contact File

 

Fionnuala McBreen, Marine Protected Sites Monitoring Officer

Sophie Elliott, Marine Fisheries Adviser

Tel: +44 (0)1733 866930/866927

 

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