Deepwater diaries

Surveying sites in the English Channel

 

JNCC marine staff joined partners from the Centre for Environment, Fisheries and Aquaculture Science (Cefas) for a two-week survey of the Wight-Barfleur Reef candidate Special Area of Conservation (cSAC) and Bassurelle Sandbank Site of Community Importance (SCI). The main aim of the survey was to gather additional evidence to aid the development of management advice for these two sites.

 

An Elephant Hide sponge, some green Jewel Anemones and an Edible Crab cling to the rocks at Wight-Barfleur Reef ©JNCC-Cefas

The expedition set sail aboard the RV Cefas Endeavour from Portland on 18 March. The first site visited was the Wight-Barfleur Reef cSAC. This is a huge 1,373km2 area of bedrock and stony reef situated in the English Channel, between St Catherine’s Point on the Isle of Wight and Barfleur Point in northern France. The reef areas support a diverse range of fauna, including a wide variety of sponges, anemones and soft coral.

 

The survey began with the collection of acoustic data from the first of five ‘nested’ boxes within the site, each similar in size to Lake Windermere. Multibeam and sidescan sonar, which use sound to detect depth and features of the seafloor, were deployed to build up a picture of the type of seabed habitats likely to be present beneath the waves. In what was hoped wasn’t a portentous turn of events, the group unexpectedly discovered a shipwreck within the first few hours.

 

Next up was a ‘groundtruthing’ campaign using specialist equipment to allow a close up look at the habitats, animals and types of sediment at approximately 120 ‘stations’ across the site. The underwater ‘drop camera’ was lowered off the side of the ship and controlled by a joystick-wielding member of the deck crew. The operator skilfully hovered the camera above the seabed, while video footage and still images were taken for later analysis of species and habitats. A Hamon grab (a metal scoop mounted on a pyramidal frame that is hoisted over the side of the ship) was used to collect samples of sediment, along with any creatures burrowed within, from the seabed. These samples help complete the picture of the complex ecosystem that exists at the bottom of the sea.

 

"Moderate" conditions off the stern ©Neil Golding_JNCCAfter eight days of round-the-clock work, through some challenging sea conditions, the team successfully completed the planned groundtruthing and acoustics with the addition of some further stations. The team said au revoir to Wight-Barfleur and bonjour to Bassurelle! 

 

Bassurelle Sandbank SCI is an area streaked with sandwaves and megaripples, which harbours biological communities containing polychaete worms, sand eels and weever fish. The site is located in the Dover Strait and straddles the traffic separation zone - a central reservation that divides the two busy shipping lanes of the English Channel. The site is much smaller than Wight-Barfleur (roughly 1/20th of the size) and the sample stations were much closer together (approximately 1 km apart) than they had been at Wight-Barfleur (where they were approximately 5 km apart).

 

In addition to being smaller than Wight-Barfleur Reef, Bassurelle Sandbank is also much shallower - so much so that there is an area in the centre of the site that was dubbed the "Bassurelle Triangle".  

 

The RV Cefas Endeavour arrived back in Lowestoft on Easter Monday after an overnight steam home. Once the data has been analysed and interpreted, the evidence will be handed over the SAC management advice team who are leading JNCC’s advice to Government on management measures for offshore Special Areas of Conservation.

 

 

Contact File

 

Mike Nelson & Joey O'Connor

Survey Scientists

Tel: +44 (0) 1733 866816/

        +44 (0) 1224 266598

 

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