European Ocean Biodiversity Information System

"This dataset contains information on infaunal abundance & biomass & associated habitat biotope from sediment grabs & video tows carried out off the North Antirm coast. This survey was carried out as a baseline survey of the benthos in an area that had been proposed as an offshore windfarm. The survey area contained the proposed tidal site and potential routes for cables, 1 leading from the tidal site to Ballycastle (historic route) or leading to Drumnakill Point (northern edge of Murlough Bay) The analysis of this dataset also addressed the conservation important of the benthic communities identified along with their potential sensitivity to certain physical factors by referring to the Northern Ireland Priority Species List as well as information from the Marine Life Information Network for Britain & Ireland (MarLIN). The methodologies for both the video tows & grab samples are detailed below. Video survey & Analysis • The video system used in this survey was an Osprey camera attached to an epibenthic sledge which was also fitted with a Go-Pro camera. This provided a field of view of 1m2 (oblique) for video analysis. • The epibenthic sledge was chosen over the drop frame camera as it is a more stable platform for camera footage, especially in stronger currents (current speeds can reach up to 3ms-1 at the survey site). The sledge was towed between the sites as they were relatively close together & to optimise efficiency. • A GPS overlay was recorded on the osprey to allow the position on the seabed to be estimates. Notes were taken of the ship’s position as well. • Due to site hydrodynamics, the video footage had poor visibility and was much faster than ideal. Epifauna of ~3cm and larger were identified. Biotopes were classified according to the UK MNCR classification. Benthic grabs & analysis • To obtain sediment samples for infaunal analysis both a pipe dredge & a day grab were used in attempt to obtain more sediment. • A 0.1m2 day grab was used to take a sample of the sediment & associated infaunal communities. • When the sample reaches the deck, a 250ml sample is taken for PSA and a further 25ml is taken for C & N analysis. The rest of the sample is carefully sieved to reveal any infauna. • Fixed Formalin (4% buffered formaldehyde) is added to the remains of the sample and these are placed in labelled buckets. • The samples are sent to accredited taxonomic laboratories were they are identified to as high a level as possible and weighed. • Due to the presence of large cobbles in many regions the jaws became blocked of the day grab which meant that a large amount of sediment was lost by the time the grab reached the ship. • Only 4 sediment PSA were retained for analysis and 24 samples were retained for infaunal analysis (abundance & biomass data). "