UK Atlantic Margin Environmental Survey: Introduction and overview of bathyal benthic ecology

• Published in: Continental shelf research 2001-05, Vol.21 (8), p.917-956
• Main Author: Bett, Brian J
• Format: Article
• Language: English
• Subjects: 10°W–01°E; 56–63°N; Bathyal; Corals; Ecology; Faroe–Shetland Channel; Macrobenthos; Marine; Megabenthos; Norwegian Basin; Phytodetritus; Rockall Trough; UK Atlantic Margin; Xenophyophores
• ISSN: 0278-4343; 1873-6955
• DOI: 10.1016/S0278-4343(00)00119-9

The recent expansion of the Oil and Gas Industry in to the deep waters of the UK Atlantic Frontier prompted the industry and its regulator to reappraise the needs and means of environmental monitoring. In concert, deep-sea academics, specialist contractors, the regulator and the Industry, through the Atlantic Frontier Environmental Network (AFEN), devised and implemented a large-scale environmental survey of the deep waters to the north and west of Scotland. The AFEN-funded survey was carried out during the summers of 1996 and 1998, and involved two steps; an initial sidescan sonar mapping of the survey areas, followed up with direct seabed investigations by coring and photography. This contribution deals with the latter step. Seabed samples were collected to assess sediment type, organic content, heavy metals, hydrocarbons and macrobenthos. Photographic and video observations were employed to provide both ‘routine’ seabed assessments and to investigate particular sidescan features of note. Although essentially intended as a ‘baseline’ environmental survey, anthropogenic impacts are already evident throughout the areas surveyed. Indications of the effects of deep-sea trawling were frequently encountered (seabed trawl marks and areas of disturbed sediments), being present in almost all of the areas studied and extending to water depths in excess of 1000 m. Evidence of localised contamination of the seabed by drilling muds was also detected, though background hydrocarbon contamination is predominantly of terrestrial origin or derived from shipping. The benthic ecology of the UK Atlantic Margin is dominated by the marked differences in the hydrography of the Faroe–Shetland Channel (FSC) and the Rockall Trough (RT). Comparatively warm North Atlantic Water is common to both areas; however, in the FSC, cold (subzero) waters occupy the deeper parts of the channel (>600 m). The extreme thermal gradient present on the West Shetland Slope has a substantial influence on the distribution and diversity of the macrobenthos. While there is continuous variation in the fauna with depth, warm and cold water faunas are nonetheless quite distinct. The boundary region, centred on 400 m water depth, may be best characterised as an ecotone, having a mixed warm and cold water fauna with a distinctly enhanced diversity. The Wyville–Thomson Ridge largely prevents the cold waters of the deep FSC from entering the RT (they certainly do not influence the areas of the Malin/Hebrides Sl