Seafloor biotope analysis of the deep waters of the SEA4 region of Scotland's seas 2012

Abstract

This project aimed to identify, map and describe deep-water seafloor biotopes in the SEA4 area of Scotland’s seas. The area comprises parts of the Faroe Bank and Faroe-Shetland Channels and the Norwegian Basin located to the west and to the north of Shetland. By simple definition, a biotope is a uniform environment supporting a uniform biological community. A more practical definition would be 'a spatially coherent area of relatively homogeneous environmental characteristics with a relatively homogeneous fauna'.

For the present study, the fauna assessed was the macrobenthos – the invertebrate fauna of marine sediments retained when passed through a sieve of 0.5 mm mesh. The primary environmental characteristics assessed were (i) water depth, thought to be among the top three environmental gradients on the planet; (ii) seabed sediment type, a key control on the distribution of the macrobenthos; and (iii) hydrography, the oceanography of the SEA4 area is unusual, dynamic and extreme, and thought to be a major control on the distribution of biological communities in the region. The purpose of the biotope analysis is to contribute evidence-based information to the environmental management of Scotland’s deep-water areas.

This work draws very heavily on a series of five dedicated environmental surveys carried out in the SEA4 area between 1996 and 2002. The first two (1996 and 1998) were undertaken on behalf of AFEN (Atlantic Frontier Environmental Network, a consortium of oil companies, UK government environmental advisers (JNCC, FRS) and the UK Department for Trade and Industry (now the Department of Energy & Climate Change, DECC). A further three surveys (1999, 2000, 2002) were carried out as part of DECC’s Strategic Environmental Assessment (SEA) process, specifically areas SEA1 and SEA4. Note that the SEA1 area is generally no longer referred to, it was a fringe area along the UK-Faroe boundary that is effectively now part of the SEA4 area.

At the time, these surveys were rather unusual in that they incorporated extensive seafloor mapping, particularly sidescan sonar. These geophysical mapping efforts are not reviewed here, but were crucial to the design of the field sampling programmes on which the present work depends.