This report is a contribution to the Strategic Environmental Assessment (SEA6) conducted by the Department of Trade and Industry (now Department of Energy and Climate Change). This report provides a synthesis of current knowledge of the benthic communities and seabed habitats in the SEA6 area. The area is a predominantly shallow, well flushed, fully saline, partially enclosed, temperate sea. The seabed is predominantly sedimentary, ranging between mud and cobbles but consisting mainly of sand. The coastal fringe hosts excellent examples of a broad range of habitat types including exposed rocky shores, sheltered rias, highly productive sand flats, estuaries and areas exposed to rapid tidal currents. This diverse range of habitats supports a broad range of animals and plants with numerous species.

The focus of the report is on dominant species and broad descriptions of community types (biotopes). The benthos associated with the littoral (intertidal) and sublittoral zones from the Mull of Kintyre and the Northern Irish coast in the north to Milford Haven, Pembrokeshire in the south are discussed. This area includes the important industrial estuaries of Morecambe, Liverpool and the Mersey, together with a number of minor estuaries, and the major islands of Anglesey and the Isle of Man. The deep water (depth greater than 50 m) and offshore areas are also discussed.

Where appropriate, details of rare or unusual species are included, together with the threat offered by oil and gas related activities. Other major human activities in the SEA6 area that are currently affecting the benthos are also discussed.