Figure 2. Deep-sea sponge aggregation sub-types in UK waters symbolised by confidence
Faroe Bank Channel, Faroe Plateau, Faroe-Shetland Channel, north of Shetland
Verified high confidence deep-sea sponge aggregation records were already held in GeMS from previous habitat analyses and predictive habitat models (Axelsson, 2003; Howell et al 2010, 2011), which the present verification exercise supported (Table 2). This confirmed that sponge grounds occur in the Faroe-Shetland Channel, including the West Shetland Slope (Bett, 2001) as well as in an area north of Shetland (Bett, 2001). These occur in a particularly narrow ‘sponge belt’ centered around the 500m bathymetric contour and are associated with iceberg ploughmarks on mixed gravelly sediments and occasional boulders in waters that range in temperate from about -2 to 8°C. Densities of sponges in the sponge belt ranged from 0.001–0.818 sponges/m2 (Axelsson, 2003).
These aggregations in the Faroe-Shetland Channel, including the West Shetland Slope, conform to the description of boreal ostur (Klitgaard & Tendal, 2004; Figure 3): a mix of primarily large structural geodiid sponges such as Geodia barretti, G. macandrewi, G. atlantica, and G. phlegraei (synonym for Isops phlegraei) as well as numerous other lobose and encrusting species.
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