Figure 9. The hexactinellid stalked sponge Hyalonema on the Hebrides continental slope, as habitat for a dark coloured epizootic zoanthid on its stem (photo credit Enterprise Oil & JM Roberts).
George Bligh Bank
None of the seven suspected records of deep-sea sponge aggregations on George Bligh Bank could be verified with high or even medium confidence (Table 2), due primarily to a lack of available density or habitat classification data. These potential aggregations are comprised mostly of the hexactinellid Aphrocallistes and Pheronema in waters 855–1115m deep, on coral framework and boulders interspersed by sandy patches (Narayanaswamy et al 2006). These are associated with other habitat-forming fauna such as Stichopathes, Lophelia and Keratoisis, which may represent overlap with cold-water coral reefs and coral gardens. In this respect, these potential aggregations appear similar to those verified with high confidence for Hatton Bank (Narayanaswamy et al 2006; Roberts et al 2008; Bullimore et al 2013). However density data combined with SIMPER analyses could provide a more robust verification.
Hatton-Rockall Basin
The Hatton-Rockall Basin is predicted to support dense aggregations of the bird’s nest sponge Pheronema carpenteri (Ross & Howell 2012). The verification exercise adopted a conservative approach using photographic and video survey data that supports this prediction, with four records of areas that contain such aggregations particularly in areas with polygonal fault gullies that were not predicted by habitat models. These occur in a narrow depth range in the basin from 1100–1161m water depth on mud, sand and lebenspurren-marked seabed (Figure 10).
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