Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006) Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006)
Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006)
Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006)
Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006) Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006) Deep-sea grenadier fish, Nezumia sp. (© NOC 2006)
Deep-sea grenadier fish, Nezumia sp. (© NOCS 2006)
 

On rocky ground

A conventional view of the deep-sea floor is that it is a large expanse of apparently barren, flat mud - a habitat unlikely to excite much interest from outside the academic deep-sea biology community. The UK’s deep-water habitats, however, encompass a much broader range of seabed habitat types – a range of variation likely to rival that of any comparable deep-sea area.

Fine gravel habitat



This photograph (left) shows a fine gravel habitat from the foot of the Faroe Plateau / Faroe Bank Channel area - there is near uniform gravel cover at the surface that is carpeted with brittlestars, with occasional larger megabenthic animals (this image shows a featherstar and an anemone).


At the lower slope of the Faroe Plateau (photographs below), sediments are coarser still, with a further change in the associated fauna. The lack of fine sediments in this area is indicative of significant bottom water currents. Here there is continuous cover by gravel, cobbles and boulders which allows the development of larger sessile megabenthos such as sponges and soft corals.

Coarse sediments on lower slope of Faroe Plateau

Coarse sediments on lower slope of Faroe Plateau



Iceberg Ploughmark Zone

Coarse sediment habitats are not restricted to the deeper reaches of the Faroe-Shetland Channel area, and indeed are particularly widespread on the upper slope (at about 300-500m) in a more-or-less continuous band known as the “iceberg ploughmark zone” .During glacial periods, grounding icebergs gouged furrows in the seabed turning coarser sediments (cobbles and boulders) aside in an action similar to that of a plough harrow. The action of bottom currents has subsequently, at least partially, infilled the furrows with finer sediments.

Iceberg Ploughmark Zone habitat

Iceberg Ploughmark Zone habitat


These processes have acted to produce a complex, spatially heterogeneous, mosaic habitat that can repeatedly alternate from “piles of boulders” to open fine sediment areas. The coarse sediment (cobble and boulder) area can support diverse biological communities that exhibit significant local variation in their composition and abundance. The photographs (above) show this mosaic of habitats clearly with the photograph on the left showing the finer sediment areas with heart urchin feeding, and the photograph on the right illustrates the coarse sediment with a well-developed encrusting epifauna (sponges) and abundant populations of mobile megabenthos (here numerous feather-stars are shown).

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