Habitat point records from 1986-87 OPRU/MNCR Shetland, Foula and Fair Isle survey

The Shetland Islands are Britain's most northerly extremity and have a long, complex coastline with numerous islands, sheltered inlets and tide-swept channels. They lie at the confluence of the Atlantic Ocean and the North Sea and are separated from Faeroe and Norway by deep trenches. Deep pockets of water occur close inshore at several points around the islands. They are surrounded by clear oceanic water, but there is a high organic input into the voes from extensive peat bogs. Currently the only major pressures on the marine environment are from the Sullom Voe Oil Terminal, salmon farming and fishing but there is no evidence to suggest that any of these has a long-term effect on the marine communities. Previous marine studies in Shetland have been reviewed in Hiscock, 1986. The present survey visited the islands in August 1987 with the aim of filling in the gaps in the marine biological knowledge of Shetland. Particular emphasis was put on sediment communities, open rocky coasts and outlying islands. Diving and intertidal surveys of the epibiota were supplemented with samples collected for infaunal analysis by coring on sediment shores, a diver-operated suction sampler and dredging. Photography was used to illustrate habitats, communities and species. A total of 153 sites was surveyed, comprising 132 sublittoral sites, 36 littoral sites and 21 dredge hauls. The infauna was analysed from 13 dredge samples, 7 suction samples and 5 intertidal core samples. Habitats and communities were classified under 46 categories, covering a wide range of environmental conditions and substrata. The islands were also divided into 10 convenient regions with an outline description of the habitats present in each. It is apparent that the habitats are widely distributed throughout the archipelago with no latitudinal or regional gradients. The major environment gradient identified is one of wave exposure, with habitats ranging from extremely sheltered shallow obs to very exposed deep bedrock. Species diversity is low in most habitats apart from the infauna of slightly muddy gravel and stable sand which both proved very rich. Zonation patterns were observed to be unusual at very exposed sites; the normal intertidal zones are elevated by several metres, apparently the result of a combination of wave surge and damp atmospheric conditions, and the subtidal zones extend to considerable depths. Kelp plants are present to at least 32 m and encrusting coralline algae dominate to over 50 m. A number of other significant features have also been listed in the discussion. Three factors are considered of particular importance in determining zonation patterns; exposure to wave action, water clarity and grazing by the urchin Echinus esculentus. The latter occurs in considerable numbers at moderately exposed sites where it apparently controls the species composition and lower limits of the infralittoral. Availability of substratum and scour are considered of secondary importance. Specific sites are used as illustrations of the above. The sublittoral zonation of very exposed sites was observed to be more complex than normally encountered and this has resulted in some inconsistances in recording between individual biologists. Monospecific stands of both plants and animal are noted in several habitats. The flora and fauna are strongly northern in character; species of interest because of their geographic distribution are discussed. Several species were recorded for the first time in Shetland and others were rare or unusual. The results from this survey have been compared briefly with previous studies in Shetland and with other areas of the British Isles. A direct comparison of sediment communities proved difficult due to the variability of the data but other habitats and communities compared well. This survey has considerably extended and amplified the habitat descriptions of previous workers. A complete assessment of nature conservation importance will be carried out in the full conservation review, but 11 sites or habitats are noted here as being of particular interest. Records currently considered sensitive have been removed from this dataset.

Organization: Joint Nature Conservation Committee