Habitat point records from 1982 OPRU Jura and Islay sublittoral survey

1. This report describes the results of surveys of nearshore sublittoral habitats and communities around the Hebridean islands of Jura and Islay in June and July 1982. 2. Sites were selected to ensure that as wide a range of habitats as possible was surveyed and sampled in the two weeks of survey. Survey was carried out using diving and systematic records were made of the habitats present and of the abundance of conspicuous species in those habitats. Photographs were taken to illustrate the communities and species present. 3. Fifty sites including about 110 stations were surveyed along the 350 km of coastline within the survey area. The sites were distributed all around the islands and included locations from sites that were exposed to extremely strong water movements to those sheltered within sea lochs. Twenty-three different habitats and associated communities were distinguished and the occurrence of 540 species described as a result of the survey. 4. The upper infralittoral (dominated by Laminaria hyperborea) extended to 15 to 17 m on the open coast. The extent of the infralittoral (dominated by foliose algae) appeared to be only a little deeper but records were difficult to obtain because of the small amount of sublittoral bedrock present in deep water. For the same reason, records of the extent of the upper circalittoral (where foliose algae are still present) were not confidently obtained although spots of encrusting algae and one small piece of a foliose alga were collected at 36 to 38 m in the Sound of Jura. 5. The main contrasts in community types were between the bedrock sites extremely exposed to water movement and those extremely sheltered from water movement with a very large number of sites with basically similar communities present in between. Some of the communities were 'classic' exposed coast, tidal sound, rapids or sea loch communities characterised by species not encountered or rare elsewhere. Several habitats were searched for but not found including deep bedrock habitats at open-coast sites sheltered from strong wave action and in Loch Tarbert sheltered from both wave action streams. The algal flora was rich at many sites. However, animal communities were not, in general, very rich, and this was considered at least partly due to the domination of rocks by Balanus crenatus, high densities of Echinus esculentus at some locations, and to the absence of circalittoral bedrock at most sites. 6. Several species, mostly algae, considered of scientific interest in their presence on Jura and Islay, are listed. 7. Compared with other sites surveyed on the west coast of Scotland, most of the communities encountered on Jura and Islay were similar to those described elsewhere. However, the communities on rock at locations exposed to very strong water movement (in the Gulf of Corryvreckan, off Orsay and in the Sound of Islay) have not been described elsewhere. The communities present in Loch Indaal were also unusual and the Zostera marina community was particularly rich. The communities present in Loch Tarbert appeared less rich than some others described in sea lochs or very sheltered areas. Only a very few records of southern or western animal species were made compared to some other areas. 8. Conclusions regarding the conservation importance of sites around Jura and Islay point to the high scientific interest of sites on the south-west coast of Islay, at the Mull of Oa, in the Sound of Islay, in the Gulf of Corryvrecken and in Loch Indaal. Records currently considered sensitive have been removed from this dataset.

Organization: Joint Nature Conservation Committee