The survey was carried out in July 1983 to obtain information on the communities present in the extensive shallow sublittoral sediments of the Isles of Scilly in relation to the proposals to establish a marine nature reserve there. Sites were chosen to be representative of different depths and exposures and also fairly evenly spaced throughout the survey area. A total of 9 sites were sampled. Sampling was achieved by means of a diver-operated suction sampler. Two 0.1 m/2 samples were obtained from each site for biological analysis and also one core sample for sediment analysis. All animals present in the samples were identified and the individuals of each taxon counted although no quantitative analyses of the data were attempted. Numbers of taxa obtained in each 0.2 m/2 area of sea bed ranged from 31 in homogeneous sand sediment to 104 from mixed gravel. Sediments around the Isles of Scilly were found to support a diverse fauna, especially at the deeper sites. The large variation in habitat conditions resulted in a mosaic of community types, some of which resembled communities previously described from other areas. Sediment particle size analyses were carried out for 6 of the 9 sites. Sediments were predominantly coarse gravel with small quantities of fine sand associated organic material. Many of the species present in the Isles of Scilly were characteristic of coarse sediments although areas of fine sand sediment were also present. The extensive beds of Zostera marina were of interest as they provided a particular habitat for a variety of species. The present survey was sufficient to describe only a limited number of sites. However, the results confirm the high diversity of communities present in the Isles of Scilly and demonstrate the very wide variety of rich and unusual shallow sedimentary habitats present within a small area.
