The report summarises fieldwork undertaken in 1985 and 1986 in the Isles of Scilly. Photographic monitoring of communities on circalittoral bedrock was continued and changes in populations of Mediterranean-Atlantic species of high nature conservation importance recorded. The density, size and extent of Zostera plants at 2 locations within the island group was studied and the report incorporates an account of the algal flora associated with Zostera at these sites in 1985. The dominant component species of the circalittoral communities remained little changed between 1984 and 1986. Little apparent growth was noted in individual cup corals, soft corals and branching sponges. No recruitment to the cup coral populations was observed, although a few cup corals and sponges were lost from the monitoring sites. (Some of these losses may be attributable to damage during the monitoring exercise). These results are very similar to those obtained for the monitoring studies being undertaken at similar sites at Lundy and Skomer. The study of Zostera marina has demonstrated the dynamic nature of these sea-grass beds which show marked movement of the vegetated areas from year to year and variation in plant density and average leaf length.
