The Isles of Scilly Biodiversity Audit 2008 - Cornwall Wildlife Trust

Rocky reef with jewel anemones Corynactis vividis. Photo: Malcolm NimmoCoral on slightly tideswept moderately exposedcircalittoral rock’ as a highly sensitive habitat.Some areas of the BAP habitat ‘Fragile sponge andanthozoan communities on subtidal rock’ would fallinto this category. According to MarLIN this habitatis particularly sensitive to substratum loss, changesin salinity, physical disturbance, extraction and otherstressors.Subtidal rocky reefs are recognized as importantin the EU Habitats Directive and this has led to thedesignation of Special Areas of Conservation in theUK based on the presence of reefs. In the Isles ofScilly, reefs are one of three key habitats which havetriggered the area’s selection as an SAC (the other twobeing ‘mudflats and sandflats not covered by water atlow tide’ and ‘sandbanks which are slightly coveredby seawater all the time’).Trends and IssuesResearchSeasearch volunteer divers have been conductingannual subtidal surveys since 2004. Many of the sitessurveyed are areas of rocky reef which support thishabitat. Some reef sites have been surveyed repeatedlyat yearly intervals. Surveyors record species presentand other features of the habitat with abundanceestimates for each species.The great wealth of knowledge of the local diveoperators should be recorded for scientific andeducational use. Photographic records collected overyears of diving need to be analysed and archived.Visiting divers should be urged to participate inmarine life recording schemes.Fishing impactsAlthough scallop dredging is restricted within fourmiles of the islands there is evidence that damagehas occurred to fragile sponge and anthozoancommunities as a result of this activity in the past.Fragile sponges are easily damaged by potting whichoccurs in these areas.SedimentationExcess sediment can be suspended in the watercolumn as a result of coastal development. Depositionof this silt can easily damage fragile spongecommunities.Isles of Scilly biodiversity audit Page 59