The Isles of Scilly Biodiversity Audit 2008 - Cornwall Wildlife Trust

die-off occurred. The timid burrowing anemoneEdwardsia timida, another BAP species, may have alsodeclined for this reason because it requires stablesediment in which to burrow. The only records of thisspecies are from the 1980s and it is not known whetherit still occurs in the Isles of Scilly.A number of nationally rare and scarce cnidarians arefound in Scilly, these include Weymouth carpet coralHoplangia durotrix, a nationally rare species has beenrecorded at Gap Point in the 1980s by 2 recorders.Two hydroids, Laomedea angulata and Aglaopheniakirchenpaueri (NBN Gateway), yellow cluster anemoneParazoanthus axinellae, latticed corklet Cataphelliabrodricii, the soft coral Alcyonium hibernicum, theglaucus pimplet Anthopleura thallia are all nationallyscarce and found in the Isles of Scilly (Barne et al,1996).Some southern species of cnidarian are found in theIsles of Scilly such as the trumpet anemone Aiptasiamutabilis (English Nature, 2000) which is found atseveral sites there but is nationally scarce and littlerecorded elsewhere in the UK.Apolemia uvaria, a string jelly was recorded in largenumbers off the southwest of England including Scillyin the autumn of 2007. This species is planktonic andits sudden appearance in these waters may be relatedto changes in sea surface temperatures associated withclimate change although no solid conclusions can yetbe drawn with so little data (K.Hiscock, pers. comm.,P.Gainey, pers. comm.).Trends and IssuesSunset cup coral Leptopsammia pruvoti is classified asvery highly sensitive to substratum loss, smothering,dessication, emergence, salinity, physical disturbanceand displacement as well as being highly sensitive tocertain other stressors. Its larvae are short-lived andtend to settle very near the parent therefore there canbe problems with larval supply once adult coloniesare removed from an area and there may be no furtherrecruitment.ResearchA checklist of the Cnidaria and Ctenophora of Scillywas published in the Journal of Natural History in1969 as part of the series of papers on the marine life ofScilly (Robins, 1969).The Seasearch pink sea fan survey has been conductedby volunteer divers in Scilly and at other sitesnationally. It aims to identify important areas forpink sea fans and to discover more about their habitatrequirements and biology. Divers photograph andmeasure individual colonies, noting the presence ofsea fan anemones, sea fan nudibranchs, the conditionof the fan and any debris entangling the colony.Fisheries ImpactsCorals are generally slow-growing and fragile.Branching species such as sea fans are particularlyvulnerable to damage by bottom gear. Trawling cancompletely remove colonies in just one event. Pottingmay also have direct physical impacts on sea fansand lost fishing line or net is often found entanglingcolonies.Pink sea fans were once commonly collected by diversas souvenirs however once it became known that thisspecies is so slow growing and scarce these recreationdivers quickly instigated a self-imposed moratoriumon their collection. The pink sea-fan is protected underSchedule 5 of the Wildlife and Countryside Act 1981against killing, injuring, taking possession and sale.Climate ChangePlanktonic species like jellyfish are brought to the Islesof Scilly by prevailing currents and winds. Any changein current patterns brought about by climate changemay influence the occurrence of these species in Scilly.Habitat LossBurrowing anemones may have been more abundantin the past when sediment was stabilized by extensiveZostera beds, their habitat was affected by the largescaleseagrass die off in the 1930s (Manuel, 1988). Theeffect of this would also have been noticed in seagrassassociated hydroids such as the nationally scarceLaomedea angulata (Barne et al, 1996)Sea fan seaslug Tritonia nilsodneri on pink sea fan Eunicellaverrucosa (pink colour morph). Photo: Malcolm NimmoIsles of Scilly biodiversity audit Page 21