The Isles of Scilly Biodiversity Audit 2008 - Cornwall Wildlife Trust

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2.2.1.8 Cnidaria - sea anemones,jellyfish, corals and relativesOverviewThis group of predominantly soft bodied, simpleanimals is characterised by the presence of stingingcells or nematocysts. They use these nematocystsand their tentacles to catch prey from the watercolumn. Sea anemones, jellyfish, hydroids, sea pensand corals are all members of the phylum Cnidaria.Many cnidarians have both planktonic and benthiclifestages, while some, such as most jellyfish, are solelyplanktonic.Benthic cnidarians are sessile and may be attached toa range of substrates including rock, seaweed, shells,wreckage and in soft sediments. Members of thisgroup are important to the recreational dive industryas they are some of the most colourful and attractivecomponents of the underwater landscape. Hydroidsare feathery, fairly inconspicuous members of thisgroup which often dominate rocky areas and areheavily grazed by seaslugs.Important AreasOn rocky shores beadlet anemones, Actinia equinaare very common, especially on vertical rock faces atmid-tide level, while elegant anemones Sagartia elegansmay form local aggregations in pools and underoverhangs. Hard substrate in these areas precludesdevelopment of a burrowing fauna (Harvey, 1969)but on the sand flats burrowing anemones may occurwhere sediment is stable. Sea pens also grow in softsediment. Planktonic cnidarians such as jellyfish maybe encountered anywhere in the waters around Scillyand are sometimes found dead on beaches where windand currents have stranded them.Pink sea fans Eunicella verrucosa occur in areas withpredictable currents, though never in great numbers inScilly. Important sites include East Trinity, Gugh Reef,Hoe Point, Hard Lewis Rock, Darrity’s Hole, NorthChapel Rock, Flat ledge, Plympton and Hather wreck(Seasearch 2006). Sea fan anemones Amphianthusdohrnii have been found on pink sea fans at NorthChapel Rock and Flat ledge.Conservation ImportanceThe Anthozoa (corals and anemones) are part ofthe BAP habitat ‘fragile sponge and Anthozoancommunities on subtidal rock habitats’.The pink sea fan Eunicella verrucosa is nationally scarceand is a BAP species; furthermore it is host to anotherBAP species, the sea fan anemone Amphianthus dohrniiwhich is nationally rare. Sea fan anemones are foundin low numbers in Scilly (Seasearch, 2004). Pink seafans are also host to the sea fan nudibranch Tritonianilsodneri which is nationally scarce and lays its eggsAn anemone Sagartia sp. Photo: Malcolm Nimmoon pink sea fans. Pink sea fans are protected underSchedule 5 of the Wildlife and Countryside Act 1981.Due to their branching structure sea fans are thoughtto provide important attachment sites for the egg casesof some elasmobranchs.Pink sea fans occur in forests in Scilly although theseare not as dense as those around mainland Cornwall,possibly because the exposure is greater in Scilly(Seasearch, 2004). Colonies are also generally smallcompared to mainland sea fans. In Scilly the whitecolour morph is predominant, unlike Cornwall wherepink individuals are much more common. The whitecolour morph occurs in other areas such as Gibraltarand the west coast of Ireland. Populations of pink andwhite sea fans may be quite separate genetically (C.Wood, pers. comm. and B.Picton, pers. comm.)Scarlet and gold cup coral Balanophyllia regia, anationally scarce species has been recorded at two sitesand the nationally rare sunset cup coral Leptopsammiapruvoti, a BAP species, is growing at Gap Point (K.Cook, pers comm.) Wingletang Ledges and theCita wreck (Seasearch, 2006). The sunset cup coralpopulations in southwest England are at the northernlimit of their distribution and are thought to be a relicof a former, more extensive distribution approximately700 years ago (Jones et al n.d.). The Isles of Scilly isone of only four areas it is known to occur in the UK(Seasearch, 2007).Three species of BAP stalked jellyfish occur in Scilly;Haliclystus auricular, Lucernariopsis campanulata andLucernariopsis cruxmelitensis. These small cnidariansare usually fixed to algae or seagrass by their stalk andmay have suffered from habitat loss when the seagrassIsles of Scilly biodiversity audit Page 20
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
Page 1 and 2: The Isles of ScillyBiodiversity Aud
Page 3 and 4: ContentsForeword Page 5Acknowledgem
Page 5 and 6: ISLES OF SCILLY BIODIVERSITYForewor
Page 7 and 8: ExecutiveSummary1 IntroductionObjec
Page 9 and 10: 1Introduction1.1 Objectives of Isle
Page 11 and 12: 2Isles of ScillyBiodiversityThe bio
Page 13 and 14: 2.2.1.1 Marine algae - seaweedsOver
Page 15 and 16: 2.2.1.2 Charophytes - StonewortsOve
Page 17 and 18: 2.2.1.5 Bryophytes - Mosses andLive
Page 19: 2.2.1.7 Porifera - spongesOverviewS
Page 23 and 24: 2.2.1.10 Arachnida - Spiders andrel
Page 25 and 26: 2.2.1.12 Myriapoda - Centipedes and
Page 27 and 28: 2.2.1.14 Orthoptera - Crickets,Gras
Page 29 and 30: 2.2.1.16 Lepidoptera - Butterflies
Page 31 and 32: 2.2.1.18 Hymenoptera - Wasps andBee
Page 33 and 34: 2.2.1.20 Coleoptera - BeetlesOvervi
Page 35 and 36: 2.2.1.22 Mollusca - Slugs, snails,b
Page 37 and 38: 2.2.1.24 Echinoderms - sea urchins,
Page 39 and 40: 2.2.1.26 Lesser-studied phylaOvervi
Page 41 and 42: 2.2.1.27 Amphibia - frogs, toads an
Page 43 and 44: with herring Clupea harengus and ma
Page 45 and 46: 2.2.1.29 Terrestrial ReptiliaOvervi
Page 47 and 48: 2.2.1.31 BirdsOverviewSeabirdsThe I
Page 49 and 50: 2.2.1.32 Terrestrial MammalsOvervie
Page 51 and 52: commonest species of dolphin in the
Page 53 and 54: Habitat Areas -An IntroductionSt Ma
Page 55 and 56: 2.2.2.1 Arable Field MarginsOvervie
Page 57 and 58: 2.2.2.3 Coastal Vegetated ShingleOv
Page 59 and 60: Rocky reef with jewel anemones Cory
Page 61 and 62: 2.2.2.6 Intertidal BouldersOverview
Page 63 and 64: 2.2.2.8 Lowland HeathlandOverviewLo
Page 65 and 66: 2.2.2.10 Marine Sands and GravelsOv
Page 67 and 68: 2.2.2.11 Maritime Cliff and SlopesO
Page 69 and 70: 2.2.2.13 ReedbedsOverviewReedbeds a
Page 71 and 72:
2.2.2.15 Seagrass BedsOverviewSeagr
Page 73 and 74:
2.2.2.16 Standing Open Water(Eutrop
Page 75 and 76:
2.2.2.18 Wet WoodlandOverviewThis h
Page 77 and 78:
3.1 Nature ConservationOverviewPubl
Page 79 and 80:
3.2 AgricultureOverviewAlthough tou
Page 81 and 82:
3.3 FisheriesOverviewFor many years
Page 83 and 84:
3.4 Built DevelopmentOverviewAs wit
Page 85 and 86:
3.6 Air & Terrestrial PollutionOver
Page 87 and 88:
chemical dispersants will only be u
Page 89 and 90:
3.9 Climate Change / Sea LevelRiseO
Page 91 and 92:
3.11 Economic DevelopmentOverviewTh
Page 93 and 94:
4Priorities for BiodiversityConserv
Page 95 and 96:
Gracilaria bursa-pastoris A red sea
Page 97 and 98:
Eriopus apiculatus A moss RDB Shade
Page 99 and 100:
Spergularia bocconei Greek Spurrey
Page 101 and 102:
Lucernariopsiscampanulata A stalked
Page 103 and 104:
Agrochola lychnidis Beaded Chestnut
Page 105 and 106:
Aphrosylus mitis A fly NS Uncommon
Page 107 and 108:
RecommendationRecommendationRecomme
Page 109 and 110:
Prionace glauca Blue Shark BAP Comm
Page 111 and 112:
22Cygnus columbianusbewickiiTundra
Page 113 and 114:
RecommendationMARINE MAMMALSSpecies
Page 115 and 116:
5Recommendationsfor ActionThe role
Page 117 and 118:
Glossary6Alluvial sediment - partic
Page 119 and 120:
Bibliography7Aprahamian M and Robso
Page 121 and 122:
Harris T (1972) The Marine Flora an
Page 123 and 124:
Scilly, Journal of Conchology 4, 28
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The Isles of Scilly Biodiversity Audit 2008 - Cornwall Wildlife Trust

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