CYNGOR CEFN GWLAD CYMRU

COUNTRYSIDE COUNCIL FOR WALES

SITE OF SPECIAL SCIENTIFIC INTEREST: CITATION

YNYS MÔN ARFORDIR GOGLEDDOL PENMON

Local Planning Authority: CYNGOR SIR YNYS MÔN

Date of Notification: 1953, 1994, 2003

National Grid Reference: SH 575814 – SH 641811

OS Maps: 1:50,000 Sheet number: 115

1:10,000 Sheet number: SH58SE & SH68SW

Site Area: 103.2 102.8 ha (approx)

Description:

Extending over 7 km along the eastern tip of Anglesey (from Trwyn Du to west of Bryn Offa), this site is selected for its geological, botanical, ornithological and marine biological features.

GeologyICAL INTEREST

The geological interest of the site comprises Tandinas quarry (a large disused limestone quarry) and associated north facing cliffs overlooking Traeth Coch. This site is of special interest as the type locality for the Carboniferous Limestone Tandinas Formation, defined here at Tandinas Quarry, and which is the thickest and most complete section through this Asbian unit. The succession shows the finest Asbian examples of minor cycles, with many rhythmic repetitions of lithologies, frequently with just two beds representing a cycle. Terrestrial fabrics in the limestones are common, indicating emergence of the area as land. This is a key site for environmental interpretation in what was a very shallow marine to emergent situation in late Dinantian times. These beds have a common shelly fauna which is important for regional correlation within the Carboniferous Limestone outcrops of North Wales.

Terrestrial BiologyICAL INTEREST

The terrestrial interest of the site is of special interest for its comprises wet heath, calcareous dry heath, neutral grassland, maritime grassland and base-rich flushes, as well as for a large population of lesser butterfly orchid Platanthera bifolia and breeding colonies of cormorant Phalacrocorax carbo. Cepphus grylle and the notable species associated with these.

Situated largely on Carboniferous Limestone sea cliffs and clifftop, this site enjoys the relatively dry sunny climate of southeast Anglesey, although its northerly aspect brings cool conditions and a later growing season. Limestone rock outcrops on the cliffs and sporadically elsewhere but is often covered by glacial till, reflected in a patchwork of soils and vegetation. Fedw Fawr common supports wet heath on peaty gley soils. It is characterised by cross- leaved heath Erica tetralix, and bog moss Sphagnum compactum with bell heather Erica cinerea, western gorse Ulex gallii, and heather Calluna vulgaris prominent along with more local species such as petty whin Genista anglica. Along drainage lines and hollows, purple moor- grass Molinia caerulea is more abundant with black bog- rush Schoenus nigricans, and bog asphodel Narthecium ossifragum and these areas are particularly rich in species such as saw-wort Serratula tinctoria and common butterwort Pinguicula vulgaris. Mountain everlasting Antennaria dioica and fir clubmoss Huperzia selago are found here in one of their few Anglesey locations. The perimeter of willow Salix spp. and European gorse Ulex europaeus bushes contribute to the value of the common, especially for its invertebrate fauna such as the lunar hornet moth Sphecia bembeciformis and the sallow kitten Harpya furcula, and for its bird fauna. At Bryn Offa common an area of unusual calcareous heath, situated on Precambrian schists but influenced by calcareous drift, combines both acid and lime tolerant species such as bell heather and western gorse with common rock-rose Helianthemum nummulariuma, quaking grass Briza media, columbine Aquilegia vulgaris, carline thistle Carlina vulgaris and burnet rose Rosa pimpinellifolia.

Neutral grasslands with common knapweed Centaurea nigra, crested dog's-tail Cynosurus cristatus and common bird’s-foot- trefoil Lotus corniculatus occur in fields adjoining the heath and the seacliffs. In places, where the soil is more acid, heath-grass Danthonia decumbens and tormentil Potentilla erecta are frequent. Notable species of these grasslands include fragrant orchid Gymnadenia conopsea, lesser butterfly-orchid (need to emphasise as of special interest in its own right) Platanthera bifolia and green -winged orchid Orchis morio. The particularly large population of the declining lesser butterfly-orchid Platanthera bifolia found on Fedw Fawr is also of special interest also. (LATIN NAME ALREADY GIVEN ABOVE, DOESN’T NEED REPEATING).

Where lime rich water flows down to the coast and cliff there are stands of flushed mire vegetation characterised by a flora of black bog rush, blunt- flowered rush Juncus subnodulosus, grass- of- parnassus Parnassia palustris, cowslip Primula veris, bog pimpernel Anagallis tenella and a profusion of sedges and mosses. Maritime grasslands dominated by red fescue Festuca rubra, thrift Armeria maritima and Yorkshire- fog Holcus lanatus clothe much of the cliff with species tolerant of salt spray such as sea plantain Plantago maritima (which here supports the nationally scarce weevil Trichosirocalus dawsoni) and areas of blackthorn Prunus spinosa scrub.

Other notable species include sea- kale Crambe maritima on areas of shingle and sea stork’s-bill Erodium maritimum. A nationally important breeding population of over 100 pairs of cormorant utilise the site’s sea cliffs, and the cliffs below Fedw Fawr also support Britain’s most southerly breeding colony of black guillemot. The cliffs are also used as breeding sites by peregrine falcon, fulmar, and shag and a large colony of cormorant (emphasise as above) and also include the most southerly breeding colony of black guillemot (emphasise as above) in Britain.

Marine BiologyICAL INTEREST

The shore is the best example of marine communities typical of limestone shores exposed to moderate degrees of wave exposure in the area between Bardsey Island and Great Orme’s Head. It is also of special interest for the presence of diverse rockpool and rock overhang communities, extensive rocky shore community zonation patterns and for the presence of two communities of restricted national distribution. The topography of the shore is extremely varied, with steep limestone cliffs, and gently sloping or horizontal platforms with vertical or undercut edges and numerous eroded crevices. In places the cliffs have eroded to form beaches of cobbles, pebbles or huge boulders. This variety of habitats gives rise to a wide range of marine plant and animal communities.

Rocky shore communities form visible ‘zones’ down a good proportion of the shore. Such patterns of zonation are the result of different species’ tolerance’s to desiccation, temperature extremes and sunlight and their abilities to compete with other species for space. Yellow and grey lichen communities dominate bedrock and boulder surfaces above mean high water, with barnacles, the black tar lichen Verrucaria maura and the seaweeds channel wrack Pelvetia canaliculata and spiral wrack Fucus spiralis dominating rock surfaces immediately below. A wide band of barnacles, particularly the acorn barnacle Semibalanus balanoides, common limpets Patella vulgata and common mussels Mytilus edulis occurs on steep mid-shore sections. These sections are interspersed with gently sloping limestone platforms which are less exposed to wave action, and here the seaweed serrated wrack Fucus serratus is abundant within the barnacle, limpet and mussel zone. In places, however, the limestone platforms are scoured by sand and tidal action, such that the only species to survive are ephemeral species of seaweed with occasional clusters of common mussels in crevices.

Lower on the shore bedrock, boulder and cobble surfaces are covered by a range of seaweeds, including serrated wrack, and the red seaweeds Mastocarpus stellatus and Ceramium sp. At the lowest reaches oarweed Laminaria digitata forms a narrow zone along most of the shore. In places, vertical limestone bedrock and boulder surfaces in both the oarweed and the serrated wrack zones are burrowed into by piddocks and wrinkled rock borers Hiatella arctica. These communities are uncommon in Wales, being found only on a few limestone shores on north-east Anglesey, the Great Orme and south Pembrokeshire.

Diverse communities of marine plants and animals inhabiting rockpools and the surfaces under rock overhangs occur on this shore. Of particular interest are shallow rockpools with coral weed Corallina officinalis and other red seaweeds, as well as deeper rockpools with brown seaweeds (fucoids) and kelp, and sediment-floored rockpools with fucoids and other seaweeds. These rockpools occur along the length of the site. Under rock overhangs on the lower shore many species benefit from the damp, shaded conditions, including sponges (Haliclona viscosa, Hymeniacidon perleve, purse sponge Grantia compressa, breadcrumb sponge Halichondria panicea and boring sponge Cliona celata), sea-squirts (Morchellium argus and Botrylloides leachi), worms (Polydora sp., Pomatoceros sp. and greenleaf worm Eulalia viridis), anemones (Sagartia elegans and plumose anemone Metridium senile), and species of bryozoan, hydroid, soft coral, mollusc, barnacle and algae.

Remarks:

Certain areas of the site below mean high water form part of Y Fenai a Bae Conwy/Menai Strait and Conwy Bay candidate Special Area of Conservation (cSAC), under the EC Habitats Directive (Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora 1992). The site contains areas of Shallow Inlets and Bays and Reefs , habitats listed on Annex I of the Directive which are important features of the cSAC.

Between 1953 and January 2001, part of the site was notified as Fedw Fawr SSSI under the National Parks and Access to the Countryside Act, 1949. Parts of that site were renotified as Fedw Fawr – Caeau Ty Cydwys SSSI and Tandinas Quarry SSSI in 1994 under the Wildlife and Countryside Act 1981 (as amended).

This site is within the Anglesey Area of Outstanding Natural Beauty (AONB).

The Biodiversity Action Plan Habitats of lowland heathland, unimproved neutral grasslandlowland meadows, fen, and maritime cliff and slope, purple moor grass and rush pastures and lowland calcareous grassland s are found on the site.

Part of this site has been selected in the Nature Conservancy Council’s Geological Conservation Review, a national survey and evaluation of sites of geological and geomorphological interest. The site is described in the following GCR volume: COSSEY, P.J. et al. In prep. British Lower Carboniferous Stratigraphy. Geological Conservation Review Series, Joint Nature Conservation Committee, Peterborough.