Pen Llŷn a'r Sarnau/ Lleyn Peninsula and the Sarnau

General site character

• Marine areas, Sea inlets (92.6%)
  
• Tidal rivers, Estuaries, Mud flats, Sand flats, Lagoons (including saltwork basins) (5.4%)
  
• Salt marshes, Salt pastures, Salt steppes (1.2%)
  
• Coastal sand dunes, Sand beaches, Machair (0.5%)
  
• Shingle, Sea cliffs, Islets (0.2%)
  
• Bogs, Marshes, Water fringed vegetation, Fens (0.1%)
  

Annex I habitats that are a primary reason for selection of this site

• 1110 Sandbanks which are slightly covered by sea water all the time

  Pen Llyn a’r Sarnau on the north-west coast of Wales includes the sandbanks of Devil’s Ridge, Bastram Shoal, the Tripods, and areas within and to the south of Tremadog Bay. These include examples of fully marine salinity, tide-swept sandbanks and relatively sheltered sandbanks. On Devil’s Ridge, Bastram Shoal and the Tripods strong tides mean that the sand, shell and gravel sediments are constantly shifting, and as a result the sandbanks support animals that can tolerate these high levels of disturbance.

• 1130 Estuaries

  Pen Llyn a’r Sarnau has representative examples of bar-built estuaries in north-west Wales, and includes the Glaslyn/Dwyryd, Mawddach and Dyfi estuaries. There is a continuous gradient between the clean sands near the entrance to the sea and the mud or muddy sands in the sheltered extremes of the estuaries. The intertidal sandflats support communities of burrowing invertebrates, including dense populations of polychaete worms, crustaceans, bivalve molluscs and gastropod molluscs. Saltmarsh fringing the shores of the estuaries, and the saltmarsh creeks and pools, are important habitat features for juvenile fish.

• 1150 Coastal lagoons  * Priority feature

  Morfa Gwyllt lagoon is a small percolation lagoon that consists of a depression in a shingle bar across the mouth of the Afon Dysynni in mid Wales. This is the only example of a percolation lagoon in Wales. The substrate is a mosaic of medium sand over/amongst shingle, with muddier patches within the deeper pockets, and scattered larger pebbles. Three lagoonal specialists have been found at this site: the amphipod Sphaeroma hookeri, the bryozoan Conopeum seurati and the alga Chaetomorpha linum.

• 1160 Large shallow inlets and bays

  The seabed of Tremadog Bay on the south side of the Lleyn Peninsula, north-west Wales, consists of a mosaic of different sediment types, which support a diverse mixture of plant and animal communities. Areas of cobbles and pebbles in shallow water support algal species that can tolerate sand-scour, such as Naccaria wiggii and Scinaia spp. There are patchy areas of maerl around St Tudwal’s Islands. Maerl has been found at only one other site in Wales, in Milford Haven. Burrowing animals, including bivalves, crabs, brittlestars, urchins and worms, dominate the muddier sediments in Tremadog Bay. There are also beds of eelgrass Zostera angustifolia and muddy gravel shores within Tremadog Bay, both uncommon habitats. The gravelly beach at Traeth Crugan supports the nationally rare amphipod Pectenogammarus planicrurus. Several unusual species that are more often seen in warmer Mediterranean waters have been found in Tremadog Bay, such as the bearded red seaweed Anotrichium barbatum and the mantis shrimp Rissoides desmaresti.

• 1170 Reefs

  This site on the coast of north-west Wales encompasses a varied range of reef habitats, including an unusual series of submerged and intertidal glacial moraines. The areas of bedrock, boulders, cobbles, sandy rock, surge gullies and the tide-swept area of Bardsey Sound support a diverse array of plant and animal communities. There are distinctive communities on bedrock and boulders, ranging from sites exposed to very strong wave action and/or tidal streams to sites sheltered from strong water movement. For example, reefs on the north coast of the Llyn are dominated, in different locations, by either the mussels Musculus discors and Mytilus edulis or horse mussels Modiolus modiolus, or ascidians, or the tube worm Sabellaria spinulosa. Ross coral Pentapora foliacea has been recorded from these reefs and elsewhere around Bardsey and south-west Llyn. Several Mediterranean-Atlantic species have been recorded from south-east Bardsey. Reefs formed by honeycomb worm Sabellaria alveolata are found south and east of Pwllheli. The Sarnau (Sarn Badrig, Sarn-y-Bwch and Cynfelyn Patches) are very unusual shallow subtidal reefs, which extend many kilometres from the coast into Cardigan Bay. The Sarnau are glacial moraines (resulting from the last glaciation) and are composed entirely of boulders, cobbles and pebbles mixed with various grades of sediments. Fast tidal streams and strong wave action have a profound influence on the marine communities present, and the reefs are characterised by a large number of species resistant to scour and sand cover. Algal communities are dominant over much of the reefs, with growths of foliose red and brown algae forming very dense beds in many places, in the absence of shading from kelp. The brown algae Chorda filum and Laminaria saccharina and red algae flourish on or near the reef crest, while the number of algae species on pebbles increases with depth. In certain areas there are extensive forests of sea-oak Halidrys siliquosa. Rich animal-dominated biotopes are found in the deeper parts of the reefs, including crustaceans, cnidarians, sponges, hydroids and encrusting bryozoans.

Annex I habitats present as a qualifying feature, but not a primary reason for selection of this site

• 1140 Mudflats and sandflats not covered by seawater at low tide
• 1310 Salicornia and other annuals colonizing mud and sand
• 1330 Atlantic salt meadows (Glauco-Puccinellietalia maritimae)
• 8330 Submerged or partially submerged sea caves

Annex II species that are a primary reason for selection of this site

• Not Applicable

Annex II species present as a qualifying feature, but not a primary reason for site selection

• 1349 Bottlenose dolphin Tursiops truncatus
• 1355 Otter Lutra lutra
• 1364 Grey seal Halichoerus grypus