Afon Gwyrfai a Llyn Cwellyn

General site character

• Inland water bodies (Standing water, Running water) (100%)
  

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

• 3130 Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea

  Llyn Cwellyn, north Wales, is an oligotrophic glacial lake (Type 3) representative of oligotrophic lakes found in the mountains of Snowdonia. It is a relatively large, deep lake, in contrast to Llyn Idwal, also in Snowdonia. Because of its depth the lake stratifies during the summer, with a thermocline developing at 10-15 m depth that has a marked effect upon the ecology of the site. Although the site has acidified since the late 19^th century, water quality remains high and Llyn Cwellyn supports one of the few native Welsh populations of Arctic charr Salvelinus alpinus (‘Torgoch’ in Welsh). The macrophyte flora of Llyn Cwellyn is characterised by abundant shoreweed Littorella uniflora, water lobelia Lobelia dortmanna, quillwort Isoetes lacustris, bulbous rush Juncus bulbosus and alternate water-milfoil Myriophyllum alterniflorum. The rare awlwort Subularia aquatica is abundant in places and 1831 Floating water-plantain Luronium natans occurs at this site. Six-stamened waterwort Elatine hexandra has been recorded in shallow water off the north shore and bog pondweed Potamogeton polygonifolius occurs in stream inflows in the south.

• 3260 Water courses of plain to montane levels with the Ranunculion fluitantis and Callitricho-Batrachion vegetation

  The Gwyrfai is a good example of the small, steep rivers that occur in north-west Wales. It is dominated by base-poor rock and contains extensive beds of the most oligotrophic end of sub-type 3 of this habitat, dominated by stream water-crowfoot Ranunculus penicillatus ssp. penicillatus, intermediate water-starwort Callitriche hamulata, aquatic mosses Fontinalis spp. and bulbous rush Juncus bulbosus. The conservation value of the site is enhanced by the presence of good adjacent river corridor habitat, and by the presence of Llyn Cwellyn, a good example of a Littorella – Lobelia – Isoetes oligotrophic lake.

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

• Not Applicable

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

• 1106 Atlantic salmon Salmo salar

  The Afon Gwyrfai in north-west Wales is representative of the small montane rivers in this region. It contains a largely unexploited salmon population with a characteristically late run. Environment Agency electrofishing data indicates the presence of healthy juvenile populations downstream of Llyn Cwellyn.

• 1831 Floating water-plantain Luronium natans

  Llyn Cwellyn and its outflow, the Afon Gwyrfai, support one of the largest and most diverse populations of floating water-plantain Luronium natans anywhere in Britain. There are extensive submerged, vegetative beds of this species in the clear, oligotrophic waters of the lake and (generally) several small flowering colonies around its edge whilst, downstream from the lake, L. natans occupies a highly unusual – and vulnerable – habitat along several hundred metres of slow-moving river. The diversity of growth forms and their range across the Cwellyn-Gwyrfai makes this an internationally significant site for the species.

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

• 1355 Otter Lutra lutra