COUNTRYSIDE COUNCIL FOR WALES
SITE OF SPECIAL SCIENTIFIC INTEREST: CITATION
ANGLESEY LLYN LLYGEIRIAN
National Grid Reference: SH347899
Site Area: 29.8 ha
Llyn Llygeirian is selected for its biological interest as an example of a moderately base-rich lake in West Gwynedd.
The flora of the lake as a whole includes a range of aquatic macrophyte species. Low-growing species, e.g. shore weed Littorella uniflora, occur on the more exposed margins; various floating-leaved plants, including the regionally rare frogbit Hydrocharis morsus-ranae, and submerged macrophytes, e.g. the water-milfoils Myriophyllum alterniflorum and M. spicatum, are present; reedswamp with a variety of emergent species, e.g. bulrush Typha latifolia, flowering rush Butomus umbellatus and bottle sedge Carex rostrata, is well represented and there are also peripheral willow carr and mire communities.
Llyn Llygeirian is additionally important for the occurrence of several nationally uncommon aquatic species: the two waterworts Elatine hydropiper and E. hexandra needle spike-rush Eleocharis acicularis, spring quillwort Isoetes echinospora and pillwort Pilularia globulifera. Although this lake is not of major significance for wildfowl, it does support a number of over wintering species, notably gadwall and whooper swans.