3110 Oligotrophic waters containing very few minerals of sandy plains (Littorelletalia uniflorae)
Description and ecological characteristics
This type of waterbody is restricted to sandy plains that are acidic and low in nutrients, and are therefore very scarce. The water is typically very clear and moderately acid. The catchment area of the machair lochs in the Outer Hebrides is acid moorland and that of the other UK sites in the New Forest and on the Cheshire Plain is acid lowland heathland. Destruction of lowland heaths, land drainage and nutrient enrichment have contributed to the scarcity of the habitat type.
The habitat type is characterised by the presence of Littorelletalia-type vegetation. Such vegetation is characterised by the presence of water lobelia Lobelia dortmanna, shoreweed Littorella uniflora, or quillwort Isoetes lacustris. Only one species needs to be present to conform with the definition of this Annex I type and typically the vegetation consists of zones in which the individual species form submerged, monospecific lawns.
Away from sandy plains, oligotrophic waters with similar plant assemblages are widespread and locally abundant in the uplands of Scotland and Wales and the Lake District (3130 Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea).
European status and distribution
This is a rare habitat type throughout the Atlantic Biogeographical Region of Europe.
UK status and distribution
The only known high-quality examples of this habitat type occur on fluvio-glacial deposits in the New Forest and on the Cheshire Plain, and on more recent sand deposits of marine origin in the Outer Hebrides.
Click here view UK distribution of this species
Dorset Heaths (Purbeck and Wareham) and Studland Dunes
Dorset and Somerset
Little Sea is a shallow lake at Studland Dunes in south-west England. It is of recent origin (<500 years old), formed as a large body of seawater became landlocked by the growing sand dunes (hence the name Little Sea). This water is now fresh and is replenished by acidic, oligotrophic water draining off the adjacent heathland, which then flows through the dune slacks and into the sea. The submerged vegetation is characterised by communities of alternate water-milfoil Myriophyllum alterniflorum, shoreweed Littorella uniflora and spring quillwort Isoetes echinospora, together with bladderwort Utricularia australis and less frequently six-stamened waterwort Elatine hexandra.
Oak Mere, in the West Midlands of England, is a lake formed within sediments that are low in nutrients and oligotrophic. It is a large waterbody that has formed in a kettle hole in the fluvio-glacial sands of the Cheshire Plain. The site has clear water of low nutrient status characteristic of oligotrophic waters and a marginal zone of shoreweed Littorella uniflora. The site supports an assemblage of plants that are now rare in the lowlands of England, including floating mats of bog-moss Sphagnum spp. and the scarce narrow small-reed Calamagrostis stricta.
South Uist Machair
Highlands and Islands
This site encompasses a series of oligotrophic lochs on the machair plains of the west coast of South Uist in the Outer Hebrides. It is considered to be the most important site in the UK for the conservation of this habitat type, owing to the diversity and extent of the habitat type and because these lochs contain all three characteristic plant genera (water lobelia Lobelia, shoreweed Littorella and quillwort Isoetes). The oligotrophic lochs form one element of a series of lochs, which range from dystrophic lochs on inland peat bogs, through oligotrophic lochs of this type in areas of transitions between peat and calcareous sands, to calcareous lochs of the main machair plain and brackish sea lochs closest to the sea. Oligotrophic waters in this composite site are Lochs Fada, na Tanga, na Cuithe Mòire, a’Phuirt-ruaidh, a’Chnoic Bhuidha and Schoolhouse Loch.
The New Forest
Gloucestershire, Wiltshire and Bristol/Bath area, Hampshire and Isle of Wight
Hatchet Pond in the New Forest in the south of England is in fact three ponds, one of which is an example of an oligotrophic waterbody amidst wet and dry lowland heath developed over fluvial deposits. It contains shoreweed Littorella uniflora and isolated populations of northern species such as bog orchid Hammarbya paludosa and floating bur-reed Sparganium angustifolium, alongside rare southern species such as Hampshire-purslane Ludwigia palustris. Hatchet Pond is therefore important as a southern example of this lake type where northern species, more common in the uplands of the UK, co-exist with southern species.
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