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

European status and distribution

This type of waterbody occurs in the majority of EU Member States and is relatively abundant in the more mountainous areas of Europe.

UK status and distribution

In the UK this habitat type is widespread and frequent in the north and west; it also occurs rarely elsewhere.

Click here view UK distribution of this species

Site accounts

• Afon Gwyrfai a Llyn Cwellyn West Wales and The Valleys
  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.
• Beinn Dearg Highlands and Islands
  This mountain massif in the north-west Highlands of Scotland includes a number of small oligotrophic lochs, some of these at relatively high altitude. The massif has a wide variety of landforms created by glacial activity and a diversity of rock types leading to a range of plant communities within the lochs. Notably, several of the lochs support the rare awlwort Subularia aquatica, a plant indicative of oligotrophic water.
• Ben Lawers Eastern Scotland
  The principal freshwater loch on Ben Lawers in the central Highlands is Loch nan Cat, which is representative of oligotrophic standing waters and drains a calcareous schist catchment, a rare type in Britain. The loch is at high altitude (710 m), has a variety of substrates, is of very low nutrient status (Type 3) and supports a relatively diverse flora, including quillwort Isoetes lacustris, which is indicative of this oligotrophic freshwater habitat type. In addition, the flora includes several pondweed Potamogeton spp. and delicate stonewort Chara virgata.
• Cadair Idris West Wales and The Valleys
  Within the Cadair Idris range, Llyn Cau is a mountain lake representative of this type, located in an upland cirque. The lake’s conical basin, which reaches a water depth of almost 50 m, results from glacial scour of Ordovician volcanic and sedimentary rocks. Quillwort Isoetes lacustris is abundant and shoreweed Littorella uniflora occurs frequently. The boulder-dominated shore has abundant growths of liverworts and mosses, including Sphagnum denticulatum and Rhytidiadelphus squarrosus. There are distinct associations of I. lacustris, starwort Callitriche hamulata and bulbous rush Juncus bulbosus var. fluitans, the latter being most abundant adjacent to inflow streams. The water is moderately acid with low conductivity but relatively high nitrate concentrations for an upland lake. A lake sediment study did not reveal any evidence of acidification. It has been classified as a type 1 (dystrophic lake) on the basis of its vegetation but its water transparency is very high with a distinctive blue colour. It stratifies with a thermocline at 10-15 m depth. Brown trout Salmo trutta fario are present.
• Cairngorms Highlands and Islands, North Eastern Scotland
  The Cairngorm mountains contain the highest oligotrophic waterbodies in the UK. This complex of lochs has a range of high altitude conditions. The very highest waters (corrie and plateau lochs at >900 m) have rocky substrates and very low nutrient status, and suffer the harshest climate. In combination, these factors lead to low species diversity and the absence of aquatic macrophytes. This is an extreme variation of the habitat type. Lochs in the valley floors enjoy more sheltered conditions and the occurrence of finer sediments allows limited establishment of higher plants, although these are still extremely oligotrophic systems. Key species for this habitat type are present in Loch Einich (altitude 500 m), which supports quillwort Isoetes lacustris and shoreweed Littorella uniflora. The rare six-stamened waterwort Elatine hexandra has also been recorded here. The lochs in this area are classified as Type 3 or in some cases Type 2.
• Caithness and Sutherland Peatlands Highlands and Islands
  Caithness and Sutherland Peatlands supports a range of high-quality freshwater loch habitats that include Oligotrophic to mesotrophic standing waters. The lochs are part of large, generally nutrient-poor, drainage systems which characterise this part of the northern Highlands. The site covers an area greater than 140,000 ha and includes several hundred freshwater lochs of which the larger are oligotrophic. The lochs are generally located within 7130 blanket bog and peatlands that sit on nutrient-poor rocks. The aquatic vegetation is dominated by a very narrow range of species typical of northern, upland, lochs but there is much local variation in their abundance. The most characteristic species are shoreweed Littorella uniflora, water lobelia Lobelia dortmanna, bulbous rush Juncus bulbosus, bog pondweed Potamogeton polygonifolius and alternate water-milfoil Myriophyllum alterniflorum. More mesotrophic lochs support a wider range of pondweed Potamogeton species; other species present include stoneworts Chara spp. and Nitella spp. and least bur-reed Sparganium natans. The margins of a few lochs support two nationally scarce plants; bog hair-grass Deschampsia setacea and marsh clubmoss Lycopodiella inundata. Other notable species include awlwort Subularia aquatica and water sedge Carex aquatilis. The range of aquatic invertebrates includes the nationally rare water beetle Oreodytes alpinus.
• Dunkeld - Blairgowrie Lochs Eastern Scotland
  This site, comprising five lochs along the Lunan Burn on the northern edge of the central Scottish lowlands, provides a natural example of gradually-increasing eutophy. The three upper lochs (Craiglush, Lowes and Butterstone) lie north of the Highland Boundary Fault with catchments which are predominantly upland and acidic; the lower lochs (Clunie and Marlee) lie south of the Fault with predominantly agricultural and more enriched catchments. The series provides examples of relatively unpolluted oligotrophic to mesotrophic loch types, which are rare and decreasing habitats in Britain, especially in the lowlands. The aquatic flora is exceptionally diverse, with the number of pondweeds Potamogeton spp. at Loch of the Lowes and Loch Clunie being outstanding. 1833 slender naiad Najas flexilis occurs in each of the lochs. The site also contains a very large number of plant species, including many of local or national rarity, and is notable for the extensive area of poor-fen.
• Eryri/ Snowdonia West Wales and The Valleys
  Llyn Idwal, in the mountains of Snowdonia, represents oligotrophic waters (Type 3) in north Wales. It is a relatively small, shallow, upland corrie, in contrast to Llyn Cwellyn, also in Snowdonia, and complete ice cover has been recorded in winter. No overall change in the lake’s water chemistry has been found since the mid-19^th century, and the water quality is considered to be high. The site has a good representation of typical plant species, including quillwort Isoetes lacustris, water lobelia Lobelia dortmanna, shoreweed Littorella uniflora, bulbous rush Juncus bulbosus, alternate water-milfoil Myriophyllum alterniflorum and intermediate water-starwort Callitriche hamulata. Bog pondweed Potamogeton polygonifolius has been recorded from stream inlets, and pillwort Pilularia globulifera is reported from this site. Emergent and floating vegetation is mainly confined to the shallow sub-basin at the south end of the site, where floating bur-reed Sparganium angustifolium forms extensive mats, alongside stands of common reed Phragmites australis, water horsetail Equisetum fluviatile and bottle sedge Carex rostrata.
• Foinaven Highlands and Islands
  Foinaven supports a gradient of high-quality freshwater loch habitats including Oligotrophic to mesotrophic standing waters. The oligotrophic waterbodies range from dubh lochans to relatively large lochs on the lower moors, all of which are part of small unproductive catchments typical of the north-west Scottish Highlands. The majority of these lochs are undisturbed, with a high degree of naturalness. The lochs support populations of shoreweed Littorella uniflora, quillwort Isoetes lacustris, water lobelia Lobelia dortmanna, awlwort Subularia aquatica, bulbous rush Juncus bulbosus and floating water bur-reed Sparganium angustifolium, all characteristic of oligotrophic conditions.
• Glen Coe Highlands and Islands
  Glen Coe includes Loch Achtriochtan, representing oligotrophic lochs in the mountainous western Highlands of Scotland. The loch contains high-quality oligotrophic habitat with vegetation typical of nutrient-poor conditions on a substrate dominated by stones. The loch supports populations of shoreweed Littorella uniflora, quillwort Isoetes lacustris, water lobelia Lobelia dortmanna, awlwort Subularia aquatica and bulbous rush Juncus bulbosus, all characteristic of oligotrophic conditions. Stands of reed canary-grass Phalaris arundinacea are established at the western end of the loch and smooth stonewort Nitella flexilis has been recorded from the inflow. The surrounding semi-natural land use has protected the site from disturbance or eutrophication.
• Insh Marshes Highlands and Islands
  Insh Marshes is a major wetland site covering a representative section of the River Spey from Newtonmore to Kincraig. The flood-plain mire supports several waterbodies that are excellent representatives of oligotrophic to mesotrophic standing waters. The waterbodies range from the relatively large Loch Insh to small un-named lochans. Loch Insh is an excellent example of a mesotrophic, species-rich loch supporting populations of shoreweed Littorella uniflora, water lobelia Lobelia dortmanna and quillwort Isoetes lacustris and is noted for its exceptionally rapid water turnover, as the River Spey flows through the loch. The River Spey is one of the largest, least polluted and unmodified river systems in Britain and the waterbodies have a high degree of naturalness.
• Inverpolly Highlands and Islands
  Inverpolly supports a large number of high-quality freshwater loch habitats, the majority of which are oligotrophic standing waters There are several large lochs within the site, including Loch Sionascaig, together with many other smaller waterbodies which contribute to the overall habitat representation. The remote location and lack of environmental pressures means that the majority of lochs are undisturbed. The nutrient-poor lochs support a typically low diversity of plant species, including bulbous rush Juncus bulbosus, shoreweed Littorella uniflora and water lobelia Lobelia dortmanna. Larger lochs such as Loch Sionascaig have a more varied flora including other species such as quillwort Isoetes lacustris, awlwort Subularia aquatica and alternate water-milfoil Myriophyllum alterniflorum. The diversity of plant species is further enhanced by the range of marginal habitats, which include open stony shores, soft sediment embayments and wetland areas
• Lake District High Fells Cumbria
  Lake District High Fells has many upland tarns throughout, representing the habitat type in the uplands of north-west England. The tarns are typically species-poor, but species occurring throughout include water-starwort Callitriche hamulata, quillwort Isoetes lacustris, shoreweed Littorella uniflora, water lobelia Lobelia dortmanna and floating bur-weed Sparganium angustifolium. Awlwort Subularia aquatica, a locally rare species, occurs in Sprinkling and Styhead Tarns (Scafell Pikes), Dock and Blea Tarns (Armboth Fells). The rare powan Coregonus lavaretus (locally called ‘schelly’) occurs in Red Tarn in Helvellyn and Fairfield.
• Lewis Peatlands Highlands and Islands
  This site in the Outer Hebrides represents the western extreme of oligotrophic to mesotrophic standing waters in the UK, and is part of the vast flow-ground on Lewis. Lewis Peatlands contrasts with many of the other UK sites with this habitat type as it comprises an undulating terrain subject to oceanic influences, which is not located within a mountainous landscape. It supports high-quality freshwater loch habitats. The site includes lochs within watershed flows, characteristic of the northern part of Lewis, and lochs within a more dissected terrain in the south of the site. The peatlands and bog systems within the site support nutrient-poor lochs and lochans that contain vegetation typical of the oligotrophic conditions including shoreweed Littorella uniflora, pondweeds Potamogeton spp. and bulbous rush Juncus bulbosus.
• Loch Maree Complex Highlands and Islands
  This site in the north-west Scottish Highlands includes Loch Maree, an excellent example of oligotrophic to mesotrophic standing waters, and numerous smaller, higher-altitude waterbodies. Loch Maree is of particular note as having the largest surface area of any loch in the north-west Highlands and being one of the most pristine waterbodies in the area. It is a large, deep loch and although many parts of its shoreline are unsuitable for plant growth, due to wave action and steep rocky outcrops, areas of predominantly sand and silt substrate, particularly around several large islands, support populations of pondweeds Potamogeton spp., water lobelia Lobelia dortmanna and quillwort Isoetes lacustris. The quality of Loch Maree suggests that it has not been subject to significant perturbation.
• Loch Ruthven Highlands and Islands
  Loch Ruthven in the north central Scottish Highlands is a high-quality representative of an oligotrophic loch with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea. Water quality data shows that Loch Ruthven is a moderately rich oligotrophic water tending towards the mesotrophic end of the spectrum, and supports a variety of flora including quillwort Isoetes lacustris, shoreweed Littorella uniflora and water lobelia Lobelia dortmanna. Potamogeton species are well represented and include red pondweed P. alpinus, curled pondweed P. crispus, broad-leaved pondweed P. natans, perfoliate pondweed P. perfoliatus and bog pondweed P. polygonifolius. A comparison with historic conditions has shown that the loch has changed little in recent years. In common with many oligotrophic and mesotrophic lochs it has a variety of shoreline features which range from open shore to fen areas, and which include a succession of habitat types from semi-natural birch woodland to open water.
• Loch Ussie Highlands and Islands
  Loch Ussie in the north-east Highlands lies in a shallow basin of Old Red Sandstone rocks and is one of the best mesotrophic lochs in Scotland. The distribution of natural mesotrophic lochs in Scotland is restricted, occurring most commonly at the junction of upland and lowland areas where the geochemical characteristics of these areas are manifested in the one waterbody. This gives rise to water quality conditions which allows the flora and fauna of upland and lowland areas to thrive. Water quality data show that Loch Ussie has a neutral pH and is moderately rich in nutrients, and a comparison with historical conditions show that it has changed little in the last 100 years. The assemblage of water plants is very diverse with nine pondweed Potamogeton species present, including the rare Shetland pondweed Potamogeton rutilus. The fringing sedge beds and shore support such species as bladder-sedge Carex vesicaria and pillwort Pilularia globulifera.
• Lough Melvin Northern Ireland
  Lough Melvin is a large mesotrophic lough that represents oligotrophic to mesotrophic standing waters in Northern Ireland. The north-east corner of the lough is in Fermanagh but the majority lies in Leitrim in the Republic of Ireland. It is the least-disturbed of the large loughs of Northern Ireland, the other sites having suffered from eutrophication and hydrological manipulation. The macrophyte flora is typical of a mesotrophic lake with affinities to oligotrophic waters. The flora is indicative of high water quality and is characterised by quillwort Isoetes lacustris, shoreweed Littorella uniflora, water lobelia Lobelia dortmanna, alternate water-milfoil Myriophyllum alterniflorum and a variety of pondweeds, including various-leaved pondweed Potamogeton gramineus, perfoliate pondweed P. perfoliatus and bright-leaved pondweed P. x nitens, which are widespread. The Lough also supports important native fish populations. Arctic charr Salvelinus alpinus occurs here at its only remaining Northern Ireland site and the Lough contains three genetically distinct populations of brown trout Salmo trutta fario.
• Muir of Dinnet North Eastern Scotland
  This site in the Dee valley, Grampian, Scotland includes two lochs, Kinord and Davan, in a complex area of morainic landforms and granite hills that supports a wide variety of habitats. Lochs Kinord and Davan represent high quality oligotrophic to mesotrophic freshwater habitats, and a rich aquatic flora. This includes species such as shoreweed Littorella uniflora, quillwort Isoetes lacustris and water lobelia Lobelia dortmanna, along with the white water-lily Nymphaea alba. Various pondweeds Potamogeton spp. are also present. In transitions from open water, the lochs also support a wide range of swamp and fen communities, dominated by common club-rush Scirpus lacustris, common reed Phragmites australis or bottle sedge Carex rostrata. Bog myrtle Myrica gale is a prominent feature of much of the adjacent fen. Fen carr characterised by willows Salix spp. is also present, along with other woodland habitats.
• Rannoch Moor Eastern Scotland, Highlands and Islands
  Rannoch Moor contains the most extensive complex of western blanket and soligenous/valley mire in Britain and supports a range of nutrient-poor freshwater habitats from dystrophic to oligotrophic waterbodies. The waterbodies vary in size from small lochans to relatively large lochs such as Loch Bà and Loch Laidon. Many of the small lochans have a predominantly peaty substrate resulting in a very low nutrient status, and consequently low species diversity. However the larger lochs support vegetation typical of oligotrophic to mesotrophic standing waters including water lobelia Lobelia dortmanna and bulbous rush Juncus bulbosus. In addition the site supports other uncommon species including least water-lily Nuphar pumila and floating bur-reed Sparganium angustifolium.
• River Derwent and Bassenthwaite Lake Cumbria
  Bassenthwaite Lake in the Lake District, north-west England, is an example of a mesotrophic waterbody (Type 5), an unusual type in mountain areas. It is a large lake with an extensive catchment area and consequently is subject to rapid through-flow of water and moderate nutrient status. A wide variety of pondweeds Potamogeton spp. are found, including perfoliate pondweed Potamogeton perfoliatus, small pondweed P. berchtoldii and curled pondweed P. crispus, which are widespread, whilst red pondweed P. alpinus, various-leaved pondweed P. gramineus and lesser pondweed P. pusillus are more locally distributed. Uncommon species present in the community are autumnal water-starwort Callitriche hermaphroditica and six-stamened waterwort Elatine hexandra. The shorelines are extensive and relatively undisturbed compared with other major Cumbrian lakes. Much of the shore is of shingle or gravel, but soft peat has accumulated around Bowness Bay. Several sedge species are found in such areas, including a local northern species, water sedge Carex aquatilis. On stony shores common spike-rush Eleocharis palustris is locally abundant amongst species such as globeflower Trollius europaeus, saw-wort Serratula tinctoria and the nationally rare thread rush Juncus filiformis. The lake also supports one of only two surviving UK populations of a rare fish, vendace Coregonus albula. Now extinct in Scotland, the only other known surviving population of vendace is found in Derwent Water, also in the Lake District.
• River Eden Cumbria, North Yorkshire, Northumberland and Tyne and Wear
  Ullswater, in the catchment of the River Eden, is the second-largest of the Cumbrian lakes. It is chosen as an example of a relatively deep lake with both oligotrophic and mesotrophic elements in its fauna and flora. The south-western part of the lake is surrounded by high fells of the Borrowdale Volcanics with enclosed farmland confined to the valley bottoms. The north-eastern arm is in gentler terrain with deeper soils and a greater extent of enclosed farmland. The lake flows into the River Eamont, one of the major tributaries of the River Eden. The lake has an extremely rich aquatic flora, including eight species of Potamogeton. These include various-leaved pondweed P. gramineus, red pondweed P. alpinus and long-stalked pondweed P. praelongus. The nationally scarce six-stamened waterwort Elatine hexandra is also found in some of the bays. Ullswater supports one of the few populations of powan Coregonus lavaretus in the UK. Arctic charr Salvelinus alpinus was formerly present but is believed to have become extinct in the 1940s, possibly because of mining pollution in spawning areas.
• Ronas Hill - North Roe Highlands and Islands
  This site represents oligotrophic lochs and lochans (Types 2 and 3) on peatlands in Shetland. The waterbodies are concentrated on the northern side of Ronas Hill. The lochs support vegetation typical of oligotrophic habitat including water lobelia Lobelia dortmanna, quillwort Isoetes lacustris, bulbous rush Juncus bulbosus and shoreweed Littorella uniflora. Many of the lochs also support the scarce spring quillwort Isoetes echinospora. Several of the lochs contain small holms that support important relicts of Shetland’s tree and scrub habitat. In addition the site supports one of the densest aggregations of breeding red-throated divers Gavia stellata in the UK and important aquatic invertebrate populations including the arctic water-flea Eurycercus glacialis, which occurs in the highest lochan on Ronas Hill and has been found at only one other site in Britain.
• Rum Highlands and Islands
  The mountainous terrain of the island of Rum off the west coast of Scotland supports waterbodies typical of oligotrophic to mesotrophic standing waters. The lochs in this site are classified as Type 2 or 3 and can be extremely oligotrophic with a low species diversity. However, some coastal lochs exhibit a strong maritime influence and, as a consequence, support a greater diversity and abundance of macrophytes. The three major rock types on the island, Torridonian sandstone and ultrabasic and granitic igneous rocks, influence the trophic status of the lochs. The site contains several species of note including awlwort Subularia aquatica, floating bur-reed Sparganium angustifolium and common reed Phragmites australis. The remote location of the island and its National Nature Reserve status means that the lochs have not been subject to significant unnatural change.
• South Uist Machair Highlands and Islands
  South Uist Machair includes the largest machair system in the British Isles and contains excellent examples of transition from marine to freshwater habitats including oligotrophic freshwaters. At this site, oligotrophic conditions are present within lochs that receive drainage from the acidic blacklands, hills and moors. The principal oligotrophic loch in this site is Loch Druidibeg which has a catchment that lies over Lewisian gneiss, a rock type which weathers to produce acid and nutrient-poor soils. Loch Druidibeg is a large, shallow loch that supports a flora typical of its nutrient-poor status.
• The New Forest Gloucestershire, Wiltshire and Bristol/Bath area, Hampshire and Isle of Wight
  In the New Forest vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea occurs on the edge of large temporary ponds, shallow ephemeral pools and poached damp hollows in grassland, which support a number of specialist species in a zone with toad rush Juncus bufonius. These include the two nationally scarce species coral-necklace Illecebrum verticillatum and yellow centaury Cicendia filiformis, often in association with allseed Radiola linoides and chaffweed Anagallis minima. Heavy grazing pressure is of prime importance in the maintenance of the outstanding flora of these temporary pond communities. Livestock maintain an open habitat, controlling scrub ingress, and trampling the surface. Commoners’ animals also transport seed in their hooves widely from pond to pond where suitable habitat exists. Temporary ponds occur throughout the Forest in depressions capable of holding water for part of the year. Most ponds are small (between 5-10 m across) and, although great in number, amount to less than 10 ha in total area.
• Wast Water Cumbria
  Wast Water is a relatively large and deep example of an oligotrophic waterbody (Type 3) in the Lake District, north-west England. Except for a small portion on Eskdale granite, Wast Water lies entirely on Borrowdale Volcanics rocks, and rocky substrates predominate along 73% of its shoreline. The submerged macrophyte communities of Wast Water are typical of oligotrophic lakes. Species such as bulbous rush Juncus bulbosus, quillwort Isoetes lacustris, shoreweed Littorella uniflora, awlwort Subularia aquatica and stoneworts Nitella spp. are known to occur. Least bur-reed Sparganium natans and floating bur-reed Sparganium angustifolium occur in more sheltered bays and are more typical of mesotrophic situations. Blunt-leaved pondweed Potamogeton obtusifolius has been recorded and bog pondweed P. polygonifolius occurs in the stream outlets. The macro-invertebrates of Wast Water are typical, including gastropod species (wandering snail Lymnaea peregra and river limpet Ancylus fluviatilis), the leech Erpobdella octoculata and the triclad Polycelis nigra. Arctic charr Salvelinus alpinus occur in the lake.

SACs where this Annex I habitat is a qualifying feature, but not a primary reason for site selection

• Afon Teifi/ River Teifi West Wales and The Valleys
• Ben Nevis Highlands and Islands
• Ben Wyvis Highlands and Islands
• Coll Machair Highlands and Islands
• Creag Meagaidh Highlands and Islands
• Elenydd East Wales, West Wales and The Valleys
• Fannich Hills Highlands and Islands
• Garron Plateau Northern Ireland
• Loch Fada Highlands and Islands
• Merrick Kells South Western Scotland
• Migneint-Arenig-Dduallt West Wales and The Valleys
• Mointeach nan Lochain Dubha Highlands and Islands
• Mointeach Scadabhaigh Highlands and Islands
• North Harris Highlands and Islands
• Pettigoe Plateau Northern Ireland
• Rhinog West Wales and The Valleys
• River Tay Eastern Scotland, Highlands and Islands
• Sligachan Peatlands Highlands and Islands
• Strathglass Complex Highlands and Islands
• Taynish and Knapdale Woods Highlands and Islands