Habitat account - Freshwater habitats


3160 Natural dystrophic lakes and ponds 

Background to selection

Distribution of SACs/SCIs/cSACs with habitat 3160 Natural dystrophic lakes and ponds.  Click image for enlarged map.
Distribution of SACs/SCIs/cSACs with habitat 3160 Natural dystrophic lakes and ponds. Click image for enlarged map.

Description and ecological characteristics

 

Dystrophic systems most often occur on 7130 Blanket bogs and may include isolated seasonal pools, random collections of irregularly-shaped more-or-less permanent waters, and ordered linear or concentric arrays of pools and small lochs. Dystrophic pools may be also found on raised bogs situated mainly on plains and valley bottoms.

 

These water bodies are very acidic and poor in plant nutrients. Their water has a high humic acid content and is usually stained dark brown through exposure to peat. Most examples are small (less than 5 ha in extent), shallow, and contain a limited range of flora and fauna. In northern Scotland (where they are known as ‘dubh lochans’) bog-mosses Sphagnum spp. typically dominate and lesser bladderwort Utricularia minor is often found. Some dystrophic lakes have developed a ‘schwingmoor’ where bog-mosses are found in association with cottongrass Eriophorum angustifolium and white water-lily Nymphaea alba. The pools are naturally species-poor and a littoral zone is often absent. Fringing vegetation is that characteristic of the habitat in which the pools occur. Several notable scarce dragonfly species are associated with dystrophic lakes and ponds.

 

NVC types M1 Sphagnum auriculatum bog pool community and M2 Sphagnum cuspidatum/recurvum bog pool community are excluded from the Annex I definition, while non-dystrophic examples may be referable to Annex I type 3130 Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea.

European status and distribution

 

The status of Natural dystrophic lakes and ponds in the EU is unknown.

UK status and distribution Click to view UK distribution of this habitat

 

In the UK Natural dystrophic lakes and ponds are widespread in the north-west and scarce in the south.

Site selection rationale

 

Site selection has taken account of the UK distribution of dystrophic water bodies and reflects the narrow range of ecological variation exhibited by this habitat. The selected sites each contain a number of dystrophic water bodies, and sites with relatively large examples have been favoured.

 

Dystrophic waters are a common feature of 7130 Blanket bogs in Scotland but are extremely rare in England and Wales, where the number of sites of SAC quality is correspondingly small. The preponderance of sites in Scotland reflects the uneven distribution of this habitat type in the UK. A small number of dystrophic pools occur in the lowlands of England; those associated with bogs in the West Midlands have been seen as having particular value for nature conservation because of the rarity of the habitat type in this part of the UK.


Site accounts

Caithness and Sutherland Peatlands Highlands and Islands
This site represents Natural dystrophic lakes and ponds on 7130 Blanket bogs in northern Scotland. The scale and diversity of the peatlands of Caithness and Sutherland make them unique in Europe. They are three times larger than any other peat mass in the UK. Dystrophic waters are especially common in the Peatlands. Compared to most other blanket bog systems, at this site waterbodies account for a high proportion of the bog surface. Dystrophic water bodies here range in size from pools to medium-sized lochans. Surface patterns and pool complexes occur in a variety of forms, reflecting different climatic and hydrological conditions within the site.
Foinaven Highlands and Islands
Foinaven in the north-west Highlands of Scotland supports dystrophic lochs and lochans formed in upland bogs. The ponds are generally small (<1 ha), un-named waterbodies and are located on the blanket bogs formed over most of the flat gneiss terrain and on the terraces alongside the River Dionard. The lochs support an impoverished flora that typically includes bog-mosses Sphagnum spp. and bogbean Menyanthes trifoliata.
Hoy Highlands and Islands
Hoy provides an important representation of dystrophic lochs and pools on 7130 Blanket bogs and heathlands. The dystrophic lochs and ponds range in size and substrate type from pool complexes to moderate-sized lochs with peat, sand or stone substrates. The waterbodies support a limited flora typical of the acidic, low-nutrient habitat that includes bulbous rush Juncus bulbosus. As with many upland sites the remote location has protected the waterbodies from significant disturbance.
Inverpolly Highlands and Islands
Inverpolly supports high-quality freshwater loch habitats including dystrophic standing waters. The lochs are part of small unproductive drainage systems which characterise this part of the north-west Highlands. The naturally dystrophic pools are small (usually <1 ha) un-named waters, which are highly acidic, of very low productivity, and are often characterised by the presence of bog-mosses Sphagnum spp. The small size of lochans in this category and their remote geographical location has protected them against significant disturbance.
Lewis Peatlands Highlands and Islands
This site in the Outer Hebrides is part of the vast flow-ground on Lewis and represents dystrophic standing waters in western Scotland. Lewis Peatlands is a complex landscape of broad plateaux, valleys, hollows and gentle slopes that supports extensive 7130 Blanket bogs and moorland where dystrophic water systems occur. The dystrophic waters vary in shape in size but are generally small pools and lochans that can have a complex, interconnected form. The waterbodies are typical of this habitat type being highly acidic, very poor in nutrients and supporting abundant bog-mosses Sphagnum spp.
North Harris Highlands and Islands
North Harris is representative of dystrophic lochans on 7130 Blanket bogs and heathland in a mountain environment that experiences a strong oceanic influence. The naturally dystrophic waterbodies tend to be small un-named dubh lochans which are highly acidic, of very low productivity and support an impoverished flora and fauna typical of this habitat. The lochans typically contain a peat or silt substrate that supports bulbous rush Juncus bulbosus and bogbean Menyanthes trifoliata. The lochans are also characterised by the presence of bog-mosses Sphagnum spp.
Pettigoe Plateau Northern Ireland
The uplands of Pettigoe Plateau, which extend from County Fermanagh in Northern Ireland into County Donegal in the Republic of Ireland, are covered by an extensive area of undulating western 7130 Blanket bogs and heathland with numerous wetlands. The site contains the largest series of bog pool complexes in Northern Ireland. These natural dystrophic lakes and ponds are all less than 0.5 ha in size, and tend to be steep-sided, with banks and bed formed by layers of deep peat. The flora and fauna of these is generally rather impoverished, which is typical of such low-nutrient and base-poor waters.
Rannoch Moor Eastern Scotland, Highlands and Islands
Rannoch Moor in the southern Scottish Highlands is representative of dystrophic pools formed in upland 7130 Blanket bogs. The dystrophic lochans of this site exhibit considerable diversity in size, depth and shoreline type, including those with mineral shorelines, a relatively uncommon variant. These upland dystrophic waters are characteristically shallow and base-poor, with an impoverished flora and fauna.
Ronas Hill - North Roe Highlands and Islands
Ronas Hill is representative of dystrophic pools and lochans formed in 7130 Blanket bogs in Shetland. The dystrophic pools and lochans typically have a peat substrate and support an impoverished plant flora. The site has considerable aquatic invertebrate interest. Notable species include the northern aquatic beetles Potamonectes griscostriatus and Agabus arcticus.
Rum Highlands and Islands
Rum, on the west coast of Scotland, contains dystrophic lochans formed mainly at mid-altitude in areas of upland 7130 Blanket bogs and 4010 Northern Atlantic wet heaths with Erica tetralix over Torridonian sandstone. The impoverished aquatic flora is typical of this habitat type and includes bulbous rush Juncus bulbosus and bogbean Menyanthes trifoliata. The dystrophic lochans vary in size but are typically relatively small unnamed waters that are highly acidic and have a range of substrates, from boulders to organic mud or peat. Their small size and remote location has helped to protect the lochans from any significant unnatural change.
Slieve Beagh Northern Ireland
Slieve Beagh in Northern Ireland is an extensive area of undulating upland 7130 Blanket bogs and heathland that extends into County Monaghan in the Republic of Ireland. Within Northern Ireland, the peatland complex contains a number of natural dystrophic lakes and ponds that range in size from 5.5 ha to less than 0.5 ha. The site contains the largest concentration of medium- to large-sized dystrophic lakes in Northern Ireland. The smaller lakes and ponds are steep-sided with banks and bed formed by layers of deep peat. The larger lakes have shallow, shelving shores and hard, stony beds. Although the base-poor waters are low in plant nutrients and tend to have a characteristically impoverished flora and fauna, some important communities are present on the site. The most common type is characterised by the aquatic mosses Sphagnum cuspidatum, S. denticulatum, Drepanocladus spp. and the liverwort Jungermannia sp. The floating and marginal vegetation tends to be sparse and restricted, and consists of a scattered swamp and acid poor-fen fringe. The lakes are also important for a range of upland invertebrates.
Sligachan Peatlands Highlands and Islands
Sligachan Peatlands on the Island of Skye occupies parts of low-lying valleys near the head of Loch Sligachan and contains many standing waters of dystrophic character. The dystrophic pools and lochans sit in a complex terrain of slopes, ridges, knolls and hollows that support blanket bog and oceanic mires. The dystrophic waters vary in shape from rounded to linear lochans but are predominantly complex, interconnected systems. They support a typically impoverished plant flora which includes such species as bogbean Menyanthes trifoliata, bladderworts Utricularia spp. and bog-mosses Sphagnum spp. The lochans also support pipewort Eriocaulon aquaticum, often in abundant populations, and the site is thought to represent the British stronghold for this rare species.
West Midlands Mosses Cheshire, Shropshire and Staffordshire
West Midlands Mosses contains three pools, one at Clarepool Moss and two at Abbots Moss, that are examples of dystrophic lakes and ponds in the lowlands of England and Wales, where this habitat type is rare. The lake at Clarepool Moss is unusual as a dystrophic type on account of its relatively base-rich character, which is reflected in the presence of a diverse fauna and flora. The two at Abbots Moss are more typical, base-poor examples. The dystrophic lakes and ponds at this site are associated with Schwingmoor development, a characteristic of this habitat type in the West Midlands. Schwingmoor is an advancing floating raft of bog-moss Sphagnum, often containing NVC type M3 Eriophorum angustifolium bog pool community, which grows from the edge of the pool and can completely cover over the pool; the site has also been selected for this Annex I feature (7140 Transition mires and quaking bogs).
Woolmer Forest Hampshire and Isle of Wight
Within Woolmer Forest, Cranmer Pond is a southern example of a dystrophic pond in an area of 4010 Northern Atlantic wet heaths with Erica tetralix and 7150 Depressions on peat substrates of the Rhynchosporion. The 8 ha pond is thought to originate from peat-cutting, and has an average depth of 1 m. The aquatic flora is comprised of bulbous rush Juncus bulbosus var. fluitans, which grows submerged and forms dense mats at the margins, and bog-mosses Sphagnum spp. which grow in shallower areas. To the north and south of Cranmer Pond are areas of 7140 Transition mires and quaking bogs.

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

Cairngorms Highlands and Islands, North Eastern Scotland
Cuilcagh Mountain Northern Ireland
Feur Lochain Highlands and Islands
Garron Plateau Northern Ireland
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
Tingon Highlands and Islands
 

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