Lake Group - Description - Summary
Lake Group A -
Small, predominantly northern dystrophic peat or heathland pools, dominated by Sphagnum spp.
- Lake group A summary:
Vegetation: Very species-poor. Dominated by Sphagnum; Juncus bulbosus frequently present.
Affinities: Equivalent to Type 1 in Palmer (1992) and Palmer et al. (1992). Distribution: Small water bodies on peat or heathland, usually 100-350 m above sea level. Almost confined to Scotland, mainly in the western half of the country but a heavy concentration on the blanket bog of the Flow Country (Photo 1). The southerly outliers are: Abbot's Moss (Cheshire, basin mire), Sphagnum pools, Swanholme Pits (Lincolnshire heathland), Woolmer Ponds (Hampshire heathland), Little Sea Mere (Dorset heathland).
Chemistry: Highly acidic, low conductivity, very low alkalinity. NVC: M1 (Sphagnum auriculatum bog pool).
M2 (S. cuspidatum/recurvum bog pool).
EC Habitats Directive: Natural dystrophic lakes are represented by pools on blanket bog in Scotland (e.g. in the Flow Country of Caithness and Sutherland) and on raised bogs (e.g. Abbots Moss, Cheshire). Oligotrophic waters containing very few minerals of sandy plains (Littorelletalia uniflorae) are represented by Little Sea, a shallow lake at Studland Dunes in southwest England.
Rare Species: The following species each occur in a single site in this group: Apium inundatum Special Responsibility; Eleogiton fluitans Special Responsibility; Eriocaulon aquaticum Nationally Rare, Special Responsibility; Nuphar pumila Nationally Scarce.
Lake Group B -
Widespread, usually low-lying acid moorland or heathland pools and small lakes, with a limited range of plants, especially Juncus bulbosus, Potamogeton polygoniofolius, and Sphagnum spp.
- Lake group B summary:
Vegetation: Moderately species-poor. Typified by P. polygonifolius, J. bulbosus and Sphagnum spp.; Nymphaea alba, Potamogeton natans frequently present. Affinities: Closest to Type 2 in Palmer (1992) and Palmer et al. (1992).
Distribution: Small waters on peat or heaths, usually <200 m above sea level. Mainly north and west Scotland and the Lake District. Southerly outliers include Broad Pool and Llyn Lech Owain (South Wales), Oak Mere (Cheshire; Photo 2), ponds on the Surrey and Hampshire heaths, Priddy Pool (Mendips), Stover Lake (Devon), pools on the Lizardheathland.
Chemistry: Acidic, low conductivity, low alkalinity.
NVC: A7 (Nymphaea alba), A9c (Potamogeton natans: Juncus bulbosus- Myriophyllum alterniflorum subcommunity) and A24 (Juncus bulbosus).EC Habitats Directive: Oligotrophic waters containing very few minerals of sandy plains (Littorelletalia uniflorae) are represented by Oak Mere (West Midlands of England). Hard oligo-mesotrophic waters with benthic vegetation of Chara formations are represented by Croft Pascoe as a local variant of the habitat type within the Lizard Pools SAC.
Rare Species: Apium inundatum Special Responsibility (15 sites); Eleogiton fluitans Special Responsibility:this species is strongly associated with Group B (98 sites); Eriocaulon aquaticum Nationally Rare, Special Responsibility: Group B is the lake type most strongly associated with this species (22 sites); Nuphar pumila Nationally Scarce (17 sites); Nymphoides peltata Nationally Scarce (1 site); Pilularia globulifera Nationally Scarce, Species Action Plan (1 site); Potamogeton filiformis Nationally Scarce (1 site); Ranunculus hederaceus Special Responsibility (2 sites); Ranunculus omiophyllus Special Responsibility (1 site);
Note: The Pant-yr-Ochain Pools, Wales, are misclassified in this group because of the small number of plant records.
Lake Group C1 -
Northern, usually small to medium-sized, acid, largely mountain lakes, with a limited range of plants, but Juncus bulbosus and Sparganium angustifolium constant.
- Lake group C1 summary:
Vegetation: Species-poor. Typified by Juncus bulbosus and Sparganium angustifolium; Sphagnum frequently present sometimes in association with Littorella uniflora, Lobelia dormanna and Isoetes lacustris.
Affinities: Similar to Type 3 in Palmer (1992) and Palmer et al. (1992), but with Sphagnum more prominent, so tending towards Type 2.
Distribution: Generally small to mediumsize upland waters, mostly on peat and 100-400 m above sea level. Almost exclusively in north and west Scotland. Southern outlier sites are a pit at Swanholme, Lincolnshir and Llyn Cau, at 470 m on Cadair Idris and Llyn Llagi, Snowdonia (Wales; Photo 3).
Chemistry: Acidic, low conductivity, very low alkalinity; some sites have very clear water.
NVC: A combination of A22 (Littorella uniflora-Lobelia dortmanna), A23 (Isoetes lacustris/setacea) and A24 (Juncus bulbosus).
EC Habitats Directive: Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea are represented by Llyn Cau (North Wales).
Rare Species: Eleogiton fluitans Special Responsibility (7 sites); Eriocaulon aquaticum Nationally Rare, Special Responsibility (2 sites); Nuphar pumila Nationally Scarce (1 site).
Note: Swanholme Pits are located on heathland at low altitude.
Lake Group C2 -
North western, predominantly large, slightly acid upland lakes, supporting a diversity of plant species, Juncus bulbolus constant, often with Littorella uniflora and Lobelia dortmanna, in association with Myriophyllum alterniflorum.
- Lake group C2 summary:
Vegetation: Greater species diversity than C1. Typified by Juncus bulbosus, Littorella uniflora, Lobelia dortmanna, Myriophyllum alterniflorum, Potamogeton polygonifolius and P. natans.
Affinities: Equivalent to a mixture of Types 2 and 3 in Palmer (1992) and Palmer et al. (1992).
Distribution: A wide size range, including some large lakes, mostly below 250 m above sea level. A very heavy concentration in north and west Scotland, but very few in Orkney, eastern, central or southern Scotland (e.g. Loch an Eilein near Aviemore; Photo 4). Most of the Lake District tarns and lakes, and many upland lakes in Wales, are in this group. The only sites in southern England are a pit at Swanholme (Lincolnshire), Blackbrook Reservoir, (Leicestershire), ponds on Hampshire heathland and a pool on the Lizard.
Chemistry: Acidic, low conductivity, low alkalinity.
NVC: A combination of A22 (Littorella uniflora-Lobelia dortmanna), A23 (Isoetes lacustris/setacea), A24 (Juncus bulbosus), A7 (Nymphaea alba), A9c (Potamogeton natans) and A14 (Myriophyllum alterniflorum). A13 (Potamogeton perfoliatus-Myriophyllum alterniflorum) may be present in the more enriched situations.
EC Habitats Directive: Oligotrophic waters containing very few minerals of sandy plains (Littorelletalia uniflorae) are represented by several sites located on the South Uist machair (Lochs Fada, Cuithe
Moire, a'Phuirt-ruaidh, a'Chnoic Bhuidha, Schoolhouse Loch).Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea are represented by Llyn Cwellyn and Llyn Idwal (Snowdonia), Loch Einich (Cairngorms), Loch Achtriochtan (Glen Coe), Wast Water and tarns in the high fells of the Lake District. Hard oligo-mesotrophic waters with benthic vegetation of Chara spp. are represented by Loch Cill Chriosd (Isle of Skye).
It is possible that natural dystrophic lakes with diverse macrophyte assemblages may occur in this group.
Rare Species: Apium inundatum Special Responsibility (32 sites); Eleogiton fluitans Special Responsibility: Group C2 is the lake type most strongly associated with this species (371 sites); Eriocaulon aquaticum Nationally Rare,
Special Responsibility (22 sites); Luronium natans EC Habitats Directive/Bern Convention, Schedule 8, Nationally Scarce, Special Responsibility, Species Action Plan (3 sites); Najas flexilis EC Habitats Directive/Bern Convention, Schedule 8, Nationally Scarce, Species Action Plan (7 sites); Nuphar pumila Nationally Scarce (17 sites); Nymphoides peltata Nationally Scarce (2 sites); Pilularia globulifera Nationally Scarce, Species Action Plan (9 sites); Potamogeton coloratus Nationally Scarce (1 site); Potamogeton epihydrus Vulnerable, Species Action Plan: Group C2 contains the only site (in Skye) in the database for this species; record to be confirmed; Potamogeton filiformis Nationally Scarce (7 sites);Potamogeton rutilus Nationally Rare, Species Action Plan (1 site); Ranunculus hederaceus Special Responsibility (1 site); Ranunculus omiophyllus Special Responsibility (5 sites); Chara curta Nationally Scarce, Special Responsibility, Species Action Plan (2 sites); Nitella confervacea Nationally Rare: this
species is strongly associated with Group C2 (5 sites); Nitella gracilis Vulnerable, Species Action Plan (2 sites). Note: More than 40% of the lakes in the dataset are in this group and they cover a
wide range of lake habitat types, as illustrated by the links made with the NVC and Habitats Directive. Water colour may vary from dystrophic brown water to clear oligotrophic water. The classic
oligotrophic waters are in this group. Examples are Loch Ard (Trossachs), East Loch Ollay (South Uist), Buttermere, Wast Water and Hodson's Tarn (Lake District, England) and Llyn Idwal (Wales). Tarn Dub in upper Teesdale appears to be misclassified in this group because of the lack of Chara records in the survey data.
Lake Group D -
Widespread, often large, mid-altitude circumneutral lakes, with a high diversity of plants including Littorella uniflora, Myriophyllum alterniflorum, Callitriche hamulata, Fontinalis antipyretica and Glyceria fluitans.
- Lake group D summary:
Vegetation: A species-rich group. Typified by Littorella uniflora, Myriophyllum alterniflorum, Callitriche hamulata, Fontinalis antipyretica and Glyceria fluitans. The most constant pondweeds are P. natans, P.
polygonifolius, P. perfoliatus and P. berchtoldii. Nitella spp. and, to a lesser extent, Chara spp. are represented.
Affinities: Contains many of the sites in Type 5A in Palmer (1992) and Palmer et al. (1992) together with some Type 3 and Type 4 waters.
Distribution: This lake group has a wide size range, including some large lakes, mostly < 250 m above sea level. Numerous and scattered throughout Scotland, frequent in the Lake District (e.g. Bassenthwaite Lake; Photo 5) and Wales. Sites are very rare in southern England and include two pits at Swanholme (Lincolnshire), and ponds on Berkshire heathland.
Chemistry: Weakly acidic, low conductivity and moderate alkalinity.
NVC: A combination of A22 (Littorella uniflora-Lobelia dortmanna), A23 (Isoetes lacustris/setacea), A13 (Potamogeton perfoliatus-Myriophyllum alterniflorum), A7 (Nymphaea alba), A9c (Potamogeton natans: Juncus bulbosus- Myriophyllum alterniflorum subcommunity) and A15 (Elodea canadensis); in more nutrient-poor areas probably also A14 (Myriophyllum alterniflorum) and A24 (Juncus bulbosus).
EC Habitats Directive: Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea are represented by Loch of Clunie and Loch Maree (Scottish Highlands), Loch Insh (River Spey), Loch Kinord (Dee Valley, Scotland), Bassenthwaite Lake (English Lake District).
Rare Species: Apium inundatum Special Responsibility (48 sites); Elatine hydropiper Nationally Scarce (4 sites); Eleogiton fluitans Special Responsibility (26 sites); Luronium natans EC Habitats Directive/ Bern Convention, Schedule 8, Nationally Scarce, Special Responsibility, Species Action Plan: Group D is the type most strongly associated with this species (5 sites); Najas flexilis EC Habitats Directive/Bern Convention, Schedule 8, Nationally Scarce, Species Action Plan (4 sites); Nuphar pumila Nationally Scarce: Group D is the type most strongly associated with this species (17 sites); Pilularia globulifera Nationally Scarce, Species Action Plan: Group D is the type most strongly associated with this species (10 sites); Potamogeton coloratus Nationally Scarce (1 site); Potamogeton compressus Nationally Scarce, Species Action Plan: Group D contains the only site (Loch of Aboyne) in the database for this species; Potamogeton filiformis Nationally Scarce (2 sites); Ranunculus hederaceus Special Responsibility (17 sites); Ranunculus omiophyllus Special Responsibility (3 sites); Nitella gracilis Vulnerable, Species Action Plan (1 site).
Note: This group includes classic mesotrophic sites such as Loch Insh, Lochs Clunie, Marlee and Craiglush (Perth, Scotland), the Lake of Menteith(Stirling), Bassenthwaite Lake and Windermere (The Lake District), Llyn Eiddwen and Llyn Fanod (mid-Wales) and Bala Lake/Llyn Tegid (north Wales). Llyn Y Fan Fawr (Brecon Beacons, Wales) is probably misclassified in this group as a result of the small number of plant records for this site
Lake Group E -
Northern, often large, low altitude and coastal, above-neutral lakes with a high diversity of plant species including Littorella uniflora, Myriophyllum alterniflorum, Potamogeton perfoliatus and Chara spp.
- Lake group E summary:
Vegetation: A species-rich group. Typified by Littorella uniflora, Myriophyllum alterniflorum, Potamogeton perfoliatus and Chara. Other common pondweeds are P. natans, P. gramineus, P. berchtoldii, P. polygonifolius and P. filiformis.
Affinities: Closest to Type 4 in Palmer (1992) and Palmer et al. (1992), but some similarities to Type 3 and 5A. Distribution: A wide size range, including some large lakes, mostly < 100 m above sea level. Largely coastal lakes in north and west Scotland, especially on the islands (e.g. Loch of Hundland, mainland Orkney; Photo 6); scattered sites inland. Rare in the Lake District (e.g. Ullswater) and Wales (only Llyn Helyg). Sites are very rare in southern England and include four pits at Swanholme (Lincolnshire).
Chemistry: Circumneutral and above pH, moderate conductivity and alkalinity.
NVC: A combination of A22 (Littorella uniflora-Lobelia dortmanna), A23 (Isoetes lacustris/setacea), A13 (Potamogeton perfoliatus-Myriophyllum alterniflorum), A9c (Potamogeton natans: Juncus bulbosus- Myriophyllum alterniflorum subcommunity) and A10 (Polygonum amphibium). In more nutrient-poor areas of these waters A14 (Myriophyllum alterniflorum) and A24 (Juncus bulbosus) probably occur.
EC Habitats Directive: Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the Isoëto-Nanojuncetea are represented by Loch nan Cat (Ben Lawers), Loch Ussie (Scottish Highlands), Loch Davan (Dee Valley), Ullswater (Lake District).Hard oligo-mesotrophic waters with benthic vegetation of Chara spp. are represented by the Scottish Durness cluster of three marl lochs (Croispol, Borralie and Caladail), several lochs in the South Uist machair (Loch Hallan, Grogarry Loch, Loch an Eilean, Mid Loch Ollay and Loch Toronish). Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation are represented by Loch of Wester, Loch Roag, Loch na Liana Moire, Loch of Isbister (Scotland), and Greenlee and Broomlee Loughs (Northumberland). Coastal lagoons are represented by a complex at Loch Roag on the Western Isles.
Rare Species: Apium inundatum Special Responsibility: Group E is the type most strongly associated with this species (45 sites); Eleogiton fluitans Special Responsibility (17 sites); Najas flexilis EC Habitats Directive/Bern Convention, Schedule 8, Nationally Scarce, Species Action Plan: Group E is the type most strongly associated with this species (11 sites); Nymphoides peltata Nationally Scarce
(1 site); Pilularia globulifera Nationally Scarce, Species Action Plan (4 sites); Potamogeton coloratus Nationally Scarce, (1 site); Potamogeton filiformis Nationally Scarce: Group E is the type most closely
associated with this species (77 sites); Potamogeton friesii Nationally Scarce (3 sites); Potamogeton rutilus Nationally Rare, Species Action Plan: Group E is the type most strongly associated with this species (7 sites); Ranunculus hederaceus Special Responsibility (7 sites); Ruppia cirrhosa Nationally Scarce (2 sites); Chara aculeata (pedunculata) Nationally Scarce: the only site in the database for this species is Loch Ballygrant (Island of Islay); Chara curta Nationally Scarce, Special Responsibility, Species Action Plan: this species is strongly associated with Group E (5 sites); Nitella confervacea Nationally Rare (2 sites);
Nitella mucronata Nationally Scarce: the only site in the database for this species is in Shetland.
Note: Classic coastal, moderately to strongly calcareous marl sites are included here, such as Loch Eye, and some machair lochs in South Uist, Coll and Tiree (e.g. Mid Loch Ollay, Loch Hallan, Loch Roag). At Swanholme, some of the pits that appear to be fed by calcareous groundwater are in this group. Broomlee and Greenlee Loughs, (Northumberland) are other inland examples
Lake Group F -
Widespread, usually medium sized, lowland, above neutral lakes, with a limited range of species, but typified by water lillies and other floating-leaved vegetation.
- Lake group F summary:
Vegetation: A species-poor group. Typified by Nuphar lutea, accompanied by Nymphaea alba, Lemna minor, Callitriche stagnalis and Persicaria amphibia.
Affinities: Nearest to Type 9 in Palmer (1992) and Palmer et al. (1992), but some similarities to Type 8.
Distribution: Mostly medium-sized lakes < 100 m above sea level. Centred on the West Midland Meres, but with a few outliers in Scotland, Wales and the rest of England (e.g. Slapton Ley, Devon; Photo 7).
Chemistry: Above neutral pH, moderate conductivity, high alkalinity.
NVC: A8b and c (Nuphar lutea: Callitriche stagnalis-Zanichellia palustris and Nymphaea sub-communities).
EC Habitats Directive: Hard oligo-mesotrophic waters with benthic vegetation of Chara formations are represented by Llyn yr Wyth Eidion (Anglesey) and Hawes Water (Silverdale, northern England).
Rare Species: Nuphar pumila Nationally Scarce (1 site); Pilularia globulifera Nationally Scarce,Species Action Plan (1 site); Ranunculus hederaceus Special Responsibility (2 sites); Ranunculus omiophyllus Special Responsibility (2 sites).
Note: This group contains classic waterlily sites, including Llyn yr Wyth Eidion (Anglesey, Wales), and the West Midlands Meres that have water-lily vegetation.
Lake Group G -
Central and eastern, above neutral, lowland lakes with Lemna minor, Elodea canadensis, Potamogeton natens and Persicaria amphibia.
- Lake group G summary:
Vegetation: A moderately species-rich group. Typified by Lemna minor, Elodea canadensis, Potamogeton natans and Persicaria amphibia.
Affinities: Nearest to Type 10A in Palmer (1992) and Palmer et al. (1992), but with elements of Type 8. Distribution: Mostly small to mediumsized lakes < 100 m above sea level. A widespread group, well represented in lowland England, especially the West Midlands Meres (e.g. The Mere, Ellesmere; Photo 8), common in south and east Scotland but rare in Wales.
Chemistry: Circumneutral pH, moderate conductivity, high alkalinity.
NVC: A2 (Lemna minor), A9b (Potamogeton natans: Elodea canadensis sub-community), A10 (Polygonum amphibium) and A15 (Elodea canadensis).
EC Habitats Directive: Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation are represented by Llyn Coron (Anglesey, Wales).
Rare Species: Alisma gramineum Schedule 8, Critically Endangered: the only site for this species (Westwood Great Pool, Worcestershire) is in Group G; Apium inundatum Special responsibility (18 sites); Callitriche truncata Nationally Scarce: the only site for this species (Clumber Park Lake) is in Group G; Elatine hydropiper Nationally Scarce: Group G is the type most strongly associated with this species (9 sites); Nuphar pumila Nationally Scarce (2 sites); Nymphoides peltata Nationally Scarce (3 sites); Potamogeton coloratus Nationally Scarce (2 sites); Potamogeton filiformis Nationally Scarce (1 site); Potamogeton friesii Nationally Scarce (4 sites); Ranunculus hederaceus Special Responsibility (25 sites); Ranunculus omiophyllus Special Responsibility (2 sites); Ruppia cirrhosa Nationally Scarce (1 site); Wolffia arrhiza Nationally Scarce: the only site for this species (Southlake Moor, Somerset) is in Group G; Chara rudis Nationally Rare (1 site).
Note: This is the commonest lowland eutrophic lake type. Well-known sites in England include Semer Water, some of the Cotswold Water Park Pits and Sunbiggin
Lake Group H -
Northern, small, circumneutral, lowland lakes, with low species diversity characterised by the presence of Glyceria fluitans and Callitriche stagnalis.
- Lake group H summary:
Vegetation: A very species-poor group. Typified by Glyceria fluitans and Callitriche stagnalis.
Affinities: No near counterpart in Palmer (1992) and Palmer et al. (1992), but elements of Type 8. Distribution: Mostly small water bodies < 100 m above sea level. An almost exclusively lowland Scottish lake type, with a heavy concentration in eastern Orkney (e.g. Mill Loch, Eday, Orkney; Photo 9). Southerly outliers are Blelham Fish Pond (Lake District), Peckforton Mere (West Midlands) and Pippingford
Park Lakes (south-east England). No representative in Wales.
Chemistry: Circumneutral pH, moderate conductivity, high alkalinity.
NVC: A16 (Callitriche stagnalis).
EC Habitats Directive: None. Rare Species: Apium inundatum Special responsibility (11 sites); Potamogeton filiformis Nationally Scarce (2 sites); Ranunculus hederaceus Special Responsibility (6 sites); Ranunculus omiophyllus Special Responsibility (1 site).
Note: A closer investigation of the sites on Orkney may provide an insight into the environmental characteristics of this lake group.
Lake Group I -
Widespread, mostly moderately large, base rich lowland lakes, with Chara spp., Myriophyllum spicatum and a diversity of Potamogeton species.
- Lake group I summary:
Vegetation: A moderately species-rich group. Typified by Chara, Myriophyllum spicatum, Callitriche stagnalis and C. hermaphroditica, Zannichellia palustris and a wide range of pondweeds - P. filiformis, P. pectinatus, P. pusillus. P. filiformis is characteristic of the Scottish coastal sites.
Affinities: A mixture of Types 10A and 7 in Palmer (1992) and Palmer et al. (1992). Distribution: Widespread distribution. Mostly medium-sized water bodies < 75 m above sea level. In Scotland, there are concentrations in Orkney, on the machair of the Outer Hebrides and Tiree, and the Central Lowlands. Uncommon but widespread in England and Wales.
Chemistry: Relatively high pH, moderate conductivity, high alkalinity.
NVC: A11 (Potamogeton pectinatus- Myriophyllum spicatum) and probably all three sub-communities (P. pusillus, Elodea canadensis and P. filiformis) occur. Some possible affinities with A16 (Callitriche stagnalis).
EC Habitats Directive: Hard oligomesotrophic waters with benthic vegetation of Chara formations are represented by Malham Tarn (northern Yorkshire, England; Photo 10), and Kenfig Pool (South Wales), Loch Baile a'Ghobhainn and Loch Fiart (Island of Lismore, Argyll, Scotland). Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation are represented by Llangorse Lake and Llyn Dinam (Wales), Crag Lough (Northumberland), Loch a'Phuill, Loch Achnacloich, Loch Watten and Loch Bhasapol (Scotland) and lochs in the Outer Hebrides (Loch nam Feithean, West Loch Ollay, Loch Ardvule, Loch Stilligarry).
Rare Species: Apium inundatum Special Responsibility (15 sites); Elatine hydropiper Nationally Scarce (2 sites); Eleogiton fluitans Special Responsibility (1 site); Nuphar pumila Nationally Scarce (2 sites); Nymphoides peltata Nationally Scarce (4 sites); Potamogeton coloratus Nationally Scarce, Special Responsibility: Group I is the lake type most strongly associated with this species (4 sites); Potamogeton filiformis Nationally Scarce: this species is strongly associated with Group I (77 sites); Potamogeton friesii Nationally Scarce: Group I is the type most strongly associated with this species (21 sites); Ranunculus hederaceus Special Responsibility (10 sites); Ranunculus omiophyllus Special Responsibility (4 sites); Ruppia cirrhosa Nationally Scarce (1 site); Chara rudis Nationally Rare (1 site).
Note: This group seems to be a mixture of coastal and inland calcareous lakes. For instance, in Wales, this group is represented by Kenfig Pool lying within an extensive coastal sand-dune system, while Llangorse Lake is located inland on a tributary of the River Wye. In England, Hornsea Mere occurs on the coast, and contrasts with the location of most of the Cotswold Water Park lakes, several Breckland Meres, Crag Lough (Roman Wall), Malham Tarn (Yorkshire) and two pits at Swanholme (Lincolnshire). In Scotland, the coastal lochs in South Uist and Loch Lanlish (Durness) differ from the more inland locations of Lochs Leven, Branxholme Easter (Borders), and Watten (Caithness). Many of the sites in this group are marl lakes on limestone, chalk or machair.
Lake Group J -
Northern, coastal, brackish lakes, with Potamogeton pectinatus, Enteromorpha spp., Ruppia maritima and Fucoid algae.
- Lake group J summary:
Vegetation: A very species-poor group. Typified by Enteromorpha, Ruppia maritima, Potamogeton pectinatus, Callitriche stagnalis, and sometimes fucoid algae.
Affinities: Equivalent to Type 6, but many of the brackish sites in Palmer (1992) and Palmer et al. (1992) were not included in the JNCC dataset. Distribution: Small to medium-sized water bodies at sea level. Exclusively coastal, occurring in Shetland, Orkney (the main concentration; e.g. Loch of the Stack, Westray; Photo 11), the Outer Hebrides and the west coast of mainland Scotland.
Chemistry: High pH, conductivity and alkalinity.
NVC: A12 (Potamogeton pectinatus).
EC Habitats Directive: The vegetation of coastal lagoons may include Zostera spp., Ruppia spp., Potamogeton spp. and stoneworts.
Rare Species: Apium inundatum Special Responsibility (1 site); Eleogiton fluitans Special Responsibility (1 site); Potamogeton filiformis Nationally Scarce (2 sites); Ranunculus hederaceus Special Responsibility (4 sites).
Note: Two sites - one of the Stibbington Gravel pits (only records Nuphar lutea and Potamogeton pectinatus) and Hell Kettles (only records Lemna minor, Potamogeton pectinatus and Ranunculus circinatus) - are misclassified as J because of their extremely poor flora.