Permanent oligotrophic waterbody with very soft-water species
Quick facts
Red List habitat type | code RLC1.1a |
---|---|
Threat status | |
Europe | Near Threatened |
EU | Near Threatened |
Relation to |
|
Source | European Red List habitat factsheet |
European Red List of habitats reports | |
European Red List of habitats (Excel table) |
Summary
Oligotrophic waters of sandy plains and rocky substrates (granites, gravel, stones, till, moraines) containing very few minerals. The substrates are covered by a thin layer of detritus. The water is carbon deficient and very poorly buffered (low alkalinity). The water is weakly acid to circumneutral. Concentrations of nitrogen and phosphorus are very low and in the oligotrophic range. The water is clear sometimes humic (brown) but always with a very low concentration of chlorophyll. The vegetation is low in species diversity and dominated by aquatic isoetids, i.e. submerged plants with a small rosette of stiff leaves and an extended root system. Aquatic isoetids are adapted to low carbon availability (low pH) by taking up carbon from the sediment through their extended root system, by an adapted carbon fixation (C4), and by re-using carbon-dioxide produced during respiration. The vegetated layer extends from the littoral to lower parts of the sub-littoral zone. The vegetation and its substrate are mechanically influenced by water movement, ice sheets and wind exposition. Sometimes these oligotrophic water bodies can be almost totally unvegetated. In the temperate, Atlantic zone the characteristic isoetid vegetation occurs in lakes fluctuating in water levels where they may be semi-permanent in the summer periods (Arts, 2002; Dierssen, 1996). Apart from the dominant isoetid aquatic macrophytes (i.e. Isoëtes spp.), other plants may be present in addition (Rørslett & Brettum 1989). Important accompanying isoetid species are Lobelia dortmanna, Subularia aquatica in Northern Europe, Eriocaulon aquaticum in Northern-Atlantic Europe or Luronium natans and Isolepis fluitans in Western Europe zones. Subularia aquatica also extends into the mountainous areas of Iberia in this habitat type (Molina et al., 1999).
Many large lakes in northern Europe represent this type or the more mesotrophic type C1.1b in terms of water chemistry and abundant isoetid vegetation. Occurrence and abundance of other growth forms vary according to shore and bottom material, topography, exposition and fetch. Exposed shores have sparse stands of aquatic vegetation, in sheltered bays vegetation has clear zonation, but the stands are still open (Mäkirinta 1978, Rintanen 1982, Toivonen & Lappalainen 1980). The lower limit of submerged vegetation reaches typically the depth of 3-6 meters, sometimes close to 10 meters. Due to postglacial history deeper lakes host some glacial relict crustaceans and vertebrates, including salmonid fish and a critically endangered fresh water seal (Pusa hispida saimensis). Large lakes have diverse waterfowl populations and are important parts of bird migration routes Main differences between this habitat type and the C1.1b is that this one is constantly in the oligotrophic range and therefore is generally poorer than C1.1b in species and communities. Indicators of good quality isoetid species are the most characteristic species of this habitat.
The following characteristics may be used as indicators of a favourable quality:
• Large stands of isoetid species;
• Absence or very low abundance of peat mosses;
• Absence or very low abundance of water plants from eutrophic and alkaline waters;
• Low abundance of water plants with other growth forms than the isoetid growth form, e.g. floating or emerged plants e.g. Potamogeton species or Sparganium angustifolium stands or helophytes (Phragmites australis, Eleocharis spp., Equisetum fluviatile, Carex spp.);
• Long-term habitat stability, with no rapid successional trends (e.g. no trends in acidification or eutrophication);
• Low concentrations of nutrients and chlorophyll (approximately P < 15 μg/L and chlorophyll < 3 μg/L.);
• pH weakly acid to circumneutral ( pH 5.5 - 7), alkalinity < 0.5 meq/L. (Note: Chemical and physical parameters are only indicative, they may change in different geographical area and climatic conditions).
• Thin layer of detritus (no accumulation of organic mud);
• No/ little impact from acidification or regulation;
• Absence or very low abundance of submerged or floating mats of macrophytes e.g. Juncus bulbosus;
• Occurrence of conspicuous populations of salmonid fish, but population of roach (Rutilus rutilus) and other Cyprinidae low.
Threat status
Synthesis of Red List assessment
EU | |
Red List Category | Red List Criteria |
Near Threatened | C/D1, C/D2 |
Europe | |
Red List Category | Red List Criteria |
Near Threatened | C/D1, C/D2 |
Confidence in the assessment
Pressures and threats
- Agriculture
- Cultivation
- Modification of cultivation practices
- Agricultural intensification
- Pollution
- Pollution to surface waters (limnic, terrestrial, marine & brackish)
- Diffuse pollution to surface waters due to agricultural and forestry activities
- Nutrient enrichment (N, P, organic matter)
- Air pollution, air-borne pollutants
- Nitrogen-input
- Natural System modifications
- Human induced changes in hydraulic conditions
- Landfill, land reclamation and drying out, general
- Flooding modifications
- Water abstractions from surface waters
- Natural biotic and abiotic processes (without catastrophes)
- Biocenotic evolution, succession
- Species composition change (succession)
- Eutrophication (natural)
- Climate change
- Changes in abiotic conditions
- Temperature changes (e.g. rise of temperature & extremes)
- Changes in biotic conditions
- Habitat shifting and alteration
Habitat restoration potential
Trends in extent |
|
Average current trend in quantity |
|
Stable ![]() |
Unknown ![]() |
EU28 | EU28+ |
Trends in quality |
|
Average current trend in quality |
|
Decreasing ![]() |
Decreasing ![]() |
EU28 | EU28+ |
Conservation and management needs
List of conservation and management needs
- Measures related to wetland, freshwater and coastal habitats
- Restoring/Improving water quality
- Restoring/Improving the hydrological regime
- Managing water abstraction
- Measures related to spatial planning
- Establish protected areas/sites
- Legal protection of habitats and species
- Measures related to hunting, taking and fishing and species management
- Regulation/Management of fishery in limnic systems
- Measures related to urban areas, industry, energy and transport
- Urban and industrial waste management
Distribution
Geographic occurrence and trends
EU28 | Present or presence uncertain | Current area of habitat (Km2) | Recent trend in quantity (last 50 years) | Recent trend in quality (last 50 years) |
---|---|---|---|---|
Austria | Present | <1 | Decreasing | Decreasing |
Belgium | Present | marginal | Unknown | Decreasing |
Czech Republic | Uncertain | Unknown | Unknown | Unknown |
Denmark | Present | Unknown | Unknown | Unknown |
Estonia | Present | 5 | Decreasing | Decreasing |
Finland mainland | Present | 6230 | Decreasing | Stable |
Aland Islands | Present | 6230 | Decreasing | Stable |
France mainland | Present | Oct-15 | Decreasing | Decreasing |
Germany | Present | <3 | Decreasing | Stable |
Ireland | Present | 407 | Decreasing | Stable |
Italy mainland | Present | 0.1-0.5 | Decreasing | Decreasing |
Latvia | Present | Unknown | Unknown | Unknown |
Netherlands | Present | 0.4 | Decreasing | Decreasing |
Poland | Present | Unknown | Unknown | Unknown |
Portugal mainland | Present | 0.1 | Unknown | Decreasing |
Romania | Uncertain | Unknown | Unknown | Unknown |
Slovakia | Present | Unknown | Unknown | Unknown |
Spain mainland | Present | 2 | Decreasing | Decreasing |
Sweden | Present | 912 | Unknown | Stable |
United Kingdom | Present | 11 | Stable | Stable |
Greece (mainland and other islands) | Uncertain | Unknown | Unknown | Unknown |
Lithuania | Present | Unknown | Unknown | Unknown |
EU28 + | Present or presence uncertain | Current area of habitat (Km2) | Recent trend in quantity (last 50 years) | Recent trend in quality (last 50 years) |
---|---|---|---|---|
Albania | Uncertain | Unknown | Unknown | Unknown |
Iceland | Present | Unknown | Unknown | Unknown |
Former Yugoslavian Republic of Macedonia (FYROM) | Uncertain | Unknown | Unknown | Unknown |
Montenegro | Present | Unknown | Unknown | Unknown |
Norway Mainland | Present | 4400 | Unknown | Stable |
Switzerland | Present | x | Decreasing | Stable |
Extent of Occurrence, Area of Occupancy and habitat area
Extent of Occurrence (EOO) (Km2) | Area of Occupancy (AOO) | Current estimated Total Area | Comment | |
---|---|---|---|---|
EU28 | 5394350 | 3662 | ca. 8000 | |
EU28+ | 3826 | ca. 12500 | Data from Norway has been estimated |
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).