Red List habitat classification > RLC - Freshwater habitats > RLC1.2a Permanent oligotrophic to mesotrophic waterbody with Characeae

Permanent oligotrophic to mesotrophic waterbody with Characeae

Quick facts

Red List habitat type code RLC1.2a
Threat status
Europe Vulnerable
EU Vulnerable
Relation to
Source European Red List habitat factsheet
European Red List of habitats reports
European Red List of habitats (Excel table)


Water bodies belonging to this habitat are characterized by the occurrence of stonewart beds (Characeae family, so-called Chara-lakes). The waters are most often permanent, clear sometimes humic (brown) freshwater lakes and can be either mesotrophic or oligotrophic, either deep or shallow. The sediments are generally mineral (sand or clay) or lightly organic. The alliances Charion vulgaris and Nitellion syncarpo-tenuissimae are representative of more basic and nutrient rich (sometimes even eutrophic) waters. The waters are mostly rich in calcium (Ca > 20 mg/L) and are circumneutral to alkaline, moderately to highly buffered. The alliance Nitellion flexilis may occur in acid waters. In some cases this habitat type may be in contact with the habitat C1.2b (Mesotrophic to eutrophic waters with floating and/or submerged angiosperms). In Eastern Europe, Lychnothamnus barbatus may occur in this habitat; it is a rare species having its northern distribution in Poland and Lithuania.

Charophytes communities are usually poor in species diversity and are often represented by monospecific or very species-poor stands where one species is dominating. The stands may form an open or continuous and closed vegetation bed. The habitat includes pioneer vegetation types or vegetation types in an early successional stage. The habitat conditions that favour the development of Stonewart vegetation include: bare sandy or clayish substrate (e.g. after periodically dredging), relatively high influence of wind that contribute to maintain the lake surface without vegetation, dynamic water levels and periodical emergence of parts of the water body, high light conditions in early spring.

Temporary waters are included as far as related to Charion vulgaris vegetation type. It also includes calcium-rich marl and calcium supersaturated lakes, instead Chara-dominated communities of brackish waters belong to the Charion canescentis alliance and those are included in C1.5 (Permanent inland saline and brackish waters).

Aquatic vascular plants can accompany the Chara species, however stonewarts are largely dominating this habitat type.

Indicators of good quality:

  • Large stands of Chara species
  • Absence or very low abundance of plant species characteristic of eutrophic waters
  • Low abundance of plant species with other growth forms than the Chara growth form, e.g. rooting or floating plants such as Potamogeton spp. or Lemna spp.
  • Low concentrations of nutrients and chlorophyll (approximately P < 30 μg/L and chlorophyll < 7 μg/L)
  • Low turbidity and clear water due by low concentrations of chlorophyll and suspended detritus and sediments in the water column
  • pH weakly acid to circumneutral to alkaline (usually pH 6-8)
  • A thin layer of detritus (no accumulation of organic mud).

Note: Chemical and physical parameters are only indicative, they may change in different geographical area and climatic conditions.

Characteristic species
For full habitat description, please download the habitat factsheet.

Threat status

Synthesis of Red List assessment

This habitat reaches the qualification of Vulnerable, because of its reduction in quantity over the last 50 years and before, and for the high percentage of the habitat moderately affected by biotic and abiotic reduction. For this assessment data from Poland were not available. As Polish lakes form an important part of this habitat in Europe, the assessment is not complete. The assessment for EU 28+ was only slightly different from the assessment for EU 28 as only data from a few countries could be added.
Red List Category Red List Criteria
Vulnerable A1, C/D1
Red List Category Red List Criteria
Vulnerable A1, C/D1

Confidence in the assessment

Red List of habitat categories and criteria descriptions

Pressures and threats

  • Pollution
    • Pollution to surface waters (limnic, terrestrial, marine & brackish)
    • Diffuse pollution to surface waters due to agricultural and forestry activities
    • Pollution to groundwater (point sources and diffuse sources)
    • Diffuse groundwater pollution due to agricultural and forestry activities
  • Invasive, other problematic species and genes
    • Invasive non-native species
  • Natural System modifications
    • Human induced changes in hydraulic conditions
    • Canalisation & water deviation
    • Canalisation
    • Modification of hydrographic functioning, general
    • Modification of standing water bodies
  • Natural biotic and abiotic processes (without catastrophes)
    • Species composition change (succession)
    • Accumulation of organic material
    • Eutrophication (natural)
  • Climate change
    • Water flow changes (limnic, tidal and oceanic)

Habitat restoration potential

Experience from North-Western Atlantic Europe has shown that the vegetation can be restored from a hypertrophic status by a reduction of the hydraulic residence time, by intervention in the fish populations and by elimination of the external nutrient inputs. Intervention in the fish populations means the removal of big sediment-disturbing bream.

Trends in extent

Average current trend in quantity

Decreasing Decreasing
EU28 EU28+

Trends in quality

Average current trend in quality

Decreasing Decreasing
EU28 EU28+

Conservation and management needs

The current approaches to conservation and management of permanent oligotrophic to mesotrophic waters with Characeae include minimizing the input of nutrients from agriculture and forestry. It requires the elimination of all external nutrient inputs into the lake. Characeae vegetation is especially vulnerable to eutrophication with phosphorous. Lowering the nutrient input might also require the inlet of water via a longer route or via an extra vegetation filter. Maintaining buffer zones around lakes might contribute to prevent direct nutrient inputs, as they prevent agricultural fields bordering the lakes. Lowering the nutrient status of this habitat might require lowering the hydraulic retention time of the water in the lake, if this is possible to realize in the water management scheme of the specific lake.

List of conservation and management needs

  • Measures related to agriculture and open habitats
    • Adapting crop production
  • Measures related to wetland, freshwater and coastal habitats
    • Restoring/Improving water quality
    • Restoring/Improving the hydrological regime
  • Measures related to spatial planning
    • Establish protected areas/sites
  • Measures related to hunting, taking and fishing and species management
    • Regulation/Management of fishery in limnic systems
    • Specific single species or species group management measures


For each habitat a distribution map was produced from a wide variety of sources indicating known and potential occurrences of the habitat in 10x10 km grids within Europe. Occurrences in grid cells were given in two classes: actual distribution from relatively reliable sources (surveys, expert knowledge), and potential distribution based on models or less reliable indicators. Please download the fact sheet to see the map.

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 50 Decreasing Decreasing
Belgium Present 3.3 Unknown Stable
Bulgaria Present 0.74 Decreasing Decreasing
Croatia Present 1.5 Unknown Stable
Cyprus Present 0.5 Unknown Unknown
Czech Republic Present 0.43 Decreasing Decreasing
Denmark Present Unknown Unknown Unknown
Estonia Present 26.9 Unknown Decreasing
Finland mainland Present 48 Decreasing Stable
Aland Islands Uncertain 48 Decreasing Stable
France mainland Present 100 Decreasing Decreasing
Corsica Uncertain 100 Decreasing Decreasing
Germany Present 1150 Decreasing Decreasing
Greece (mainland and other islands) Present 0.13 Unknown Unknown
Crete Uncertain 0.13 Unknown Unknown
East Aegean Uncertain 0.13 Unknown Unknown
Italy mainland Present 70 Decreasing Decreasing
Sardinia Present 70 Decreasing Decreasing
Sicily Present 70 Decreasing Decreasing
Hungary Present 1 Decreasing Decreasing
Ireland Present 556 Decreasing Stable
Latvia Present Unknown Unknown Unknown
Lithuania Present 180 Decreasing Decreasing
Luxembourg Present Unknown Unknown Unknown
Malta Uncertain Unknown Unknown Unknown
Netherlands Present 92 Stable Stable
Romania Present 4 Decreasing Decreasing
Slovenia Present 4200 Decreasing Stable
Sweden Present 311 Stable Stable
Portugal mainland Present 9.8 Unknown Decreasing
Portugal Azores Uncertain 9.8 Unknown Decreasing
Madeira Uncertain 9.8 Unknown Decreasing
Savage Islands Uncertain 9.8 Unknown Decreasing
Slovakia Present 0.2 Decreasing Decreasing
United Kingdom Present 97 Decreasing Stable
Northern Island Uncertain 97 Decreasing Stable
Gibraltar Uncertain 97 Decreasing Stable
Poland Present Unknown Unknown Unknown
Spain mainland Uncertain Unknown Unknown Unknown
Balearic Islands Uncertain Unknown Unknown Unknown
Canary Islands Uncertain 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)
Bosnia and Herzegovina Present 5 Decreasing Decreasing
Former Yugoslavian Republic of Macedonia (FYROM) Present 10.49 Decreasing Decreasing
Switzerland Present 3 Decreasing Increasing
Norway Mainland Present 120 Decreasing Decreasing
Svalbard Uncertain 120 Decreasing Decreasing
Jan Mayen Uncertain 120 Decreasing Decreasing
Albania Present unknown Unknown Unknown
Andorra Uncertain Unknown Unknown Unknown
Faroe Islands Uncertain Unknown Unknown Unknown
Guernsey Uncertain Unknown Unknown Unknown
Iceland Uncertain Unknown Unknown Unknown
Isle of Man Uncertain Unknown Unknown Unknown
Jersey Uncertain Unknown Unknown Unknown
Kaliningrad Present Unknown Unknown Unknown
Kosovo Uncertain Unknown Unknown Unknown
Liechtestein Uncertain Unknown Unknown Unknown
Monaco Uncertain Unknown Unknown Unknown
Montenegro Uncertain Unknown Unknown Unknown
San Marino Uncertain Unknown Unknown Unknown
Serbia Present unknown Unknown Unknown
Vatican City Uncertain Unknown Unknown Unknown

Extent of Occurrence, Area of Occupancy and habitat area

Extent of Occurrence (EOO) (Km2) Area of Occupancy (AOO) Current estimated Total Area Comment
EU28 9375800 4742 5039.3 Poland is lacking and forms a large contribution to both AOO and EOO
EU28+ 4767 5184 Poland is lacking and forms a large contribution to both EOO and AOO
AOO = the area occupied by a habitat measured in number of 10x10 km grid cells.
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).

Characteristic species

Not available

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Other classifications

Not available
European Environment Agency (EEA)
Kongens Nytorv 6
1050 Copenhagen K
Phone: +45 3336 7100