Permanent oligotrophic to mesotrophic waterbody with Characeae

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.

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats