Isoetes lacustris
Isoetes lacustris L.
Isoetes setacea auct. bulg., non Lam.1
Isoetaceae – Quillworts family
Conservation status. Endangered [EN B1ab(iii)+2ab(iii,iv)]. BDA. Glacial relict.
Morphology and biology. Perennial aquatic, submerged herb. Stem short, tuber-like, 2-lobed, 0.5–1.5(3) cm in diameter. Leaves rigid, erect, spreading or slightly curved outwards, dark green upwards, whitish at base, 4–10(15) cm long and 1.5–3 mm thick, linear-subulate, tapering at apex; leaf-base flattened and spathulate, with wide membranous margins, abruptly narrowing above sporangium. Heterosporous. Spores ripening VII–IX.
Habitats and populations. On sandy-silty or stony bottoms at the periphery of high-mountain lakes, beneath relatively shallow water layer (from a few centimetres to a few metres). The species inhabit oligotrophic and mesotrophic waters. Populations are numerous, relatively well-developed, but very fragmented. At some places individuals are very numerous and very dense, forming communities, but in small areas. On the periphery of some lakes individuals grow in small groups or solitary together with other plant species.
Distribution in Bulgaria. Pirin Mts (northern); above 1900 m alt.
General distribution. In the temperate and cold regions of the northern hemisphere. Europe (mainly in northern regions, very locally southwards), N America (eastern parts of Canada and north-eastern parts of USA), S Greenland.
Threats. Climate aridisation; limited distribution of the species; vegetation change and overgrowth of the lakes; accumulation of organic ooze; water pollution.
Conservation measures taken. Protected species according to the national Biodiversity Act. Species localities are in Pirin National Park and in a site of the European ecological network Natura 2000 in Bulgaria.
Conservation measures needed. Research on population number and range; population monitoring; habitat maintenance and conservation.
References. Achtarov & Jordanov 1963; Bozhilova & Tonkov 1984; Jermy & Akeroyd 1993; Stefanova & Ivanova 2000.
Author: Daniella Ivanova
