Lakes of Gypsum Karst
Small permanent lakes situated in active gypsum karst areas and characterised by large fluctuations of water level, high saturation of Ca2+ and SO42- ions, and frequently the development of specific plankton communities. There may be thermal and/or chemical stratification. High SO42- or H2S- saturations may allow unique colonies or mats of green (Chlorobiaceae) and purple (Chromatiaceae) sulphurous bacteria to develop.
Notes on habitat mapping
Direct mapping of the lakes is only possible with the aid of sulphate ion saturation and pH measurements at different water depths to determine salt water influence. Limnological tests must also be done to show the make-up of the plankton. The depth and maximum water-level fluctuations given in the EU Commission’s Interpretation Manual relate to habitats known so far in Lithuania and should not therefore be regarded as maxima for the habitat type in general. Type 3190 differs from habitat type 3180 (turloughs) in that type 3190 lakes hold water permanently rather than only intermittently. There may be overlaps with habitat types 3140 and 3150 on account of trophic status and aquatic vegetation. Priority should be given in such cases to type 3190.
Old, near-natural post-mining waterbodies are included where they display the above characteristics.
Sulphate-rich waterbodies of other provenance, such as ones found in lignite mining districts, do not belong to habitat type 3190.