Ciliates from a fresh water sulfuretum

Ciliates were collected from a freshwater sulfuretum, Lake Cisó, which is part of a gypsum karstic area whose main feature is Lake Banyoles (Girona, Spain). Chromatium, Lamprocystis and Chlorobium are the major phototrophic sulfur bacteria in Lake Cisó. Blooms of a photosynthetic cryptomonad (up to 5 × 105 ind ml-1) were found at the metalimnion. The community of ciliates could be divided in three groups: (a) aerobic, cosmopolitan, genera such as Stentor and Vorticella, in the epilimnion; (b) a large population (up to 104 ind ml-1) of Coleps, adapted to low concentrations of both oxygen and sulfide, together with a few individuals of the equally sulfide-tolerant genus Paramecium, in the metalimnion, and (c) anaerobic, true sulfide-loving genera such as Plagiopyla and Metopus, in the hypolimnion, where sulfide concentration was between 0.6 and 1.2 mM. © 1986.