Limnología del lago de Montcortès (ciclo 1978-79) (Pallars Jussà, Lleida).

Resum

Limnology of the Montcortes Lake (1978-79 cycle) (Lleida, NE Spain). Lirnnology of Montcortes lake (pallars Jussà, Lleida, Spain) was studied during the annual cycle of 1978-79. The following parameters were evaluated: temperature, light, transparency, oxygen, nutrients, sulphides, pH, alkalinity , chlorophyll, phytoplankton and zooplankton. During the studied cycle, the lake was homogenized in winter and fall times, being stratified in spring and summer. During the summer there was a clear thermocline at 10 meters depth, but we did not find an anaerobic hypolirnnion, as was previously stated by CAMPS et al. (1976). Phytoplankton was composed essentially of Cyclotella sp., Oscillatoria rubescens, Peridinium sp. and Ceratium hirundinella. During spring there was a great bloom of Cyclotella in surface waters which depleted dissolved silicate. A very dense population of Oscillatoria rubescens was located below the thermocline. Zooplankkton was composed by Daphnia longispina, Ceriodaphnia, Bosmina longirostris, Keratella quadrata and Polyarthra vulgaris. The greatest population of D. longispina was found from April to June at superficial waters. B. long irostris had its maxirnums in December-January and June-July.