ECOLOGICAL CHARACTERISTICS OF A HIGH-MOUNTAIN LAKE-OUTLET STREAM (TATRA MOUNTAINS, POLAND)

Detailed hydrobiological investigations were carried out in a high mou ntain lake-outlet (Tatra Mts, Poland). The stream water had low concen trations of ions, nutrients and organic matter (DOM, POM). The stream had intermittent flow. In the spring, when the water started flowing, the initial communities were composed of organisms adapted to survivin g the freezing period such as, blue-green algae Chamaesiphon polonicus (ROSTAFINSKI) HANSGIRG, Diptera: Simuliidae, Chironomidae Diamesa. Th e main food source was particulate organic matter (POM) carried out fr om the lake. In the summer, development of attached algae (green algae Klebsormidium rivulare (KUTZ.) STARMACH) resulted in faunal changes. Algivorous oligochaetes, Nais variabilis PIG., which probably originat ed from the lake, pre-dominated at that time. The above communities, e specially in the spring time, were similar to a typical ''lake-outlet community''.