Reactions of dominant of phytoplankton towards different ranges of temperature amplitude in mesotrophic Kaliszany Duże Lake. Fragmenta Floristica et Geobotanica Polonica 10: 259–265. Kraków. PL ISSN 1640 629X. ABSTRACT: Phytoplankton observations were conducted in mesotrophic Kaliszany Duże Lake during 1994–1996. These included identifying the seasonal development of the major phylogenetic categories and characteristic taxa and their vertical composition in the epilimnion, metalimnion, and hypolimnion. Dominant and sub dominant taxa were also associated with three distinct ranges of water temperature. The characteristic species within these categories were: (1) Closterium acutum Brébisson ex Ralfs and Aphanizomenon flos aquae fo. gracile (Lemm.) Elenk. at water temperatures ranging from 0.5 to 0.9°C; (2) Coelastrum reticulatum (Dang.) Senn, Asterionella formosa Hassal, Cyclotella radiosa (Grunow) Lemm., and Chroomonas acuta Utermöhl within the range from 2.8 to 6.9°C; and (3) over a wider range of temperatures from 4.5 to 19.0°C, represented by Rhodomonas minuta Skuja.