This is a survey of the diatom flora of rivers in the influenced area of Caxias' Power Plant, in the district of Capitão Leônidas Marques, southwest of Paraná State, Brazil. Samples were collected from March 1997 to February 1998, in eight sampling stations in the Iguaçu River and its tributaries: Cotegipe, Jaracatiá, Chopim, Tormenta, Adelaide, and Guarani rivers. Nine taxa belonging to the family Fragilariaceae were identified: Asterionella formosa Hassal var. formosa, Fragilaria capucina var. fragilarioides (Grunow) Ludwig & Flôres, F. capucina var. vaucheriae (Kützing) Lange-Bertalot, F. delicatissima (Wm. Smith) Lange-Bertalot var. delicatissima, F. javanica Hustedt var. javanica, Martyana martyi (Héribaud) Round var. martyi, Pseudostaurosira brevistriata (Grunow) Williams & Round var. brevistriata, Synedra goulardii Brébisson var. goulardii and S. ulna (Nitzsch) Ehrenberg var. ulna. Martyana martyi and Fragilaria delicatissima were reported for the first time for Paraná State.
diatoms; Fragilariaceae; Iguaçu river; lotic ecosystem; river basin
