The freshwater flora of Ecuador is poorly known. This report provides preliminary information about the freshwater Pyrrhophyta and two families in the Chlorophyta. There has been some work on diatoms but other groups remain unstudied. In June 2001 samples were collected as whole water or by using a 10mm plankton net from 52 locations in the interior (Amazonian) and Andean regions and examined within hours using a Swift field microscope. Nine additional samples from Ecuador have been provided by Dr. Miriam Kannan. Amazonian sites consisted of oxbow lakes along the Rio Shiripuno, and small ponds and lakes along the road from the river to Coca. Andean sites were principally in the Cajas National Park near Cuenca. Genera in the Closteriaceae include Closterium, Gonatozygon, Spinoclosterium, and Penium. Desmidiaceae include Arthrodesmus, Bambusina, Cosmarium, Desmidium, Euastrum, Hyalotheca, Micrasterias, Pleurotaenium, Spondylosum, Staurastrum, Staurodesmus, Triploceras, and Xanthidium. Pyrrhophyta include Ceratium, Gymnodinium, Peridinium, Sphaerodinium, and Woloszynskia.

Key words: Ceratium, Closteriaceae, Desmidiaceae, freshwater algae of Ecuador, Gymnodinium, Peridinium, Pyrrhophyta, Sphaerodinium, Woloszynskia