Abstract

Planktonic Cyanobacteria species composition and seasonal change in the La Nga river were studied during the June 2004 and May 2005. Eighty-eight cyanobacterial species belonging to order Oscillatoriales from La Nga river were examined, in which, two genera of Oscillatoria and Phormidium were high diversity with 26 and 24 species, respectively. More than other 30 species were found in genera such as Planktothrix, Lyngbya, Homoeothrix, Geitlerinema, Komvophoron, Pseudanabaena, Planktolyngbya, Spirulina, and Borzia. Thirty-three species of these and genera of Homoeothrix were the first time recorded to Cyanobacterial flora of Vietnam. Descriptions and photographs of these new species were made.