Abstract: his paper first presents a report on the composition and distribution of microalgae in the intertidal zones of the Deception Island, Antarctica. These microalgae samples were collected from six mud-sand flats stations on 21 January 1987. 179 taxa of microalgae belonging to Bacillariophyta (125 species, 25 varieties and 2 forma, 34 genera), Cyanophyta (18 species and 2 varieties, 6 genera), Pyrrophyta (6 species, 4 genera) and Chrysophyta (1 species 1 genus) were observed. The six dominant microalgae in each habitat are Fragilaria bongrainii, F. oceanica, F. striatula, F. islandica, Navicula antarctica and Synedra kerguelensis var. antarctica. Rhabdonema arcuatum, Cocconeis antiqua and Licmophora gracilis are abundant in station 4, 5 and 6. Oscillatoria spp., Lyngbya antarctica, Phormidium antarcticum and Nodularia spp. are also abundant in station 1, 2 and 3. The values of diversity indice for microalgae varied from 2. 85 to 6.86. The values of similarity indice in microalgae composition between biotopes ranged from 32 to 79 for pairs of stations. Microalgal species composition and quantitative distribution are depended on per cent contents of mud-sand and claysilt at different stations.

Key words: Microalgae, Deception Island, Intertidal zones, Mud-sand flats