Biodiversity of Chlorophyceae in two of the greatest reservoirs from the metropolitan region of São Paulo municipality, Billings and Guarapiranga, which supply water for millions of people, was studied. The samples were collected every two months, in specific sites in both reservoirs, from January to December 2004. The samples were filtered using a plankton net (20 µm) and preserved with formaldehyde. Thirty six taxa belonging to two orders, ten families and 24 genera, were identified, described and illustrated. The genus Desmodesmus presented the highest species richness (four), followed by Ankistrodesmus e Scenedesmus (three species each). Ten taxa are firstly reported to the studied reservoirs. Eight taxa were found exclusively in Guarapiranga reservoir and three only in Billings reservoir, whereas 70% of the identified taxa were common to both reservoirs. The high species richness of Chlorophyceae confirms the floristic dominance of this class in tropical and commonly eutrophyzed water bodies.
Chlorophyceae; phytoplankton; reservoirs; water supply
