Dataset provides phytoplankton densities recorded in Lake Santo Parmense on one date in may 1990. Samples were collected by means of a Ruttner bottle at different depths over the whole water column at the point of maximum depth of the lake. An integrated sample was subsequently obtained by combining equal proportions of samples collected at the various depths and phytoplankton were identified and counted with an inverted microscope according to Utermöhl (1958).