The mission aims to provide a quality manner microscopic analyzes and species compositions for the biological quality element for phytoplankton Flemish rivers, this according to the European Water Framework Directive. The phytoplankton counts should go through inverted microscope according to the CEN standard. To this end, -, cell counts are carried out up to 400 units; - is determined at least to genus level; - of each taxon are measured a number of dimensions for the calculation of the biomass; so that each of the taxon relative contribution can be determined with respect to the total phytoplankton biomass and so as to calculate the index score.