Six DNA extraction methods were tested in pure cultures of different nano and picoplankton species. The same extractions were checked in non-axenic mock communities formed mainly by three species. One fragment of 18S rRNA gene was amplified from the mock samples using the universal priemrs recommended by Earth Microbiome Project and the results were analyzed with seven different bioinformatic pipelines until taxonomic assignment. The best protocol (DNa extraction & Bioinformatic pipeline) were finally tested over one environmental sample of seawater filtered to check the usefulness of the developed protocol.