ABSTRACT
Prasinophytes clade VII is a group of pico/nano-planktonic green algae (division Chlorophyta) for which numerous rRNA sequences have been retrieved from the marine environment in the last 15 years. A large number of strains have also been isolated but have not yet received a formal taxonomic description. A phylogenetic analysis of available strains using both the nuclear 18S and plastidial 16S rRNA genes demonstrates that this group is composed of at least 10 different clades: A1 to A7 and B1 to B3. Analysis of sequences from the variable V9 region of the 18S rRNA gene collected during the Tara Oceans expedition and the frame of the Ocean Sampling Day consortium reveal that clade VII is the dominant Chlorophyta group in oceanic waters, replacing Mamiellophyceae which have this role in coastal waters. At some location prasinophytes clade VII can even be the dominant photosynthetic eukaryote representing up to 80 % of photosynthetic metabarcodes overall.