"Planktonic eukaryotes are keystone players in the global carbon cycle, yet knowledge about their population diversity is late. This is not surprising since we are still actively investigating species richness, within these very diverse organisms. Phytoplankter are difficult to isolate and grow in the lab, so that direct analysis of their DNA sequence is the unique way to gain knowledge into their diversity and lifestyle. PICOPOP is about developing a population genomics approach, the analysis of the genetic variation between individuals from the same species at the genome level, to unravel intraspecific diversity in one model picophytoplanktonic species, Ostreococcus tauri, (OT). This approach has been successfully applied to species ranging from bakers’ yeast to humans, plants and insects. Knowledge about these population parameters is essential to gain insights into the species adaptive potential in response to environmental variation as climate change. OT provides an ideal model for the enclosed timely and feasible research proposal on intraspecific eukaryotic phytoplankton diversity because it is ubiquitous and the availability of a complete reference genome sequence. The JGI has recently accepted our project to sequence 20 complete genomes of OT strains isolated in the Mediterranean sea, using 454 technology. From an analytical point of view, research is late in the treatment of this new kind of data. PICOPOP thus assembles appropriate expertise of complementary partners (biologists, bioinformaticians and population geneticists) to adapt and develop the tools required throughout the analysis from raw 454 reads interpretation to analysis. Unicellular eukaryotic organisms represent much of the ocean’s reserve of biodiversity, and we expect that the results and methods developed in PICOPOP on a picophytoplanktonic model organism will both provide state of the art sequence analysis tools and shed light on the lifestyle and diversity of other planktonic species."