| Unicellular diazotrophic cyanobacteria (UCYN2-Fix lineage) were detected using whole-cell hybridization of specific Nitro821 oligonucleotide probe at the coastal and oligotrophic station SOMLIT off Marseilles (France). This station was sampled monthly, for a year and a half (June 2006-November 2007). The UCYN2-Fix community was dominated at 99.9% by picoplankters (0.7-1.5 mu m) mainly as free living in the 0.2-3-mu m size fraction. They were present all the year long with a mean density of 4.6 cell mL(-1), except in summer 2006, when concentrations reached 1.9 x 10(3) cell mL(-1) and 5.3 x 10(3) cell mL(-1) in June and July, respectively. During this bloom, picoplanktonic UCYN2-Fix represented 10.7% of the picocyanobacterial community. The larger size... |
