Communities of diverse Bacteria, Archea, and Protista have been estimated to account for more than 98 present of oceanic primary production. These are the microscopic factories and essential catalysts for most chemical reactions within the biogeochemical cycles of the ocean. In this way they shape the basis of the marine ecosystem and influence the environment which other organisms higher in the food chain live in. However, information on bacteria and archea are very limited in the Icelandic marine ecosystems. A pioneering study on the diversity of nano- and pico- size marine microorganisms in the waters around Iceland was initiated by some water samplings in 2010. Since then, sampling has been continued annually during the second half of May. The aim of the study was to establish the relationship between abundance and diversity of the small microorganisms and relevant environmental parameters (location, depth, temperature, salinity, concentrations of nutrients). As expected, abundances of microorganisms are positively related with coastal regions, surface layer and temperature. DNA sequencing provided diversity profiles of bacterioplankton taxa which showed significant differences around Iceland. A clear distinction was found between ocean regions, on the one hand for that north and south of Iceland and on the other hand between coastal, off-shore and deep waters. The presented results are analysis of these first data on microbial diversity and abundance in the waters around Iceland.