Marine cyanobacteria ( Synechococcus cells<2 μm in size) are a group of small unicellular autotrophic procaryotes. Since their discovery by Waterbury (1979), it has become evident that the cyanobacteria are abundant and widespread in the world's ocean. One of most significant recent advances in marine biogeochemistry has been the realisation that small organisms, such as microbes, are important in the cycling of organic matter in the ocean. In the microbial community, it is now known that picoplankton n...