Although cyanobacteria blooms can dominate annual production and phytoplankton biomass in some marine regions, little is known on the fate of these large aggregations of autotrophic, surface-dwelling prokaryote populations. The importance of bloom-forming Trichodesmium spp. and Nodularia spumigena-Aphanizomenon flos-aquae in carbon and nutrient dynamics of tropical and sub-arctic regions, respectively, will be discussed. The limited collected data indicate that surface blooms funnel C, N and P through an active microbial loop, leading to substantial regeneration in surface waters.