Photosynthetic picoplankton, represented primarily by the genera Synechococcus and Prochlorococcus, are major contributors of biomass and primary production in oligotrophic oceanic ecosystems (JOHNSON & SIEBURTH, 1979; WATERBURY et al., 1979; PARTENSKY et al., 1999a). In the oligotrophic Mediterranean Sea, picophytoplankton has a great contribution to total phytoplankton biomass and production ...

Ninety-four stations were sampled in the Atlantic subtropical gyres during 10 cruises carried out between 1995 and 2001, mainly in boreal spring and autumn. Chlorophyll a (Chl-a) and primary production were measured during all cruises, and phytoplankton biomass was estimated in part of them. Picoplankton (o2mm) represented 460% of total Chl-a concentration measured at the surface, and their con...

The ocean's interior is Earth's largest biome. Recently, cultivationindependent ribosomal RNA gene surveys have indicated a potential importance for archaea in the subsurface ocean. But quantitative data on the abundance of speci®c microbial groups in the deep sea are lacking. Here we report a year-long study of the abundance of two speci®c archaeal groups (pelagic euryarchaeota and pelagic cre...

Many ecosystem models have been developed to study the ocean’s biogeochemical properties, but most of these models use simple formulations to describe light penetration and spectral quality. Here, an optical model is coupled with a previously published ecosystem model that explicitly represents two phytoplankton (picoplankton and diatoms) and two zooplankton functional groups, as well as multip...