We investigated the effect of diel variation in cell properties of picoplankton prey and the intrinsic grazing rhythm of heterotrophic nanoflagellates (HNF) on the diel periodicity of HNF grazing. To achieve this aim, 2-point dilution experiments with short incubation time were performed over 24 h in the South China Sea and Hong Kong (HK) coastal water to assess the prey cell properties and HNF...

We studied the growth of six culturable bacterial lineages from coastal North Sea picoplankton in environmental samples under different incubation conditions. The grazing pressure of heterotrophic nanoflagellates (HNF) was reduced either by double prefiltration through 0.8- micro m-pore-size filters or by 10-fold dilutions with 0.2- micro m (pore-size) prefiltered seawater. We hypothesized that...

[1] The equatorial Pacific Ocean is the largest natural source of CO2 to the atmosphere, and it significantly impacts the global carbon cycle. Much of the large flux of upwelled CO2 to the atmosphere is due to incomplete use of the available nitrate (NO3) and low net productivity. This high-nutrient low-chlorophyll (HNLC) condition of the equatorial upwelling zone (EUZ) has been interpreted fro...

We investigated the influence of geographic distance, environmental variables, and water mass origin on picoeukaryote (phytoplankton and other protists ,3 mm) assemblages to assess the presence of biogeographic patterns. The study region was an area of converging Arctic and Atlantic currents where several distinct water masses were overlain and intersecting. Denaturing gradient gel electrophore...

We investigated and compared the impact of organic loads due to the biodeposition of mussel and fish farms on the water column of a coastal area of the Tyrrhenian Sea (Western Mediterranean). Physico-chemical data (including oxygen, nutrients. DOC and particulate organic matter), microbial variables (picoplankton and picophytoplankton density and biomass) and phytoplankton biomass (as chlorophy...

-The size distribution of pelagic producers and the size and trophic position of consumers determine the composition and magnitude of sinking fluxes from the surface communities in a simple model of oceanic food webs. Picoplankton, the dominant producers in the model, contribute little to the sinking material, due primarily to the large number of trophic steps between picoplankton and the consu...

Sharp boundaries in the physical environment are usually associated with abrupt shifts in organism abundance, activity, and diversity. Aquatic surface microlayers (SML) form a steep gradient between two contrasted environments, the atmosphere and surface waters, where they regulate the gas exchange between both environments. They usually harbor an abundant and active microbial life: the neuston...