Density of the major size groups of benthic fauna and trophic input in deep basins of the Atlantic Ocean

Seven deep-sea areas were studied in the Atlantic Ocean. An intensive and comparable benthic sampling program was conducted during several deep-sea biology cruises with IFREMER research ships and mainly with the RV Jean Charcot, in the Norwegian Sea, the Bay of Biscay, the Porcupine Seabight, the Vema Fracture Zone, the Demerara abyssal plain, the Cape Verde Basin, the Angola and Cape basins near the Walvis Ridge. A synthesis of community structure data has been realized and the benthic fauna, quantitatively sampled, was separated into three main size categories (meiofauna, macrofauna sensu stricto and megafauna). Comparison of population densities in the different stations, dominated by pelagic sedimentation, shows that the range of abundance differs for the three major size groups and that meiofaunal and macrofaunal density are positively linearly related; the biomass of the macrofauna is roughly twice that of the meiofauna. The megafaunal pattern of abundance differs from meiofaunal and macrofaunal abundance and shows an exponential relationship with the two other groups. The abundance of meiofauna and macrofauna has a positive linear relationship with the “burial” organic carbon flux, which has been evaluated from mean organic carbon concentration in the surface sediment and the rate of sediment accumulation during the Holocene. The relationship observed would be expected if the biomass is dependent of the flux of particulate organic carbon to the deep-sea floor and therefore demonstrates that this flux is the first order parameter which controls biomass distribution in the deep Atlantic Ocean