ABSTRACT
The quantitative distribution of echinoderm populations in the deep sea has been poorly investigated while as part of the benthos, the echinoderms play a significant role both in reworking the sediment and recycling the organic matter. Intensive sampling conducted using a similar strategy in several abyssal Atlantic basins, between 1900 and 5250 m depth, allowed a comparison of the echinoderm populations. This study points out: - a great variability of the mean density of the echinoderms as a function of depth and of geographic area (from 1 ind./104 m2 to 15000 ind./104 m2), - a variable dominance of echinoderm classes, - an exceptionnally high abundance of holothuroids which dominates all other taxa in the Norwegian Sea, - a relatively small variation of the concentration of organic matter in the sediment between the different basins prospected which mostly shows the result of bioturbation and consumption by the fauna, - a significant correlation between holothuroids density with organic carbon content and terrigenous fraction of the sediment at tropical stations, where trophic input estimated by sediment traps, correlates better to the abundance of some echinoderm populations.
