Distribution and diversity of asteroids in atlantic abyssal basins

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Abstract
Since the last survey of the distribution of the echinoderm fauna in the deep sea, worked out by Madsen, more than 100 trawlings in various areas of the Atlantic Ocean give new possibilities of characterizing the faunal assemblages of several basins at depths greater than 1800 m. During 12 cruises conducted by the Centre Océanologique de Bretagne, seven atlantic basins (Gape, Angola, European, Labrador, Greenland, and Norwegian Basins) have been intensively prospected. Comparisons of the asteroid faunas (43 species on the whole) are approached with appropriate similarity index, especially the second Kulczynski coefficient, and estimates of density and diversity of the fauna are analysed within each basin for two ranges of depths ( < and = 3000 m). The distinct fauna, and the correlation of low diversity with high densities observed in the Greenland, Norwegian, Mediterranean, and Gape Basins confirm the isolation of such areas either by topographic barriers or by special ecological conditions.