Diversity and distributional patterns of Polychaeta in the deep South Atlantic

This study provides new information about the composition, diversity and zoogeography of abyssal polychaetes in the little-studied South Eastern Atlantic (Angola Basin). During the austral winter of 2000, twenty-five box core samples (total area sampled 6 m) were taken along a 500-km transect in five work areas at depths exceeding 5000 m. A total of 1047 individuals representing 86 species belonging to 32 families was collected. Well over half the polychaetes (58 species; 67%) appear to be new to science, with the highest number of new species among the Cirratulidae, Paraonidae, Phyllodocidae, Ampharetidae, Opheliidae, and Spionidae. Eight of these new species were among the 16 dominant species in the deep Angola Basin whereas, 32 species (37%) were considered to be rare with only 1–2 individuals collected. Species accumulation curves did not level off at a fixed number of species, indicating that diversity would increase with additional sampling. Polychaete community assemblages among box core samples were highly variable. Ten of the known species are biogeographically widespread outside the Angola Basin whereas five appear to be restricted to the deep Atlantic. Two species have only been recorded in the Southern Ocean, and one in the southern hemisphere. Twenty (35%) of the species considered to be new to science were also found in samples from the deep Southern Ocean, whereas eight of the known species found in the Angola Basin have not been reported from the Southern Ocean to date. Surface deposit feeders and carnivores were the dominant functional groups both in terms of number of individuals and number of species. Necessary steps to further our knowledge of the little-known abyssal ecosystem are discussed. & 2010 Elsevier Ltd. All rights reserved.