Our knowledge of the biodiversity of the Southern Ocean (SO) deep benthos is scarce. In this review, we describe the general biodiversity patterns of meio-, macro- and megafaunal taxa, based on historical and recent expeditions, and against the background of the geological events and phylogenetic relationships that have influenced the biodiversity and evolution of the investigated taxa. The relationship of the fauna to environmental parameters, such as water depth, sediment type, food availability and carbonate solubility, as well as species interrelationships, probably have shaped present-day biodiversity patterns as much as evolution. However, different taxa exhibit different large-scale biodiversity and biogeographic patterns. Moreover, there is rarely any clear relationship of biodiversity pattern with depth, latitude or environmental parameters, such as sediment composition or grain size. Similarities and differences between the SO biodiversity and biodiversity of global oceans are outlined. The high percentage (often more than 90%) of new species in almost all taxa, as well as the high degree of endemism of many groups, may reflect undersampling of the area, and it is likely to decrease as more information is gathered about SO deep-sea biodiversity by future expeditions. Indeed, among certain taxa such as the Foraminifera, close links at the species level are already apparent between deep Weddell Sea faunas and those from similar depths in the North Atlantic and Arctic. With regard to the vertical zonation from the shelf edge into deep water, biodiversity patterns among some taxa in the SO might differ from those in other deep-sea areas, due to the deep Antarctic shelf and the evolution of eurybathy in many species, as well as to deep-water production that can fuel the SO deep sea with freshly produced organic matter derived not only from phytoplankton, but also from ice algae.

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The present paper contains descriptions of 14 new species of dorvilleid polychaetes that are part of a highly diverse benthic infauna sampled on the U.S. Atlantic slope and rise between the Canadian border and South Carolina. Quantitative samples were taken with a Hessler‐Sandia box core during 18 cruises between 1983 and 1987. Samples were sieved through screens having a mesh opening of 300 μ. The newly described species belong to the genera Ophryorrocha. Exallopus. Parophryotrocha and two new genera, Pseudophryotrocha gen.n. and Anchidorvillea gen.n. An emended generic diagnosis of Ophryotrocha is provided to accommodate some of the new species, but also to include a group of atypical species described earlier by several authors who had modified the generic concept of Ophryotrocha without providing a formal emendation. The genus Ophryotrocha is revised to contain 31 species helonging to two species groups. A comparison of a suite of morphologic characters, however. indicates that these species addressed in this paper are discussed in the context of the entire family Dorvilleidae.

Composition, abundance, and distribution of suprabenthos from a depth between 1 and 1.33 m above the seafloor were analysed. The samples were taken during ANT XV/3 with RV Polarstern in February and March 1998 by means of the supranet of an epibenthic sledge along two transects in the southern Weddell Sea (Vestkapp and Halley Bay) and one east of King George Island. At each of these three transects, five to six stations were taken in water depth between 200 and 2000 m. In total, 34 057 specimens were sampled at 16 stations, yielding 1 205 050 individuals for all stations standardized to 1000 m3 hauls. Of these, copepods were usually the most abundant group in the supranet (805 822 ind 1000 m−3. The suprabenthic fauna of the southwest of Vestkapp (Weddell Sea) transect was dominated by planktonic taxa in terms of individual numbers especially at the deeper stations (938–1983 m). At Halley Bay the total abundance of plankton was lower but its relative abundance (> 80%) was also high, whilst off King George Island peracarid crustaceans were an important fraction.

During the expedition EASIZ II with RV 'Polarstern' in 1998 a multibox corer yielded 151 quantitative samples from 26 stations between 120 and 2415 m water depth for benthic community analysis. From this material a total of 235 polychaete species out of 37 families was determined. Forty-seven species are new to science. The polychaete fraction contributed 41.9% to total benthic abundance and 6.5% to total benthic biomass at these stations. Overall mean polychaete abundance (ind m 72 ) and biomass (g wet weight m 72 ) at the stations were 1617 and 49, respectively.Multidimensional scaling procedure clearly grouped the stations into south-eastern Weddell Sea shelf stations, deep-water stations, and stations mostly around the Antarctic Peninsula. Di¡erences between these groups existed in terms of polychaete abundance and biomass as well as species composition, diversity, and evenness.