IMIS - Marine Onderzoeksgroepen

A complete list of stations is available from the PANGEAE data system (http://www.pangaea.de/PHP/CruiseReports.php?b=Polarstern), including a cruise report (http://epic-reports.awi.de/3694/1/PE_72.pdf). The dataset includes 50 records, with individual counts ranging from 1-10, reaching a total of 132 specimens. The andeep3-Asteroidea is a unique dataset as it covers an under-explored region of the Southern Ocean, and that very little information was available regarding Antarctic deep-sea star fish. Before this study, most of the information available focused on star fish from shallower depths than 1000m. This dataset allowed to make unique observations, such as the fact that some species were only present at very high depths (Hymenaster crucifer, Hymenaster pellucidus, Hymenaster praecoquis, Psilaster charcoti, Freyella attenuata, Freyastera tuberculata, Styrachaster chuni and Vemaster sudatlanticus were all found below -3770m), while others displayed remarkable eurybathy, with very high depths amplitudes (Bathybiaster loripes (4842m), Lysasterias adeliae (4832m), Lophaster stellans (4752m), Cheiraster planeta (4708m), Eremicaster crassus (4626m), Lophaster gaini (4560m) et Ctenodiscus australis (4489m)). Even if the number of records is relatively small, the data brings many new insights on the taxonomy, bathymetric and geographic distributions of Southern starfish, covering a very large sampling zone. The dataset also brings to light 6 species, newly reported in the Southern Ocean. The quality of the data was controlled very thoroughly, by means of onboard Polarstern GPS systems, checking of identification by a renown specialist (Prof. Michel Jangoux, Université Libre de Bruxelles), and matching to the Register of Antarctic Marine Species (RAMS) and World Register of Marine Species (WoRMS). The data is therefore fit for completing checklists, for inclusion in biodiversity patterns analysis, or niche modeling. Its also nicely fills an information gap regarding deep-sea starfish from the Southern Ocean, for which data is very scarce at this time. The authors may be contacted if any additional information is needed before carrying out detailed biodiversity or biogeographic studies.
Geographic coverage: ANDEEP 3 cruise track, from Cape Town (SA) to Punta Arenas (CH). Four study regions were selected, but the main focus was on the Powell Basin and the Weddell Basin of the Weddell Sea, and their slopes. Two comparative samples were taken further north in the adjacent Agulhas and southern Cape Basins, which are separated from each other by the Agulhas Ridge. Four study regions were selected, but the main focus was on the Powell Basin and the Weddell Basin of the Weddell Sea, and their slopes. The major South Atlantic deep-sea basins started forming during Jurassic and Cretaceous times in connection with the Gondwana break-up and seafloor spreading (Brandt et al., 2004a, 2007; Lawver and Gahagan, 2003). The Weddell Basin is separated from the northerly basins by the South- west India Ridge (LaBrecque, 1986). The Powell Basin on the western side of the Weddell Sea was formed in the Tertiary by geological processes opening the Drake Passage and tectonic movements in the Scotia Sea (Lawver and Gahagan, 2003; Mitchell et al., 2000). The oceanography of the deep South Atlantic seafloor is defined by its prominent water mass, the Antarctic Bottom Water (Tomczak and Godfrey, 2001). The Antarctic Bottom Water expands north- wards into the Atlantic basins east and west of the Mid-Atlantic Ridge, like the Agulhas Basin, but can only enter the basins north of the Walvis Ridge (e.g., Cape Basin) via the northerly Romanche Fracture Zone. The Weddell Sea Bottom Water (WSBW), defined by a temperature of 0.7 1C and a salinity of 34.64 ppt (Orsi et al., 1993), is the main water mass above the Weddell Sea benthos (Fahrbach et al., 2001). The WSBW flows from the western Weddell Sea into the Scotia Sea and South Sandwich Forearc, and its circulation is driven by the Weddell Sea gyre. The sediments in the bathyal and abyssal Weddell and Powell Basins are dominated by silt and clay.
Taxonomic coverage: This dataset focuses on Starfish (Echinodermata: Asteroidea). It includes data on 6 orders (Forcipulatida, Notomyotida, Paxillosida, Spinulosida, Valvatida, Velatida) and 11 families (Asteriidae, Astropectinidae Benthopectinidae, Echinasteridae, Freyellidae, Goniasteridae, Labidiasteridae, Notasteriinae, Porcellanasteridae, Pterasteridae, Solasteridae). The most represented families are the Astropectinidae (Paxillosida), followed by Porcellanasteridae (Paxillosida) and Pterasteridae (Velatida).
Sampling method: A 3-m wide Agassiz trawl (AGT) was deployed at two locations in the South Atlantic and 14 locations in the Southern Ocean during the PFS Polarstern expedition ANT XXII/3 WECCON 2005— ANDEEP III in January–April 2005. The sample depths ranged from 1047 to 4931 m, sampling continental slopes of the eastern Weddell Sea (off Kapp Norvegia) and western Weddell Sea and the South Orkney Islands, and deep Cape, Agulhas, Weddell and Powell Basins. At the stations 074-7, 078-11 and 081-9, the cod end mesh size was 10mm, while at all other stations, an inlet of 500 mm mesh size was inserted. The 500 mm mesh size was used because of smaller adult size of deep- sea macrobenthos compared to shelf macrobenthos. The deployment protocol was standardised to 10 min trawling at 1 knot with 1.5x cable length to water depth to facilitate comparability between the different sites. At station 059-10, the AGT was trawled for 20 min. The haul distances were calculated from the time the Agassiz trawl travelled on the ground. The tension meter of the winch clearly indicated when the AGT left the seabed. Haul length varied from 731 to 3841m. Sample volumes were estimated and the general sediment composition was noted. Mega- and larger macrofauna were separated by eye on deck. The taxa of each trawl sample were identified to morphospecies level.
The asteroids of the ANDEEP3 expedition have been identified in detail, based on the observation of external morphological characters using a binocular microscope. A wide variety of morphological characters was taken into consideration for the identification of the asteroids. For instance, shape and size of the pedicellaria, the skeletal structure (réseau squelettique) and the ossicles that form the mesh (number of spines/ossicle), thickness and aspect of the body wall, the position of the papula, the number of podia rows and the shape of the podia, structure and armature of the marginal plates, number and form of the adambulacral spines as well as the spines of the dental plates, etc. By means of a preexisting identification key of Atlantic asteroids (A.M. Clark, 1994), the observation of the morphological characters permitted to identify the order, the family, the genus and sometimes the species to which the considered individual belonged to. For the time being, there are no existing identification keys for Antarctic asteroids. For this reason, we consulted in addition multiple works of previous Antarctic expeditions (A.M. Clark (1962, 1994), R. Köhler (1906, 1907, 1908, 1911, 1912, 1917, 1920, 1923), W.K. Fisher (1911,1940), Sladen (1889), Mortensen (1932), E. Perrier (1891a), H. Ludwig (1905), Th. Studer (1874), I. Bernasconi (1967, 1964, 1966, 1972), Madsen (1950)) which allowed us to improve the identifications in dubious cases, thanks of their numerous detailed illustrations and descriptions of Antarctic asteroids. Synonymy was resolved by consulting the Register of Antarctic Marine Species (RAMS), that is accessible via internet and that compiles the most recent information about Antarctic asteroid taxonomy (Danis & Jangoux, 2007), delivering us in this way the valid species names.