Community structure and spatial distribution of benthic fauna in the Bellingshausen Sea (West Antarctica).

9 pagesInternational audienceThe structure and spatial distribution of the macrofauna community of the Bellingshausen Sea in the western sector of Antarctica was studied during the ‘BENTART–06' oceanographic expedition. This is one of the least explored Antarctic seas. A total of 20 box cores were sampled at 11 stations ranging from 157 to 3,304 m depth, using an USNEL-type box corer (BC) dredge. Representatives of 25 higher taxa of invertebrates were collected. Deeper sampling sites were less rich in taxa (4–7 taxa), whereas the Wgures were higher at shallower sites (up to 17 taxa). Faunal density on the sea bottom revealed a horizontal spatial gradient from the western sites with extremely low Wgures (90 indiv./m2) towards the eastern ones with the highest Wgures (1,360 indiv./m2) close to the Antarctic Peninsula. Several abiotic factors (depth, redox, organic matter, carbonates and particle size of surWcial sediments) were measured simultaneously on the sea Xoor to characterise the substrate preferences of the fauna. Positive correlations were found between the faunal distribution and a combination of depth, redox values, and organic matter content of sediments. This indicates decreasing availability of food in the deeper bottoms of the Bellingshausen Sea with a prevalence of depauperated bottoms dominated almost exclusively by a foraminiferans community

Asteroids and Ophiuroids associated to sponge aggregations as a key of marine habitats. A compared analysis between Avilés Canyons System and Le Danois Bank

This study analyzes the fauna composition of the community of brittle and sea stars associated with sponge aggregations located in Avilés Canyons System and El Cachucho, Marine Protected Area (MPA). Diverse sampling methods were used depending on bottom morphology, such as rock dredges and specific samplers for sedimentary bottoms, mainly beam trawl models. These banks are made up of sponge and coral species that build a very appropriate substrate for the proliferation of benthic species, which together create Vulnerable Marine Ecosystems that are highly relevant for management and conservation. Among these benthic species, echinoderms are of great interest due to their value as indicators of good habitat. In total, 1261 specimens were collected (934 brittle stars and 327 starfishes), belonging to 42 species (28 ophiuroids and 14 asteroids) from INDEMARES AVILÉS, ECOMARG, and SponGES project surveys. Specimens were distributed among four sponge aggregations (F: fields) that were considered according to the sponge records obtained in the same stations (36). These fields were defined and named based on the five most common sponge species: Aphrocallistes beatrix and Regadrella phoenix (F1: Avilés Canyon); Pheronema carpenteri (F2: Intraslope basin of Le Danois Bank); Asconema setubalense (F3: Le Danois Bank); and Neoschrammeniella aff. bowerbankii (F4: Corbiro Canyon). Faunistic results show that Ophiactis abyssicola (55.55% occurrence), Brisinga endecacnemos, Ophiolycus purpureus, and Peltaster placenta (33.33%) were the most frequently found species in F1; Psilaster andromeda (80%), Pseudarchaster parelii (60%), and Nymphaster arenatus (46.67%) in F2; Ophiura carnea (71.43%) and Ophiacantha smitti (42.86%) in F3; and Ophiacantha densa, and Henricia caudani (100%) in F4. The asteroid and ophiuroid species collected seem to be composed of four different communities that fit to areas with particular morphological and biological features, related to the presence of species specialized in the use of the resources they can find there. In general, the abiotic factor controlling this structure is depth. This assemblage structure, which favors the dissimilarity between the canyons and the bank, is not so clear, since the deepest stations are located on the intraslope basin of El Cachucho, Marine Protected Area (MPA), therefore, using it a priori could lead to misunderstandings. Once the structure of the echinoderm community was known, we compared the expected and obtained results to analyze evidence which should prove the existence of any association between echinoderms and sponges, which enabled us to refute the incongruous hypothesis.Postprin

Physical oceanography, sea-bed photographs and videos of benthos from the Weddell Sea taken with remote operated vehicle CHEROKEE during POLARSTERN cruise ANT-XXIII/8

The marine ecosystem on the eastern shelf of the Antarctic Peninsula was surveyed 5 and 12 years after the climate-induced collapse of the Larsen A and B ice shelves. An impoverished benthic fauna was discovered, that included deep-sea species presumed to be remnants from ice-covered conditions. The current structure of various ecosystem components appears to result from extremely different response rates to the change from an oligotrophic sub-ice-shelf ecosystem to a productive shelf ecosystem. Meiobenthic communities remained impoverished only inside the embayments. On local scales, macro- and mega-epibenthic diversity was generally low, with pioneer species and typical Antarctic megabenthic shelf species interspersed. Antarctic Minke whales and seals utilised the Larsen A/B area to feed on presumably newly established krill and pelagic fish biomass. Ecosystem impacts also extended well beyond the zone of ice-shelf collapse, with areas of high benthic disturbance resulting from scour by icebergs discharged from the Larsen embayments