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No other group of animals typifies the uniqueness of Antarctic life more than Pycnogonida (sea spiders), with 20% of all known species found in the Southern Ocean, and 64% of these endemic to the Antarctic. Despite nearly 200 years of research into pycnogonids and other benthic phyla in Antarctica, the parameters which drive the distribution and diversity of benthic fauna are still poorly understood. This study aimed to investigate the diversity and connectivity of pycnogonid communities on either side of the Antarctic Polar Front, with an emphasis on the role of water depth, using an occurrence dataset containing 254 pycnogonid species from 2187 sampling locations. At depths shallower than 1000 m, communities to the north and south of the Antarctic Polar Front were distinct, while below this depth this geographic structure disintegrated. The Polar Front, or the expanse of deep ocean it bisects, seemingly acts as a semipermeable barrier to species exchange between well-sampled shallow communities. The less sampled and less understood deep sea appears to be better connected, with high levels of shared species following the northward flow of Antarctic Bottom Water. The exceptionally high diversity and endemism of Antarctic pycnogonids may reflect an apparent competitive advantage in cold waters which leaves them vulnerable to ongoing ocean warming, with increased competition and predation pressures. [ABSTRACT FROM AUTHOR]

Three essential questions remain unresolved about the present Antarctic biota: its antiquity, origin, and ubiquity. Some benthic animals are capable of active self-dispersal following shallow corridors between islands. Identifying and characterizing the biota in such corridors is fundamental for biogeographic studies and the delimitation of priority sites to conserve biodiversity. The Scotia Arc provides an example of such passages, being a system of islands and underwater ridges connecting the Magellan Region to the Antarctic Peninsula and South Shetland Islands (Maritime Antarctic). Specimens of the free-living flatworm Orthoplana bregazzii Karling 1973 (Proseriata, Otoplanidae) were obtained in King George Island (South Shetland Islands). This is the first report of the family Otoplanidae from Antarctica, and the first rediscovery of the species 50 years after its original description. The present article provides a complete description of the Antarctic material of O. bregazzii, complements its original description, and provides an identification key to the species of Orthoplana. We analyze the distribution of the genus and species and argue that the range expansion reported here could be the result of a recent, successful colonization event. This work, therefore, gives insights into the systematics and biogeography of one of the lesser-known groups in the Antarctic fauna. [ABSTRACT FROM AUTHOR]

Antarctica is a remote place, the continent is covered by ice and its surrounding coastal areas are frozen for the majority of the year. Due to its peculiarity the observation of the underwater organisms is particularly difficult, complicated by logistic factors. We present a long-term dataset consisting of 755 images acquired by using a non-invasive, autonomous imaging device and encompassing both the Antarctic daylight and dark periods, including the corresponding transition phases. All images have the same field of view showing the benthic fauna and part of the water column above, including fishes present in the monitored period. All the images are manually annotated after a visual inspection performed by expert biologists. The extended monitoring period and the annotated images make the dataset a valuable benchmark suitable for studying the dynamics of the long-term Antarctic underwater fauna as well as for developing and testing algorithms for automated image analysis focused on the recognition and classification of the Antarctic organisms and the automated analysis of their long-term dynamics. Measurement(s) Coastal Benthic Megafauna Technology Type(s) Autonomous Imaging Device Factor Type(s) None Sample Characteristic - Organism Sterechinus neumayeri • Odontaster • Trematomus • Polynoidae • Diplasterias • Ophiuridae • Ammothea • Neobuccinum eatoni • Staurocucumis • Flabegraviera mundata Sample Characteristic - Environment coastal sea water Sample Characteristic - Location East Antarctica [ABSTRACT FROM AUTHOR]

The article describes the features and results of using the autonomous underwater vehicle (AUV) MMT-3000 for research of Antarctic ecosystems and deep-sea biological resources of the South Seas. The methodology for working with an AUV in the extreme conditions of Antarctica and the technical solutions used to visually assess the distribution of bottom animals are discussed. The results of processing the data obtained by AUV during deep-sea missions in the Atlantic sector of the Antarctic during the expedition of the RV Akademik Mstislav Keldysh (cruise 79) in 2020 are presented. At the same time, the data of image analysis and trawl catch were compared. Based on the experience gained, the requirements to be implemented in the new AUV MMT-3500, which is designed and manufactured to effectively carry out deep-sea research in subsequent expeditions in the Southern Ocean, are determined. [ABSTRACT FROM AUTHOR]

The rapid changes in the climate of Antarctica are likely to pose challenges to living communities, which makes monitoring of Antarctic fauna an urgent necessity. Benthos is particularly difficult to monitor, and is sensitive to local environmental changes. At the same time, long‐term monitoring is complicated by logistical factors. It is therefore urgent to develop advanced instruments to set up autonomous and long‐term monitoring programmes to obtain the lacking biological knowledge needed to understand this complex and remote marine environment.We present a pilot study to set up a non‐invasive and sustainable autonomous monitoring activity in Antarctica, leveraging on a specifically designed automated camera recording, computer vision and machine learning image processing techniques. We also present and analyse the high‐resolution image dataset acquired for an extended period of time encompassing both the summer and the Antarctic night and the corresponding transition periods.The results of this study demonstrate both the effectiveness of such an autonomous imaging devices for acquiring relevant long‐term visual data and the effectiveness of the proposed image analysis algorithms for extracting relevant scientific knowledge from such data. The presented results show how the extracted knowledge discloses dynamics of the observed ecosystems that can be obtained only through continuous observations extended in time, not achievable with the state‐of‐the‐art monitoring approaches commonly implemented in Antarctica.The success of this pilot study is a step towards the collection of continuous data near shore in Antarctic areas and in general in all the remote and extreme underwater habitats. Moreover, the presented stand‐alone and autonomous imaging device can be used for increasing the number of the monitoring sites in remote environments and when complemented with the acquisition of physical and bio‐chemical variables it can be used for obtaining data collections of great scientific value difficult to acquire otherwise. [ABSTRACT FROM AUTHOR]

The seasonal and interannual variability of feeding in 15 species of benthic marine suspension feeder was studied over 8 yr at Ryder Bay, Antarctica. Feeding was strongly seasonal in bryozoans, gorgonians, polychaetes, and dendrochirote holothurians. The winter non‐feeding period was longest in the holothurians and shortest in bryozoans. Bryozoans started feeding in late winter at very low chlorophyll concentrations, often when surface fast‐ice was still present. In hydroids and actinians, feeding tentacles were deployed continuously throughout the year, though hydroid feeding intensity declined slightly in late winter. Water column phytoplankton biomass was strongly seasonal with marked interannual variability in the timing and intensity of the bloom, driven principally by ice dynamics. Correlation across years between the start of feeding and the development of the bloom was poor, and in seasons when a dense spring bloom of benthic filamentous microalgae developed, the start of feeding in many benthic species was delayed. This study indicates that feeding in benthic marine suspension feeders in Antarctica is influenced by factors additional to the seasonal availability of food in the water column. [ABSTRACT FROM AUTHOR]

In the Antarctic seas, where hard substrates are scarce, the presence of secondary bio-substrates formed by calcareous organisms is an essential condition to increase the epibiosis and therefore the diversity of sessile benthic fauna. The aggregations of stylasterid hydrozoa, with their branched carbonate structures, are an example of a secondary habitat defined as a 'deep marine animal forest'. The three-dimensional habitat made by these corals supports a high biodiversity of associated organisms, usually invertebrates. Recently, deep remotely operated vehicle (ROV) exploration of the Iselin Bank and the Hallett Ridge (Ross Sea, Antarctica) documented wide areas characterised by large thanatocoenosis of stylasterid skeletons lying on flat muddy substrates, with scattered living colonies generally made of few short branches. In our study, sponges associated with 54 dead colonies of two stylasterid species recorded in these areas were investigated. The analysis led to the discovery of a remarkable number of specimens (127) ascribed to 38 sponge species (31 encrusting and 7 massive). Two of these sponges, Asbestopluma (Asbetopluma) sinuosa and Lissodendoryx (Ectyodoryx) inferiolabiatae, are new. In light of the present data, we can assume that, in Antarctica, stylasterid skeletal remains, due to their three-dimensional structure, play an important role in maintaining sponge biodiversity. This is also due to the ability of sponge specie to produce miniaturised specimens able to colonise these peculiar substrata. [ABSTRACT FROM AUTHOR]

An expedition to study the ecosystems of the Atlantic sector of the Antarctic was carried out in cruise 87 of R/V Akademik Mstislav Keldysh between January 19 and February 14, 2022. The studies were carried out in the key regions for understanding modern processes in the ecosystem of the Southern Ocean and in the regions of interest for Russian fisheries, namely, the Powell Basin of the Weddell Sea, the Bransfield Strait, Antarctic Sound, and at the test site east of the South Orkney Islands. Materials characterizing the state of the environment, pelagic communities, including the population of the Antarctic krill and mesopelagic fish, benthic fauna, and the spatial and temporal variability of the most important components of ecosystems, were obtained. [ABSTRACT FROM AUTHOR]

To better understand the biodiversity-biogeographic polar connections between southern South America and Antarctica (SSA & A), we used benthic communities of hydroids as a model to investigate marine assemblages by evaluating classic spatial divisions at different geographical resolutions. Using a georeferenced dataset of 249 species and multivariate analyses, we investigated species' distribution, composition and biogeographic connectivity, and defined assemblages of ecoregions and provinces for the area. Hotspots of rich biodiversity at risk of depletion were defined. Analyses of ecoregions have a more stratified biogeographic structure, and reveal critical regions susceptible to loss of diversity. Analyses of provinces show a clear division between Atlantic-Pacific and Antarctic-Subantartic assemblages, with high biogeographic isolation of the Subantarctic islands. Depending on spatial resolution, the biogeographic position of the Magellan area is spatially contradictory, clustering on the one hand with SSA ecoregions and on the other with Antarctic provinces. Our patterns appear to be driven by different combinations of processes and barriers, reflected in the stratified distribution of hydroids. The high level of endemism and concentration of species at the edge of distribution in the Magellan area and Scotia Arc suggest their transitional nature and particular importance for understanding the historical and ecological connections between SSA & A. [ABSTRACT FROM AUTHOR]

All coastal systems experience disturbances and many across the planet are under unprecedented threat from an intensification of a variety of stressors. The West Antarctic Peninsula is a hotspot of physical climate change and has experienced a dramatic loss of sea‐ice and glaciers in recent years. Among other things, sea‐ice immobilizes icebergs, reducing collisions between icebergs and the seabed, thus decreasing ice‐scouring. Ice disturbance drives patchiness in successional stages across seabed assemblages in Antarctica's shallows, making this an ideal system to understand the ecosystem resilience to increasing disturbance with climate change. We monitored a shallow benthic ecosystem before, during and after a 3‐year pulse of catastrophic ice‐scouring events and show that such systems can return, or bounce back, to previous states within 10 years. Our long‐term data series show that recovery can happen more rapidly than expected, when disturbances abate, even in highly sensitive cold, polar environments. [ABSTRACT FROM AUTHOR]

Hydrozoans are one of the main and most characteristic zoological groups of Antarctic benthic communities, yet there are Antarctic areas where the hydrozoan fauna is completely unknown (e.g. the Admunsen Sea, West Antarctica) or scarcely known (e.g. Adélie Land, East Antarctica). Hitherto, only one study, published in 1972, has been devoted to hydroids inhabiting marine bottoms off Adélie Land. The present study contributes to a better knowledge of the benthic hydroid fauna of this region by studying material from the Antarctic Specially Protected Area of Pointe Géologie Archipelago (ASPA 120), area of considerable biological value and great importance for scientific research. 35 species of benthic hydroids were found, belonging to 14 families and 18 genera. 15 species represent new records for the area, bringing the number of species reported in the zone to 45. Leptothecata is dominant, with 30 species, while Anthoathecata is represented by just five species. Symplectoscyphidae is the most speciose family, with 11 species (31%), whereas Kirchenpaueriidae has the highest biomass due to Oswaldella terranovae, the species with the highest abundance and biomass and that could be considered a true habitat builder and biodiversity hotspot. The study of the hydroid assemblages has revealed the overwhelming dominance in the area of a community characterised mainly by O. terranovae; three other assemblages are present, albeit much less represented. The hydroid fauna is clearly dominated by eurybathic species (65%) and most of the species studied (88%) are restricted to Antarctic or Antarctic/sub-Antarctic waters, with 65% endemic to the Antarctic region. [ABSTRACT FROM AUTHOR]

Throughout the Quaternary, the continental‐based Antarctic ice sheets expanded and contracted repeatedly. Evidence suggests that during glacial maxima, grounded ice eliminated most benthic (bottom‐dwelling) fauna across the Antarctic continental shelf. However, paleontological and molecular evidence indicates most extant Antarctica benthic taxa have persisted in situ throughout the Quaternary. Where and how the Antarctic benthic fauna survived throughout repeated glacial maxima remain mostly hypothesised. If understood, this would provide valuable insights into the ecology and evolution of Southern Ocean biota over geological timescales. Here we synthesised and appraised recent studies and presented an approach to demonstrate how genetic data can be effective in identifying where and how Antarctic benthic fauna survived glacial periods. We first examined the geological and ecological evidence for how glacial periods influenced past species demography in order to provide testable frameworks for future studies. We outlined past ice‐free areas from Antarctic ice sheet reconstructions that could serve as glacial refugia and discussed how benthic fauna with pelagic or non‐pelagic dispersal strategies moved into and out of glacial refugia. We also reviewed current molecular studies and collated proposed locations of Southern Ocean glacial refugia on the continental shelf around Antarctica, in the deep sea, and around sub‐Antarctic islands. Interestingly, the proposed glacial refugia based on molecular data generally do not correspond to the ice‐free areas identified by Antarctic ice sheet reconstructions. The potential biases in sampling and in the choice of molecular markers in current literature are discussed, along with the future directions for employing testable frameworks and genomic methods in Southern Ocean molecular studies. Continued data syntheses will elucidate greater understanding of where and how Southern Ocean benthic fauna persisted throughout glacial periods and provide insights into their resilience against climate changes in the future. [ABSTRACT FROM AUTHOR]

Ice retreat in West Antarctica and Antarctic Peninsula has led to important changes in seafloor communities and gains in benthic blue carbon. In most of the Antarctic, however, sea ice increased between the 1970s and 2014, but its effects on the benthos remain largely unexplored. Here, we provide a 1988–2014 record of macro- and megafauna from the north-eastern Weddell Sea shelf, where benthic biomass decreased by two thirds and composition shifted from suspension feeders to deposit feeders. Concomitant increases in sea-ice cover suggest a reduced flux of primary production to the benthos. As benthic communities are major repositories for Antarctic biodiversity and play an important role in biogeochemical cycling, the observed changes have far-reaching consequences for the Antarctic ecosystem and its feedback to the climate system. The findings underscore the importance of long-term ecological monitoring in a region vulnerable to warming and ice-shelf collapse. Sea-ice cover in Antarctica has increased over the last decades and reached a maximum in 2014. Here, the authors report strong declines in zoobenthic biomass and abundance and changes in community composition on the NE Weddell Sea shelf over 26 years, with implications for blue carbon and biochemistry in a globally important marine region. [ABSTRACT FROM AUTHOR]

The article presents data on the activity of the radionuclide 137Cs in seawater, sediment, macroalgae, and zoobenthos from different locations in Admiralty Bay, King George Island, maritime Antarctica. The activity of 137Cs in the macrophytobenthos remained relatively stable across species, oscillating at the level of 1 Bq kg−1dw. However, a few individuals exhibited higher activity, particularly at stations closer to the glacier front. This result could have been caused by specific conditions resulting from melting glaciers and meltwater inflow and mixing with oceanic water. The activities of 137Cs in zoobenthic were in the range from 0.12 Bq kg−1dw (Asteroidea) to 24.2 Bq kg−1dw (Porifera) and the total doses in marine species were several orders of magnitude lower than reference levels. Stable isotopes of δ13C and δ15N suggest that the main factor influencing 137Cs activity may be the source of carbon (marine vs. terrestrial/glacial), rather than feeding strategy or trophic niches. [Display omitted] • 137Cs in Antarctic biota were still detected. • Low activity of 137 Cs is observed in most cases of the Antarctic ecosystem. • Carbon cycling may affect radionuclides activity in zoobenthos. • Total dose from 137Cs in Antarctic species was negligible. [ABSTRACT FROM AUTHOR]

Field works on cruise 79 of the R/V Akademik Mstislav Keldysh aimed at investigating the ecosystems in the Atlantic sector of Antarctica were conducted from January 16 to March 1, 2020. Hydrophysical and biological studies were carried out in the Drake Passage and the Bransfield and Antarctic Sound straits. The regions of Russian fishery interest were covered. Data were collected that characterize the environmental state; plankton communities, including krill, ichthyoplankton, macronecton; bottom fauna; and spatiotemporal variations in the most important ecosystem components. [ABSTRACT FROM AUTHOR]

The Southern Ocean is a very sensitive ecosystem, with the Antarctic Peninsula being one of the most rapidly warming regions on Earth. Accordingly, studies of its biodiversity are of urgent interest. In this context, taxonomical surveys of Antarctic tanaidacean species become relevant, since it is one of the lesser-known Antarctic macrofaunal groups. The present study aims to elucidate the species composition as well as spatial and vertical distribution of tanaidaceans in the shallow sublittoral zone of Admiralty Bay, one of the Antarctic Specially Managed Areas. Sediment samples were taken in the years 2005 and 2010 from 20 and 50 m depth zones at two sites in each of five chosen stations. Three replicate box-corer samples were taken at each site, and the retained sediment was stratified (0–2, 2–6, and 6–10 cm sediment layers). Nine Tanaidacean species (superfamily Paratanaoidea) were identified, with two new species records for Admiralty Bay: Arhaphuroides parabreviremis and Parakanthophoreus antarcticus. In general, Nototanais antarcticus was the dominant species. Significant abundance differences were found among stations, except at 20 m depth in 2005. The Ullmann Point station stood out by the absence of tanaidaceans. No significant differences were found between depths, although 20 m depth sites exhibited higher abundance than 50 m depth ones, which in turn presented higher species richness. Tanaidaceans were concentrated in the first six cm of sediment. Data suggest that the Tanaidacea assemblages in Admiralty Bay have very heterogeneous spatial distribution, reflecting the variety of habitats present in this region. [ABSTRACT FROM AUTHOR]

The biogeography of the Southern Ocean and its subdivisions has attracted the interest of the scientific community for many years, especially for those border regions with great sub-Antarctic influence. The Scotia Arc, located between the Antarctic Peninsula and the Magellan region, has been considered as a biogeographic bridge and hence widely discussed, but there are still gaps in the knowledge of some zoological groups and its inclusion in truly Antarctic waters still constitutes an unresolved topic. The faunistic affinities between the benthic hydroids from the Scotia Arc and those from nearby regions (i.e., High Antarctica, Patagonian region and Bouvet Island) were evaluated with different similarity index and hierarchical analyses in order to put into evidence the biogeographic connectivity among those regions. The results show that the Scotia Arc archipelagos have greater affinity with continental Antarctica than with the Patagonian region, with an increasing similarity while approaching to High Antarctica, highlighting their importance as a biogeographic bridge and the effectiveness of the Polar Front as a major oceanographic barrier. Evidences from the present study on benthic hydroids supports the placement of the whole Scotia Arc within of the Antarctic region. Present data were compared with those from other benthic invertebrates groups to contribute to a better understanding of the biogeography of the Scotia Arc as a whole. [ABSTRACT FROM AUTHOR]

The Southern Ocean is widely recognized for its unique benthic ecosystems, but benthic sampling has been largely restricted to shallower continental zones and much remains to be learned about the biodiversity in the bathyal and abyssal zones. In this study, we collected and investigated the deep-sea benthic habitat using geological dredges, a multiple corer, and a bait trap on-board the R/V Hakuho Maru in bathyal to abyssal depths between the latitude of 39°38.16′S–66°36.03′S and the longitude of 62°19.55′W–67°37.95′E in the Southern Ocean and the surrounding subantarctic region, focusing on West Antarctica. We carried out 20 geological dredges, 14 multiple corers, and a bait trap survey. Here, we present the taxonomic and distributional records of 180 species of Annelida, Mollusca, Ostracoda, Decapoda, and Echinodermata identified from our samples, including species-level identifications and detailed occurrence information where possible. Although West Antarctica is a highly investigated area for benthic biodiversity around Antarctica, our collection includes the annelid Flabelligena hakuhoae Jimi et al. 2020 which was new to science at the time of collection, and other potentially undescribed species of Annelida, Ostracoda, Asteroidea, and Holothuroidea. Several specimens collected updated the distribution ranges of their species. [ABSTRACT FROM AUTHOR]

Ten benthic fauna taxa in a polluted marine area adjacent to McMurdo Station, Antarctica were deemed to be potential biomonitors because PCBs, DDTs, PAHs, copper, lead and/or zinc in their tissues were significantly higher than in tissues of taxa living in reference areas (p < 0.05). Concentrations of PCBs and DDT were highest in Trematomus (fish). Total PAH concentrations were highest in Alcyonium antarcticum (soft coral), Isotealia antarctica (anemone) and L. elliptica. Copper and lead concentrations were highest in Laternula elliptica (bivalve) and Flabegraviera mundata (polychaete), and lowest in Trematomus and Parbolasia corrugatus (nemertean). However, copper concentrations were even higher in the asteroids Perknaster fuscus antarcticus, Odontaster validus and Psilaster charcoti. Bioaccumulation factors for different species were highest for PCBs and DDT, and lowest for lead. Bioaccumulation of some contaminants are likely prevalent in benthic taxa at McMurdo Station, but concentrations are usually low relative to human consumption standards. [Display omitted] • The sea floor adjacent to McMurdo Station, Antarctica is contaminated. • Six contaminants were all found in higher concentrations in benthic fauna. • Bioaccumulation is widespread among benthic taxa (10 of 12 taxa sampled). • Most whole-body concentrations are below human consumption standards. [ABSTRACT FROM AUTHOR]

Ten triangle trawls in Prydz Bay were collected from 97 m to 638 m. A total of 206 species of macro- and mega-benthos were identified, belonging to 9 phyla and 118 families, of which pycnogonids (41 species), gammarid amphipods (38 species) and echinoderms (36 species) were the most dominant groups. The species richness per station varied from 1 to 92. The abundance of macro- and mega-benthos (1 × 10−3-0.24 Ind./m2) was low, compared to that in the southeastern Weddell Sea (131–1.28 × 103 Ind./m2) and South Shetland waters (160–4.38 × 103 Ind./m2). The results were similar to the Amundsen Sea abundances (1.10 × 10−3-0.40 Ind./m2) at comparable depths and in the Antarctic deep sea. The macrobenthic community had 2 types, Sessile Suspension Feeders with Associated fauna - dominated by sponges (SSFA-SPO) and mobile deposit feeders, infauna and grazers - epifauna dominated (MOIN-EPI). The macrobenthic community in Prydz Bay showed a dispersed patchy distribution pattern which may result from the Antarctic water mass and iceberg scouring. [ABSTRACT FROM AUTHOR]

Antarctic sea ice and the cold waters surrounding the continent are key elements of the global climate system, influencing heat redistribution, oceanic circulation and the absorption of carbon dioxide from the atmosphere. However, the Southern Ocean is predicted to warm by 1-6°C over the next century, altering sea ice extent, thickness and permanence. To better understand the connections between coastal sea ice conditions and the functioning of Antarctica's unique marine benthic ecosystems, we performed manipulative experiments on the seafloor at two southwestern Ross Sea sites with contrasting sea ice conditions. Benthic systems at both study sites were net heterotrophic during the study period (early November), with primary production most likely limited by light availability rather than nutrients. There was five times more fresh algal detrital material in benthic sediments at the site with the thinner, snow-free, annually formed sea ice, relative to the site with thicker, multiyear sea ice. This elevated quantity and quality of algal detrital matter corresponded with a significantly greater rate of sediment oxygen utilization by the benthos and an altered pathway of nitrogen regeneration (tighter coupling between nitrification and denitrification). Large benthic animals (brittle stars, Ophionotus victoriae) enhanced the efflux of dissolved inorganic nutrients from the sediment to the water column and played a greater role in nutrient regeneration at the site with more food. Although changes in sea ice characteristics in the Western Ross Sea are difficult to predict at present, large benthic organisms can be expected to have an expanded role in mediating the effects of elevated coastal productivity and detritus supply on ecosystem dynamics in this part of Antarctica. [ABSTRACT FROM AUTHOR]

Ophiuroids are a conspicuous and often dominant component of the Antarctic continental shelf benthos. Here we report on the ophiuroids collected from the Burdwood Bank, off the Patagonian Shelf, through the shallow water areas of the Scotia Arc, down the west Antarctic Peninsula and as far south as Pine Island Bay in the eastern Amundsen Sea. This preliminary and primarily pattern based study identifies some regional differences in assemblages and highlights the role of the Antarctic Circumpolar Current as a barrier, as well as a facilitator, to dispersal. In order to effectively compare between studies we highlight the need for accurate, expert taxonomic identification of specimens. [ABSTRACT FROM PUBLISHER]

Sponges play a key role in Antarctic marine benthic community structure and dynamics and are often a dominant component of many Southern Ocean benthic communities. Understanding the drivers of sponge distribution in Antarctica enables us to understand many of general benthic biodiversity patterns in the region. The sponges of the Antarctic and neighbouring oceanographic regions were assessed for species richness and biogeographic patterns using over 8,800 distribution records. Species-rich regions include the Antarctic Peninsula, South Shetland Islands, South Georgia, Eastern Weddell Sea, Kerguelen Plateau, Falkland Islands and north New Zealand. Sampling intensity varied greatly within the study area, with sampling hotspots found at the Antarctic Peninsula, South Georgia, north New Zealand and Tierra del Fuego, with limited sampling in the Bellingshausen and Amundsen seas in the Southern Ocean. In contrast to previous studies we found that eurybathy and circumpolar distributions are important but not dominant characteristics in Antarctic sponges. Overall Antarctic sponge species endemism is ∼43%, with a higher level for the class Hexactinellida (68%). Endemism levels are lower than previous estimates, but still indicate the importance of the Polar Front in isolating the Southern Ocean fauna. Nineteen distinct sponge distribution patterns were found, ranging from regional endemics to cosmopolitan species. A single, distinct Antarctic demosponge fauna is found to encompass all areas within the Polar Front, and the sub-Antarctic regions of the Kerguelen Plateau and Macquarie Island. Biogeographical analyses indicate stronger faunal links between Antarctica and South America, with little evidence of links between Antarctica and South Africa, Southern Australia or New Zealand. We conclude that the biogeographic and species distribution patterns observed are largely driven by the Antarctic Circumpolar Current and the timing of past continent connectivity. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the foraging behaviors of benthic animals such as pinniped. The study used Bayesian Markov Chain Monte Carlo (MCMC) simulation, ArcMap, and algorithms. Results show that crabeater seals or the Lobodon carcinophagus and fur seals or the Callorhinus ursinus have favored seamounts for pelagic foraging in Antarctic.

The Bellingshausen Sea constitutes the third largest sea in the Southern Ocean, though it is widely recognized as one of the less-studied Antarctic areas. To reduce this lack of knowledge, a survey to study the biodiversity of its marine benthic communities was carried out during the Bentart 2003 and Bentart 2006 Spanish Antarctic expeditions. The study of the hydroid collection has provided 27 species, belonging to ten families and 15 genera. Twenty-one out of the 27 species constitute new records for the Bellingshausen Sea, raising the total number of known species to 37, as also do nine out of the 15 genera. Candelabrum penola, Lafoea annulata, and Staurotheca juncea are recorded for the second time. Most species belong to Leptothecata. Sertulariidae with 13 species (48%) is by far the most speciose family, and Symplectoscyphus with seven species (26%), including S. bellingshauseni sp. nov. and S. hesperides sp. nov., the most diverse genus. Considering the whole benthic hydroid fauna of the Bellingshausen Sea, 18 species (69%) are endemic to Antarctic waters, either with a circum-Antarctic (12 species, 46%) or West Antarctic (6 species, 23%) distribution, 23 (88%) are restricted to Antarctic or Antarctic/sub-Antarctic waters, and only three species have a wider distribution. Bellingshausen Sea hydroid fauna is composed of a relatively high diversity of typical representatives of the Antarctic benthic hydroid fauna, though with a surprisingly low representation of some of the most diverse and widespread Antarctic genera ( Oswaldella and Schizotricha), what could be related to the fact that its shelf-inhabiting hydroid fauna remains practically unknown. [ABSTRACT FROM AUTHOR]

Abstract: Lipid, protein and carbohydrate concentrations have been determined in sediment cores from the continental shelf in the South Eastern Weddell Sea (SEWS), where no ice shelves have been present at least for thousands of years, and the continental shelf off the Eastern Antarctic Peninsula (EAP), in the area where two ice shelf collapses occurred in 1995 and 2002. On one hand, SEWS presents an important flux of fresh organic matter to the seabed during summer, whereas on the other hand, the presence of ice shelves in EAP hampered photosynthesis restricting the input of organic matter to advected refractory material. In the present study, biochemical variables and benthic macrofauna abundance, biomass and diversity confirmed differences between the two regions. Lipid concentrations were higher in SEWS than in EAP, whereas carbohydrate concentrations were higher in the latter region. These differences were attributed to the higher concentration of labile and refractory material, respectively. Biomass, abundance and diversity of the macrofauna were higher in SEWS than in EAP, where benthic communities started receiving a fresh organic matter input only after the recent ice shelf collapses. As regards macrofauna composition, both regions presented macrobenthic communities associated to early stages of recolonization. [Copyright &y& Elsevier]

Abstract: Stable isotopes of carbon and nitrogen were used to determine the different carbon pathways and trophic assemblages amongst coastal benthic fauna of the Windmill Islands, East Antarctica. Macroalgae, pelagic POM, sediment POM and sea ice POM had well-separated δ13C signatures, which ranged from −36.75‰ for the red alga Phyllophora antarctica, to −10.35‰ for sea ice POM. Consumers were also well separated by δ13C, ranging from −21.42‰ for the holothurian Staurocucumis sp. up to −7.47‰ for the urchin Sterechinus neumayeri. Analysis of δ13C and δ15N revealed distinct groups for suspension feeders, grazer/herbivores and deposit feeders, whilst predators and predator/scavengers showed less grouping. Consumers spanned a δ15N range of 8.71‰, equivalent to four trophic levels, although δ15N ratios amongst consumers were continuous, rather than grouped into discrete trophic levels. The study has built a trophic model for the Windmill Islands and summarises three main carbon pathways utilised by the benthos: (1) pelagic POM; (2) macroalgae/epiphytic/benthic diatoms and (3) sediment POM/benthic diatoms. The movement of carbon within the coastal benthic community of the Windmill Islands is considered complex, and stable isotopes of carbon and nitrogen were valuable tools in determining specific feeding guilds and in tracing carbon flow, particularly amongst lower-order consumers. [Copyright &y& Elsevier]

The distribution patterns of macrozoobenthic communities as shown by the biomass of the higher taxa were investigated in Admiralty Bay. Material was collected at depths ranging from 4 to 500 m (102 quantitative samples), representing the full depth range of this basin and including areas characterized by the different levels of glacial influence. Five community groups were distinguished by multivariate analysis (clustering, MDS) based on the Bray--Curtis similarity index. In the Ezcurra Inlet, the area characterized by intensive glacial processes resulting in a high sedimentation rate, the distribution of biomass was not depth related, but was associated with the intensity of glacial disturbance along the axis of the fjord. The innermost part of this fjord, which receives strong outflows from glaciers, had a low biomass value (2.9 g/0.1 m) and was dominated by polychaetes. The middle part of the fjord which is not so heavily disturbed had higher biomass values (46.1 g/0.1 m) due to the dominance of bivalves. A clear depth gradient of biomass distribution was observed in bottom areas located far from glaciers, in the central basin of the bay, with three zones within the depth ranges 4-30, 40-380, and 400-500 m. The highest mean biomass values (92.5 g/0.1 m) were found in the middle sublittoral (40-380 m) dominated by ascidians. In the shallow and deep assemblages, the biomass was lower (33.8 g/0.1 and 30.9 g/0.1 m respectively), most probably associated with the ice disturbance in the shallows and lower food supply in the deepest part of the shelf. [ABSTRACT FROM AUTHOR]

Abstract: Antarctica is structured by a narrow and deep continental shelf that sustains a remarkable number of benthic species. The origin of these species and their affinities with the deep-sea fauna that borders the continent shelf are not clear. To date, two main hypotheses have been considered to account for the evolutionary connection between the faunas: (1) either shallow taxa moved down to deep waters (submergence) or (2) deep-sea taxa colonized the continental shelf (emergence). The regular sea urchin genus Sterechinus is a good model to explore the evolutionary relationships among these faunas because its five nominal species include Antarctic and Subantarctic distributions and different bathymetric ranges. Phylogenetic relationships and divergence times among Sterechinus species were established using the COI mitochondrial gene by assuming a molecular clock hypothesis. The results showed the existence of two genetically distinct main groups. The first corresponds exclusively to the shallow-water Antarctic species S. neumayeri, while the second includes all the other nominal species, either deep or shallow, Antarctic or Subantarctic. Within the latter group, S. dentifer specimens all formed a monophyletic cluster, slightly divergent from all other specimens, which were mixed in a second cluster that included S. agassizi from the continental shelf of Argentina, S. diadema from the Kerguelen Plateau and S. antarcticus from the deep Antarctic shelf. These results suggest that the deeper-water species S. dentifer and S. antarcticus are more closely related to Subantarctic species than to the shallow Antarctic species S. neumayeri. Thus, for this genus, neither the submergence nor emergence scenario explains the relationships between Antarctic and deep-sea benthos. At least in the Weddell quadrant, the observed genetic pattern suggests an initial separation between Antarctic and Subantarctic shallow species, and a much later colonization of deep water from the Subantarctic region, probably promoted by the geomorphology of the Scotia Arc. [Copyright &y& Elsevier]

Abstract: Physical and biological characteristics of benthic communities are analysed from underwater video footage collected across the George V Shelf during the 2007/2008 CEAMARC voyage. Benthic habitats are strongly structured by physical processes operating over a range of temporal and spatial scales. Iceberg scouring recurs over timescales of years to centuries along shallower parts of the shelf, creating communities in various stages of maturity and recolonisation. Upwelling of modified circumpolar deep water (MCDW) onto the outer shelf and cross-shelf flow of high-salinity shelf water (HSSW) create spatial contrasts in nutrient and sediment supply, which are largely reflected in the distribution of deposit- and filter-feeding communities. Long-term cycles in the advance and retreat of icesheets (over millennial scales) and subsequent focussing of sediments in troughs such as the Mertz Drift create patches of consolidated and soft sediments, which also provide distinct habitats for colonisation by different biota. These physical processes of iceberg scouring, current regimes and depositional environments, in addition to water depth, are important factors in the structure of benthic communities across the George V Shelf. The modern shelf communities mapped in this study largely represent colonisation over the past 8000–12,000 years, following retreat of the icesheet and glaciers at the end of the last glaciation. Recolonisation on this shelf may have occurred from two sources: deep-sea environments and possible shelf refugia on the Mertz and Adélie Banks. However, any open-shelf area would have been subject to intense iceberg scouring. Understanding the timescales over which shelf communities have evolved and the physical factors which shape them will allow better prediction of the distribution of Antarctic shelf communities and their vulnerability to change. This knowledge can aid better management regimes for the Antarctic margin. [Copyright &y& Elsevier]

Abstract: Ice-shelf collapses in the Larsen A and B embayments along the Weddell side of the Antarctic Peninsula resulted in new open-water areas that are likely reorganizing benthic communities. It is a natural laboratory to assess colonization of the sea bottom under new conditions. We tested the hypothesis that the epibionts associated to cidaroid echinoids could promote or enhance the colonization of hard surfaces. In fact, being vagile, cidaroids might improve dispersal capabilities of the sessile animals that are attached to their spines, e.g., promoting the colonization of areas where the fauna has been eradicated by iceberg scouring. If this hypothesis is correct, pioneer sessile species present locally on stones might have affinities with ectosymbionts on cidaroids, and the sessile fauna present both on cidaroids and stones should be more similar in the Larsen embayments than in undisturbed areas. We therefore compared sessile species living on cidaroids with those living on stones in three areas: Larsen A and B embayments and two undisturbed and geographically different areas, Atka Bay and Elephant Island. Overall, richness, evaluated as ‘morphotypes’ richness, was lower in the Larsen area than in other areas, but levels of species diversity were similar among the three zones. The estimate of similarity between assemblages (using the C 22 index of ) also suggests that cidaroid epibionts are either species-specific or specific to cidaroids, while the composition of sessile fauna on stones is more variable and probably dependent on local factors. In the two undisturbed areas, sessile fauna are highly different between stones and cidaroids. This contrasts with the Larsen embayments where cidaroids share more than 80% of epibionts with the surrounding stones. These results suggest that ectosymbioses linked to cidaroids strongly contribute to benthic colonization of the seafloor in the Larsen enbayments. With time, secondary successions are expected to occur, increasing the difference between epibiotic communities on cidaroids and those on stones, and lead to the situations observed in unperturbed sites. [Copyright &y& Elsevier]

Abstract: A thorough census of Admiralty Bay benthic biodiversity was completed through the synthesis of data, acquired from more than 30 years of observations. Most of the available records arise from successive Polish and Brazilian Antarctic expeditions organized since 1977 and 1982, respectively, but also include new data from joint collecting efforts during the International Polar Year (2007–2009). Geological and hydrological characteristics of Admiralty Bay and a comprehensive species checklist with detailed data on the distribution and nature of the benthic communities are provided. Approximately 1300 species of benthic organisms (excluding bacteria, fungi and parasites) were recorded from the bay’s entire depth range (0–500m). Generalized classifications and the descriptions of soft-bottom and hard-bottom invertebrate communities are presented. A time-series analysis showed seasonal and interannual changes in the shallow benthic communities, likely to be related to ice formation and ice melt within the bay. As one of the best studied regions in the maritime Antarctic Admiralty Bay represents a legacy site, where continued, systematically integrated data sampling can evaluate the effects of climate change on marine life. Both high species richness and high assemblage diversity of the Admiralty Bay shelf benthic community have been documented against the background of habitat heterogeneity. [Copyright &y& Elsevier]

In early 2004 the Victoria Land Transect project sampled coastal north-western Ross Sea shelf benthos at Cape Adare, Cape Hallett, Cape Russell and Coulman Island from 100-500m deep. We describe the benthic macrofaunal assemblages at these locations and, to assess the use of seafloor sediment characteristics and/or depth measures in bioregionalizations, determine the extent to which assemblage compositions are related to measured differences in these factors. Percentages of fine sand and silt, the ratio of sediment chlorophyll a to phaeophytin, and depth were identified as important explanatory variables, but in combination they explained only 17.3% of between-location differences in assemblages. Consequently, these variables are clearly not strong determinants of macrofaunal assemblage structure. Latitude per se was not a useful measure of community variability and change. A significant correlation between both number of individuals and number of taxa and sediment phaeophytin concentration across locations suggests that the distribution of the benthos reflects their response to seafloor productivity. A number of factors not measured in this study have probably influenced the structure and function of assemblages and habitats. We discuss the implications of the results to marine classifications, and stress the need to incorporate biogenic habitat complexity into protection strategies. [ABSTRACT FROM AUTHOR]

A prospecting search for antitumoural activity in polar benthic invertebrates was conducted on Antarctic and sub-Antarctic benthos in three different areas: Bouvet Island (sub-Antarctic), eastern Weddell Sea (Antarctica) and the South Shetland Islands (Antarctica). A total of 770 benthic invertebrate samples (corresponding to at least 290 different species) from 12 different phyla were assayed to establish their pharmacological potential against three human tumour cell lines (colorectal adenocarcinoma, lung carcinoma and breast adenocarcinoma). Bioassays resulted in 15 different species showing anticancer activity corresponding to five different phyla: Tunicata (5), Porifera (4), Cnidaria (3), Echinodermata (2) and Annelida (1). This appears to be the largest pharmacological study ever carried out in Antarctica and it shows very promising antitumoural activities in the Antarctic and sub-Antarctic benthos. [ABSTRACT FROM AUTHOR]

Abstract: To determine the potential of Antarctic bivalve shells as biomonitors for environmental and climatic variations in polar marine areas, we developed a growth model for juvenile Adamussium colbecki Smith, 1902 based on the use of in situ temporal calcein markings to calibrate growth patterns in the external striae formation. To minimize scallop stress caused by excessive handling, in situ benthic chambers were used for the marking experiment, during an exposure time of 6h. Once marked, scallops remained on site in a benthic cage and were collected 18, 26, and 41days later. Apart from a few specimens affected by possible calcein toxicity effects, the detectable mark in all shells revealed a higher austral summer growth rate for A. colbecki compared to other Antarctic bivalves. Using calcein labeling, we identified a near 14-day periodicity in the striae formation associated with the fortnightly seawater level regime. Striae counting and increment width measurements showed an annual cycle, with no clear cessation of growth in juvenile specimens, allowing age determination. Because of the relatively high growth rate for a polar species and easily recognizable sclerochronological calendar in the shell striae formation, A. colbecki is an appropriate species for high-resolution (infra-monthly) geochemical sampling. Comparison between LA-ICP-MS analyses (Li, B, Mg, Mn, Co, Sr, Ba, Pb) from one shell and hydrological parameters (sea level, temperature, salinity) measured in seawater suggests, however, that more work is needed to calibrate the trace element proxies. Nevertheless, the shell of the Antarctic scallop A. colbecki has tremendous potential for recording environmental conditions from time periods covering months to a few years in polar waters, notably the ice melting date. [ABSTRACT FROM AUTHOR]

Abstract: The surface of the shell of the pelagic Antarctic gastropod, Limacina helicina antarctica forma antarctica, was smooth, with rib-like structures also observed. The larger specimen, with six to seven whorls, had visible ribs on its most outer whorl. The shell thickness of L. helicina antarctica forma antarctica was very thin, approximately 5–7 μm, on an individual with a shell diameter of 1.4 mm. Shell microstructure, as examined by SEM, was composed mostly of a crossed-lamellar structure. Shell thickness of the dominant benthic bivalve Laternula elliptica, was approximately 99–132 μm on an individual of shell length 19 mm. It was composed of two calcareous layers, including a thick outer homogeneous or granular layer and a thin nacreous inner layer. The characteristics of shell structure are discussed with reference to previous results, and in terms of adaptation to Antarctic waters. [Copyright &y& Elsevier]

Owing to large-scale ice-shelf disintegration events, the Antarctic Larsen A and B areas recently became ice-free. During the ANT-XXIII/8 Polarstern campaign, this region was sampled for the first time. Our study is the first to investigate benthic communities in this area and their response to the collapse of ice shelves in the Antarctic. The nematofauna appears to be strongly influenced by the sudden ice-cover removal, although its response differs from that of the macro- and megabenthos. Our results indicate that precollapse, sub-ice communities were impoverished and characterized by low densities, low diversity and high dominance of a few taxa. This might still be visible at a station located deep inside the Larsen B embayment, where Halomonhystera was dominant. Post-collapse recolonization of the ‘inner’ stations, i.e. those located furthermost from the former ice-shelf edge, is believed to be a long-time process. At the time of sampling, community structure at the inner stations was not or only slightly influenced by colonization, and might be structured by local environmental conditions. Our results indicate that a locally increased food supply after ice-cover removal could provoke a faster, local response of the nematode assemblages compared with the response due to recolonization. Thalassomonhystera is recognized as an opportunist, taking advantage of increased food supply at inner stations A_South and B_North. Communities living close to the former ice-shelf edge are believed to be at an intermediate or late stage of succession, with a dominance of Microlaimus, a common Antarctic genus and quick colonizer. Densities here were comparable with those at other Antarctic stations, whereas they were considerably decreased at the inner stations. In general, the collapse of the Larsen ice shelves initially has a positive effect on the shelf nematode fauna in the area, both in terms of abundance and diversity. [ABSTRACT FROM AUTHOR]

Chinstrap, Pygoscelis antarctica, and gentoo, P. papua, penguins are sympatric species that inhabit the Antarctic Peninsula. To evaluate differences in the foraging habitat of these two species, we recorded their foraging locations and diving behavior using recently developed GPS-depth data loggers. The study was conducted on King George Island, Antarctica during the chick-guarding period of both species, from December 2006 to January 2007. The area used for foraging, estimated as the 95% kernel density of dive (>5 m) locations, overlapped partially between the two species (26.4 and 68.5% of the area overlapped for chinstrap and gentoo penguins, respectively). However, the core foraging area, estimated as the 50% kernel density, was mostly separate (12.8 and 25.0% of the area overlapped for chinstrap and gentoo penguins, respectively). Chinstrap penguins tended to use off-shelf (water depth > 200 m) regions (77% of the locations for dives >5 m), whereas gentoo penguins mainly used on-shelf (water depth < 200 m) areas (71% of dive locations). The data on foraging locations, diving behavior, and bathymetry indicated that gentoo penguins often performed benthic dives (28% of dives >5 m), whereas chinstrap penguins almost always used the epipelagic/mid-water layer (96% of dives >5 m). Diving parameters such as diving bottom duration or diving efficiency differed between the species, reflecting differences in the use of foraging habitat. The diving parameters also suggested that the on-shelf benthic layer was profitable foraging habitat for gentoo penguins. Conversely, the relationship between trip duration, date, and stomach content mass suggested that the chinstrap penguins went further from the colony to forage as the season progressed, possibly reflecting a reduction in prey availability near the colony. Our results suggest that chinstrap and gentoo penguins segregated their foraging habitat in the Antarctic coastal marine environment, possibly due to inter- and intra-specific competition for common prey resources. [ABSTRACT FROM AUTHOR]

The article discusses research on benthic foraminifera in Admiral Bay of the West Antarctic fiord environments. Samples from the water depths of 520 meters are multi-chambered monothalamous benthic foraminifera which include the softwalled allogromiids. The study also identified 138 taxa and three new taxa. According to the authors, results of the study will be integrated for updating data and putting them in a broader perspective that would include the vertically distributed Rose Bengal stained foraminifera.

Sensitivity (chemoreception) to different amino acids was studied in six invertebrate species: Serolis polita, Glyptonotus antarcticus, Abyssochromene plebs, Waldeckia obesa, Odontaster validus, and Sterechinus neumayeri. The sensitivity was estimated by the changes in basic metabolism (respiration rate). Starvation increased the sensitivity in all the species. The metabolism rates increased in the presence of L-glutamic acid in G. antarcticus, A. plebs, O. validus, and St. neumayeri. The serine and arginine amino acids had a significant impact on the metabolism of the necrophagous species S. polita and W. obesa. The chemical information may be mediated by means of L-glutamic acid via glutamate receptors, which can be blocked by kynurenic acid, as occurs in the experiments with G. antarcticus and A. plebs. [ABSTRACT FROM AUTHOR]

Due to different oceanographic and geological characteristics, benthic algal communities of Antarctica and the Arctic differ strongly. Antarctica is characterized by high endemism, whereas in the Arctic only a few endemic species occur. In contrast to the Antarctic region, where nutrient levels never limit algal growth, nutrient levels in the Arctic region are depleted during the summer season. Both regions have a strongly seasonally changing light regime, fortified by an ice covering throughout the winter months. After months of darkness, algae are suddenly exposed to high light caused by the breaking up of sea ice. Simultaneously, harmful ultraviolet radiation (UVR) enters the water column and can significantly affect algal growth and community structure. In the intertidal zone, fluctuations of temperature and salinity can be very large. Ice scours can further influence growth and settlement of intertidal algae. The subtidal zone offers a more stable habitat than the intertidal, permitting the growth of larger perennial algae and microbial mats. Polar regions are the areas most affected by global climate change, i.e., glacier retreat, increasing temperature and sedimentation, with as yet unknown consequences for the polar ecosystem. [ABSTRACT FROM AUTHOR]

Despite several works that have documented patterns of diversity in deep sea organisms, trends of diversity and the processes responsible for such trends still remain unclear. To date very few studies have documented the effects of variables such as latitude and longitude in deep-sea organisms in the Antarctic region. We explored the spatial patterns of diversity of benthic gastropods and bivalves in an extensive region about 2200 km long and 500 km wide from the South Shetland Islands to the Bellingshausen Sea in West Antarctica. A total of 134 species from 54 sites was recorded. Alpha diversity and beta diversity (measured as Whittaker's and Bray-Curtis similarity indices) were highly variable among areas. None of the species richness estimators measured as Sobs, Chao2, Jacknife1 and Jacknife2, stabilized towards asymptotic values in any area. The number of rare species was large with almost half of species represented by 1 or 2 individuals (41%) and most species (62%) restricted to 1 or 2 sites. The partial Mantel test revealed that similarity between sites increased with the decrease of depth differences, but not with horizontal separation. [ABSTRACT FROM AUTHOR]

Background: As Earth warms, temperate and subpolar marine species will increasingly shift their geographic ranges poleward. The endemic shelf fauna of Antarctica is especially vulnerable to climate-mediated biological invasions because cold temperatures currently exclude the durophagous (shell-breaking) predators that structure shallow-benthic communities elsewhere. Methodology/Principal Findings: We used the Eocene fossil record from Seymour Island, Antarctic Peninsula, to project specifically how global warming will reorganize the nearshore benthos of Antarctica. A long-term cooling trend, which began with a sharp temperature drop ~41 Ma (million years ago), eliminated durophagous predators-teleosts (modern bony fish), decapod crustaceans (crabs and lobsters) and almost all neoselachian elasmobranchs (modern sharks and rays)- from Antarctic nearshore waters after the Eocene. Even prior to those extinctions, durophagous predators became less active as coastal sea temperatures declined from 41 Ma to the end of the Eocene, ~33.5 Ma. In response, dense populations of suspension-feeding ophiuroids and crinoids abruptly appeared. Dense aggregations of brachiopods transcended the cooling event with no apparent change in predation pressure, nor were there changes in the frequency of shell-drilling predation on venerid bivalves. Conclusions/Significance: Rapid warming in the Southern Ocean is now removing the physiological barriers to shellbreaking predators, and crabs are returning to the Antarctic Peninsula. Over the coming decades to centuries, we predict a rapid reversal of the Eocene trends. Increasing predation will reduce or eliminate extant dense populations of suspensionfeeding echinoderms from nearshore habitats along the Peninsula while brachiopods will continue to form large populations, and the intensity of shell-drilling predation on infaunal bivalves will not change appreciably. In time the ecological effects of global warming could spread to other portions of the Antarctic coast. The differential responses of faunal components will reduce the endemic character of Antarctic subtidal communities, homogenizing them with nearshore communities at lower latitudes. [ABSTRACT FROM AUTHOR]

A total of 36 species of benthic hydroids, belonging to nine families and 16 genera, were found in the hydroid collection gathered during the Brazilian Antarctic expeditions PROANTAR III and IV. Seven of the species were identified only to generic level. There is a clear dominance of the subclass Leptothecatae with 33 species. By far the most diversified family was the Sertulariidae, with 16 species (44%). Symplectoscyphus with eight species, including Symplectoscyphus magnificus sp. nov., is the most diversified genus. Almost 70% of the species diversity is restricted to just six genera (38%). Sixty-eight percent of the species is Antarctic endemics and 86% is restricted to Antarctic or Antarctic/sub-Antarctic waters. Eudendrium antarcticum and Amphisbetia operculata are recorded for the first time from Antarctic waters. [ABSTRACT FROM AUTHOR]

Abstract: Although biological work in the Southern Ocean extends back well over a century, studies in the past two decades have changed significantly our understanding of the ecology, diversity, biogeography and evolution of Antarctic marine benthos. Exploration of new areas coupled with an emphasis on primary taxonomy have resulted in the description of many new taxa, though continued work in the deep sea coupled with the further application of molecular techniques will undoubtedly add further to documented Antarctic diversity. We now recognise that the diversity of Antarctic continental shelves exceeds that of the Arctic, and is comparable with temperate and even some non-reef tropical shelves. Biogeographic regions have been refined, though the basic structure reflects that established over a century ago, and interdisciplinary work continues to deepen our understanding of the influence of climatic and tectonic changes in the evolution of the Antarctic marine fauna. [Copyright &y& Elsevier]

A newly discovered Konservat-Lagerstätte from the Middle Miocene of the western Olympus Range, Dry Valleys, Antarctica, yields cypridoidean ostracods complete with preserved body and appendages. This is the first record of three-dimensionally fossilized animal soft tissues from the continent. The ostracods are preserved in goethite, secondary after pyrite, representing a novel mode of exceptional preservation. They signal a high-latitude (greater than 77°south) lake setting (Palaeolake Boreas) viable for benthic animal colonization prior to 14Myr ago. Their presence supports the notion of warmer, tundra-like environmental conditions persisting in the Dry Valleys until the Middle Miocene. [ABSTRACT FROM AUTHOR]

Abstract: The West Antarctic Peninsula (WAP) shelf experiences intense seasonal and interannual variability in phytoplankton production and particulate-organic-carbon flux to the seafloor. To explore the response of the megabenthic community to this production variability, we conducted video surveys of epibenthic megafauna at three stations on the WAP shelf in Nov–Dec 1999, Mar 2000, Jun 2000, Oct–Nov 2000, and Feb–Mar 2001. The epibenthic megafauna was dominated (>90%) by elasipod holothurians, irregular urchins and anthozoans, with total abundances ranging from 19 to 152 ind. 100m−2. The abundance of three of the dominant taxa (Protelpidia murrayi, Peniagone vignoni, and Amphipneustes spp.) varied significantly across seasons (p<0.05), although variations were not tightly correlated with the summer bloom cycle. The irregular urchins in the genus Amphipneustes varied 5-fold in abundance at single stations, with maximum densities (an average of 10.1 ind. 100m−2) attained in Jun 2000. Abundances of the elasipod holothurians P. murrayi (1–121 ind. 100m−2) and P. vignoni (0.7–27.5 ind. 100m−2) fell within the range for elasipod holothurians from other bathyal regions measured using image analysis. The abundance of P. murrayi increased up to 6-fold from a single Jun–Oct recruitment pulse, while changes in the abundance of P. vignoni (over 2-fold higher in Feb–Mar 2001) apparently resulted from immigration during the presence of a 1–2cm thick carpet of fresh phytodetritus. Based on the ratio of the number of fecal casts per individual, elasipod holothurians increased surface-deposit feeding rates by ⩾2-fold while phytodetritus was present at the seafloor. Nonetheless, these surface-deposit feeders appeared to feed and egest sediments throughout the winter, which is consistent with year-round persistence of a labile food bank in surficial sediments on the deep WAP shelf. [Copyright &y& Elsevier]

Abstract: Naturally occurring 234Th (24-d half-life) was used on the West Antarctic continental shelf to evaluate temporal variations in the flux of particulate material reaching the seabed, bioturbation intensity, the seasonal continuity of feeding by benthic fauna, and trends in particle selection during ingestion for six common detritivores (four surface deposit feeders and two subsurface deposit feeders). These measurements were made at three stations during the five FOODBANCS cruises (December 1999, March, June, and October 2000, and March 2001) to assess the nature of pelagic–benthic coupling on the shelf and to evaluate the seabed as a potential food bank for deposit feeders when surface primary production is minimal. Two summer regimes were sampled (March 2000 and March 2001) with the latter exhibiting a distinct 1–2-cm-thick phytodetritus layer in nearly all sediment core samples. At site B, the 234Th fluxes into the near-bottom (150/170mab) sediment traps were indistinguishable for the December–March 2000, March–June 2000, and June–October 2000 sampling intervals (fluxes ranging from 170 to 280dpmm−2 d−1). However, the sediment-trap 234Th flux measured for the October 2000–March 2001 interval (1000dpmm−2 d−1) was ∼5-fold greater than during the other three sampling periods, consistent with the deposition of a phytodetritus layer. The steady-state 234Th fluxes derived from seabed inventories at site B were 2.4–2.7 times greater than the sediment-trap 234Th fluxes, indicating substantial scavenging of this particle-reactive radiotracer in the bottom 150m of the water column and/or lateral transport near the seabed. The seabed 234Th inventories at the three stations showed no variation during the first four cruises, but were significantly greater during cruise FB-V (March 2001), when the phytodetritus layer occurred. Based on 234Th distributions in the seabed, bioturbation intensities (quantified using the diffusive mixing coefficient, D b) varied from 0.5 to 97cm2 yr−1. Mixing coefficients were significantly lower during FB-II than during FB-III, but no other time comparisons were statistically significant (p>0.05). 234Th D bs showed no distinct seasonality, and no correlation with either organic carbon flux into the sediment traps or 234Th inventory in the seabed. The four surface deposit feeders examined, an echiuran worm and three holothurians (Protelpidia murrayi, Bathyplotes fuscivinculum, and Peniagone vignoni), exhibited greater particle selection for recently deposited sediment during ingestion than the two subsurface deposit feeders studied (a head-down deposit feeding holothurian, Molpadia musculus, and an irregular urchin, Amphipneustes lorioli). All six deposit feeders contained excess 234Th activity in gut sediments during all five cruises, indicating sediment ingestion year round, even during the austral winter. The lack of seasonal variation in bioturbation intensity and the demonstration of year-round feeding in deposit feeders are consistent with the hypothesis that the seafloor sediments accumulate labile organic matter produced during periods of high primary production and that deposit feeders utilize this food source as a food bank on a year-round basis. [Copyright &y& Elsevier]

Fixed-point and probabilistic sampling designs were compared to investigate which design best detected known contamination gradients in the marine ecosystem adjacent to McMurdo Station, Antarctica. The fixed-point sampling design included transects along historical contamination and physical disturbance gradients. The probabilistic sampling design used randomly selected hexagons spaced at 50 m intervals. In both designs, 15 stations were sampled over a small area (~1 km²) that extended from Winter Quarters Bay to Cape Armitage. Sediment quality triad components (sediment chemical contaminants, sediment toxicity, and a benthic index of biotic integrity) were measured to indicate chemical, toxicological, and biological effects. There were higher correlations between sediment quality triad components for the fixed-point sampling design than for the probabilistic design. The fixed-point design was better at detecting the intensity of alteration because disturbance of the marine ecosystem at McMurdo Station is localized within a small area. Based on these results, a limited fixed-point design with nine stations detected no significant change in macrofaunal community structure over a four year period from 2000-2004. However, the macrofaunal assemblages present in the contaminated portions of Winter Quarters Bay are indicative of a disturbed benthic community that has been subject to organic enrichment and toxic chemical exposure. [ABSTRACT FROM AUTHOR]

We have limited understanding of which environmental factors structure the distribution patterns and composition of Antarctic macrobenthos assemblages, and the spatial scales on which such factors operate. In 2004, the “BioRoss Survey” was conducted on the northwestern Ross Sea shelf between Cape Adare and Cape Hallett in depths of 50–750 m to describe and quantify the assemblage patterns of benthic macroinvertebrates. In order to determine the influence of primary productivity, disturbance and habitat heterogeneity on the distribution and composition of the macrofaunal assemblages, polychaete data derived from 52 grab samples were analysed. Although differences in the composition of polychaete assemblages among different sampling transects and depth strata were not particularly pronounced (yet statistically significant), the results suggested that large-scale differences in both primary productivity and iceberg disturbance influence distribution patterns. The combination of sediment chl a content, sorting coefficient, sponge spicule content and distance to the nearest iceberg scour best explained polychaete assemblage patterns. This finding supports previous contentions that multiple environmental drivers working at varying scales influence Antarctic shelf assemblages. The results do not supply support for a pronounced decoupling of pelagic and benthic systems, as has been suggested by another study of deeper water benthic assemblages on the Ross Sea shelf. [ABSTRACT FROM AUTHOR]