bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemotactic tube-foot responses of the spongivorous sea star Perknaster fuscus to organic extracts of sponges from McMurdo Sound, Antarctica
Authors: McClintock J.B. , Baker B.J. , Amsler C.D. , Barlow T.L.
Published: December 2007

Studies were continued to investigate the ability of secondary metabolites sequestered in Antarctic sponges to cause feeding deterrent responses (tube foot retractions) in a common predator of Aritarctic sponges, the sea star Perknaster fuscus. Lipophilic (dichloromethane/methanol) and hydrophilic (methanol/water) extracts of 15 new species of Antarctic marine sponges were tested for their ability to induce sustained tubefoot retraction. One additional species, Cinchyra antarctica, was re-tested from a previous study because we discovered a colour morph that was of comparative interest. Employing established protocols, sponge extracts were imbedded in silicone and presented to an extended tube-foot on the tip of a glass rod. Extracts of ten of the 15 new species of sponges (67%) caused significantly longer tube-foot retractions than controls. Among all sponges tested, significant tube-foot retraction activity was primarily associated with dichloromethane/methanol extracts (eleven sponge species or colour morphs), while significant tube-foot retraction activity was less common in response to methanol/water extracts (three sponges species or colour morphs). Both lipophilic and hydrophilic extracts from the sponges C. antarctica (yellow morph) and Scolymastia joubini elicited significant tube-foot retraction activity, suggesting that more than one compound from these speciesmight elicit tube-foot retractions in P. fuscus. Overall these findings lend considerable support to the hypothesis that there has been significant evolutionary selection for chemical defences among Antarctic marine sponges in McMurdo Sound, in contrast to earlier biogeographic selection models that predicted low levels of chemical defences in polar marine invertebrates.
A new species of Ammothea and other pycnogonids from around Livingston Island, South Shetland Islands, Antarctica
Authors: León Tomás Munilla
Published: December 2007

Specimens of 22 species of pycnogonids belonging to twelve genera and seven families were collected during a cruise near Livingston Island, South Shetland Islands. Twenty two of the 94 stations yielded pycnogonids: the new species Ammothea hesperidensis is described fully, illustrated, and compared with similar species. The family Nymphonidae provided both the greatest diversity of species (seven) and number of specimens (35). The most abundant species were Achelia hoekii and Nymphon australe.
A pigment analysis of feeding modes of Thelepus extensus (Polychaeta, Terebellidae) in relation to wave exposure at the Îles Kerguelen
Authors: Riaux-Gobin Catherine , Klein Bert , Duchêne Jean-Claude
Published: December 2007

Pigment analysis (HPLC and fluorometry) and light microscopy observations of the gut content of Thelepus extensus (Terebellidae) and surrounding sediments were carried out at two hydrodynamically contrasting sites at subantarctic Îles Kerguelen; 1) a sheltered site (Port-Raymond) with a dense population of large-bodied animals, and 2) an exposed site (Port-aux-Français) with a scarce population of smaller individuals. Chlorophyll a derivatives (phaeophorbide a-like) were the most abundant pigments in sediments and polychaete digestive tracts. The second important group of pigments consisted of five unknown carotenoids of which two were present only in the polychaete digestive tract. Pigments in the muddy sediment at the sheltered site appeared to originate from the grazing activity of the polychaetes, as suggested by the high concentrations of degradation products and the same phaeophorbides observed both in the sediment and in the gut contents. Material originating from the dense Macrocystis pyrifera (Phaeophyceae) and Ulvae (Chlorophyceae) cover constituted a large part of the polychaetes' diet at this sheltered site, as indicated by macroalgal debris in the gut contents and the presence of violaxanthin in the sediment and lutein/zeaxanthin in both polychaetes and sediments. The polychaetes seem to adapt their grazing mode to the environmental conditions, preferring suspension feeding in the sheltered site and deposit feeding at the exposed site. The different morphologies, behaviours and life spans of the two conspecific populations may by linked to the contrasting hydrodynamics of the two sites and to their respective diets.
Snow and blue-ice distribution patterns on the coastal Antarctic Ice Sheet
Authors: Liston Glen E. , Winther Jan-Gunnar , Bruland Oddbjørn , Elvehøy Hallgeir , Sand Knut , Karlöf Lars
Published: December 2007

Surface patterns of alternating snow and blue-ice bands are found in the Jutulgryta area of Dronning Maud Land, Antarctica. The snow-accumulation regions exist in the lee of blue-ice topographic ridges aligned perpendicular to winter winds. The snow bands are c. 500–2000 m wide and up to several kilometres long. In Jutulgryta, these features cover c. 5000 km2. These alternating snow and blue-ice bands are simulated using a snow transport and redistribution model, SnowTran-3D, that is driven with a winter cycle of observed daily screen-height air temperature, humidity, and wind speed and direction. The snow-transport model is coupled to a wind model that simulates wind flow over the relatively complex topography. Model results indicate that winter winds interact with the ice topographic features to produce alternating surface patterns of snow accumulation and erosion. In addition, model sensitivity simulations suggest that subtle topographic variations, on the order of 5m elevation change over a horizontal distance of 1 to 1.5 km, can lead to snow-accumulation variations that differ by a factor of six. This result is expected to have important consequences regarding the choice of sites for ice-coring efforts in Antarctica and elsewhere.
Structure of the Deep Freeze Range–Eisenhower Range of the Wilson Terrane (North Victoria Land, Antarctica): emplacement of magmatic intrusions in the Early Palaeozoic deformed margin of the East Antarctic Craton
Authors: Musumeci Giovanni , Pertusati Piero
Published: December 2007

In North Victoria Land (Antarctica), the Wilson Terrane is a portion of the palaeomargin of the East Antarctic Craton, deformed during the Late Cambrian–Early Ordovician Ross Orogeny. Crustal deformation, from westward subduction of the palaeo Pacific plate and terrane accretion on this palaeomargin, gave rise to the development of a transpressive fold belt and a wide magmatic arc. In the inner portion of the Wilson Terrane, (Deep Freeze Range–Eisenhower Range) a large portion of this magmatic arc is made up of intrusions and dyke systems. Intrusive rocks range from large unfoliated plutons to well foliated sheet intrusions emplaced in low and medium–high grade metamorphic rocks respectively. Field and structural data on intrusive rocks and metamorphic host rocks, coupled with parameters relative to deformation mechanism and magmatic processes (crystallization and cooling) rates, make it possible to outline an episode of diffuse synkinematic magmatism in the Wilson Terrane. The emplacement of intrusions in both the middle and upper crust was coeval and related to the development of transpressional and transtensional structures along dextral strike-slip shear zones. Furthermore the development of foliated or unfoliated fabrics is related to competition between rates of deformation and magmatic processes, which is a function of the thermal state of the host rocks.
Experimental study on a basanite from the McMurdo Volcanic Group, Antarctica: inference on its mantle source
Authors: Orlando Andrea , Conticelli Sandro , Armienti Pietro , Borrini Daniele
Published: December 2007

Experiments to reconstruct the liquidus curve and establish the phase relationships of a basanite (Mg# = 72) from the McMurdo Volcanic Group, (thought to represent a nearly primary magma) used 1.0– 3.0 GPa and 1175–1550°C. The results suggest that this basanite could be generated by partial melting either of a spinel Iherzolite (at P = 1.5–2.0 GPa and T = 1390–1490°C) or of a garnet pyroxenite (at P > 3.0 GPa and T > 1550°C) source. Several lines of petrological and geochemical evidence support the latter hypothesis. Moreover, experimental results indicate the presence of mica in the source if it is assumed that the magma lost some water during its ascent to the surface. This is supported by the presence of mica and amphibole-bearing mantle xenoliths hosted in the most primitive volcanic rocks of the McMurdo Volcanic Group. These results and observations suggest that the source of magmas underwent metasomatism prior to partial melting.
The fate of plutonium, 241Am, 90Sr and 137Cs in the Antarctic ecosystem
Authors: Jia Guogang , Triulzi C. , Marzano F. Nonnis , Belli M. , Vaghi M.
Published: December 2007

A radioecological survey around Terra Nova Bay showed that 239 + 240Pu, 238Pu, 241Am, 90Sr and 137Cs activities were detectable in nearly all the samples. The 239 + 240Pu and 241Am concentrations in seawater were slightly lower than those in the northern Pacific Ocean. The activity level of 239 + 240Pu, 241Am and 137Cs in Antarctic sediments (Ross Sea) was c. 5–20 times lower than in northern Adriatic sediments (Mediterranean Sea), but the 238Pu activities were relatively high. The 90Sr concentrations in all the sediment samples from both the Ross and Adriatic seas tended to be low which might be due to an easier exchange of 90Sr in seawater. On the other hand, high concentrations were detected in Antarctic mosses, lichens and algae and their activity levels are comparable to those in central Italy. The radionuclide ratio analyses show that the major part of 239 + 240Pu, 241Am, 90Sr and 137Cs is the result of nuclear weapon tests. A higher 241Am/239 + 240Pu ratio might be due to the fallout of earlier atmospheric nuclear tests. The 238Pu239 + 240Pu ratio in the Antarctic matrices is about seven times higher than in the Northern Hemisphere and this could suggest that the major part of 238Pu originated from the SNAP-9A satellite accident.
Ammonium and potassium in snow around an emperor penguin colony
Authors: Rankin Andrew M. , Wolff Eric W.
Published: December 2007

Snow samples taken at various distances from the emperor penguin (Aptenodytes forsteri) colony near Halley station were analysed by ion chromatography. Extremely high ammonium concentrations were encountered at the colony itself, but fell off sharply with distance from the colony, reaching background levels within a few kilometres of the colony. A seasonal effect was also seen, with the highest concentrations found in spring when the colony was at its most active. Levels of potassium and other sea-salt ions were also elevated near the colony. The ratio of sodium to potassium was lower than that found in bulk seawater, and closer to that found in the penguin's food source, indicating that the increased concentrations are due to emissions from the penguins and not merely to the proximity of open seawater to the site. The colony thus has a significant effect on the composition of the nearby snow, but this effect is strongly localised and is not likely to significantly influence snow chemistry at inland ice core drilling sites.
Nutrients, algal biomass and communities in land-fast ice and seawater off Adélie Land (Antarctica)
Authors: Riaux-Gobin Catherine , Tréguer Paul , Poulin Michel , Vétion Gilles
Published: December 2007

Land-fast ice in the vicinity of Adélie Land was sampled during spring 1995. The ice was annual, thin, with no consistent snow cover, and exposed to oceanic conditions. Temporal and spatial variations of the vertical pigment distribution were studied in relation to environmental factors, during the break up of the ice. Different levels were sampled in the congelation ice and the platelet ice-like layer (PLI). Under-ice water and open water masses were also sampled. The algal biomass was greater in the PLI (24 ±14 μg chl a l−1 offshore and up to 9 mg chl a l−1 near-shore), than in the under-ice water, and fell to 0.9 ± 0.64 μg chl al−1 in open water masses. Homogenous low pigment concentrations were detected in the upper levels of congelation ice. A gradient was identified along a 7 km seaward transect, sampled in November, with the lowest biomass offshore. The integrated pigment concentrations in fast ice reached very high levels 500 mg chl a m−2 near the coast and 0.8 mg m−2 offshore), with apparently no relationship with either the ice thickness or snow cover. In the congelation ice nutrient concentrations were low and their distribution homogenous, whereas in the PLI high concentrations of nitrate (up to 100–300 μM NO3) and silicic acid [30–100 μM Si(OH)4] were detected, often related to high pigment concentrations and proximity to islands. The sea ice algae communities were diverse, but mostly composed of chain-forming and tube-dwelling pennate diatoms (Amphiprora, Berkeleya, Nitzschia and Navicula). Cell densities in PLI reached up to 1010 cells l−1. At very low biomass and cell densities 2 104 cells l−1) the phytoplankton also had a low diversity; some species were similar to those of the PLI, such as Navicula glaciei, but other were typically planktonic (Chaetoceros). At sea ice break-up it is estimated that a significant proportion of particulate matter (up to 0.5 g chl a m−2 near-shore) was transferred to the underlying water masses (on an average 15 t POC km−1 shoreline).
Seismicity and tectonics around the northern Antarctic Peninsula from King Sejong station data
Authors: Lee D.K. , Jin Y.K. , Kim Y. , Nam S.H.
Published: December 2007

Local earthquakes recorded at the King Sejong station (62° 13′31″S, 58° 47′07″W) from 1995–96 have been analysed to study the seismicity and tectonics around the northern Antarctic Peninsula. The nature of shallow-focused normal fault earthquakes along the South Shetland Platform is still unclear. Dominant normal fault earthquakes and minor strike-slip earthquakes in the Eastern Bransfield Basin suggest 1) ongoing extension, and 2) transtensional stress transmitted from the Antarctic–Scotia transform boundaries, the South Scotia Ridge and the Shackleton Fracture Zone. A lack of seismicity in the Central Bransfield Basin supports that active seismicity in the Eastern Bransfield Basin is not a result of subduction along the South Shetland Trench. Shallow focused earthquakes have been observed along the NW–SE trending gravity low line between the Central and the Eastern Bransfield Basins that approximately coincides with the landward projection of a fracture zone in the former Phoenix Plate.
Stratigraphy of the Pliocene Sørsdal Formation, Marine Plain, Vestfold Hills, East Antarctica
Authors: Quilty Patrick G. , Lirio Juan Manuel , Jillett David
Published: December 2007

The Sørsdal Formation and one member, Graveyard Sandstone Member constitute a sedimentary sequence covering approximately 10 km2 of Marine Plain, Vestfold Hills, East Antarctica. The new Formation consists dominantly of friable diatomaceous siltstone and sandstone with dark limestone lenses. It is in situ, essentially horizontal, 7.2 m thick in its type section and lies less than 25 m a.s.l. Graveyard Sandstone Member occurs near the top of the formation, is highly lithified sandy diamictite, 30–50 cm thick and widespread through the Marine Plain region. Using diatoms, the Formation is Early Pliocene in age (Fragilariopsis barronii, 4.5–4.1Ma). The Graveyard Sandstone Member probably was deposited during the Gilbert Chron interval (lower Chron 2Ar or C3n. 1r) of reversed magnetic polarity. The Sørsdal Formation contains fossil cetaceans and a diverse and well-preserved invertebrate fauna. Foraminifera are rare partly because of diagenesis, but include Ammoelphidiella antarctica. No evidence of coeval terrestrial vegetation has been recovered. The deposit accumulated in a series of small bays probably in an environment warmer than exists in the region today. There is no lithological evidence of glacial influence except in Graveyard Sandstone Member that may represent local glacial influence in a shallow marine to intertidal environment.
A study of surface heat fluxes in the Ross Sea (Antarctica)
Authors: Budillon Giorgio , Fusco Giannetta , Spezie Giancarlo
Published: December 2007

In the polar regions, dynamical and thermodynamical interactions between atmosphere and ocean are strongly influenced by the presence or absence of the ice cover, which forms an insulating layer over the ocean, hindering sensible heat fluxes and forming an effective barrier to evaporation and thus preventing latent heat loss. In the framework of the CLIMA (Climatic Long-term Interactions for the Mass-balance in Antarctica) project of the Italian PNRA (National Program for Antarctic Research) we focused our attention on the evaluation of the heat fluxes between the ocean and the atmosphere in the Ross Sea, where the ice covers the sea for many months of the year. Wherever the ice cover is absent all year round, such as in leads or polynyas, the air-sea fluxes can be very large, especially in winter when the air-sea temperature differences are strong. In this work heat exchanges between sea and atmosphere, whether ice cover was present or not, were calculated from climatological data obtained from the European Centre for Medium Range Weather Forecasts, while sea ice data were collected from the US National Ice Center and National Climatic Data Center. Each of the terms in the sea surface heat budget were computed for 1994 with a temporal resolution of six hours and a spatial resolution of 0.5° using bulk formulae and obtaining monthly averaged horizontal distributions. The surface heat budget is dominated in November, December, January and February by shortwave radiation, while for the other months the turbulent and conductive heat fluxes dominate the heat exchange between the atmosphere and the sea surface. The annual total heat loss at the surface in 1994 has been estimated at about −90 W m−2 with the highest heat loss occurring close to the coast; the maximum heat loss occurred in May (−217 W m−2) while in January the heat gain by the ocean was 196 W m−2. In addition, weekly averaged values over the whole Ross Sea from 1994 to 1997 were calculated with the same parameterisation in order to study the temporal variability in this basin of each individual component and of the total surface heat budget. For this purpose only the data inside the continental shelf of the Ross Sea were considered in calculating the averaged fluxes. The 1994–97 total heat budget ranges from −87 to −107 W m−2with an average of −96 W m−2; this amount of heat loss was supposed to be compensated for by the heat advected by the Circumpolar Deep Water and its transport was estimated at about 2.9 Sv.
Antarctic notothenioid fishes as subjects for research in evolutionary biology
Authors: Eastman Joseph T.
Published: December 2007

Antarctica is a continental island and the waters of its shelf and upper slope are an insular evolutionary site. The shelf waters resemble a closed basin in the Southern Ocean, separated from other continents by distance, current patterns and subzero temperatures. The benthic fish fauna of the shelf and upper slope of the Antarctic Region includes 213 species with higher taxonomic diversity confined to 18 families. Ninety-six notothenioids, 67 liparids and 23 zoarcids comprise 45%, 32% and 11% of the fauna, a combined total of 88%. In high latitude (71–78°S) shelf areas notothenioids dominate abundance and biomass at levels of 90–95%. Notothenioids are also morphologically and ecologically diverse. Although they lack a swim bladder, the hallmark of the notothenioid radiation has been repeated diversification into water column habitats. There are pelagic, semipelagic, cryopelagic and epibenthic species. Notothenioids exhibit the disproportionate speciosity and high endemism characteristic of fish species flock. Antifreeze glycopeptides originating from a transformed trypsinogen gene are a key innovation. It is not known when the modern Antarctic shelf fauna assumed its current taxonomic composition. A late Eocene fossil fauna was taxonomically diverse and cosmopolitan. There was a subsequent faunal replacement with little carryover of families into the modern fauna. Basal notothenioid clades probably diverged in Gondwanan shelf locations during the early Tertiary. Dates inferred from molecular sequences suggest that phyletically derived Antarctic clades arose 15–5 m.y.a.
Some “driving forces” structuring communities of the sublittoral Antarctic macrobenthos
Authors: Gutt Julian
Published: December 2007

Community analyses of the macrobenthos living on the Weddell Sea shelf revealed a distinct horizontal patchiness. Within some systematic groups a specific faunistic classification could clearly be defined, e.g. for asterozoans and holothurians. Whilst for fish, only a general zoogeographical pattern was discernible, there were some recognisable relationships to different microhabitats. The extreme differences in the distribution of sponges observed seems to reflect their highly variable biological characteristics. Studies using underwater imaging methods for benthic research have provided strong evidence for the ecological significance of two factors. The first, iceberg scouring, leads to a variety of simultaneous stages of recolonization, which result in an increase in beta-diversity. As a consequence, it is unlikely that regionally a stage approaching a theoretical climax will ever be attained. Secondly, the structural diversity of living substrata provides the basis for an additional variety of epibiotic species. Only weak or non-detectable correlations have been found between benthic assemblages and physical parameters, such as water depth, sediment type, bathymetric features and the abundance of deposited phytodetritus. This indicates a benthic system which is relatively uncoupled from processes in the water column. The combination of stable environmental conditions and disturbances taking place over long periods of time, which are partly a special feature of Antarctica's glacial history, shaped the diversity and faunal composition of the macrobenthos. Consequently, neither Houston's “intermediate-disturbance-hypothesis” nor Sander's “stability-time-hypothesis” can be rejected for this part of the Antarctic ecosystem.
Some aspects of the great success of lichens in Antarctica
Authors: Kappen Ludger
Published: December 2007

The terrestrial vegetation in Antarctica is restricted to small, very isolated, ice-free areas on the continent and on the islands adjacent to the Peninsula region. Lichens, a symbiosis between a fungus and an alga or cyanobacterium, form the most prominent component in the vegetation. They have the greatest number of species compared with other cryptogamic and unicellular organisms. They are able to colonize all types of solid substrata and have a low mineral nutrient demand. Their physiological vigour is derived from high freezing tolerance and the ability to be photosynthetically activated by water vapour uptake from snow at temperatures as low as c. -20°C. Long-term monitoring in their natural habitats demonstrates that lichens are photosynthetically active at suboptimal temperatures. Locally, however, they can benefit from meltwater on insolated rocks, but only for short periods in early summer. Although at this time they may be exposed to substrate temperatures of > 20°C and strong light they do not suffer from photostress. If, in winter, lichens are covered and kept dark by snow with temperatures close to 0°C, lichens enter a negative carbon balance. This effect may be relevant to lichens under conditions of global or regional warming.
Biodiversity and biogeography of Antarctic copepods
Authors: Razouls Suzanne , Razouls Claude , Bovée Francis De
Published: December 2007

A census of pelagic copepods identifies 346 species from 38 families (i.e. 16.7% of all copepods). Among them, 289 species are considered “cosmopolitan” and 57 “endemic”. Most of the species were described in the late 19th or early 20th century. However, due to a resurgence of interest in biological diversity, a large number of exhaustive revisions at various taxonomic levels have recently been initiated. One hundred and thirteen documents covering the census and distribution of copepod species are analysed. The distribution of species in the South Seas is given for 24 sectors chosen in relation to the geographical coordinates of the South Atlantic, South Pacific and Southern Indian oceans and their location with respect to the Antarctic Convergence or the continental shelf. The respective roles of Lagrangian displacement, of the hydrological features characterising the Southern Ocean and of the general ocean currents are emphasised to explain the scattered distributions of the species. Twenty-one species are catalogued as bipolar, 46 species as specifically sub-Antarctic and 222 cosmopolitan ones are probably from sub-tropical/temperate regions.
Genetic diversity, mutagenesis and dispersal of Antarctic mosses – a review of progress with molecular studies
Authors: Skotnicki M.L. , Ninham J.A. , Selkirk P.M.
Published: December 2007

In investigating the extent of genetic diversity in Antarctic mosses the RAPD technique has proven especially useful in demonstrating that these mosses exhibit extensive genetic variation (levels being similar to those in temperate regions), and that within-colony variation is apparently caused not only by immigration and establishment of propagules from elsewhere, but also by mutagenesis. Dispersal of these mosses can also be followed using the RAPD technique; both short-distance dispersal by wind or water (depending on the moss species) and longer distance dispersal by wind across the ice cap has been demonstrated. Relationships with temperate mosses of the same species are being investigated to determine the origins of Antarctic populations. Genetic technology is also facilitating the taxonomic identification of moss specimens which cannot be identified morphologically due to phenotypic plasticity in Antarctica. Together, these genetic studies are starting to provide information of fundamental scientific importance for understanding the evolution, origins and dispersal mechanisms of Antarctic mosses, and their response to climate change.
Evolutionary origins of Antarctic microbiota: invasion, selection and endemism
Authors: Vincent Warwick F.
Published: December 2007

Increasing interest in the ecological roles, conservation and biotechnological potential of Antarctic microbiota has focused attention on their biodiversity and evolutionary origins. Antarctic microbial ecosystems provide useful models for general questions in evolutionary ecology given the relative isolation of the South Polar Region, the severe biological constraints imposed by the polar environment, and the absence of higher plants and animals in some Antarctic habitats. Sealed environments such as Lake Vostok and the overlying East Antarctic ice sheet provide unique, natural culture collections for studying microorganisms that have been isolated from the global gene pool over timescales of evolutionary significance. Most Antarctic environments, however, continue to receive microbial propagules from outside the region, as indicated by spore trap data, the microflora found in Antarctic snow and ice, the colonising taxa at geothermal sites, and the high frequency of apparently cosmopolitan species in most habitats. Differences in environmental stability and selection pressure among environments are likely to influence the degree of adaptive radiation and microbial endemism. The latter seems greater in the Southern Ocean by comparison with non-marine ecosystems of Antarctica, although there is some evidence of endemic species in highly specialised niches on the continent such as in the endolithic habitat and saline lakes. Analytical techniques such as 16S rDNA sequencing and DNA–DNA hybridisation are beginning to provide new insights into the genetic affinities and biodiversity of Antarctic microbiota, and are leading to a more rigorous evaluation of microbial endemism.
Diversity of thermal responses of lipid composition in the membranes of the dominant culturable members of an Antarctic fellfield soil bacterial community
Authors: White P. Lewis , Wynn-Williams David D. , Russell Nicholas J.
Published: December 2007

The eight dominant culturable members of an Antarctic fellfield soil bacterial community were four Arthrobacter species, Sanguibacter suarezii, Aureobacterium testaceum, a Bacillus sp., and a Pseudomonas sp.. All of the isolates grew at 2°C, but two of the Arthrobacter spp. were psychrophilic, while the other six bacterial species were psychrotolerant. However, the fastest growing organisms at low temperatures were not the psychrophiles, and the psychrotolerant Bacillus sp. grew fastest at temperatures up to 25°C. When the growth temperature of cultures was altered, the phospholipid content of the two psychrophilic Arthrobacter spp. decreased, whereas the phospholipid contents of the psychrotolerant spp. either increased or did not change. Only one psychrophilic and one psychrotolerant Arthrobacter sp. modified its polar lipid head-group composition in response to a lowering of growth temperature. The change in Arthrobacter sp. CL2-1 was particularly marked and novel in that at low temperatures phosphatidylethanolamine was replaced completely by a phosphoglycolipid and phosphatidylserine, neither of which was present at higher growth temperatures. All eight isolates altered the fatty acyl compositions of their membrane lipids in a manner that was only partially dependent on taxonomic status. In Bacillus sp. C2-1 the changes were opposite to that predicted on the basis of membrane fluidity considerations. The isolates used different combinations of changes in fatty acid branching, unsaturation and chain length. There was no single strategy of thermal adaptation that was employed and the variety of strategies used did not follow phylogenetic boundaries.
What is the state of the Antarctic environment?
Authors: Walton D.W.H.
Published: December 2007

The public is worried and so governments - at least the democratic ones - should also be worried. The global environment is changing and the consequences are still not understood. How much is natural and how much anthropogenic? In many cases the changes appear to be for the worse. Scientific opinion, as evidenced through the reports of the Intergovernmental Panel on Climate Change, is gloomy. By most estimates the rate of change will continue to increase and, if we cannot halt or slow the driving processes major modifications in where and how we live will be essential for survival. How do we know this and what should be done about it?
Status of white-chinned petrels Procellaria aequinoctialis Linnaeus 1758, at Bird Island, South Georgia
Authors: Berrow Simon D. , Croxall John P. , Grant Sharon D.
Published: December 2007

The white-chinned petrel (Procellaria aequinoctialis) is an abundant, widespread petrel breeding in tussock grassland at sub-Antarctic islands. Over the last decade it has been killed in large numbers in temperate and sub-tropical longline fisheries. However no data are available on the global population status. We assessed the status of white-chinned petrels at Bird Island, South Georgia by comparing the distribution and density of occupied burrows in 1981 and 1998. In both surveys white-chinned petrel burrows occurred in one-quarter of the 460–477 36-m2 quadrats surveyed. The total number of burrows in each quadrat was consistent between each survey but we estimate an overall decrease of 28% in those occupied (with considerable variation between sites). Concurrent data on breeding frequency and success showed that white-chinned petrels are essentially annual breeders at Bird Island; breeding success was consistent at around 44%. Significant factors determining densities of occupied burrows were crown height and percent tussock cover (accounting for 77% of variance). The former has decreased significantly, the latter increased significantly between 1981 and 1998 but there was no relationship between white-chinned petrel occupancy rate and habitat modification due to the presence of fur seals (Arctocephalus gazella). This suggests that any population decline is due to factors operating away from the breeding colony, such as those attributed to fishing.
Asteroids eating sponges from Tethys Bay, East Antarctica
Authors: Cerrano Carlo , Bavestrello Giorgio , Calcinai Barbara , Cattaneo-Vietti Riccardo , Sarà Antonio
Published: December 2007

In many Antarctic benthic communities, sponges can be considered as keystone species on both hard and soft bottoms, affecting community structure and sediment texture (Cattaneo-Vietti et al. 2000). Moreover, Antarctic sponges are known to be exploited by numerous organisms as atrophic source. The most important Antarctic sponge predators are asteroids and molluscs which move and digest slowly. The activity of invertebrate predators is not affected by the sponge nutritional composition: toxicity and relative abundance are considered to be the most important factors regulating predation on the Antarctic sponge fauna (McClintock 1987).
SHRIMP U–Pb geochronology from Mount Kirkby, northern Prince Charles Mountains, East Antarctica
Authors: Carson C.J. , Boger S.D. , Fanning C.M. , Wilson C.J.L. , Thost D.E.
Published: December 2007

Sensitive High Resolution Ion MicroProbe (SHRIMP) U–Pb zircon dating of pegmatites from Mount Kirkby, northern Prince Charles Mountains, east Antarctica indicates felsic intrusive activity at 991 ± 22 Ma and 910 ± 18 Ma. Pegmatite emplacement occurred during prolonged high-grade early Neoproterozoic tectonism. These ages correlate well with previously published U–Pb zircon ages obtained from felsic intrusive bodies elsewhere within the northern Prince Charles Mountains. Early Palaeozoic activity at Mount Kirkby is restricted to the emplacement of minor planar pegmatites at 517 ± 12 Ma, which provide a maximum age for local development of discrete extensional mylonites. No conclusive evidence of tectonic or metamorphic events at c. 800 Ma and c. 500 Ma, which have been recently postulated for the region, can be identified from the presently available U–Pb zircon data.
Diatom biostratigraphy and age of the Pliocene Sørsdal Formation, Vestfold Hills, East Antarctica
Authors: Harwood David M. , McMinn Andrew , Quilty Patrick G.
Published: December 2007

Fossil marine diatom assemblages from the Sørsdal Formation, a deposit of diatomaceous sand from Marine Plain in the Vestfold Hills, provide age and palaeoenvironmental information from a Pliocene coastal setting in East Antarctica. Benthic and meroplanktic diatom taxa suggest deposition in a shallow coastal embayment with water depths of 20–25 m. Diatom biostratigraphy indicates that the Sørsdal Formation belongs to the Fragilariopsis barronii Zone (4.5 to 4.1 Ma), through correlation to reference sections in the Ross Sea and Southern Ocean. Features of the other biota suggest higher sea-surface temperatures and reduced sea-ice cover, consistent with global records of higher sea level.
A study of valley-side slope asymmetry based on the application of GIS analysis: Alexander Island, Antarctica
Authors: Siegmund Mike , Hall Kevin
Published: December 2007

Geographic Information System (GIS) data from southern Alexander Island were used to evaluate valley asymmetry from an area where ground observations had suggested that south facing slopes were steeper than north facing. Using digital elevation modelling (DEM), data were collected from 2° and 10° arcs centred on the four cardinal directions in order to determine average slope angles for a whole nunatak area (Mars Oasis). It was found that south facing slopes were significantly steeper (34°) than the north facing (28°); east and west facing slopes were each 31°. Bedrock in this area is (approximately) horizontally bedded and so valley asymmetry is considered to be due to aspect-influenced periglacial weathering processes.
Eocene and Oligocene volcanism at Mount Petras, Marie Byrd Land: implications for middle Cenozoic ice sheet reconstructions in West Antarctica
Authors: Wilch T.I. , McIntosh W.C.
Published: December 2007

Evidence for one late Eocene and four middle Oligocene eruptions of Mount Petras, Marie Byrd Land provides new insights into reconstructions of middle Tertiary ice sheet configurations, surface topography, and volcanism in West Antarctica. The interpretation presented here of the volcanic record at Mount Petras, based on detailed analyses of lithofacies, petrography, 40Ar/39Ar geochronology, and geochemistry, is significantly different from previous interpretations based on reconnaissance studies. A massive, 25 m thick, mugearite lava near the summit of Mount Petras is 40Ar/39Ar dated to 36.11 ± 0.22 Ma (2 σ uncertainty), indicating an onset of Cenozoic alkaline volcanism in the Marie Byrd Land Volcanic Province in latest Eocene time. Middle Oligocene (29-27 Ma) hawaiite volcaniclastic lithofacies at Mount Petras are interpreted as products of mixed magmatic (Strombolian style) and phreatomagmatic (Surtseyan style) subaerial eruptions. The four hawaiite outcrop areas exhibit characteristics of near-vent tuff cone environments. The near-vent deposits are located at different elevations and positions on Mount Petras and suggest four separate eruptive centres, with eruptions dated to between 28.59 ± 0.22 Ma and 27.18 ± 0.23 Ma. The mixed Surtseyan and Strombolian eruptions imply local or intermittent contact with external water, which we infer was derived from melting of a thin, local ice cap or ice and snow on slopes. The 29-27 Ma volcanic deposits at Mount Petras provide the oldest terrestrial evidence for glacial ice in Marie Byrd Land. The 29-27 Ma tuff cone deposits overlie an erosional unconformity, with > 400 m of topographic relief. The relatively high relief pre-volcanic environment is suggestive of ongoing erosion and is inconsistent with previous interpretations of a regional, low relief, early Cenozoic West Antarctic Erosion Surface.
Thermohaline structure and variability in the Terra Nova Bay polynya, Ross Sea
Authors: Budillon G. , Spezie G.
Published: December 2007

Hydrological measurements from three cruises during the summers 1994/95, 1995/96 and 1997/98 in the western sector of the Ross Sea allow summer and year to year changes in heat and salt content in the Terra Nova Bay polynya to be analysed. Changes in the surface layer (upper pycnocline) followed the expected seasonal pattern of warming and freshening from the beginning to the end of the summer. These near-surface changes, expressed as net heating and salting rate, were about 11 W m−2 and -6 mg salt m−2 s−1. The heating changes were substantially lower than the estimated heat supplied by the atmosphere during the summer, which underlines the importance for this season of the advective component carried by the currents in the total heat budget. The year to year differences were about one or two orders of magnitude smaller than the seasonal changes in the surface layer. In the intermediate and deep layers, the summer heat and salt variability were of the same order as or one order higher than from one summer to the next. The differences in sign and magnitude for the heat change in the upper and in the lower pycnocline indicate a weak connection in the summer period between the surface heat fluxes and the deep waters. A local source of very cold water (with temperatures below the surface freezing point) of about 0.3 Sv has been detected close to the Terra Nova Bay coast. It arose out of the interaction of the shallow–intermediate layers of High Salinity Shelf Water with the coastal glaciers. The presence and the variability of this cold water point to the significant role of the thermohaline properties of Terra Nova Bay waters in controlling the floating glacier by governing the basal melting processes.
Low phytoplankton biomass and ice algal blooms in the Weddell
Sea during the ice-filled summer of 1997
Authors: HEGSETH ELSE N. , VON QUILLFELDT CECILIE H.
Published: December 2007

The summer of 1997 was characterized by unusually large amounts of pack ice in the southeastern
Weddell Sea, and less than 10% of the area that is commonly ice-free in summer was open. A modest
phytoplankton bloom developed in the upper mixed layer in the northernmost area (72°S). The bloom
peaked in mid-February with max chlorophyll concentrations of 1.5 μg l−1, and integrated stocks of
55–60 mg m−2. Autotrophic flagellates dominated the biomass (80–90% of the chlorophyll) at first, while
diatoms increased relative to flagellates during the bloom. Nutrient deficits, however, indicated that a much
larger biomass was produced than was observed. Freezing starting after mid-February probably terminated
the bloom, resulting in a pelagic growth season limited in time (less than two months) and space. The sea ice
had a distinct brown layer of algae, usually at 1–2 m depth, with average chlorophyll biomass of
10.3 mg m−2. The ice cover exhibited a substantial amount of ridges, with ice algae growing in cavities and
other structures, but with lower biomass than in the bands. Ice algae were also found growing on the lower
2 m of the ice shelf (visible at low tide). The overall growth season in the ice lasted several months, and ice
algal production may have exceeded pelagic production in the Weddell Sea during the growth season of
1997. Pennate diatoms, like Fragilariopsis curta and F. cylindrus, dominated both in ice and in open water
above the pycnocline, while Phaeocystis antarctica dominated in deeper layers and in crack pools.
Euphausiids, particularly young stages, were frequently observed grazing on ice algae in ridges and on all
sides of the floes, (confirmed by the gut content). Ice algae would thus have served as an ample food supply
for the krill in the summer of 1997.
Antarctic Science
Authors: Walton D.W.H. , Rycroft M.J. , Thomson M.R.A.
Published: December 2007

No apology is needed for the birth of this journal, but perhaps some explanation is called for in a world of diminishing library budgets. Antarctic science has never been so healthy. The recent marked increase in the number of participating nations has strengthened the range of scientific activities but it is in danger of weakening the routes for the exchange of information. Papers are becoming increasingly dispersed throughout the general literature, minimizing the potential for cross-fertilization between disciplines and making synthesis more difficult. Antarctic science is now not just of national political interest but of global relevance. Major advances in polar science, as in science elsewhere in the world, result increasingly from team efforts in interdisciplinary research with results and conclusions of interest to a wide range of disciplines.
Antarctic meteorites
Authors: Graham A.L. , Annexstad John O.
Published: December 2007

Antarctica is currently the most productive region of the Earth for the recovery of meteorites and over 9800 specimens have been found there, most of these since 1969. This material consists of meteoritic fragments representing a much smaller, but unknown, number of distinct meteorites. The particular climatic and environmental conditions of Antarctica result in the recovery of a much larger fraction of the extraterrestrial material that falls to Earth than would be the case in other regions. Remarkable concentrations of meteorites are found in some ‘blue ice’ areas resulting from the movement and ablation of the ice. Most meteorites are believed to have been derived from asteroids less then 200 km in diameter. The discovery in Antarctica of meteorites of lunar material proved that other sources are possible. Indeed two meteorites from Antarctica may have come from the planet Mars. Antarctic meteorites have much older terrestrial ages than non-Antarctic specimens and may be used to obtain information on the movement of the ice sheets in the past.
Energy requirements and food consumption of Eudyptes penguins at the Prince Edward Islands
Authors: Brown Christopher R.
Published: December 2007

Macaroni penguins (Eudyptes chrysolophus) and rockhopper penguins (E. chrysocome) account for a substantial proportion of the avian biomass at the subantarctic Prince Edward Islands (47°S, 38°E) in summer, when both species are breeding at the islands. Information on breeding population sizes, breeding and moulting activities, and diets were combined with measurements of the penguins' energy expenditures to construct a bioenergetic model of their energy requirements and food consumption at the islands. Total energy requirements of adults and chicks amounted to 460 × 109 kJ and 162 × 109 kJ for macaroni and rockhopper penguins, respectively. Food consumption was estimated to amount to a total of 166 000 tonnes during the seven-month breeding and moulting cycle, of which macaroni penguins consumed 75%. Most, if not all, of this food is taken within a 200-km radius of the islands. Available information suggests that potential primary production in the immediate vicinity of the islands is sufficient to support the macaroni and rockhopper penguin populations. However, the importance in the diets of the penguins of several prey species more typical of Antarctic and subtropical regions suggests that the penguins rely to a large extent on the importation of prey populations from other areas.
Field measurements of carbon dioxide exchange of the Antarctic lichen Usnea sphacelata in the frozen state
Authors: Kappen L.
Published: December 2007

Field measurements of CO2 exchange were made with an infra-red gas analyser system on lichens at Bailey Peninsula, Wilkes Land, continental Antarctica. It has been demonstrated that Usnea sphacelata, a prominent element of the cryptogamic vegetation of this area, became photosynthetically active at temperatures below 0°C when the thalli were covered by drifted snow. Carbon dioxide uptake was detected down to −10°C. The carbon production during such a ‘frost’ day was considerable for a slow-growing Antarctic lichen. The importance of snow for production in lichens is emphasized. The mechanism of water uptake when the thalli are frozen needs further investigation.
Antarctic rock weathering simulations: simulator design, application and use
Authors: Hall Kevin , Cullis Alan , Morewood Chris
Published: December 2007

The design of a computer-controlled climatic simulation cabinet used for mechanical weathering studies on Antarctic rocks is described. It is argued that if the results of simulations are to be applicable to field situations they should be firmly based on field environmental conditions. Some weathering results from a laboratory simulation based upon microclimatic data collected from the maritime Antarctic are presented and it is shown that they could not have been obtained from field measurements alone. Further simulation studies are required for the Antarctic and it is argued that the nature of Antarctic research is such that it is particularly conducive to this type of approach.