bluuebunny/crossref_metadata_2025 huggingface dataset:
FT-Raman spectroscopic analysis of endolithic microbial communities from Beacon sandstone in Victoria Land, Antarctica
Authors: Russell N.C. , Edwards H.G.M. , Wynn-Williams D.D.
Published: December 2007

Laser-based Fourier-Transform Raman spectroscopy (FTRS) has been used to identify in situ compounds of ecophysiological significance in diverse field-fresh Antarctic cryptoendolithic microbial communities. FTRS does not disrupt the community and permits characterization of visible and invisible compounds in their natural configuration within cells and their current or former microhabitat. The small “footprint” of the microscopic laser beam permits accurate analysis of discrete zones of compounds produced by extant or degraded micro-organisms with minimum destruction of the biota. This spatial chemical analysis is applicable to any translucent or exposed habitat or biotic assemblage. Two hydrated forms of biodegradative calcium oxalate were differentiated in black-pigmented and hyaline lichen zones of endolithic communities. The oxalate was restricted to zones containing fungi. Communities dominated by cyanobacteria at Battleship Promontory (77°S) and a newly discovered site at Timber Peak (74°S) contrasted chemically with those dominated by eukaryotic algae at East Beacon (78°S). FTRS also showed the zonation of pigments including chlorophyll and UV-protective carotenoids in situ. At extreme sites on the polar plateau, it revealed the presence of “fossil” endolithics where detrimental climatic changes had made the microbes non-viable or amorphous, being represented solely by their residual bio-molecules. The technique has potential for past or present life-detection anywhere in the world without destruction of the microniche.
A middle Eocene basking shark (Lamniformes, Cetorhinidae) from Antarctica.
Authors: Cione Alberto L. , Reguero M. A.
Published: December 2007

A proximal fragment of a gill raker identified as belonging to a shark of the genus Cetorhinus was collected from middle Eocene deposits of the La Meseta Formation in the northern part of Seymour Island, Antarctica. This is the first record of a fossil basking shark from Antarctica and one of the earliest records of the genus. The minimum age of Cetorhinidae is middle Eocene. The only living species of the family Cetorhinidae is a very large plankton feeder, Cetorhinus maximus. Basking sharks are unknown in subantarctic or Antarctic waters but occur on both South American coasts today. The evolution of filter-feeding vertebrates is discussed.
Ascidians (Tunicata, Ascidiacea) of Potter Cove, South Shetland Islands, Antarctica
Authors: Tatian M. , Sahade R.J. , Doucet M.E. , Esnal G.B.
Published: December 2007

Certain physical factors, substrate type and ice action appear to be important determinants for ascidian distribution. Three different substrate types were sampled at depths between 0–30 m by SCUBA diving: soft bottoms, hard bottoms and moraine deposits. The species found were Aplidium radiatum, Synoicum adareanum, Distaplia cylindrica, Sycozoa gaimardi, Sycozoa sigillinoides, Tylobranchion speciosum, Corella eumyota, Ascidia challengeri, Cnemidocarpa verrucosa, Styela wandeli, Dicarpa insinuosa, Pyura bouvetensis, Pyura discoveryi, Pyura obesa, Pyura setosa, Molgula enodis and Molgula pedunculata. Highest diversity and patchy distribution was found in less stringent environments, where epibiosis is a commmon phenomenon on stolidobranch ascidians. Differences in stalk development were found in the most abundant species Molgula pedunculata and Cnemidocarpa verrucosa. Ice action may be the main factor that determines the absence of ascidians above 15 m in all the stations sampled.
The semi-annual oscillation and Antarctic climate. Part 2: recent changes
Authors: Van Den Broeke Michiel R.
Published: December 2007

Following a weakening of the semi-annual oscillation (SAO) since the mid-1970s, the half-yearly pressure wave in the Southern Hemisphere has become less significant. As a result, May/June temperatures have decreased in East Antarctica, which has moderated Antarctic warming. Spectral analysis of 87 years of pressure data at Orcadas suggest that the recent weakening of the SAO is part of the natural variability of the Southern Hemisphere circulation on decadal timescales. We interpret the time series of composite Antarctic temperature in terms of the historical strengthening and weakening of the SAO. If the dominant oscillations that occurred in the past prove to be persistent, an accelerated East Antarctic warming trend is expected for the coming decades. There are indications that the strength of the SAO is linked to the Southern Oscillation, in the sense that warm phases of the Southern Oscillation coincide with strong westerlies, a weakly developed SAO and below-average temperatures in East Antarctica. Temperatures on the west coast of the Antarctic Peninsula show strongly deviant patterns, which can not be explained by the same mechanism that applies to East Antarctica.
An intercomparison of Antarctic sea ice extent datasets from the US Joint Ice Center (JIC) and satellite passive microwave observations for 1979–88
Authors: Harangozo S.A.
Published: December 2007

US Joint Ice Center (JIC) Antarctic sea ice extent data, the longest continuous series of its kind for this part of the world, are compared with direct passive microwave-based estimates to assess their overall consistency both spatially and temporally in the period 1979–88. Using ice edge position as a proxy for ice extent, the comparison reveals close agreement in most years, in monthly averaged ice edge positions in all Antarctic regions at the time of maximum ice extent, and also in autumn and spring in the Ross and Weddell Seas. Unexpectedly, JIC relative overestimation prevails during both autumn and spring in some other areas. Previously noted differences in JIC and passive microwave total Antarctic extent in 1979–80 result mainly from problems in the Ross Sea. Reasons for the various discrepancies may lie in differences in the methods used to produce the datasets especially in spring but those in autumn seem to often arise for other reasons. It is found that the prevalent discrepancies in the Ross Sea in 1979–80 as well as those in spring in other regions from 1981 coincide with periods of ice extent change and the evolution/intensification of ice extent anomalies.
Lithofacies distribution in relation to the geomorphic provinces of Prydz Bay, East Antarctica
Authors: Harris P.T. , Taylor F. , Pushina Z. , Leitchenkov G. , O'Brien P.E. , Smirnov V.
Published: December 2007

Over the past 15 years, Japanese, Australian and Russian expeditions to Prydz Bay have collected about 30 000 km of bathymetric data, 6000 km of sidescan sonar data and more than 250 sediment grab and core samples. These data were used in the present study to compile surficial sediment, bathymetric, and geomorphological maps of the Prydz Bay region. Lithofacies distribution was determined by surficial sediment data analysis using sample matrix (Q-mode) and cluster analysis techniques based on data from 206 sites. Data included percentage biogenic silica (opal), calcium carbonate, gravel, mud, and relative abundance of two diatom species (Fragilariopsis curta and F. kerguelensis). Five lithofacies are identified from the available data: (1) slightly gravelly sandy mud (g)sM lithofacies, (2) siliceous mud and diatom ooze (SMO) lithofacies, (3) F. kerguelensis pelagic ooze lithofacies, (4) F. curta gravelly muddy sand gmS lithofacies and (5) calcareous gravel lithofacies. In many areas the lithofacies correlate to geomorphological provinces as defined by previous investigators using 3.5 kHz and sidescan sonar data. In some cases, Holocene SMO sediments are seen to drape over iceberg plough marks, implying that these are relict features. These five lithofacies are likely to dominate most of the East Antarctic shelf region and may be helpful in defining sedimentary successions resulting from ice-sheet advance and retreat over glacial-interglacial cycles.
Late Quaternary sediment facies in Prydz Bay, East Antarctica and their relationship to glacial advance onto the continental shelf
Authors: Domack Eugene , O'Brien Phil , Harris Peter , Taylor Fiona , Quilty Patrick G. , Santis Laura De , Raker Benjamin
Published: December 2007

A marine survey in Prydz Bay, provides an unparalleled view of glacigenic and marine sedimentation across Prydz Channel and Amery Depression during the Late Quaternary. Gravity cores and a suite of eight radiocarbon dates indicate that the Late Wisconsin Glacial Maximum (LGM) was associated with grounding of a palaeo-ice shelf along the periphery of Prydz Channel. Deposition in front of the grounding line was dominated by ice-rafting. A granulated facies, containing angular clay and diamicton clasts, was producd by a combination of regelation freezing, near to the grounding line, and remelting of this basal debris in the sub-ice shelf setting. Beneath these LGM marine deposits lie two key beds of diatom ooze that are distinct in size sorting and Pliocene diatoms. These “interstadial” units can be traced across most of the Prydz Channel, and are underlain by additional glacial marine units. Debris related to the Lambert Deep is distinct from detritus from eastern Prydz Bay and deposition of these two sources within the channel oscillated during the LGM. We suggest that coastal drainage systems contributed to a limited glaciation of the shelf during the LGM, rather than direct outflow via the Lambert/Amery system. It is proposed that shelf-wide glaciation is related to the duration of glacial sea level lowstands rather than the absolute magnitude of eustatic fall during such episodes.
A Late Holocene desiccation of Lake Hoare and Lake Fryxell, McMurdo Dry Valleys, Antarctica
Authors: Lyons W.B. , Tyler S.W. , Wharton R.A. , McKnight D.M. , Vaughn B.H.
Published: December 2007

Stable isotope data from waters of lakes in the McMurdo Dry Valleys (MDV) of southern Victoria Land, Antarctica are presented in order to establish the climatic history of this region over the past two millennia. New data from Lake Fryxell and Lake Hoare in Toylor Valley, along with previously published data from Lake Vanda, Wright Valley and Lake Bonney, Taylor Valley are used to infer the recent climatic history of MDV. Lakes Vanda, Fryxell and Bonney appear to have lost their ice covers and evaporated to small, hypersaline ponds by 1000 to ~1200 yr BP. Lake Hoare either desiccated or did not exist prior to 1200 yr BP. These data indicate a major lowering of lake level prior to ~1000 yr BP, followed by a warmer and/or more humid climate since then.
Glacial–interglacial deposition on a sediment drift on the Pacific margin of the Antarctic Peninsula
Authors: Pudsey Carol J. , Camerlenghi Angelo
Published: December 2007

On the continental rise west of the Antarctic Peninsula there are nine large mounds interpreted as sediment drifts, separated by turbidity current channels. Drift 7 is 150 km long, 70 km wide and up to 700 m high and is asymmetric, with steep sides on the south-east (towards the continent) and south-west, and gentle slopes to north-west and north-east. Cores on the gentle sides of the drift show a cyclicity between brown, bioturbated, diatom-bearing mud with foraminifera and radiolarians, and grey, laminated, barren mud. Biostratigraphic evidence is consistent with a Late Quatermary age. Detailed lithostratigraphy and magnetic susceptibility data allow precise correlation over distances of tens of kilometres. On the basis of chemostratigraphy, the brown sediment is interpreted as interglacial (isotope stages 1 and 5) and the grey as glacial (stages 2–4 and 6). Sedimentation rates are 3.0–5.5 cm ka-1. Cores on the steep sides of the drift recovered a condensed section with thinner cycles and hiatuses. Fine grain size, very poor sorting and the absence of a mode in the silt size range indicate deposition from suspension with only weak current activity. There is little evidence for cyclic changes in bottom current strength. Supply of sediment to the benthic nepheloid layer was by entrainment of mud from turbidity currents, and by setting of pelagic material (biogenic grains, IRD, sediment suspended in meltwater plumes). Cyclic changes in sediment supply include more biogenic supply in interglacials with less sea ice cover, more terrigenous supply from turbidites in glacials with ice sheets grounded to the shelf edge, and changes in IRD content
Glacial and marine geological evidence for the ice sheet configuration in the Weddell Sea–Antarctic Peninsula region during the Last Glacial Maximum
Authors: Bentley Michael J. , Anderson John B.
Published: December 2007

The Weddell Sea region arguably represents the largest unknown in quantifying the Antarctic contribution to the global water balance following the Last Glacial Maximum (LGM). This paper reviews the available onshore and offshore geological evidence constraining the volume of formerly expanded ice in the Weddell Sea embayment, focusing on the West Antarctic Ice Sheet (WAIS) and provides a preliminary reconstruction of the WAIS during the LGM. Dating control is generally poor and so our WAIS reconstruction is based on the assumption that the evidence of most recent ice sheet expansion dates to the LGM. Our reconstruction is intended to provide initial constraints with which glaciological models can be compared and shows grounded ice extent, flow directions, and ice surface elevations. Both marine and terrestrial geological evidence imply a substantial expansion of ice in the Weddell Sea embayment. Marine evidence shows that ice sheets were grounded in Crary Trough in the southern Weddell Sea and on the Antarctic Peninsula continental shelf during the LGM. Inland, the ice thickened by between 400 m (Ellsworth and Palmer Land) and 1900 m (Ellsworth Mountains). Ice core evidence suggests that the interior of the ice sheet remained the same or even thinned relative to present. The main unknowns now concern the exact location of the grounding line on some sectors of the shelf and the timing of ice sheet grounding and retreat. The limited radiocarbon data that exist on the eastern shelf indicates that the East Antarctic Ice Sheet retreated from the shelf prior to the LGM.
Antarctic glacial history since the Last Glacial Maximum: an overview of the record on land
Authors: Ingólfsson Ólafur , Hjort Christian , Berkman Paul A. , Björck Svante , Colhoun Eric , Goodwin Ian D. , Hall Brenda , Hirakawa Kazuomi , Melles Martin , Möller Per , Prentice Michael L.
Published: December 2007

This overview examines available circum-Antarctic glacial history archives on land, related to developments after the Last Glacial Maximum (LGM). It considers the glacial-stratigraphic and morphologic records and also biostratigraphical information from moss banks, lake sediments and penguin rookeries, with some reference to relevant glacial marine records. It is concluded that Holocene environmental development in Antarctica differed from that in the Northern Hemisphere. The initial deglaciation of the shelf areas surrounding Antarctica took place before 10 000 14C yrs before present(BP), and was controlled by rising global sea level. This was followed by the deglaciation of some presently ice-free inner shelf and land areas between 10 000 and 8000 yr BP. Continued deglaciation occurred gradually between 8000 yr BP and 5000 yr BP. Mid-Holocene glacial readvances are recorded from various sites around Antarctica. There are strong indications of a circum-Antarctic climate warmer than today 4700–2000 yr BP. The best dated records from the Antarctic Peninsula and coastal Victoria Land suggest climatic optimums there from 4000–3000 yr BP and 3600–2600 yr BP, respectively. Thereafter Neoglacial readvances are recorded. Relatively limited glacial expansions in Antarctica during the past few hundred years correlate with the Little Ice Age in the Northern Hemisphere.
Swimming in the Antarctic scallop Adamussium colbecki: analysis of in situ video recordings
Authors: Ansell Alan D. , Cattaneo-Vietti Riccardo , Chiantore Mariachiara
Published: December 2007

Swimming activity of the Antarctic scallop at a temperature of c. −1.4°C was analysed using in situ video recordings obtained from a remotely operated vehicle (ROV) in Terra Nova Bay, Ross Sea. Data are presented on swimming trajectories, distance travelled and velocity during a swimming bout, adduction frequency, shell gape angle, and the angular opening and closing velocities of shell. This scallop is an effective swimmer although swimming bouts in response to the ROV were generally short, consisting of 2–5 adduction cycles in the take-off phase followed by 1–4 (exceptionally 14) adductions during level swimming. The maximum velocity during each adduction cycle ranged from 19.4–43.1 cm s−1 and the mean velocity during a swimming bout from 12.0–23.5 cm s−1. Each adduction cycle consists of opening, closing and glide phases of approximately equal duration. Adduction frequency during swimming averaged 1.5 adductions s−1.
Algae, lichens and fungi in La Gorce Mountains, Antarctica
Authors: Broady Paul A. , Weinstein Richard N.
Published: December 2007

Two species of lichens, six cyanobacteria, one diatom, 10 chlorophytes and two mycelial fungi were found at La Gorce Mountains (86°30′S, 147°W) at an altitude of about 1750 m. The lichens Lecidea cancriformis and Carbonea vorticosa occurred at a single site which is the most southerly record of lichens. Thousands of small ponds covered extensive ice-cored moraine. Nine ponds sampled had about 30 cm of ice overlying about 26 cm of water and contained algal mats dominated by Phormidium autumnale and cf. Leptolyngbya fragilis. The very low conductivity waters had high nitrate and low dissolved reactive phosphorus concentrations. Of 124 soil samples, five contained visible algae. In 32 there were only microscopic growths but no algae were detected in 87 samples, possibly because of lack of water for much of summer. A visible mat dominated by Hammatoidea normanni occurred in a rock fissure at the lichen site. At Price Bluff, green patches of Desmococcus cf.olivaceus, up to 20 cm2, were scattered over the moraine. Growths were revealed at the soil–ice interface when overlying soil up to one centimetre thick was removed. It is suggested that although dispersal of algae from local populations may be readily achieved establishment of populations is a rare event outside the pond environment.
Hydrocarbon degradation by Antarctic coastal bacteria
Authors: Cavanagh J. E. , Nichols P. D. , Franzmann P. D. , Mcmeekin T. A.
Published: December 2007

Bacterial cultures obtained through selective enrichment of beach sand collected 60 days and one year after treatment of sites in a pilot oil spill trial conducted at Airport Beach, Vestfold Hills, East Antarctica, were examined for the ability to degrade n-alkanes and phenanthrene. The effects of different hydrocarbon mixtures (Special Antarctic Blend [SAB] and BP-Visco), fish oil [orange roughy]) and inoculation of replicate sites with water from Organic Lake (previously shown to contain hydrocarbon-degrading bacteria) on the indigenous microbial population were examined. Of the cultures obtained, those from sites treated with SAB and BP-Visco degraded n-alkanes most consistently and typically to the greatest extent. Two mixed cultures obtained from samples collected at 60 days and two isolates obtained from these cultures extensively degraded phenanthrene. 1-Hydroxy-naphthoic acid formed the major phenanthrene metabolite. Lower levels of salicylic acid, 1-naphthol, 1, 4-naphthaquinone and phenanthrene 9-10 dihydrodiol were detected in extracts of phenanthrene grown cultures. This study shows that under laboratory conditions indigenous Antarctic bacteria can degrade n-alkanes and the more recalcitrant polycyclic aromatic hydrocarbon, phenanthrene. The enrichment of hydrocarbon degrading microorganisms in Antarctic ecosystems exposed to hydrocarbons is relevant for the long term fate hydrocarbon spills in this environment.
Interannual variability in the early growth rate and size of the Antarctic fish Gobionotothen gibberifrons (Lönnberg)
Authors: North A. W. , White M. G. , Trathan P. N.
Published: December 2007

Gobionotothen gibberifrons <1 year old, of the 1977, 1980, 1981, 1985, 1986, 1990 and 1995 cohorts, were sampled using nets, in various periods during summer (December to February) at South Georgia. Growth in standard length (Ls) was estimated using the exponential model. Among the seven cohorts, average growth rate varied between 0.33–2.1% Lsd−1, and predicted Ls for mid-January varied between 21.6–29.1 mm. Average growth rate was inversely related to mean date of sampling but was not significantly related to mean Ls. Mean sea surface temperatures were available for the 1981–95 cohorts. Average growth rate and predicted Ls for mid-January were both negatively conelated with mean December–January sea temperature, but were not significantly related to mean weekly sea surface temperature during the sampling periods. Greater average growth rate and greater Ls in cooler summers may be partly due to a large-scale pattern of environmental variability, indicated by sea temperature, that governs the timing and magnitude of the production cycle and food availability.
Kelp-plucking: coastal erosion facilitated by bull-kelp Durvillaea antarctica at subantarctic Macquarie Island
Authors: Smith J. M. B. , Bayliss-Smith T. P.
Published: December 2007

Erosion of bedrock from lower intertidal reefs by waves acting on attached plants of bull-kelp (Durvillaea antarctica) was investigated over one year at Macquarie Island, Southern Ocean. At a site on the more sheltered east coast, such erosion occurred during four separate storms, each casting up 834–1078 large kelp plants km−1 of coast, of which 30–45% were still attached to jagged, freshly quarried bedrock fragments over 2.5 cm long. The largest fragment weighed was 74.6 kg; rounded cobbles and boulders attached to kelp plants and weighing up to 102.2 kg (and probably more than 160 kg) were also cast up on beaches. 19–21% of the standing crop of large kelp plants was removed by storms during the year of observation. Break points for 10 kelp stipes were found to be at least 90–161 kg. Total annual erosion by kelp-plucking is at least 1.56 tonnes of rock km−1 of coast. However, in terms of erosion this computes to only 0.1 mm yr−1, far below the rate of uplift of the island.
Spatial relationships of Adélie penguin colonies: implications for assessing population changes from remote imagery
Authors: Woehler Eric J. , Riddle Martin J.
Published: December 2007

The relationship between colony area and population density of Adélie penguins Pygoscelis adeliae was examined to determine whether colony area, measured from aerial or satellite imagery, could be used to estimate population density, and hence detect changes in populations over time. Using maps drawn from vertical aerial photographs of Adélie penguin colonies in the Mawson region, pair density ranged between 0.1 and 3.1 pairs m−2, with a mean of 0.63 ± 0.3 pairs m−2. Colony area explained 96.4% of the variance in colony populations (range 90.4–99.6%) for 979 colonies at Mawson. Mean densities were not significantly different among the 19 islands in the region, but significant differences in mean pair density were observed among colonies in Mawson, Whitney Point (Casey, East Antarctica) and Cape Crozier (Ross Sea) populations. The relationship between colony area and population may be locality-and/or species-specific, and a robust data set is required to validate the relationship.
Evidence for shallowing and uplift from bathymetric records of Deception Island, Antarctica
Authors: Cooper A. P. R. , Smellie J. L. , Maylin J.
Published: December 2007

Deception Island is a large volcanic centre in Bransfield Strait, a very young marginal basin between the South Shetland Islands and Antarctic Peninsula. It has a historical record of volcanic activity, with the most recent eruption occurring in 1970. The island is a stratovolcano with a large flooded caldera forming a natural harbour known as Port Foster. It has been a focus of human activity since early last century, as a base for whaling and sealing expeditions and the locus of several scientific stations. During that period, many bathymetric surveys were carried out, the earliest in 1829 and the most recent in 1993. This study concentrates on surveys from 1948 onwards. Because Port Foster can be classified as a restless caldera, the bathymetric records were analysed for evidence of volcano-tectonic deformation, particularly caldera resurgence (uplift) which could have significant consequences for hazard and risk assessments of the volcano. The results show that a distinctive pattern of shallowing and uplift is present, correlating well with known and inferred volcanic and volcanotectonic processes on the island. In particular, bathymetric records between 1949 and 1993 show uplift rates as high as 0.3–0.5 m a−1, far exceeding normal sedimentation rates in a caldera this size. Rapid uplift in an arcuate offshore area not affected by the sedimentation of recent eruptions suggests that volcano tectonic resurgence or tectono-magmatic effects of an upward migrating magma chamber present a significant risk to the considerable human activity taking place in the region.
The stratigraphy and geochronology of Adelaide Island
Authors: Griffiths Chris J. , Oglethorpe Richard D. J.
Published: December 2007

The Mesozoic-Cenozoic volcanic arc of the Antarctic Peninsula is represented on Adelaide Island by a sedimentary and volcanic succession intruded by plutons. 40Ar-39 Ar step-heating age spectra have been obtained from volcanic rocks and hornblende separates from sedimentary clasts of plutonic origin. These spectra show evidence for some argon loss, but, in general, have plateau ages which are consistent with the mapped stratigraphy and with other geochronological controls, suggesting that they approximate to original ages. As a result the following events in the evolution of Adelaide Island can be recognized:

1) mostly marine Mesozoic sedimentation, 2) Early Cretaceous (c. 141 Ma) plutonism (recorded in clasts from conglomerates), 3) Cretaceous volcanism, 4) Late Cretaceous (possibly Tertiary) sedimentation, 5) Early Tertiary volcanism, which was acidic in eastern outcrops and intermediate elsewhere, and 6) Eocene intermediate volcanism and deposition of arc-derived conglomerates. Volcanism was possibly coeval with known Palaeocene-Eocene plutonic activity on Adelaide Island (part of the Antarctic Peninsula Batholith) and with volcanism of similar age in northern Alexander Island and the South Shetland Islands. The volcanism on Adelaide Island and the South Shetland Islands, at least, was associated with a westward migration of the Antarctic Peninsula arc.
Conopora (Stylasteridae, Hydrozoa) from the Eocene of Seymour Island
Authors: Stolarski Jarosław
Published: December 2007

The first fossil stylasterid from Antarctic is reported from La Meseta Formation (Telm1: Early Eocene) of Seymour Island (Antarctic Peninsula): Conopora mariae sp. nov. This also is the earliest reliable fossil record of the genus Conopora. Conopora mariae differs from congeners by having much larger cyclosystems (diameter 2.5–4.5 mm). Cyclosystems of that size are exceptional among the Stylasteridae.
Ionospheric electron content across the Antarctic continent
Authors: Jones G. O. L. , Kersley L. , Heaton J. A. T. , Ciraolo L. , Spalla P.
Published: December 2007

Observations of satellite passes monitored at Halley and Terra Nova Bay have been combined to produce for the first time measurements of ionospheric electron content spanning the Antarctic continent. Results are presented from a sequence of four successive passes made during a period of some two hours that illustrate the development of the ionosphere over this wide spatial region. The observations are discussed in terms of the convective behaviour of the ionization, using results from the PACE radar and a standard model of the plasma flow.
Katabatic winds, hydraulic jumps and wind flow over the Vestfold Hills, East Antarctica
Authors: Targett Philip S.
Published: December 2007

This paper examines two strong or gale-force wind events which began suddenly at Platcha, near the Antarctic ice sheet edge in the Vestfold Hills of East Antarctica, and at a later time were recorded at Davis after progressing slowly across the intervening 25 km of relatively low hills.
Whither Antarctic science?
Authors: Thomson M.R.A.
Published: December 2007

There was a time when science in Antarctica was king. The frozen continent was still the big unknown and almost any information, a measurement, an observation, a collection of samples was seen as new, exciting and accepted as a potentially valuable contribution to scientific knowledge. Words like ‘exploration’ and ‘survey’ could be uttered without shame in polite company and even in the presence of assessors. We all knew that national presences in Antarctica were predicated by political motives, but all Antarctic programmes were nevertheless promoted on the basis of their contribution to the scientific exploration of our planet. And so it has continued, until now.
Fishes of the genus Artedidraco (Pisces, Artedidraconidae) from the Ross Sea, Antarctica, with the description of a new species and a colour morph
Authors: Eastman Joseph T. , Eakin Richard R.
Published: December 2007

Notothenioid fish of the artedidraconid genus Artedidraco are a little studied, component of the bottom fauna on the Antarctic continental shelf. Trawling in the south-western Ross Sea, especially in shallow areas with sponge beds, yielded a collection of 65 specimens of Artedidraco. These included all four species occurring in the Ross Sea as well as a new species. The new species Artedidraco glareobarbatus is described and illustrated. This species is most similar to A. orianae, but is distinguished by barbel morphology, by higher counts for dorsal rays and vertebrae, by lower counts for upper lateral-line scales and by colour pattern and visceral anatomy. A distinctive spotted colour morph of A. shackletoni is also documented and compared with the typical barred morph. Depth distribution and meristic variation among species of Artedidraco are summarized, and a taxonomic key to the six species is provided.
The base composition of the krill genome and its potential susceptibility to damage by UV-B
Authors: Jarman Simon , Elliott Nicholas , Nicol Stephen , McMinn Andrew , Newman Stuart
Published: December 2007

We have determined the base composition (percentage of guanine-cytosine base pairs, GC%) of total DNA from Euphausia superba to be 32% ± 0.5%. This is the lowest GC% recorded for a metazoan. Low GC% DNA has high concentrations of thymine (T) residues and consequently a greater abundance of adjacent T residues [T(n) arrays]. Ultraviolet B (280–320 nm, UV-B) radiation damages DNA primarily at (T)n arrays, so we suggest that krill DNA may be more susceptible to damage from increased levels of UV-B radiation over the Southern Ocean than the DNA of other Antarctic organisms.
Population status and seasonal haulout patterns of the southern elephant seal (Mirounga leonina) at Heard Island
Authors: Slip David J. , Burton Harry R.
Published: December 2007

We surveyed the southern elephant seal population at Heard Island regularly from February 1992 to March 1993, and determined the haulout patterns of the major components of the population. While haulout patterns of moulting and immature seals may give broad indices of population trends, the breeding haulout of adult females was the only reliable haulout that could be used to determine annual pup production. During the breeding season 14 277 adult females were counted. Raw counts were corrected using two models, one purely mathematical and the other based on the haulout behaviour of adult female seals. The two models have slightly different assumptions, but both provided good fits to the observed haulout patterns and estimated total population with a coefficient of variation of less than 5%. Total pup production was estimated at between 17 000 and 18 000 for 1992. Previous counts of elephant seals from 1949–51, 1985 and 1987 were corrected using the same models. The two models gave estimates of the population that were within ± 2.5% for all but one year. The population declined by about 50% between 1949 and 1985 but there appears to have been little change from 1985–92. The previous decline may be related to changes in sea-ice.
Spatial variability of Antarctic surface snow glaciochemistry: implications for palaeoatmospheric circulation reconstructions
Authors: Kreutz Karl J. , Mayewski Paul A.
Published: December 2007

Ice core glaciochemical records provide detailed information on past changes in atmospheric chemical composition and circulation, which is essential for understanding the timing and phasing of climatic change in different regions. Atmospheric circulation reconstructions based on these records require knowledge of modern chemical concentration controls (chemical source, transport pathway and strength) and spatial variability. To gain insight into these processes, glaciochemical data collected during reconnaissance drilling in West Antarctica combined with all other existing Antarctic surface snow glaciochemical records are examined for trends in chemical concentration vs distance inland, elevation, and accumulation rate. Snowpit data from inland West Antarctica displays significant spatial variability, suggesting complex patterns of atmospheric circulation and moisture transport in the region. Siple Dome sea-salt and methanesulphonic acid (MSA) concentrations are similar to coastal sites, suggesting enhanced advection of marine air masses to the site. Statistical analysis of a 110-year high-resolution Siple Dome ice core record confirms that strong lower tropospheric circulation dominates the region, which is most likely related to the strength of the Amundsen Sea low pressure system. An atmospheric circulation reconstruction based on the ice core glaciochemical data displays significant interannual and decadal-scale variability, but there is no overall trend in atmospheric circulation strength at Siple Dome in the past 110 years.
Science and commercialism in Antarctica
Authors: Howard-Williams Clive
Published: December 2007

There are increasing commercial pressures to send more people to the Antarctic. Visitor numbers each summer now exceed scientist numbers on the continent. The commercial operators working through IAATO have, to date, been largely acting in an environmentally responsible manner, realising that there is no point killing the goose with the golden egg. In fact, it has been argued that visitors to the Antarctic, many of whom are wealthy or influential, have played a significant role in increasing environmental awareness of the continent and its wildlife to politicians and to the public.
H2O2 accumulation from photochemical production and atmospheric wet deposition in Antarctic coastal and off-shore waters of Potter Cove, King George Island, South Shetland Islands
Authors: Abele Doris , Ferreyra Gustavo A. , Schloss Irene
Published: December 2007

Temporal and spatial variations of the hydrogen peroxide accumulation were measured in off-shore waters and in intertidal rockpools near Jubany Station, King George Island, South Shetland Islands. As H2O2 photoformation is mainly driven by the short wavelength radiation in the UV-B and the UV-A range of the solar spectrum, the study was conducted between the beginning of October and the end of December 1995, the period of Antarctic spring ozone depletion. Wet deposition of H2O2 containing snow was identified as a major source of hydrogen peroxide in the surface waters of Potter Cove. As the concentrations of dissolved organic carbon (DOC) in Potter Cove surface waters were low (121 ± 59 μmol Cl−1), when compared to the highly eutrophicated waters on the German Wadden coast (6000–7000 μmol Cl−1), direct UV-induced DOC photo-oxidation was of only limited significance in the Antarctic sampling site. Nonetheless, under experimental conditions, H2O2 photoformation in Potter Cove surface waters amounted to 90 ± 40 nmol H2O2 h−1 l−1 under a UV-transparent quartz plate. When high energy UV-B photons were cut-off by a WG320 filter formation continued at a rate of 66 ± 29 nmol H2O2 h−1 l−1 due to UV-A and visible light photons. Samples from freshly deposited snow contained between 10 000 and 13 600 nmol H2O2 l−1, and a snowfall event in mid November resulted in a maximum concentration of 1450 nmol H2O2 l−1 in the upper 10 cm layer of Potter Cove surface waters. Maximal H2O2 concentrations in intertidal rockpools were even higher and reached up to 2000 nmol H2O2 l−1 after the snowfall event. During a grid survey on December 17 1995, H2O2 concentrations and salinity displayed a north to south gradient, with higher concentrations and PSU at the south coast of the cove. The reasons for this spatial inhomogenety are as yet unknown, but may relate to a minor local input of photo-reactive organic matter from creeks entering the cove in the south-east, as well as to waste water discharge from the station, located on the south beach.
Reproductive biology of the icefish Champsocephalus esox (Günther, 1861) (Channichthyidae)
Authors: Calvo Jorge , Morriconi Elba , Rae Gustavo A.
Published: December 2007

Champsocephalus esox is the only icefish species found outside Antarctica. In a population from the Beagle Channel, the complete annual reproductive cycle has been determined. Gonad maturity stages have been established for males and females by histological analysis. Males are sexually mature from January–September with a maximum gonadosomatic index (GSI) of 3.63%. Histologically, testes are very homogeneous and the degree of maturation of the testicular cysts is similar among different tubules at the same maturation stage. Running ripe testes have mature sperm and a few spermatogoniae arranged near the blind end of the tubules. In sexually active females that are found from February–November, ovaries contain only ripe oocytes or postovulatory follicles, together with a batch of previtellogenic oocytes. During hydration, oocyte diameter reaches 2.7 mm, and oocyte dry weight increases due to material intake, the maximum GSI in ovulated ovaries is 21.89 and hepatosomatic index (HSI) decreases. These facts suggest a transfer of matter from liver to the gonads. Absolute fecundity ranges from 3303–8600 oocytes. Relative fecundity ranges from 22.5–43.5 oocytes per gram total weight. In C. esox, relative fecundity has a similar range to those quoted for the different C. gunnari populations, whilst mature oocyte diameter is small and reproductive season extended compared to the same parameters in other Channichthyidae.
An assessment of the value of nuclear and mitochondrial genes in elucidating the origin and evolution of Isotoma klovstadi Carpenter (Insecta, Collembola)
Authors: Frati Francesco , Carapelli Antonio
Published: December 2007

In order to infer the origin and the evolution of Antarctic Collembola, a correct phylogenetic analysis depicting relationships among Antarctic and non-Antarctic species is required. A preliminary assessment of the value of DNA sequences in reconstructing phylogenetic relationships among the Antarctic Isotoma klovstadi and other non-Antarctic species was carried out by sequencing one mitochondrial gene (Cytochrome c oxidase, subunit II) and two nuclear genes (a fragment of the 28S rDNA and the Elongation Factor-1α). Estimates of base composition heterogeneity revealed that in the two protein-coding genes (COII and EF-1α) 3rd codon position sites are compositionally very heterogeneous and the analysis of these two genes was therefore performed only on 1st and 2nd codon position sites. Phylogenetic analyses using Maximum Likelihood, Maximum Parsimony and Minimum Evolution revealed that the COII and the EF-1α genes are more suitable than the D3 fragment for the reconstruction of phylogenetic relationships within the Family Isotomidae to which Isotoma and several other genera of Antarctic Collembola belong.
The meromictic lakes and stratified marine basins of the Vestfold Hills, East Antarctica
Authors: Gibson John A.E.
Published: December 2007

Thirty-four permanently stratified water bodies were identified in a survey of the Vestfold Hills. Of these, 21 were lakes, six were seasonally isolated marine basins (SIMBs), and seven were marine basins with year round connection to the open ocean. The basins varied markedly in salinity (4 g l−1 to 235 g l−1), temperature (−14°C to 24°C), depth (5 m to 110 m), area (3.6 ha to 146 ha) and surface level (−30 m to 29 m above sea level). The stratification in all the basins was maintained by increases in salinity. During winter, a thermohaline convection cell was present in all lakes and SIMBs directly beneath the ice cover. These cells were the result of brine exclusion from the forming ice, and increased in density throughout winter, penetrating progressively deeper into the lake. Minimum stability, and therefore the maximum likelihood of turnover, occurred at the time of maximum ice formation in spring. At the end of the period of ice formation, the convection cell broke down, and stratification of the surface water occurred. When the ice melted completely, lenses of relatively fresh water capped the lakes, which reduced the effect of wind mixing. Net meltwater input increased the stability of the meromictic basins, while periods of lower water level resulted in deeper penetration of the thermohaline convection cell, increasing the possibility of turnover and destratification.
Environmental conditions during freezing, and response of microbial mats in ponds of the McMurdo Ice Shelf, Antarctica
Authors: Hawes I. , Smith R. , Howard-Williams C. , Schwarz A-M.
Published: December 2007

Environmental conditions, both external to and within three shallow ponds of the McMurdo Ice Shelf, were measured over an annual cycle between January 1997 and January 1998. We combined this with a study of the response of the benthic microbial mat communities to the transition from summer conditions to winter freezing. Over the study period air temperature was above 0°C for a few days during summer. At this time pond temperatures were higher than air temperatures, with evidence of thermo-haline stratification. The shallow areas of ponds froze between late February and early March, with bottom waters in the deepest pond remaining unfrozen until early June. Minimum winter air temperatures were below −40°C. There was little evidence of freezing point depression due to freeze-concentration of solutes, except at the very bottom of ponds. In the most conductive pond investigated, the temperature of basal freezing was −4°C and conductivity did not exceed approximately 60 mS cm−1 immediately prior to freezing. Microbial mats remained photosynthetically active up to conductivities between 40 and 80 mS cm−1, and were able to acclimate to lowered irradiance associated with ice formation. Although photosynthesis and respiration were reduced by 11% and 40% respectively at temperatures of −2°C compared to 1°C, there was no difference in light harvesting efficiency. Results from this study suggest that light limitation of photosynthesis, or freezing, determine the growth season for the microbial communities, depending on depth.
The metaconglomerates of the eastern Lanterman Range (northern Victoria Land, Antarctica): new constraints for their interpretation
Authors: Capponi Giovanni , Crispini Laura , Meccheri Marco
Published: December 2007

Highly deformed metaconglomerates, mafic to felsic in composition, characterize the eastern Lanterman Range (northern Victoria Land, Antarctica). In the literature the mafic and felsic metaconglomerates are known as Husky Conglomerate and Lanterman Conglomerate respectively. They occur in a 25 km long strip along the Lanterman Fault, which is a major tectonic boundary between the Wilson and the Bowers terranes. New field observations show that there is a gradual transition from mafic to felsic metaconglomerates: this supports a stratigraphical continuum from Husky to Lanterman Conglomerate, and indicates that they belong to the same sedimentary succession. Structural analysis indicates that Husky and Lanterman conglomerates suffered the same structural evolution. From all these evidences, there is no reason to distinguish two types of metaconglomerates, apart from the diversity in the lithological features. However the two terms “Husky Conglomerate” and “Lanterman Conglomerate” can be still used to refer to the mafic and felsic facies of the same sedimentary succession. On the basis of their lithology the Husky Conglomerate can be derived from the Glasgow volcanic arc, whereas the felsic clasts of the Lanterman Conglomerate may be derived from a continental basement below the Glasgow arc or from a continental block bounding the Bowers trough.
Mesozoic palynofloras from the Mac. Robertson shelf, East Antarctica: geological and phytogeographic implications
Authors: Truswell E.M. , Dettmann M.E. , O'Brien P.E.
Published: December 2007

Gravity cores taken from five sites in the Nielsen basin, a sinuous trough on the Mac. Robertson shelf of the East Antarctic continental margin, have yielded non-marine palynofloras of late Early Jurassic to Early Cretaceous age. The palynomorphs occur in glacimarine muds and are thus not in situ, but the composition of the samples indicates that no mixing of individual assemblages has occurred, and that the sediments were deposited very close to outcrop of the source of the palynomorphs. The sequence is oldest at the seaward end of the Nielsen basin, and youngest near the fault-bounded landward end. It is interpreted as reflecting pre-break-up deposition on a passive, rifted continental margin. The age of the assemblages has been established by comparison with the zonal scheme developed in the Perth Basin of Western Australia. Similarity of the Antarctic palynofloras with those known from basins on the east coast of India confirms continental reconstructions that show this part of East Antarctica to have been contiguous with eastern India prior to break-up. The non-marine character of the palynomorphs suggests that marine conditions in this region of the Antarctic margin did not develop until at least late Early Cretaceous time.
The hunt for Antarctic climate history
Authors: Barker Peter , Cooper Alan
Published: December 2007

ANTOSTRAT (the Antarctic Offshore Stratigraphy initiative) began 10 years ago as a collaborative study of Antarctic margin seismic data by offshore seismic profilers who set up an Antarctic Seismic Data Library System. It was soon realised that the ice-transported margin sediments retain a record of ice sheet history that could be recovered by direct sampling, and that ANTOSTRAT formed the springboard for a description of ice sheet history. ANTOSTRAT today aims to describe Antarctic climatic history over the past 100 million years or so. Of this history, by far the most important element is the Antarctic ice sheet, which probably formed 35 to 40 million years ago. Although geologically young, the ice sheet is still about ten times as old as Northern Hemisphere ice sheets. ANTOSTRAT's key aims are to establish when, how and why the Antarctic ice sheet formed.