bluuebunny/crossref_metadata_2025 huggingface dataset:
Stratigraphy and depositional setting of the Lagrelius Point Formation from the Lower Cretaceous of James Ross Island, Antarctica
Authors: Buatois Luis A. , Medina Francisco J.
Published: December 2007

The Lagrelius Point Formation (?Barremian–Aptian) is the basal unit of the Gustav Group and crops out on the north-west coast of James Ross Island. It consists of about 250 m of coarse-grained siliciclastic rocks. The type section of the Lagrelius Point Formation is defined here from just south of Lagrelius Point. The measured section comprises the uppermost 80 m of the unit and mainly consists of clast-supported, boulder, cobble to pebble conglomerates; very coarse to medium-grained sandstones occur rarely. Four sedimentary facies are recognized. A disorganized conglomerate facies (1) is interpreted as having been deposited from non-cohesive debris flows and high density gravelly turbidity currents. Inversely graded conglomerate facies (2) and normally graded to graded stratified conglomerate and pebbly sandstone facies (3) reflect sedimentation from high density gravelly turbidity currents. Massive and parallel stratified sandstone facies (4) is thought to record deposition from high density sandy turbidity currents. Two types of facies assemblages have been recognized. A major channel assemblage, represented by the lower part of the measured section and the minor channel assemblage forming the upper part of the section. The total succession is thought to represent the aggradation of a major submarine braided channel followed by the establishment and subsequent infill of a series of minor channels in a marginal terrace.
Sapphirine granulites from the Vestfold Hills, East Antarctica: geochemical and metamorphic evolution
Authors: Harley Simon L.
Published: December 2007

A varied suite of sapphirine-bearing and quartz-undersaturated granulites, the Taynaya Paragneiss, occur as boudins and enclaves within the c. 2500 Ma old felsic orthogneisses of northern Vestfold Hills. Highly magnesian varieties with XMg (=100x(Mg/(Mg+Fe)) near 95 preserve the assemblage sapphirine + enstatite + spinel, whereas sapphirine + cordierite + sillimanite + corundum occurs in aluminous and feldspathic types with XMg near 90. Phase equilibria and relative thermometry based on Al2O3 solubility in enstatite indicate equilibration of these assemblages at c. 830–880°C and 0.35–0.85 GPa. There is no evidence for the extreme temperatures (1000–1100°C) previously proposed for early metamorphism in the Vestfold Hills, and no indication in the metamorphic assemblages of isobaric cooling prior to 2500 Ma. Two types of metasomatism have altered the bulk rock compositions near boudin and enclave margins. Cordierite rinds locally formed on corundum-sillimanite granulites reflect interaction with magmatic precursors to the enclosing felsic gneisses, as supported by the isotopic and chemical compositions of cordierite channel volatiles. More extensive metasomatism producing schistose phlogopite + sapphirine rinds on all boudins involved infiltration of a LILE-enriched fluid which introduced K2O, H2O, Fe, Rb, Ba and minor Sr along the boudin margins. Whole rock geochemistry of Taynaya Paragneiss unaffected by this metasomatism is consistent with their derivation from evaporitic mudstones, and implies the existence of a basement older than the dominant 2500 Ma orthogneisses.
Southern Ocean cephalopods: life cycles and populations (Proceedings of the symposium held at Kings College Cambridge, 5–9 July 1993)
Authors: Rodhouse P.G , Piatkowski U. , Lu C.C.
Published: December 2007

The first systematic sampling in the Southern Ocean to capture cephalopods took place 120 years ago aboard HMS Challenger. Over the next century taxonomic knowledge was advanced by expeditions including the Mission du Cap Horn (France), the Valdivia Deep Sea Expedition (Germany), the Discovery expeditions (UK) the Eltanin (USA) and Academic Knipovitch (USSR). Over the last decade Southern Ocean cephalopod research has at last progressed beyond the descriptive phase and is rapidly joining other fields of Antarctic marine biology in its concerns with population biology and trophic systems, Although much taxonomic work remains to be done, ecological studies on the role of cephalopods in the diet of predators has been facilitated by advances in the identification of cephalopod beaks, development of opening-closing nets has allowed fine-scale distribution studies, and as methods for the study of growth, diet and biochemical genetics have advanced, so these have been applied to Southern Ocean cephalopods.
Embryonic development of cephalopods at low temperatures
Authors: Boletzky S.V.
Published: December 2007

No information is available on the embryonic development of Southern Ocean cephalopods. Estimations of developmental times can only be made by extrapolation using data from other geographical areas. Based on known relationships between environmental temperature and embryonic development time, it appears that below 5°C even the smallest squid eggs measuring 0.6–1.0 mm in diameter need one to two months to develop to hatching. At c. 2°C, the embryonic development of these small eggs would probably cover between three and five months. Very large octopod eggs are known to develop over time spans of at least one year. Protection of the developing embryos either by long-lasting capsules laid at appropriate spawning sites, or by active ‘brooding’ (incirrate octopods) is required for embryonic survival and hatching success. The physiological conditions controlling the onset of hatching at very low temperatures are unknown; postponement of hatching appears to be common in cold waters.
Biochemical genetic evidence supporting the taxonomic separation of Loligo gahi from the genus Loligo
Authors: Brierley Andrew S. , Thorpe John P.
Published: December 2007

Fifteen specimens of Loligo gahi caught within the Falkland Islands Interim Conservation and Management Zone during March 1988 were subject to genetic analysis using horizontal starch gel electrophoresis. Comparison of allele frequencies at 22 clearly resolving putative enzyme loci showed these animals to exhibit a degree of genetic differentiation from samples of Loligo forbesi and Loligo vulgaris vulgaris (I = 0.19 and 0.22 respectively) greater than that normally expected between congeneric species. The degree of difference was of the order typically exhibited between members of different but confamilial genera, for example as here between Loligo forbesi and Alloteuthis subulata (I = 0.22). It is therefore concluded that Loligo gahi should no longer be regarded as a member of the genus Loligo. Genetic analysis of further species is necessary to clarify whether or not Loligo gahi should, as has been suggested on morphological grounds, be united in a separate genus with other American myopsid species also currently ascribed to the genus Loligo.
Comparative morphology of two sympatric Pareledone species from South Georgia
Authors: Daly Heather I. , Rodhouse Paul G.
Published: December 2007

Morphometric data were collected for 410 specimens of Pareledone turqueti and P. polymorpha caught around South Georgia. The two species differ in beak morphology and in the male hectocotylus. The species have similar appearances although there is a small but significant difference in the mantle length/body mass relationship for females, with P. polymorpha having a relatively longer mantle. There is no significant difference in the arm length/body mass relationship between species or sexes (p>0.05), except in the case of arm IV of females. There is an interspecific significant difference between sucker number on arms I and II of males, arms I–IV of females, and between hood length and mass of the buccal mass (p<0.05), with P. turqueti having relatively lower sucker numbers, a longer hood length and greater buccal mass mass. The beak of P. turqueti is similar to that of Eledone spp. but P. polymorpha has a small, fine beak with the rostral tip ending in an elongated, sharp point. Differences in beak and buccal mass suggest that these sympatric species occupy distinct trophic niches and that the differing morphology of the male hectocotylus is a factor in reproductive isolation.
Young squid in the plankton of Prydz Bay, Antarctica
Authors: Filippova J.A. , Pakhomov E.A.
Published: December 2007

A collection of juvenile squid were caught with the Isaacs-Kidd midwater trawl (IKMT) and the Juday plankton net at 86 stations in Prydz Bay (60°–67°30′S, 60°–80°E) to a depth of 500 m but mostly at 0–200 m. Five species were identified, Psychroteuthis glacialis, Alluroteuthis antarcticus, Brachioteuthis sp. and the cranchiids Galiteuthis glacialis and Mesonychoteuthis hamiltoni. P. glacialis and the cranchiids were the most abundant species. Young P. glacialis (5–17 mm ML) were taken at depths of 5–200 m but concentrated in the upper 100 m whilst the cranchiids (5–35 mm ML) occurred over a wider vertical range (50–500 m). The regular occurrence of paralarvae and juveniles suggests that all the species reproduce in the Antarctic. Juvenile Vertical distribution appears to differ between species with P. glacialis concentrated relatively near the surface, the cranchiids in the upper part of the Circumpolar Deep Water and A. antarcticus widely distributed to a depth of 900 m.
Reproductive-somatic relationships in Loligo gahi (Cephalopoda: Loliginidae) from the Falkland Islands
Authors: Guerra Angel , Castro Bernardino G.
Published: December 2007

Samples of Loligo gahi from the Falkland Islands Interim Conservation and Management Zone collected in March 1987 were analysed to determine the relationships between mass of reproductive and somatic organs during maturation. There was a progressive increase in mass of the reproductive organs with growth in males, while in females these organs did not show a conspicuous increase in mass until a body mass of c. 40 g was reached. No change was found in the mass of the digestive gland in relation to body mass or in the water content of male and female somatic tissues during maturation. Growth of reproductive organs in L. gahi seems to be supported by diet and not at the expense of somatic tissue.
Migration as a source of bias in the measurement of cephalopod growth
Authors: Hatfield Emma M.C. , Rodhouse Paul G.
Published: December 2007

Theory predicts that, in a closed exploited population showing no sampling or other bias, the mean age of fish or squid between one sampling date and the next should increase by the time interval between samples. Age data, derived from statoliths, have been used to test the hypothesis that the effect of migration through an area where a population of Loligo gahi is sampled would be apparent as an increase in mean age per modal group of less than one day per daily time interval between samples. The data show that, in both females and males, the relationship between mean statolith increment number and elapsed time between samples is positive in some months and negative in others. The months in which the relationship between mean increment number and elapsed time is negative are similar to those months in which recruitment has previously been demonstrated to occur, in February, April/May and September for both females and males. Cohorts of squid remain available to the fishery from June–September (females) and February–May and June–July (males) thus allowing mean monthly growth rates of 0.4 mm d−1 for females and 0.7 mm d−1 for males to be calculated. The present study shows that putative age data derived from statoliths apparently demonstrate some sampling biases within a fishery and their effects on the measurement of growth. Migration through the sampled population is manifested by an increase in mean increment number of less than one per day between samples, and growth can only be assessed where the increase in mean increment number is not significantly different from the time elapsed between samples.
Food and feeding of Illex argentinus
Authors: Ivanovic Marcela L. , Brunetti Norma E.
Published: December 2007

The diet and feeding behaviour of Illex argentinus were determined from analysis of stomach contents of squid caught during four bottom trawl surveys carried out over the Bonaerensis (34–40°S, autumn–winter 1991) and Patagonian (45–55°S, summer–autumn 1992) shelves of Argentina. Crustaceans, mainly Themisto gaudichaudii and, to a lesser extent, euphausiids were the most important components of the diet in both areas and years, although there were considerable geographical differences in the relative proportion of the main prey. In the Patagonian area, during summer and autumn of 1992, almost all squid preyed on crustaceans (percentage occurrence = 85.29%), followed by squid (11.76%) and fish (2.94%). On the Bonaerensis shelf, during autumn and winter of 1991, crustaceans were most important by percentage occurrence (56.96%), but fish and squid accounted for a large proportion of the diet (29.41% and 13.62% respectively). Myctophids were prevalent among the fish and cannibalism was on I. argentinus juveniles. Changes in diet composition with squid size demonstrated the opportunistic nature of I. argentinus feeding. Although large squids were able to catch large prey (fish, squid), they also fed on small crustaceans when available, especially in the Patagonian area. The relative abundance of different prey organisms probably determined the diet. In both areas and both years I. argentinus fed mostly during daylight hours, starting in the morning and reaching a maximum in the afternoon. No difference in feeding behaviour was observed between the sexes.
Allozyme differentiation of sixteen species of ommastrephid squid (Mollusca, Cephalopoda)
Authors: Yokawa K.
Published: December 2007

Allozyme differentiation was investigated at 23 putative enzyme coding loci in 16 ommastrephid squids to identify species and to assess genetic relationships. The species examined were Illex illecebrosus, I. coindetii, I. argentinus, Todaropsis eblanae, Todarodes sagittatus, T. angolensis, T. filippovae, T. pacificus pacificus, Nototodarus sloanii, N. gouldi, Martialia hyadesi, Ommastrephes bartramii, Sthenoteuthis pteropus, S. oualaniensis, Eucleoteuthis luminosa, and Dosidicus gigas. A dendrogram based on Nei's genetic distance between the species closely approximates to the latest systematics based on morphological characters, but the positions of M. hyadesi and T. eblanae were considerably distant from all other species. The results demonstrate the benefits of further biochemical analysis to an understanding of the systematics of the ommastrephid squids.
Kondakovia longimana Filippova, 1972 (Cephalopoda: Onychoteuthidae) from the Indian Ocean sector of the Southern Ocean
Authors: Lu C.C. , Williams R.
Published: December 2007

Two specimens of Kondakovia longimana were recently obtained from the Indian Ocean sector of the Southern Ocean. One specimen, damaged but near the known maximum size, was found floating on the surface, and the other, a male subadult specimen, was captured by a pelagic trawl. Examination of the specimens, histological sections and analyses of tissue samples revealed that the muscular tissues of the tentacular stalks and the mantle contain a large amount of ammonium, more than 328 mM, a quantity that far exceeds that of Moroteuthis ingens (206.9 mM) and Moroteuthis robsoni (199.6 mM) from the South Tasman Rise. Catch data and published records suggest that the juveniles and subadults of K. longimana feed on krill in the epipelagic zone.
Distribution and lipid composition of early life stages of the cranchiid squid Galiteuthis glacialis (Chun) in the Weddell Sea, Antarctica
Authors: Piatkowski Uwe , Hagen Wilhelm
Published: December 2007

The relatively small numbers of pelagic cephalopods caught in the RMT-8 samples (0–300 m) in February/March 1983 in the Weddell Sea were dominated by early life stages of the cranchiid squid Galiteuthis glacialis. A total of 48 specimens were caught with dorsal mantle length (ML) ranging from 4–36 mm. They occurred with a mean density of 0.15 ind. × 1000 m−3 and were present in 38% of 33 RMT-8 samples. G. glacialis was the only cranchiid squid found in the Weddell Sea between 66° and 74°S. Its early life stages were concentrated in the layers below the summer thermocline (>50 m) and body sizes appeared to increase towards deeper water layers. For biochemical analyses, nine specimens of G. glacialis (ML 6–18 mm) were sampled in the eastern Weddell Sea between 185–520 m water depth in January/February 1985. Total lipid contents ranged from 8%–11% dry weight (DW) with phospholipids being the main lipid component (43–56% of total lipid). Storage lipids (triacylglycerols) made up 18–26% of total lipid. The relatively low lipid contents may reflect the early development stage of the specimens examined. The data presented give the first information on geographical and vertical distribution patterns of early life stages of G. glacialis in the high-Antarctic Weddell Sea, as well as on their lipid content and composition.
Growth, age structure and environmental history in the cephalopod Martialia hyadesi (Teuthoidea: Ommastrephidae) at the Antarctic Polar Frontal Zone and on the Patagonian Shelf Edge
Authors: Rodhouse P.G. , Robinson K. , Gajdatsy S.B. , Daly H.I. , Ashmore M.J.S.
Published: December 2007

Martialia hyadesi were collected from fishing vessels at the Antarctic Polar Frontal Zone (APFZ) and the Patagonian Shelf Edge (PASE) during the 1989 austral autumn and winter. Squid were measured, weighed, assigned a maturity stage and the paired statoliths were removed. Statolith sections revealed concentric growth rings using light and scanning electron microscopy. Counts of these putative daily micro-growth increments were made directly and by an estimating procedure. Energy dispersive (ED) and wavelength dispersive (WD) x-ray analyses of Sr and Ca content were made on subsamples of statolith sections. Estimated increment counts, which were generally higher than direct counts, were adopted for routine application. Back calculated hatching dates showed that a single cohort, with a relatively narrow size range, was sampled in each geographical area. Back calculations suggested that M. hyadesi at the APFZ had hatched in the austral winter and those at the PASE had hatched in the spring. At the PASE, growth rate was estimated to be some 30% higher than at the APFZ and PASE squid were more mature at a given age. The hypothesis that the Sr:Ca ratio along the growth axis of the statolith contains information on thermal history was examined. Sr:Ca ratios in the statolith fell in the range 0.009–0.017 and varied systematically but this variation did not apparently relate to season and ratios were not significantly different between geographical areas. A consistent feature was a relatively low Sr:Ca ratio at the time of hatching. According to the Sr:Ca thermometer hypothesis this is consistent with spawning in relatively warm water but it could equally be due to depositional differences during early statolith growth. The Sr:Ca thermometer hypothesis could neither be confirmed nor rejected by the data but there is evidence that strontium varies systematically with age in the squid statolith.
In situ evidence for a nutrient limitation of phytoplankton growth in pelagic Antarctic waters
Authors: Holm-Hansen Osmund , Amos Anthony F. , S. Nelson Silva , Villafañe Virginia , Helbling E. Walter
Published: December 2007

Studies in a large (30000 km2) sampling grid around Elephant Island, Antarctica, during January–March of four successive years (1990–1993) have shown that one of the water types within the sampling area (Drake Passage water) shows low chlorophyll a in surface waters and a subsurface maximum between 50 and 80 m depth. Ancillary data (beam attenuation, in situ chl a fluorescence) support the view that the extracted chl a values actually do represent increased phytoplankton biomass at depth; other data (oxygen concentrations and upwelling radiance at 683 nm) suggest that the phytoplankton within this subsurface maximum layer are photosynthetically active and do not represent a senescent, sinking population of cells. Such deep chl a maxima were found only in Drake Passage waters; in the other four water types sampled, chl a concentrations were maximal in surface waters and decreased with depth. Phytoplankton biomass and activity in Drake Passage waters is suggestive of a nutrient limitation for phytolankton growth in surface waters. Nutrient concentrations of N, P, and Si were high throughout the euphotic zone at all stations, and hence it is unlikely that any macronutrient would be limiting. The data presented in this paper support the hypothesis of Martin and colleagues that availability of Fe may limit phytoplankton biomass in pelagic Antarctic waters, but not in coastal waters where Fe concentrations are relatively high. All other reports on the effects of Fe on Antarctic phytoplankton have utilized deck incubations from which it is difficult to extrapolate such evidence of nutrient limitation to in situ conditions. Our data represent the first in situ evidence linking Fe limitation to the paradox of high macronutrient concentrations and low phytoplankton biomass in Antarctic pelagic waters.
Nitrate-rich inland waters of the Ross Ice Shelf region, Antarctica
Authors: Vincent Warwick F. , Howard-Williams Clive
Published: December 2007

Nutrient and major ion concentrations were measured in surface water samples from lakes, ponds and streams at sites 30–320 km south of McMurdo Sound: the Darwin Glacier region (79.7–80.0°S), Pyramid Trough in the southern Dry Valleys (78.2°S), and the McMurdo Ice Shelf ablation zone (77.8–78.4°S). These aquatic environments ranged from dilute meltwaters (conductivity <0.05 mS cm−1) to concentrated brines (>50 mS cm−1). The lowest nitrate concentrations were recorded at the sites closest to the seasonally open waters of the Ross Sea. Much higher values (100–142000mg NO3–Nm−3) were recorded at sites further south. These observations support the hypothesis that NO3 precipitation over Antarctica is of stratospheric rather than coastal marine origin. The nitrogen-rich waters contained chloride and nitrate in the ratio 5.45g Cl:1g N (C.V.=8.4%) which is within the range for Antarctic snow, and indicative of nitrate enrichment by freeze concentration processes. Cyanobacterial mats were conspicuous elements of the biota across the full range of salinities, and were usually dominated by oscilatoriacean species. Nitrogen-fixing cyanobacteria and diatoms were also represented in these benthic microbial communities at the more northern sites, but were absent from all samples from the Darwin Glacier region.
Diving depths of albatrosses
Authors: Prince P. A. , Huin N. , Weimerskirch H.
Published: December 2007

Studies of diving in seabirds have mainly been confined to penguins, alcids and cormorants. There are few data on the depths to which other seabirds dive although some species are known to have considerable abilities for diving and swimming underwater e.g. shearwaters (Kuroda 1954, Brown et al. 1978), diving petrels (Prince & Jones 1992) and gannets (Adams & Walter 1993).
Transfer faults in the western Ross Sea: new evidence from the McMurdo Sound/Ross Ice Shelf aeromagnetic survey (GANOVEX VI)
Authors: Damaske D. , Behrendt J. , McCafferty A. , Saltus R. , Meyer U.
Published: December 2007

Aeromagnetic data collected on the GANOVEX IV and GANOVEX VI expeditions are combined in this report to give a synoptic view of the western Ross Sea, Antarctica. The addition of the new GANOVEX VI data allows the identification of the southern boundary of the “Ross Sea Unit” — a magnetic unit containing rift-fabric anomalies of the West Antarctic rift system in the Victoria Land basin. Although this boundary has a similar WSW–ENE orientation to the northern boundary, as identified in the GANOVEX IV survey, the newly identified southern magnetic unit (called the “Ross Island and Ice Shelf Edge Unit”) includes evidence of the S–N rift-fabric that is not found in the north, i.e. the rift-fabric continues farther south. The linear boundaries themselves are interpreted as transfer faults as proposed by previous workers for the tectonic development of the Ross Sea area.
Central volcanoes as sources for the Antarctic Peninsula Volcanic Group
Authors: Leat Philip T. , Scarrow Jane H.
Published: December 2007

From at least the Early Jurassic to the Miocene, eastward subduction of oceanic crust took place beneath the Antarctic Peninsula. Magmatism associated with the subduction generated a N-S linear belt of volcanic rocks known as the Antarctic Peninsula Volcanic Group (APVG), and which erosion has now exposed at about the plutonic/volcanic interface. Large central volcanoes from the APVG are described here for the first time. The structures are situated in north-west Palmer Land within the main Mesozoic magmatic arc. One centre, Zonda Towers, is recognized by the presence of a 160 m thick silicic ignimbrite, containing accidental lava blocks up to 25 m in diameter. This megabreccia is interpreted as a caldera-fill deposit which formed by land sliding of steep caldera walls during ignimbrite eruption and deposition. A larger centre, Mount Edgell-Wright Spires, is dominated by coarse-grained debris flow deposits and silicic ignimbrites which, with minor lavas and fine-grained tuffs, form a volcanic succession some 1.5 km thick. Basic intermediate and silicic sills c. 50 m thick intrude the succession. A central gabbro-granite intrusion is interpreted to be a high-level magma chamber of the Mount Edgell volcano.
Holocene deglaciation of the Bunger Hills revealed by 14C measurements on stomach oil deposits in snow petrel colonies
Authors: Verkulich Sergey R. , Hiller Achim
Published: December 2007

Solidified stomach oil deposits in snow petrel colonies in the Antarctic proved to be suitable for 14C dating and provide important palaeobiogeographical and palaeoenvironmental information. Following earlier studies in the Untersee oasis (Central Dronning Maud Land) we present here 14C measurements on comparable deposits from the Bunger Hills (66°10′S, 101°E). The conventional 14C age of the basal layer reflects the occupation age of any particular nesting site and therefore a minimum age for the time when this area became ice-free. According to the 14C results the occupation of the southern part of the Bunger Hills by petrels started about 10000yr ago. The breeding colonies expanded continuously following local ice retreat. The most intensive phases of colonization seem to have been from 8–6 kyr BP and during the past 2 kyr.
F-region ionospheric irregularities over King George Island and Argentine Islands – a comparative study
Authors: Foppiano A.J. , Rodger A.S.
Published: December 2007

Spread-F is caused by the presence of ionospheric electron concentration irregularities of scale-size of order 5 km at F-region altitudes. Estimates of spread-F in the vicinity of the maximum plasma frequency of the Flayer (foF2) have been determined at 15 min intervals from ionograms recorded over a ten day period (1–10 May 1986) both at Marsh (62.2°S, 58.9°W), King George Island, and Faraday (65.2°S, 64.3°W), Argentine Islands. The interval, at low solar activity, includes periods of quiet and disturbed geomagnetic activity. Spread-F is observed on every night at both stations. It is more frequent, slightly more intense and starts earlier at Argentine Islands than at King George Island. On most nights, spread-F ceases about local sunrise at 120 km altitude at both stations. On the days of highest geomagnetic activity, the onset of spread-F is delayed compared with days of lower activity. Spread-F is usually most intense on the night(s) following largest geomagnetic activity level, as measured by the geomagnetic index, Kp. The growth rate of the plasma instability processes causing the ionospheric irregularities is inversely related to electron concentration (foF22), amongst other parameters. Thus the lower foF2 values over Argentine Islands are consistent with more spread-F being observed by the higher latitude observatory. However, no firm relationship between the absolute value of foF2, the horizontal gradient of foF2 between the two observatories, and the onset of spread-F, is found. Thus it has not been possible to determine uniquely the instability process responsible for the formation of the plasma irregularities.
Variability of aerosol extinction of solar radiation in Antarctica
Authors: Radionov V. F.
Published: December 2007

Temporal variations of the aerosol optical depth and transmission coefficient of the atmosphere are considered using data from Mirny Observatory, Antarctica. Year-to-year variability of these parameters is determined mainly by stratospheric aerosol pollution due to volcanic activity. A considerable increase of atmospheric turbidity has been observed since the end of September 1991. This phenomenon seems to be associated with the Mount Pinatubo volcanic eruption.
Long term population changes of fur seals Arctocephalus gazella and Arctocephalus tropicalis on subantarctic (Crozet) and subtropical (St. Paul and Amsterdam) islands and their possible relationship to El Niño Southern Oscillation
Authors: Guinet C. , Jouventin P. , Georges J-Y.
Published: December 2007

The population trend over the last decade for subantarctic fur seals (Arctocephalus tropicalis) on Amsterdam and St. Paul islands and on Possession Island (Crozet Archipelago) and Antarctic fur seals (A. gazella) on Possession Island are analysed. At Amsterdam Island, based on pup counts, the subantarctic fur seal population appears to have stabilized after a period of rapid growth. At Possession Island subantarctic fur seal and Antarctic fur seal, with respective annual growth rates of 19.2 and 17.4%, are reaching the maximum growth rate for the genus Arctocephalus. Annual pup censuses at Possession Island since 1978 indicate important variations from year to year with pup production for A. gazella significantly lower the year after an El Niño Southern Oscillation (ENSO) event, but with no such relationship for A. tropicalis. Several other long term demographic studies of seabirds and marine mammals at different breeding locations in the Southern Ocean indicate that the breeding success of several of these predators appears to be widely affected in years which appear to be related to the ENSO events. To clarify this, it is necessary to analyse in more detail the demographic data obtained for the different subantarctic and Antarctic locations where long term monitoring programmes are conducted.
Freshwater algae (excluding Cyanophyceae) from nine lakes and pools of Hope Bay, Antarctic Peninsula
Authors: Vinocur A. , Izaguirre I.
Published: December 2007

Fortyeight freshwater algae (excluding Cyanophyceae) were identified from nine lakes and pools at Hope Bay (Antarctic Peninsula). The geographic distribution in Antarctica and the ecological characteristics of the sampling sites are given for each taxa. Sixteen of them, new records for Antarctica, are described and illustrated. Among the algal classes treated here, Bacillariophyceae and Chlorophyceae constitute the most diverse groups. Most of the species found have been recorded from Antarctica, and many of them are widespread. Some degree of polymorphism was observed in Bacillariophyceae and Tribophyceae taxa.
The onset of deglaciation in the Larsemann Hills, Eastern Antarctica
Authors: Burgess J.S. , Spate A.P. , Shevlin J.
Published: December 2007

The Larsemann Hills is an ice-free area of over 150 lakes that are not ice covered in summer. Despite being located at 69°30'S the area is not characterized to any extent by expected glacial indicators such as till, moraine or striations. Although the lakes show signs of evaporative lowering of water levels evolution to a saline state has not advanced to any great degree. While some evidence has been advanced to suggest only recent deglaciation (less than 10000yrBP) and large accumulations of ice (200–500m) it is now suggested that the area has not been glaciated during the Wisconsin to the extent previously claimed. The paper reports moss deposits aged 24950 yrBP that are significantly older than those previously reported for the area.
The monitoring of katabatic wind-coastal polynya interaction using AVHRR imagery
Authors: Cotton Jeremy H. , Michael Kelvin J.
Published: December 2007

Coastal polynyas, which form around the Antarctic coast due to persistent katabatic winds, play an important role in enhancing air-sea interaction. This paper discusses how thermal imagery from the Advanced Very High Resolution Radiometer (AVHRR) can be used to track the direction of katabatic winds, and hence facilitate research into air-sea interaction.
A case for structured international research in Antarctic ecology
Authors: Howard-Williams Clive
Published: December 2007

In Antarctica polar conditions of real cold, desiccation and salinity extremes lie away from the sea edge. Here, where there is sufficient moisture for life to be found at all it is invariably dominated by cyanobacteria, sometimes in a profusion unmatched elsewhere in the world. Now that much of the descriptive ecology and physiology is completed where should ecology be going? There are two possibilities: 1) an ecosystem approach to the functioning of Antarctic inland areas; 2) a molecular approach to the genetic controls on survival in cold, saline and desiccated conditions.
Heavy metal contamination in some soils of the McMurdo Sound region, Antarctica
Authors: Claridge G.G.C. , Campbell I.B. , Powell H.K.J. , Amin Z.H. , Balks M.R.
Published: December 2007

Soil samples from eight sites at Marble Point and Pram Point, McMurdo Sound region, contaminated by human activities were examined for heavy metal content, using sequential extraction methods. The redistribution of lead, zinc and copper arising from point sources of these metals was demonstrated. The levels found are not considered to represent serious pollution but do indicate that human activities can change the chemistry of the Antarctic environment in localized areas.
The diets and dietary segregation of sooty albatrosses (Phoebetria spp.) at subantarctic Marion Island
Authors: Cooper John , Klages Norbert T.W.
Published: December 2007

Subantarctic Marion Island is one of the few localities where the congeneric albatrosses Phoebetria fusca and P. palpebrata breed sympatrically. Chicks of both species at Marion Island were induced to regurgitate their stomach contents after being fed. Liquid formed over half the diet by mass. Cephalopods occurred most frequently in both species' diets. In terms of mass, cephalopods formed the larger part of the diet of sooty albatrosses, whereas fish was more important to light-mantled sooty albatrosses. Crustaceans and birds were also recorded for both species. Squid of the families Onychoteuthidae, Histioteuthidae, Chiroteuthidae and Cranchiidae occurred most abundantly in both species. Most squid taken by both albatrosses were of species known to float after death, suggesting that scavenging plays an important role in the species' foraging behaviour. Light-mantled sooty albatrosses consumed more squid restricted to the south of the Antarctic Polar Front than did sooty albatrosses, supporting a trend to latitudinal segregation of the two species while foraging.
The energetic cost of egg production in Antarctic krill (Euphausia superba Dana)
Authors: Nicol Stephen , De La Mare William K. , Stolp Martin
Published: December 2007

A female Antarctic krill loses 34% of its body mass when it lays a batch of eggs. This represents a considerable input of energy which was estimated using a combination of measured mass and energy differences in female krill and from the measured energetic content of ovarian tissue. Large (c. 50 mm) female krill lose 2.9–3.8 kJ each time a batch of eggs is laid. Calculations using this figure indicate that multiple spawning by Antarctic krill in a season would require above average phytoplankton concentrations (> 0.5 μg chl a 1−1) and filtration rates which are close to the maximum reported (> 10 l h−1).
Geochemistry of a fossil hydrothermal system at Barton Peninsula, King George Island
Authors: So Chil-Sup , Yun Seong-Taek , Park Maeng-Eon
Published: December 2007

A fossil hydrothermal system on Barton Peninsula, King George Island, Antarctica, formed a series of lead-zinc- and pyrite + native sulphur-bearing epithermal quartz ± calcite veins, filling fault-related fractures in hydrothermally altered volcanic rocks of Eocene age. The lead-zinc veins occur within argillic hydrothermal alteration zones, whereas the pyrite + native sulphur veins are found within advanced argillic alteration zones. Fluid inclusion data indicate that the vein formation occurred at temperatures between about 125° and 370°C (sphalerite deposition formed at 123–211°C) from fluids with salinities of 0.5–4.6 wt.% eq. NaCl. Equilibrium thermodynamic interpretation of mineral assemblages indicates that the deposition of native sulphur in the upper and central portions of the hydrothermal system was a result of the mixing of condensates of ascending magmatic gases and meteoric water giving rise to fluids which had lower pH (<3.5) and higher fugacities of oxygen and sulphur than the lead-zinc-depositing fluids at depth. The δ34S values of sulphide minerals from the lead-zinc veins (δ34S = −4.6 to 0.7‰) are much higher than the values of pyrite and native sulphur from the pyrite + native sulphur veins (δ34S = −12.9 to −20.1‰). This indicates that the fluids depositing native sulphur had higher sulphate/H2S ratios under higher fo2 conditions. Sulphur isotope compositions indicate an igneous source of sulphur with a δ34SΣS value near 0‰, probably the Noel Hill Granodiorite. Measured and calculated δ18O and δD values of the epithermal fluids (δ18Owater = −6.0 to 2.7‰, δDwater = −87 to −75‰) indicate that local meteoric water played an important role for formation of lead-zinc and native sulphur-bearing quartz veins.
The age of the Ritscherflya Supergroup and Borgmassivet Intrusions, Dronning Maud Land, Antarctica
Authors: Moyes A.B. , Krynauw J.R. , Barton J.M.
Published: December 2007

The Ahlmannryggen-Borgmassivet area of western Dronning Maud Land comprises a relatively undeformed, unmetamorphosed sequence of sedimentary-volcanogenic rocks, the Ritscherflya Supergroup, intruded by a suite of continental tholeiites, the Borgmassivet Intrusions. New Rb-Sr and Sm-Nd whole rock data from the Högfonna Formation at Grunehogna indicate a depositional age of ≈1080 Ma, the first reported direct dating of any member of the Ritscherflya Supergroup. These rocks are interpreted as a molasse-type deposit following the Kibaran orogeny at 1200–1100 Ma, and correlation is made with the Umkondo and Koras groups of southern Africa. The Ritscherflya Supergroup is intruded by the Grunehogna and Kullen sills; the ≈1000 Ma Grunehogna sill intruded unconsolidated sediments, causing partial melting of the sediments. Rb-Sr data from the Kullen sill yield an age of 1429 Ma, clearly inconsistent with these data. Combined Sr and Nd data are compatible with crustal contamination of this sill, producing a Rb-Sr pseudo-isochron with no geological age significance. By comparison with other outcrops of the Borgmassivet Intrusions at Robertskollen and Annandagstoppane, it is concluded that contamination and pseudo-isochrons may be responsible for the wide range in reported ages older than 1000 Ma. Thus the intrusive age of the Borgmassivet Intrusions is concluded to be ≈1000 Ma old. Nd model age data indicate that all rock types were ultimately derived from material separated from a depleted mantle source at ≈2200 Ma.
Lithostratigraphy of volcanic and sedimentary sequences in central Livingston Island, South Shetland Islands
Authors: Smellie J.L. , Liesa M. , Muñoz J.A. , Sàbat F. , Pallàs R. , Willan R.C.R.
Published: December 2007

Livingston Island contains several, distinctive sedimentary and volcanic sequences, which document the history and evolution of an important part of the South Shetland Islands magmatic arc. The turbiditic, late Palaeozoic–early Mesozoic Miers Bluff Formation (MBF) is divided into the Johnsons Dock and Napier Peak members, which may represent sedimentation in upper and lower mid-fan settings, respectively, prior to pre-late Jurassic polyphase deformation (dominated by open folding). The Moores Peak breccias are formed largely of coarse clasts reworked from the MBF. The breccias may be part of the MBF, a separate unit, or part of the Mount Bowles Formation. The structural position is similar to the terrigenous Lower Jurassic Botany Bay Group in the northern Antarctic Peninsula, but the precise stratigraphical relationships and age are unknown. The (?) Cretaceous Mount Bowles Formation is largely volcanic. Detritus in the volcaniclastic rocks was formed mainly during phreatomagmatic eruptions and redeposited by debris flows (lahars), whereas rare sandstone interbeds are arkosic and reflect a local provenance rooted in the MBF. The Pleistocene–Recent Inott Point Formation is dominated by multiple, basaltic tuff cone relicts in which distinctive vent and flank sequences are recognized. The geographical distribution of the Edinburgh Hill Formation is closely associated with faults, which may have been reactivated as dip-slip structures during Late Cenozoic extension (arc splitting).
Valuing Antarctic science
Authors: Walton D W H
Published: December 2007

Looking backwards should always be instructive. The lessons that history can teach us are, of course, fundamental to progress in science but what about its management?
Hydrocarbon content of an Antarctic infaunal bivalve—historical record or life cycle changes?
Authors: Cripps G.C. , Priddle J.
Published: December 2007

The Antarctic bivalve Yoldia eightsi (Couthouy) has been assessed as a monitor species in the vicinity of a research station at Signy Island. For animals of comparable age n-alkane loading was highest at the site closest to the station. The character of the n-alkane pool of Yoldia varied with distance from the station and also differed from that of the sediment. The polycyclic aromatic hydrocarbon (PAH) loading was highest 250 m from the station. Loading of n-alkanes and PAH varied through the year; the lowest levels of n-alkanes were in October and the highest in April. The maximum for PAH was in October. Hydrocarbons increased with age for animals from five to 50 years old; 100–2000 ng animal−1 for n-alkanes and 1–21 ng animal−1 for PAH. Tissue concentrations decreased with age; 6000–500 μg kg1 for n-alkanes and 25–5 μg kg−1 for PAH. Several biogenic branched chain alkenes were also present; one C25.3 isomer was predominant at concentrations up to 290 μg kg−1 in mature animals (40% of the aliphatic fraction). Accumulation was not constant with age and concentrations reflected both anthropogenic and biogenic hydrocarbons in the marine environment. Seasonal variation in PAH load suggested the major proportion of accumulation over the year was only temporary. Yoldia eightsi were not suitable to monitor low level contamination such as that at Signy Island and past incidents were not resolved from the background input.
Magnetic investigations of the junction between Wilson and Bowers terranes (northern Victoria Land, Antarctica)
Authors: Bozzo Emanuele , Caneva Giorgio , Capponi Giovanni , Colla Alessandro
Published: December 2007

A magnetic survey was carried out in the area between Lady Newnes Bay and Evans Névé (northern Victoria Land), to ascertain whether the contact between the Wilson and the Bowers terranes could be identified remotely. The survey consisted of three ground and 12 helicopter-borne profiles. The method was calibrated on the southernmost profiles, which cover a well-exposed section of the contact between the Wilson and Bowers terranes. The northern profiles were located in an area where the contact is poorly constrained by outcrops, so that it could be tested whether the junction displays a magnetic signature. The magnetic data and the 2.5-D modeling of three selected profiles indicate that no easily recognizable magnetic signature defines this contact. The main features of the area are magnetic anomalies probably controlled by the “Meander Intrusives” and the McMurdo volcanic rocks, both characterized by high susceptibility values. If an anomaly related to the contact exists, then it is probably masked by these stronger anomalies.
Seismic investigation of the Larsen Ice Shelf, Antarctica: in search of the Larsen Basin
Authors: Jarvis E.P. , King E.C.
Published: December 2007

Seismic reflection surveys were carried out over the Larsen Ice Shelf to examine the extent of the observed sedimentary sequences of the Larsen Basin as suggested by aeromagnetic and gravity data. The surveys were carried out with a small team of six, working from Skidoo motor toboggans and Nansen sledges. Charges of up to 8 kg were fired in hot-water drilled holes up to 9 m deep and 6 sec records made by a 48 channel TI DFS V system with a 4 ms sample interval. By towing a 2.4 km cable behind a Skidoo it was possible to obtain 2.4 km of 24 fold data per day. The reflection data were supplemented by shallow refraction surveys using a 12 channel Nimbus seismograph and by a 12 km expanding spread experiment. The refraction data gave velocities of 1305 ± 20 m s−1 for surface snow and 3154 m s−1 for the top 100 m of shelf ice. The 24 km of reflection data showed high seismic velocities with weak shallow reflectors, characteristics which are quite different from the known basin fill on James Ross Island. It is concluded that the surveys were done outside the basin and that the depth to basement estimates made from the aeromagnetic data do not provide a reliable guide to the extent of the basin.
A case study of a midtropospheric subsynoptic-scale cyclone that developed over the Ross Sea and Ross Ice Shelf of Antarctica
Authors: Carrasco Jorge F. , Bromwich David H.
Published: December 2007

Satellite imagery, synoptic-scale analyses and automatic weather station data were used to study a subsynoptic-scale cyclone that developed over the Ross Sea and Ross Ice Shelf areas of Antarctica. A pre-existing subsynoptic-scale midtropospheric cyclone descended from southern Victoria Land into the semi-permanent baroclinic environment over the south-western corner of the Ross Sea. The subsynoptic-scale cyclone then developed into a frontal system travelling south-eastward over the Ross Ice Shelf and decayed five days later over Marie Byrd Land. It is concluded that stretching of the subsynoptic-scale low, while descending over 2000 m from the high plateau down to sea level, increased its cyclonic vorticity via conservation of potential vorticity. This, along with a cold katabatic outbreak into the northern part of the circulation, provided the mechanisms for its initial development. Subsequently, cold boundary-layer air over the Ross Ice Shelf spiralled into the subsynoptic-scale cyclone supporting its further development. An upper-level synoptic-scale cyclone that approached the area provided the upper-level support for its ESE displacement and development.