Magnetic, gravity and bathymetric data from Marguerite Bay are used to study the relationships between oceanic and continental tectonic evolution in the arc and fore-arc of the Antarctic Peninsula. The data are used to redefine the crustal structure of the Marguerite Bay area, providing evidence for a northward continuation of George VI Sound and the Alexander Island Mesozoic accretionary prism almost to the continental shelf edge. A two-stage model of extension, associated with changes in spreading rates and approaching ridge segments, is proposed to explain the crustal structure and Cenozoic tectonic evolution of the area. The model involves the opening of George VI trough by Tertiary dextral transtension, followed by oblique extension in an area bounded by the Tula and Adelaide fracture zones. This interpretation confirms previous work linking oceanic tectonic processes with continental arc and fore-arc structural development.

Four cores from the bottom sediments of Lake Esmeralda, Vega Island, Antarctica (60°48'S, 57°37'W) were studied. Analysis of rock magnetics indicates that the main carriers of magnetization are ferrimagnetic minerals, predominantly pseudo-single-domain (titano-) magnetite with a small proportion of paramagnetic and antiferromagnetic minerals. The magnetic grain size of the samples is in the range of 1–5 μm and the variation of the interparametric ratios is less than one order of magnitude. Demagnetization of the natural remanent magnetization shows a stable remanent magnetization in most of the samples. Thus, the samples fulfil the necessary conditions to calculate relative palaeointensity (RPI) and the curves obtained correlated with global models enabling dating of the cores. The 250 cm of sediment recovered spans the last 10 200 yr bp. Finally, some samples with high organic matter content were dated by accelerator mass spectrometry 14C. By comparison with the age defined by the RPI curves, a reservoir effect of c. 5200 years is suggested for this region of Vega Island.

Glacial and post-glacial shelf sedimentation near the Larsen C and former Larsen B ice shelves is compared to records from ice shelves farther north, which underwent mid-Holocene retreat. A core from Larsen C comprises a lower unit of deformation till, overlain by thick mud interpreted as water lain from suspension under the ice shelf. Iceberg-rafted debris occurs only in the top 50 cm, suggesting that prior to that layer's deposition, the ice shelf had not receded past the site since the last deglaciation. Subsequently the site appears to have been seasonally ice free, and the ice shelf has retreated further and is now 15 km landward of the site. A core from Larsen B also consists of a lower unit, interpreted as sub-glacial lodgement till. The overlying mud is thinner, more poorly sorted, with evidence of powerful winnowing of sediments suggesting strong currents. The absence of iceberg-rafted debris implies that this site was covered by an ice shelf continuously from the last deglaciation until its collapse in 2002. Strong currents could have facilitated basal erosion, contributing to its collapse. The Larsen C shelf is also thinning and historical records show retreat in the last hundred years. With continued rising temperatures, Larsen C may eventually retreat to a point at which it collapses.

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.

The oldest record of the hexanchiform sharks from the Southern Hemisphere and the second chondrichthyan report known from Carboniferous to Early Cretaceous beds in Antarctica is given. The material was collected in late Aptian rocks of the Kotick Point Formation outcropping in the western part of James Ross Island, near Antarctic Peninsula. It consists of an isolated tooth assignable to a hexanchiform different from the other described genera. The tooth shows putative plesiomorphic cusp (few cusps, no serrations) and apomorphic root characters (relatively deep, quadrangular). It could be related to a species close to the origin of Hexanchus (unknown in beds older than Cenomanian).

Tephra in glacial ice provide a method to obtain a depth vs chronology correlation within an ice core. Currently, core sections containing particulate must be sacrificially analysed to determine the nature of the particulate (e.g. aerosol, micrometeor, volcanic ash), and, in the case of volcanic ash, the event tied to the particle. Characterization through melting and chemical analysis precludes, de facto, its use for other purposes. A non-destructive technique to characterize particulates in ice cores prior to sectioning the samples, e.g. optical interrogation, would be useful, especially if chemical information specific to particular volcanic eruptions could be gleaned from such an analysis. We investigated the use of micro-Raman spectroscopy for this purpose. Spectra were obtained on samples of Antarctic blue ice tephra from different sources along with a reference ash sample of New Mexico Bandelier Tuff. Vitreous and crystalline particles in the samples were characterized. For vitreous material, a detailed analysis of the Raman-active vibrational bands of the glass structure was found to have the potential of being a unique identifier of the source of the glass, however, additional library development is needed for implementation.

Downward fluxes of particulate matter were investigated in the polynya of Terra Nova Bay (western Ross Sea) from February 1995 to December 1997. Biogenic silica made up the bulk of the sinking matter, reaching a maximum of 85% of the total flux in both the shallow and deep traps. Organic carbon accounted for 2.1 to 23.5% of the sample mass in the shallow trap and 2.8 to 7.2% in the deep trap. Biogenic silica and organic carbon peaks occurred in February–March over the three years and were always coupled in the top trap. Carbonate fluxes showed an uneven temporal trend, were low near the seafloor and contributed up to 69.8% of the material collected by the shallow trap. Vertical fluxes in the polynya showed large seasonal and interannual variability. Differences in primary productivity, ice cover dynamics and current energies accounted for the interannual changes in the flux of materials to the subsurface trap. Advection from sites a few hundred kilometres apart was the most likely reason for the decoupling between shallow and deep fluxes after October 1996. The seasonal pattern of downward fluxes was essentially linked to the seasonal cycle of primary production and spring–summer variations largely resulted from the composition of the phytoplankton assemblage in the overlying water column. The export of phototrophically produced materials to depth was low in late spring–early summer, at the time when Phaeocystis and small flagellates were the predominant autotrophs and the microbial food web prevailed over herbivorous feeding. Enhanced fluxes were linked to the predominance of large diatoms above the trap, in late summer. Temporal dynamics in this polynya were delayed by approximately one month as compared to the southernmost Ross Sea polynya, but showed the same temporal pattern: the time lag between production and accumulation of biogenic materials in the upper water column was a few weeks, while the delay in export from the surface layer relative to the maximum accumulation of biomass was approximately one month.

Emperor penguins require stable fast ice, sea ice anchored to land or ice shelves, on which to lay eggs and raise chicks. As the climate warms, changes in sea ice are expected to lead to substantial declines at many emperor penguin colonies. The most southerly colonies have been predicted to remain buffered from the direct impacts of warming for much longer. Here, we report on the unusually early breakup of fast ice at one of the two southernmost emperor penguin colonies, Cape Crozier (77.5°S), in 2018, an event that may have resulted in a substantial loss of chicks from the colony. Fast ice dynamics can be highly variable and dependent on local conditions, but earlier fast ice breakup, influenced by increasing wind speed, as well as higher surface air temperatures, is a likely outcome of climate change. What we observed at Cape Crozier in 2018 highlights the vulnerability of this species to untimely storm events and could be an early sign that even this high-latitude colony is not immune to the effects of warming. Long-term monitoring will be key to understanding this species' response to climate change and altered sea ice dynamics.

Field observations involving landform evaluation and the physical characterization of sediments, combined with a detailed analysis of the spatial distribution of bedrock and sediment geochemical patterns, suggests a limit to the glacial transport half-distance of c. 3 km in Vestfold Hills. Four morphologically distinct glacial deposits were sampled (small debris ridges, large debris ridges, debris drapes and valley fills) on the basis of field geometry. These landforms were subsequently distinguished by grain size, mineralogy and geochemistry. Since there are no nunataks south of Vestfold Hills, all debris is derived subglacially and sedimentological differences are attributed to the physical weathering of preglacial surfaces in Vestfold Hills and fluvial winnowing during deposition. Given that thrust geometries may occur in large debris ridges, glacial transport distances were short, and fluvial sorting of sediments was an important mechanism, reconstructions of glacial histories based on the stratigraphy of deposits in Vestfold Hills should be made with caution.

Polinices marambioensis is a naticid gastropod which is the most common constituent in fossil accumulations in the upper section of the Cucullaea I Allomember (Middle Eocene) of the La Meseta Formation in James Ross Basin, Antarctic Peninsula. This species was an important predator of infaunal bivalves and gastropods, including other naticids. The aim of this work was to assess the pattern of predation and cannibalistic behaviour of P. marambioensis. A total of 2648 specimens of P. marambioensis were examined for drill holes, which were assigned to Oichnus paraboloides. Drilling frequency data were measured as a proxy for predation intensity and statistical analyses were performed. Further, the site of each drill hole was established according to the morphological features of the shell on each specimen to assess possible preference of predators for the site of perforation. Results suggest that P. marambioensis is an efficient cannibalistic predator for a specific size range of prey (8–22 mm), and drill holes are distributed preferentially in two specific sectors of their shells. This selective cannibalistic prey behaviour in P. marambioensis affected not only the dynamics of their populations but the ecological structure of the community in which they lived.

Habitats under ice shelves are minimally explored, primarily because of technological limitations. These areas are separated from photosynthetic primary productivity by thick ice and distance to open water. Nevertheless, a diverse macrofaunal benthic community was discovered at 188 m depth, 80 km back from the edge of the McMurdo Ice Shelf. The general habitat was fine sediment with occasional dropstones, and dominant taxa were polychaetes and brittle stars, with alcyonacean soft corals and anemones on hard substrates. Gelatinous animals were abundant near the seafloor, and possibly part of a food web that supports the benthic community.

Ibises are a group of medium- to large-sized, mainly wading birds in the family Threskiornithidae (Aves: Ciconiiformes; see also discussion in Mayr 2002). They are known from all the continents except Antarctica, though one species breeds as far south as Tierra del Fuego (del Hoyo et al. 1992, p. 499). The oldest fossil bones (including skull elements) attributed to ibises are those of Rhynchaeites messelensis Wittich, 1898 from the Middle Eocene of Messel, Germany (Peters 1983, Mayr 2002). Another supposed member of this group is the Pondaung bird from the late Middle Eocene of Myanmar (formerly Burma) represented solely by an incomplete tibiotarsus (Stidham et al. 2005, fig. 2). The taxonomic position of Minggangia changgouensis Hou, 1982 from the Late Eocene of China (Hou 1982) was recently questioned by Stidham et al. (2005, p. 183). Here, we present a partial bill from the Eocene La Meseta Formation (Seymour Island, Antarctica) which most closely resembles that of ibises.

Antarctic snow samples collected from the Wilkins Runway, c. 50 km inland from the Windmill Islands, East Antarctica, contain aeolian-derived diatoms. The diatom assemblage preserved is exclusively of marine origin. As diatoms are excellent indicators of source conditions, we are able to confirm that an unusual weather event, with anomalous north-westerly winds blowing at around 10 m s-1, resulted in the deposition of coastal marine species at the Wilkins Runway. The composition of the floral assemblage collected indicate that the parent water mass was from a coastal marine region undergoing typical Antarctic summer conditions with periods of both consolidated sea ice and open water. On inspection of available satellite imagery, these conditions were found upwind of the deposition site. This study provides a methodology for diatoms found within ice cores to be identified and the source region to be determined. It also provides evidence for a large-scale aeolian deposition of marine diatoms to an ice sheet, which may have implications for the interpretation of controversial marine diatoms found in sediments that have been used as evidence for the retreat of the East Antarctic Ice Sheet.

An individual-based model is presented which describes the spatial and temporal evolution of phytoplankton growth in terms of a Lagrangian ensemble of cells affected by various physical and biological forcing factors. The motion of cells develops according to a turbulent velocity field which simulates the Antarctic mixed layer during the summer. The cell growth is a function of the irradiance regime, nutrient availability and the vertical position of the individual with respect to the other cells (in order to evaluate the self-shading effect). The values of photosynthetic parameters used to simulate the photophysiological response of the organisms are derived from measurements collected in the Ross Sea. In contrast to previous individual-based descriptions, all the physical and biological processes involved are explicitly reproduced in their dynamical features. Coupling different mixing levels with photoacclimation strategies leads to a wide range of photophysiological responses which underline the role of individual physiological histories in determining the growth of the population as a whole. Simulated photosynthetic parameters, chlorophyll a concentrations and integrated primary production correspond closely to in situ data and confirm that photoacclimation to low irradiance and strong mixing regimes may be considered as crucial factors in the photosynthetic performance of Antarctic phytoplankton.

Lipid biomarkers are potential tools for identifying the sources, diagenesis and reactivity of organic matter (OM) in marine systems, including in Antarctica where the particular environmental characteristics have motivated several studies of organic markers. Sedimentary sterol distributions were determined in two sediment cores (PGI-1 and PGI-2) collected from the marine environment around Penguin Island, Antarctica, during the 2007–08 summer. The cores were sectioned at 1 cm intervals and the sterols were analysed using gas chromatography with flame ionization detection. The results indicate that the sterols were subjected to decades of degradation and transformation with depth in both cores. However, an expected progressive conversion of stenols to stanols (evaluated by 5α-stanols/Δ5-stenols ratio) within the deepest sediment layers was not clear, suggesting low degradation rates. In PGI-1, the deposition of large quantities of penguin guano affected the distribution of sterols and, consequently, primary production was favoured by the ornithogenic soil input. The results contribute to the understanding of the current processes associated with primary sources and transformation of OM in this important region of the Antarctic environment.

Ecosystem engineers such as the Antarctic scallop (Adamussium colbecki) shape marine communities. Thus, changes to their lifespan and growth could have far-reaching effects on other organisms. Sea ice is critical to polar marine ecosystem function, attenuating light and thereby affecting nutrient availability. Sea ice could therefore impact longevity and growth in polar bivalves unless temperature is the overriding factor. Here, we compare the longevity and growth of A. colbecki from two Antarctic sites: Explorers Cove and Bay of Sails, which differ by sea-ice cover, but share similar seawater temperatures, the coldest on Earth (-1.97°C). We hypothesize that scallops from the multiannual sea-ice site will have slower growth and greater longevity. We found maximum ages to be similar at both sites (18–19 years). Growth was slower, with higher inter-individual variability, under multiannual sea ice than under annual sea ice, which we attribute to patchier nutrient availability under multiannual sea ice. Contrary to expectations, A. colbecki growth, but not longevity, is affected by sea-ice duration when temperatures are comparable. Recent dramatic reductions in Antarctic sea ice and predicted temperature increases may irrevocably alter the life histories of this ecosystem engineer and other polar organisms.

Nineteen specimens of the rare dragonfish Vomeridens infuscipinnis were evaluated for meristic counts, morphometric measurements, vomerine teeth and the supratemporal canal, anatomical and histological observations of bone, cartilage and lipid, diet, and reproductive status. Seven individuals were measured for buoyancy. All specimens had small vomerine teeth that varied in number. There was also variability in the arrangement of the supratemporal pores and canals. Vomeridens possess a body with little bone and considerable amounts of cartilage and lipid. A mean percentage buoyancy of 1.61% indicated that Vomeridens is nearly neutrally buoyant. Inferences from measurements of buoyancy and from morphological data suggest that Vomeridens lives in an epibenthic water column habitat at 400–900 m. Facilitated by its reduced body density, Vomeridens are likely to forage in the water column by hovering above the substrate. The stomach contents consisted of krill (Euphausia superba), some as large as 46–50 mm.The absolute and relative fecundity in seven female was 1576–2296 oocytes (mean 1889) and 21.3–28.9 oocytes g-1 body weight (mean 25.3), respectively. The reproductive effort in terms of egg diameter, GSI, and absolute and relative fecundity is similar to that for other bathydraconids.

Understanding the success factors underlying each step in the process of biological invasion provides a robust foundation upon which to develop appropriate biosecurity measures. Insights into the processes occurring can be gained through clarifying the circumstances applying to non-native species that have arrived, established and, in some cases, successfully spread in terrestrial Antarctica. To date, examples include a small number of vascular plants and a greater diversity of invertebrates (including Diptera, Collembola, Acari and Oligochaeta), which share features of pre-adaptation to the environmental stresses experienced in Antarctica. In this synthesis, we examine multiple classic invasion science hypotheses that are widely considered to have relevance in invasion ecology and assess their utility in understanding the different invasion histories so far documented in the continent. All of these existing hypotheses appear relevant to some degree in explaining invasion processes in Antarctica. They are also relevant in understanding failed invasions and identifying barriers to invasion. However, the limited number of cases currently available constrains the possibility of establishing patterns and processes. To conclude, we discuss several new and emerging confirmatory methods as relevant tools to test and compare these hypotheses given the availability of appropriate sample sizes in the future.

Pony Lake, at Cape Royds, Antarctica, is a shallow, eutrophic, coastal lake that freezes solid in the winter. Changes in Pony Lake's physicochemical parameters and microbial community were studied during the transition from ice to open water. Due to rising water temperatures, the progressive melt of the ice column and the gradual mixing of basal brines into the remaining water column, Pony Lake evolved physically and chemically over the course of the summer, thereby affecting the microbial community composition. Temperature, pH, conductivity, nutrients and major ion concentrations reached their maximum in January. Pony Lake was colonized by bacteria, viruses, phytoflagellates, ciliates, and a small number of rotifers. Primary and bacterial production were highest in mid-December (2.66 mg C l-1 d-1 and 30.5 μg C l-1 d-1, respectively). A 16S rRNA gene analysis of the bacterioplankton revealed 34 unique sequences dominated by members of the β- and γ-proteobacteria lineages. Cluster analyses on denaturing gradient gel electrophoresis (DGGE) banding patterns and community structure indicated a shift in the dominant members of the microbial community during the transition from winter ice, to early, and late summer lakewater. Our data demonstrate that temporal changes in physicochemical parameters during the summer months determine community dynamics and mediate changes in microbial species composition.

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.