first_imgThe bibliography lists 166 references on the paleontology of Lesser Antarctica and the Scotia Ridge. It aims to identify all the paleontological discoveries made and to list all the major works on the subject. It is selective to the extent that many review papers are omitted if they add nothing new to previous literature. Conversely, essentially non-paleontological papers are noted if they contain an important item of paleontological data or comment. It runs from 1833 to 1975 and is presented in two parts: a list of papers in author order with a summary of each and a complete list of the species described, and a systematic index further subdivided by stratigraphical age.last_img read more

first_imgInvestigation of the seasonal changes in composition of an immature Antarctic fellfield cyanobacterial/microalgal community has demonstrated a repeated periodicity. The community consisted of only 14 species. Early spring growth of filamentous chlorophytes under snow and ice was followed by summer dominance of the community by cyanobacteria, particularly Phormidium autumnale. Limitation of the chlorophyte populations appeared to be a result of either dehydration of the soil or increased irradiance. The population maximum of the cyanobacteria occurred in mid-summer, although there were no obvious reasons for the cessation of growth at this time, and declined rapidly in late summer. Regrowth of the community occurred from very small inocula each spring, most of the biomass having been lost during late summer or during the washout associated with the spring thaw. This regrowth demonstrates the potential for the population to establish an immature fellfield community very rapidly foliowing exposure by glacial retreat or physical disturbance.last_img read more

first_imgLead concentrations from an Antarctic snow pit show the pattern of Pb reaching the Antarctic atmosphere over the last 70 years. Between 1920 and 1950, the Pb concentration shows significant variations around a mean of about 2.5 ng kg−1. Between 1950 and 1980, there is a clear increase to 6 ng kg−1, with an apparent reduction after that. A few high concentrations in the late 1970s are probably due to local contamination from aircraft using leaded gasoline (petrol). Excluding these anomalously high values, the chronological pattern in lead concentrations can be reconciled with estimates of emissions from vehicles and metal production processes in the southern hemisphere.last_img read more

first_imgThe hypothesis that rates of carbon exchange and recovery following dehydration by Antarctic bryophytes are related to habitat water availability was investigated. Carbon fixation was measured using an infra-red gas analysis system. As the water content of the bryophytes was reduced, respiration rates fell less quickly than those for gross photosynthesis. As a result, net photosynthesis moved from positive to negative, before tending to zero. Xeric species maintained a greater percentage of their photosynthetic capacity at reduced water contents than hydric species, although this trend was not reflected in terms of absolute carbon fixation. Comparison of the experimental observations with measurements of field water contents suggested that water contents of hydric and mesic species remained above those required to maintain maximal rates of photosynthesis through most of the growing season, whereas photosynthesis by xeric species was often water-limited. Recovery following rehydration demonstrated the typical bryophyte resaturation respiration burst and slower recovery of photosynthesis. Times taken to reach the compensation point were generally longer than those reported for non-polar species. Recovery was faster in xeric than in hydric species, although there was no correlation with the final degree of recovery. The results partially support the hypothesis tested, and provide a basis for the inclusion of water content and desiccation events in models of Antarctic bryophyte productivity.last_img read more

first_imgEcophysiological features, including survival and recovery from freezing and determination of the freezable water content, are reported for a cold-adapted cockroach Celatoblatta quinquemaculata Johns 1966 (Dictyoptera, Blattidae) inhabiting alpine communities at altitudes greater than 1300 m a.s.l. in mountains of Central Otago, New Zealand. Nymphs ranged from 15 to 51 mg live weight of which 67% was water. Cockroaches had a mean supercooling point temperature of −5.4 ± 0.1°C; with recovery from freezing close to this temperature being rapid, but no recovery was observed when frozen at −9 to −10°C. The duration of exposure to freezing conditions and the time allowed for recovery (24–96 h) both influenced individual recovery and subsequent survival. Comparison of supercooling point data and survival shows that this species possesses a few degrees of freeze tolerance, and individuals have been found frozen in the field when subzero temperatures occur. Differential scanning calorimetry showed ≈ 74% of body water froze during cooling and between 24 and 27% of total body water was osmotically inactive (unfreezable under the experimental conditions). Carbohydrates, other than glucose at 7.5μg/mg fresh weight, were in low concentrations in the body fluids, suggesting little cryoprotection. No thermal hysteresis from antifreeze protein activity was detected in haemolymph samples using calorimetric techniques. It is suggested that slow environmental cooling rates, together with high individual supercooling points, confer a small amount of freezing tolerance on this species enabling it to survive low winter temperatures. This has allowed it to colonize and maintain populations in alpine habitats > 1300 m a.s.1. in New Zealand.last_img read more

first_imgThe existence of seasonal changes in concentrations of water-soluble carbohydrates in arthropods (both freezing-tolerant and intolerant species) from Signy Island was demonstrated. Seasonal patterns of variation, imposed by seasonality of the maritime Antarctic environment, in the production of soluble carbohydrates in response to low temperatures and/or dehydration for a range of terrestrial arthropods were confirmed. The freshwater copepod Pseudoboeckellapoppei exhibited much lower levels of soluble carbohydrates, with glycerol as the main component, and smaller seasonal fluctuations relative to the four terrestrial species. The two Antarctic mites (Alaskozetes antarcticus and Gamasellus racovitzai) accumulated glycerol (as a single-component cryoprotective system), in agreement with previous work reporting increased glycerol levels and lowering of the supercooling point in A. antarcticus. In the case of G. racovitzai, increased levels of glycerol may function in a different manner. The larval dipteran Eretmoptera murphyi and the collembolan Cryptopygus antarcticus have complex multi-component cryoprotective systems involving trehalose that may be related to low temperature acclimation and dehydration. These findings are discussed in relation to published work on single and multiple cryoprotective systems, supercooling points and the involvement of dehydration as a complementary stress in overwintering insects.last_img read more

first_imgIn this paper we first summarise major findings of recent atmospheric studies of nitrogen and sulphur species present in the boundary layer of coastal Antarctic regions. We then discuss the implications of such atmospheric data for the interpretation of nitrate, ammonium, methanesulphonate and sulphate records in deep ice cores extracted from central Antarctica in terms of past atmospheric chemistry changes.last_img

first_imgThe mega-epibenthos of two different geographic areas, the Antarctic Peninsula and the high Antarctic (eastern Weddell Sea), were investigated using underwater video. The distribution of the marine fauna at shallow depths between 55 and 160 m in these two areas was investigated to determine whether there are any zoogeographic differences at the community level. A total of 237 taxa represented by 85,538 individuals was identified. Multivariate analyses revealed significant faunal differences between northern Marguerite Bay (western Antarctic Peninsula) and the stations from the Weddell Sea, Atka Bay and Four-Seasons Bank. Echinoderms, especially ophiuroids, dominated Marguerite Bay, bryozoans and ascidians were abundant at Atka Bay, and hydroids and gorgonians were well represented at Four-Seasons Bank. These clear differences can mainly be explained by the influence of local environmental conditions that are probably the primary feature responsible in shaping the Antarctic shallow-water epifauna and not an intensive exchange with larger depths or a limited dispersion due to scarce and isolated shallow areas. In addition, modes of reproduction and characteristics of the early life history (e.g. brooding, viviparity or budding) of key taxa may also shape patterns of species distribution in shallow benthic Antarctic communities.last_img read more

first_imgWith proposals that micro-miniaturised Raman spectrometers could soon be part of a suite of analytical instrumentation on the surface of Mars, it is critically important to examine the spectral information that could be forthcoming from attempts to determine key molecular biosignatures under the hostile conditions of extra-terrestrial planetary exploration. Current approaches include the analysis of genuine martian geological material in the form of the SNC class meteorites, the formulation of simulated martian regoliths and the examination of putative martian terrestrial analogues; the latter provide the basis of this paper in the form of Antarctic extremophile habitats. In particular, specimens of epilithic, chasmolithic and endolithic lichen and cyanobacterial colonies sampled along a progressively worsening transect towards a “limits of life” situation, beyond which survival of organisms becomes impossible, provide what is arguably the best terrestrial proving-ground for prototype Raman spectrometers for martian exploration. Here, we report the results of experiments on these extant Antarctic extremophile colonies using a range of Raman excitation wavelengths and experimental conditions and also include a compilation of molecular spectral biosignatures, which may be considered as a suitable database for recognition of bioorganic modification of geological strata.last_img read more

first_imgIn August 2010, a 253 km2 ice island calved from the floating glacial tongue of Petermann Glacier in Northwest Greenland. Petermann Ice Island (PII)-B, a large fragment of this original ice island, is the most intensively observed ice island in recent decades. We chronicle PII-B’s deterioration over four years while it drifted more than 2,400 km south along Canada’s eastern Arctic coast, investigate the ice island’s interactions with surrounding ocean waters, and report on its substantial seafloor scour. Three-dimensional sidewall scans of PII-B taken while it was grounded 130 km southeast of Clyde River, Nunavut, show that prolonged wave erosion at the waterline during sea ice-free conditions created a large underwater protrusion. The resulting buoyancy forces caused a 100 m × 1 km calving event, which was recorded by two GPS units. A field team observed surface waters to be warmer and fresher on the side of PII-B where the calving occurred, which perhaps led to the accelerated growth of the protrusion. PII-B produced up to 3.8 gigatonnes (3.8 × 1012 kg) of ice fragments, known hazards to the shipping and resource extraction industries, monitored over 22 months. Ice island seafloor scour, such as a 850 m long, 3 m deep trench at PII-B’s grounding location, also puts subseafloor installations (e.g., pipelines) at risk. This long-term and interdisciplinary assessment of PII-B is the first such study in the eastern Canadian Arctic and captures the multiple implications and risks that ice islands impose on the natural environment and offshore industries.last_img read more