The growth and reproduction of Antarctic flowering plants

first_imgThe presence of flowering plants within the Antarctic botanical zone (as defined by Greene 1964 a) has been known for nearly 150 years. The first to be discovered was a small, wiry grass of tufted or mat-forming habit, now called Deschampsia antarctica Desv., while the second proved to be a small cushion-forming pearlwort—Colobanthus crassifolius (D’Urv.) Hook. f. Skottsberg (1954) provided the first maps of their Antarctic distribution and summarized the small amount of information available about their reproduction and behaviour. As known at present, the two species extend from Neny Island (68° 12′ S, 67° 02′ W) in Marguerite Bay, northwards along the west coast of the Antarctic Peninsula to many islands of the Scotia Ridge (figure 59). Elsewhere D. antarctica reaches as far north as ca. 34° S in South America and eastwards to some of the Sub-Antarctic islands of the south Indian Ocean. The world distribution of C. crassifolius is uncertain owing to taxonomic confusion about the relationship of plants in New Zealand with those in South America, as well as doubts about the homogeneity of the taxon in the latter area. If the species in South America is considered in its widest sense, i.e. as embracing all the ‘grassyleaved pearl worts’, then C. crassifolius sensu lato extends much farther north than D. antarctica, certainly well into Peru (to 12° S), with localities north of the equator in Mexico.last_img read more

Pelites of the Glen Urquhart serpentinite–metamorphic complex, west of Loch Ness (Anomalous local limestone–pelite successions within the Moine outcrop: III)

first_imgThe c. 6 km2 complex comprises graphitic/pyritic, mainly kyanite-rich pelites, interbanded with metalimestones and invaded by foliated serpentinites. It is enveloped by typically Moinian psammites, semipelites and pelites. Previously regarded as a Lewisian inlier, or as integral to the Moine succession, or as a transitional Moinian–Dalradian or Dalradian–Durness Limestone facies, its allochthonous status is in fact suggested by (1) its singular lithology; (2) its unique association with a large serpentinite; (3) associated sharp and local gravity and magnetic anomalies; (4) a blastomylonitic slide zone separating the complex from its Moine envelope; (5) local and regional petrological differences between pelites of the complex and Moine succession. A previous model, in which muscovite-rich Moine pelites developed by K-metasomatism (‘granitisation’) of kyanite-schists within the complex, via (a) shimmerisation (conversion of kyanite to shimmer aggregate); and (b) coarsening of shimmer aggregate to muscovite, is ruled out by new whole-rock and microprobe data. These suggest shimmerisation was a near-isochemical, small-scale redistribution of alkalis and water [approximately kyanite + biotite + quartz + water = muscovite (shimmer aggregate) + chlorite], and show large compositional differences between shimmer aggregates and coarse muscovites. Rb–Sr isotopic data imply Late Caledonian (c. 459 Ma) metamorphism in the complex, but also imply a significant earlier history for the kyanite-schists. Overall, data not merely invalidate a Glen Urquhart ‘Lewisian inlier’, but also as yet preclude correlation of the complex with the Moine or Dalradian. It is attributed in the interim to a separate lithotectonic unit, the ‘Albynian’, which may lie between (or be diachronous with) some part of the Moinian or Dalradian successions.last_img read more

Syn-depositional deformation in a Cretaceous succession, James Ross Island, Antarctica. Evidence from vitrinite reflectivity

first_imgA detailed vitrinite reflectivity study has been made through the Cretaceous sedimentary rocks of northwest James Ross Island, Antarctica. The results show that a progressive increase in reflectivity does not occur with depth and that values (0.45 %) from the base of the succession are lower than expected for the sequence as described by previous authors. Using a synthesis of sedimentological and stratigraphic information, the sequence is reinterpreted as an apparent monoclinal syncline, strongly influenced by syndepositional tectonics, with a thickness appreciably less than previously described.last_img

Taxonomy of the fungus commonly known as Stropharia aurantiaca, with new combinations in Leratiomyces

first_imgThe taxonomy and nomenclature of the fungus commonly referred to as Stropharia aurantiaca was investigated. Molecular analysis of the ribosomal RNA large subunit gene confirmed the exclusion of the species from Stropharia. The results from further molecular and morphological comparison with type species indicated that ‘S. aurantiaca’ is congeneric with a number of other taxa currently placed in Leratiomyces, Stropharia and Weraroa. These taxa are transferred to Leratiomyces and an emended diagnosis and brief discussion of this genus are provided.last_img

Frost flower surface area and chemistry as a function of salinity and temperature

first_imgFrost flowers play a role in air-ice exchange in polar regions, contribute to tropospheric halogen chemistry, and affect ice core interpretation. Frost flowers were observed and collected on the Hudson Bay in March 2008. Their specific surface area (SSA) was measured using CH4 adsorption at 77 K. The Brunauer-Emmett-Teller analysis produced SSA values between 63 and 299 cm(2) g(-1) (mean 162 cm(2) g(-1), accuracy and reproducibility 5%). This range is very similar to that of Domine et al. (2005) but our correlation of results with growth time and chemistry reveals the factors responsible for the wide range of SSA values. Longer growth time leads to higher SSA at low temperatures, so frost flowers are more likely to affect total surface area during colder periods. Chemical analysis was performed on frost flower melt and on local seawater and brine. We examined salinity and sulfate and bromide enrichment. The relationship between growth time and salinity varied spatially because of a freshwater plume from a nearby river and of tidal effects at the coast. Enrichment of certain ions in frost flowers, which affects their contribution to atmospheric chemistry, depends heavily on location, growth time, and temperature. No significant enrichment or depletion of bromide was detected. The low surface area index of frost flowers plus their lack of destruction in wind suggest their direct effect on sea salt mobilization and halogen chemistry may be less than previously thought, but their ability to salinate wind-blown snow may increase their indirect importance.last_img read more

Diurnal rhythm in British Antarctic personnel

first_imgIntroduction: The diurnal rhythm of saliva cortisol and its association to adaptation, performance and health were examined in personnel over-wintering at two British Antarctic stations. Methods: In total, 55 healthy individuals (49 males, 6 females) participated in the study. Cortisol in saliva was sampled on 3 consecutive days (at awakening, 15 and 45 min after waking, at 15.00 h, and 22.00 h) immediately after arrival at the station, midwinter, and the last week before departure. Subjective health complaints were also measured at arrival, midwinter, and the last week before departure, while depression (Burnam screen for depression) and positive and negative affect (PANAS) were measured at midwinter only. At the end of the winter appointment, base commanders evaluated the performance of all personnel. Results: The variations in external light (darkness during winter, midnight sun during arrival and departure) did not influence the diurnal rhythms. The normal peak level in the morning, and the normal and gradual fall towards the evening were observed at arrival, midwinter, and before departure. Immediately after arrival the cortisol values were relatively high and correlated positively with base commander’s evaluation of performance. During midwinter, approximately 58% scored for depression on the Burnam scale. However, when examining these data more closely, only 4 participants (7%) reported depression, the main reason for the high score on the depression scale was related to sleep problems and tiredness. Conclusions: There was no indication that over-wintering led to any disturbance in the diurnal rhythm of cortisol in British Antarctic personnel. There were no other indications of any ‘over-wintering syndrome’ than reports of subjective sleep problems and tiredness.last_img read more

Organisms and responses to environmental change

first_imgThere is great concern currently over environmental change and the biotic responses, actual or potential, to that change. There is also great concern over biodiversity and the observed losses to date. However, there has been little focus on the diversity of potential responses that organisms can make, and how this would influence both the focus of investigation and conservation efforts. Here emphasis is given to broad scale approaches, from gene to ecosystem and where a better understanding of diversity of potential response is needed. There is a need for the identification of rare, key or unique genomes and physiologies that should be made priorities for conservation because of their importance to global biodiversity. The new discipline of conservation physiology is one aspect of the many ways in which organismal responses to environmental variability and change can be investigated, but wider approaches are needed. Environmental change, whether natural or human induced occurs over a very wide range of scales, from nanometres to global and seconds to millennia. The processes involved in responses also function over a wide range of scales, from the molecular to the ecosystem. Organismal responses to change should be viewed in these wider frameworks. Within this overall framework the rate of change of an environmental variable dictates which biological process will be most important in the success or failure of the response. Taking this approach allows an equation to be formulated that allows the likely survival of future change to be estimated: Ps = (f(PF) x f(GM) x f(NP) x f(F) x f (D)xf(RA)) / (Delta Ex f(C)x f(PR) x F(HS)), where Ps = Probability of survival; PF = Physiological flexibility; GM = Gene pool modification rate; NP = number in population; F = Fitness; D = Dispersal capability; RA = Resource availability; Delta E = rate of change of the environment; C = Competition; PR = Predation and parasitism; HS = Habitat separation. Functions (f) are used here to denote that factors may interact and respond in a non-linear fashionlast_img read more

A review of sea ice proxy information from polar ice cores

first_imgSea ice plays an important role in Earth’s climate system. The lack of direct indications of past sea ice coverage, however, means that there is limited knowledge of the sensitivity and rate at which sea ice dynamics are involved in amplifying climate changes. As such, there is a need to develop new proxy records for reconstructing past sea ice conditions. Here we review the advances that have been made in using chemical tracers preserved in ice cores to determine past changes in sea ice cover around Antarctica. Ice core records of sea salt concentration show promise for revealing patterns of sea ice extent particularly over glacial–interglacial time scales. In the coldest climates, however, the sea salt signal appears to lose sensitivity and further work is required to determine how this proxy can be developed into a quantitative sea ice indicator. Methane sulphonic acid (MSA) in near-coastal ice cores has been used to reconstruct quantified changes and interannual variability in sea ice extent over shorter time scales spanning the last ∼160 years, and has potential to be extended to produce records of Antarctic sea ice changes throughout the Holocene. However the MSA ice core proxy also requires careful site assessment and interpretation alongside other palaeoclimate indicators to ensure reconstructions are not biased by non-sea ice factors, and we summarise some recommended strategies for the further development of sea ice histories from ice core MSA. For both proxies the limited information about the production and transfer of chemical markers from the sea ice zone to the Antarctic ice sheets remains an issue that requires further multidisciplinary study. Despite some exploratory and statistical work, the application of either proxy as an indicator of sea ice change in the Arctic also remains largely unknown. As information about these new ice core proxies builds, so too does the potential to develop a more comprehensive understanding of past changes in sea ice and its role in both long and short-term climate changes.last_img read more

Global ocean heat content in the Last Interglacial

first_imgThe Last Interglacial (129–116 thousand years ago (ka)) represents one of the warmest climate intervals of the past 800,000 years and the most recent time when sea level was metres higher than today. However, the timing and magnitude of the peak warmth varies between reconstructions, and the relative importance of individual sources that contribute to the elevated sea level (mass gain versus seawater expansion) during the Last Interglacial remains uncertain. Here we present the first mean ocean temperature record for this interval from noble gas measurements in ice cores and constrain the thermal expansion contribution to sea level. Mean ocean temperature reached its maximum value of 1.1 ± 0.3 °C warmer-than-modern values at the end of the penultimate deglaciation at 129 ka, which resulted in 0.7 ± 0.3 m of thermosteric sea-level rise relative to present level. However, this maximum in ocean heat content was a transient feature; mean ocean temperature decreased in the first several thousand years of the interglacial and achieved a stable, comparable-to-modern value by ~127 ka. The synchroneity of the peak in mean ocean temperature with proxy records of abrupt transitions in the oceanic and atmospheric circulation suggests that the mean ocean temperature maximum is related to the accumulation of heat in the ocean interior during the preceding period of reduced overturning circulation.last_img read more

National Plans of Action (NPOAs) for reducing seabird bycatch: Developing best practice for assessing and managing fisheries impacts

first_imgFisheries bycatch is one of the biggest threats to seabird populations. Managers need to identify where and when bycatch occurs and ensure effective action. In 1999, the Food and Agriculture Organization of the United Nations released the International Plan of Action for Reducing Incidental Catch of Seabirds in Longline Fisheries (IPOA-s) encouraging states to voluntarily assess potential seabird bycatch problems and implement a National Plan of Action (NPOA) if needed. However, the IPOA-s is ambiguous about the steps and objectives, diminishing its value as a conservation tool.last_img