Gotowa bibliografia na temat „Antarctic”

New populations of the two species of calanoid copepods known to inhabit freshwater lakes in East Antarctica, Boeckella poppei (Mrázek, 1901) and Gladioferens antarcticus Bayly, 1994, have recently been discovered. The morphology of the populations of B. poppei showed significant differences, notably a reduction in the armature of the male fifth leg, when compared with typical specimens from the Antarctic Peninsula and South America. Gladioferens antarcticus had previously been recorded from a single lake in the Bunger Hills, but has now been recorded from three further lakes in this region. A recent review of Antarctic terrestrial and limnetic zooplankton suggested that neither of these species can be considered an East Antarctic endemic, with B. poppei being listed as a recent anthropogenic introduction and G. antarcticus a ‘marine interloper’. We conclude differently: B. poppei has been present in isolated populations in East Antarctica for significant lengths of time, possibly predating the current interglacial, while G. antarcticus is a true Antarctic endemic species whose ancestors have been present in the region since before Australia separated from Antarctica.

Abstract Antarctic material of the genus Bryoerythrophyllum P. C. Chen was studied from all specimens present in KRAM. Bryoerythrophyllum recurvirostrum (Hedw.) P. C. Chen var. antarcticum L. I. Savicz & Smirnova is treated as a distinct species: B. antarcticum (L. I. Savicz & Smirnova) P. Sollman, stat. nov. Three species are now known in the Antarctic region: B. antarcticum, B. recurvirostrum and B. rubrum (Jur. ex Geh.) P. C. Chen. Bryoerythrophyllum rubrum is reported for the first time from the Antarctic. It is a bipolar species. A key to the taxa is given. These species are described and briefly discussed, with notes on illustrations, reproduction, habitat, world range, distribution and elevation in Antarctica.

For the first time, the widely spread Antarctic species Leptochiton antarcticus was found at the Emperor Seamounts in the North Pacific Ocean. In spite of a large distance between the Emperor Seamounts and Antarctica, the found specimen have very similar shell, girdle, radula and gill features to the type material. I propose that L. antarcticus spread to the North Pacific from the Antarctic via a deep-water current near the ocean floor, and perhaps it inhabits the slopes of islands and continents from the South Ocean to the Emperor Seamounts.

Circoviruses infect a variety of animal species and have small (~1.8–2.2 kb) circular single-stranded DNA genomes. Recently a penguin circovirus (PenCV) was identified associated with an Adélie Penguin (Pygoscelis adeliae) with feather disorder and in the cloacal swabs of three asymptomatic Adélie Penguins at Cape Crozier, Antarctica. A total of 75 cloacal swab samples obtained from adults and chicks of three species of penguin (genus: Pygoscelis) from seven Antarctic breeding colonies (South Shetland Islands and Western Antarctic Peninsula) in the 2015−2016 breeding season were screened for PenCV. We identified new variants of PenCV in one Adélie Penguin and one Chinstrap Penguin (Pygoscelis antarcticus) from Port Charcot, Booth Island, Western Antarctic Peninsula, a site home to all three species of Pygoscelid penguins. These two PenCV genomes (length of 1986 nucleotides) share > 99% genome-wide nucleotide identity with each other and share ~87% genome-wide nucleotide identity with the PenCV sequences described from Adélie Penguins at Cape Crozier ~4400 km away in East Antarctica. We did not find any evidence of recombination among PenCV sequences. This is the first report of PenCV in Chinstrap Penguins and the first detection outside of Ross Island, East Antarctica. Given the limited knowledge on Antarctic animal viral diversity, future samples from Antarctic wildlife should be screened for these and other viruses to determine the prevalence and potential impact of viral infections.

AbstractDue to the remote location of colonies of Antarctic shags (Phalacrocorax (atriceps) bransfieldensis) in Antarctica, there is only sparse data on the abundance of this species. An unmanned aerial vehicle (UAV) survey for known and unknown Antarctic shag colonies along the coasts of Nelson Island and western King George Island, Antarctica, was conducted in December 2016. Four colonies, one of them previously unknown, were detected. For the first time since the 1980s, the total population size of the colonies in that area was determined. A comparison with previous estimates revealed evidence of a population increase by a factor of 2.86. To support future survey campaigns, several characteristic features of Antarctic shag colonies, nests and individuals in aerial imagery were identified. This makes possible more reliable detection and determination of population size in Antarctic shag colonies. These characteristic features were compared with those of chinstrap penguin colonies (Pygoscelis antarcticus) because these species often overlap spatially and are difficult to distinguish. In addition, the optimal weather conditions and flight parameters for an aerial survey were specified.

Antarctic silverfish (Pleuragramma antarcticum) play a crucial intermediary role in connecting top predators and krill in the food web of the Antarctic Ocean. Despite their crucial role, research on their abundance is lacking. In this study, we estimated the abundance of juvenile Antarctic silverfish as foundational data for predicting their abundance. The density of juvenile Antarctic silverfish was estimated using an acoustic backscattering theoretical model. The mean volume backscattering strength was used to investigate the vertical and horizontal distributions of juvenile Antarctic silverfish in the Antarctic Ross Sea. The survey area was located near Cape Hallett, Antarctica, where Antarctic krill (Euphausia superba), ice krill (E. crystallorophias), and Antarctic silverfish coexist. The survey was performed four times using the Korean Antarctic research ship, RV Araon (R/V, 7507 GT). Frame trawls were conducted to identify the length and weight of the target fish species in the survey area. Captured Antarctic silverfish captured measured 3–9 cm. The maximum target strength (TS) was −92.93 dB at 38 kHz, −86.63 dB at 120 kHz, and 85.89 dB at 200 kHz. The average TS was −100.00 dB at 38 kHz, −93.00 dB at 120 kHz, and −106.90 dB at 200 kHz. Most juvenile Antarctic silverfish were found at a depth of 100 m and were distributed closer to sea ice. Between nearshore and polynya waters, the fish demonstrated a proclivity for polynya waters.

This work contributes to the knowledge on distribution, diversity and ecology of the Antarctic soil biota. Different soil habitats from several ice-free coastal sites were sampled along the Victoria Land across 7° of latitude from 71° to 78°S during five austral summer seasons between 2003/04 and 2011/12. In this paper we report preliminary data on soil tardigrades (water bears) from Edmondson Point, Northern Victoria Land. Tardigrades were found to be present in 23 of the 41 examined soil samples (56%). Their presence was associated exclusively with soil samples collected from bryophytes communities and under cyanobacterial mats, whereas they were completely absent in fellfield and ornithogenic soils. Tardigrades were least numerous among all soil micrometazoans, their abundance in the positive samples was very variable and ranged from 3 to 1824 individuals per 100 g of soil DW. High water content seemed to be the major factor determining occurrence of tardigrades in the soils investigated. On the other hand low water content and toxic compounds from penguin guano seemed to act as a strong constraint on their existence in the Antarctic soils. Taxonomic evaluation of the extracted tardigrades revealed presence of only two species belonging to class Eutardigrada: Acutuncus antarcticus (Richters, 1904) and Milnesium antarcticum Tumanov, 2006. While A. antarcticus has already been reported previously as the most widespread and abundant tardigrade across the Victoria Land, the information on M. antarcticum is novel, both for Victoria Land and the continental Antarctica.

AbstractA prospecting search for antitumoural activity in polar benthic invertebrates was conducted on Antarctic and sub-Antarctic benthos in three different areas: Bouvet Island (sub-Antarctic), eastern Weddell Sea (Antarctica) and the South Shetland Islands (Antarctica). A total of 770 benthic invertebrate samples (corresponding to at least 290 different species) from 12 different phyla were assayed to establish their pharmacological potential against three human tumour cell lines (colorectal adenocarcinoma, lung carcinoma and breast adenocarcinoma). Bioassays resulted in 15 different species showing anticancer activity corresponding to five different phyla: Tunicata (5), Porifera (4), Cnidaria (3), Echinodermata (2) and Annelida (1). This appears to be the largest pharmacological study ever carried out in Antarctica and it shows very promising antitumoural activities in the Antarctic and sub-Antarctic benthos.

Antarctica is an ice-dominated continent and all its terrestrial and freshwater habitats are fragmented, which leads to genetic divergence and, eventually, speciation. Acutuncus antarcticus is the most common Antarctic tardigrade and its cryptobiotic capabilities, small size and parthenogenetic reproduction present a high potential for dispersal and colonisation. Morphological (light and electron microscopy, karyology) and molecular (18S rRNA and cytochrome c oxidase subunit I (COI) genes) analyses on seven populations of A. antarcticus elucidated the genetic diversity and distribution of this species. All analysed populations were morphologically indistinguishable and made up of diploid females. All specimens presented the same 18S rRNA sequence. In contrast, COI analysis showed higher variability, with most Victoria Land populations presenting up to five different haplotypes. Genetic distances between Victoria Land specimens and those found elsewhere in Antarctica were low, while distances between Dronning Maud Land and specimens from elsewhere were high. Our analyses show that A. antarcticus can still be considered a pan-Antarctic species, although the moderately high genetic diversity within Victoria Land indicates the potential for speciation events. Regions of Victoria Land are considered to have been possible refugia during the last glacial maximum and a current biodiversity hotspot, which the populations of A. antarcticus mirror with a higher diversity than in other regions of Antarctica.

The breeding season diet of the three surface-nesting petrel species on the Rauer Islands, Prydz Bay were examined. The stomach contents of cape petrel (Daption capense), Antarctic petrel (Thalassoica antarctica), and southern fulmar (Fulmarus glacialoides) were sampled by collecting regurgitates and by stomach flushing during the 1987/88 early chick-rearing period. Pleuragramma antarcticum and Euphausia superba dominated the diets of all species. By mass they constituted 78% and 22% of Antarctic petrel diet, 63% and 36% of southern fulmar diet, and 14% and 85% of cape petrel diet respectively. P. antarcticum increased in importance in the diet of Antarctic petrels during the course of the study, while E. superba became increasingly important in the diets of southern fulmars and cape petrels. Previous studies conducted during incubation consistently reported the diets as comprising chiefly cephalopods and euphausiids, whilst studies during chick-rearing have reported fish and euphausiids dominating, and very little cephalopod material.

The distribution, abundance, chemical composition, metabolism, and feeding ecology of the tentaculate ctenophore, Callianira antarctica (Chun 1897), were investigated during austral winter 2001and autumn & winter 2002, in the vicinity of Marguerite Bay west of the Antarctic Peninsula. Callianira antarctica had a widespread distribution during autumn and winter, and variable abundance (0.02 to 2.6 ind. m-2) during winter 2001 associated with specific circulation features. Size frequency distributions for autumn and winter suggest that more than half of the C. antarctica population may have experienced 'degrowth' during winter due to low food availability. Callianira antarctica is a fairly robust ctenophore with geometric mean (geomean) carbon (C) and nitrogen (N) values of 8.41 and 1.83% dry weight (DW), respectively. Winter oxygen consumption and ammonium excretion rates ranged from 0.059 to 0.410 micro l O2 [mg DW]-1 h-1 and 0.60 to 31.1 µg-at N [g DW]-1 h-1, respectively, at 0oC. Daily minimum maintenance rations based on respiration experiments were 2.7% to 3.6% of the total body carbon (TBC) for small ctenophores, and 1.4% to 1.9% TBC for larger ctenophores. Calanoid copepods and larval and juvenile Antarctic krill were offered to ctenophores in incubation experiments. Digestion times were variable, lasting 8 to 20 h, and were independent of ctenophore size and dependent on number and type of prey. Gut content analysis from one autumn and two winter seasons indicated C. antarctica preyed on both copepods and krill in situ, with an increased dependence on larval krill during winter. Lipid biomarker analysis on C. antarctica and their potential prey confirmed these results. Divers observed aggregations of C. antarctica passively drifting with tentacles extended near dense concentrations of larval Euphausia superba during winter. These observations along with gut content and lipid biomarker analysis suggest that larval krill is an important prey item for C. antarctica during winter.

The thesis analyses the expedition (TAE) led by Dr.Vivian Fuchs and Sir Edmund Hillary from three vantage points: 1)the years from 1948 to 1955 leading up to the expedition 2) the interaction between the IGY and the TAE projects and 3) the role of the US Navy as the expedition unfolded. The thesis also investigates key events including the purchase of the ship Endeavour from Britain, the competition for leadership of the UK and NZ parties, the 'dash to the Pole' by Hillary, and the search for base sites and routes to the Polar Plateau. The thesis contains an overview historical introduction, a comprehensive literature review as well as a broad-based set of conclusions.

In light of growing international awareness and interests in the ‘frozen continent’ of Antarctica, the topic of Values in Antarctica has recently gained more research interest. Due to the complexity of the concept of value, values in Antarctica have been approached from many different perspectives, including Antarctic wilderness and aesthetic values, values manifested in Antarctic law or value based behavioural changes through the Antarctic experience. The present thesis addresses values as human connections to Antarctica with a focus on Antarctic policy-making. The investigation contained three analytical stages that built on each other. The first stage has been an interdisciplinary literature review examining what values are and how values can be studied, but also considered values in the context of environment, human behaviour and policy. Value and value-related concepts were selected in view of a potential application to the Antarctic. The second analytical stage involved a general framework analysis of the Antarctic Treaty System to identify key elements and structures in the system suitable for a study of Antarctic values, and to develop the research questions. The third stage of analysis included empirical investigations of two Antarctic case studies. Key elements that influence the Antarctic Treaty System in a way that is relevant for a study of Antarctic values include external factors and events, action situations and actors participating in these action situations. Antarctic Treaty Meeting of Experts appeared as an action situation particularly suitable for a study of Antarctic values. The last two Antarctic Treaty Meeting of Experts on ship-borne tourism and climate change have been chosen as case studies, presenting two topical issues in Antarctic policy. Using discourse analysis based on documents submitted to the meetings and the meetings’ reports, values that are driving the discourses were to be identified through structures and patterns in the discourses. Further, based on the discourse analysis following three research questions were to be answered: What role is ascribed to Antarctica concerning contemporary issues? Where and why do conflicts arise in the ATS policy-making process that are based on conflicting values? What changes in the underlying belief-systems are driving policy-making processes and what has caused the change? Based on the literature, values are defined as internalised codes that affect behaviour and include judgements on what is good and desirable. Through the framework analysis it was identified that Antarctic policy involves a multi-layered system of different value systems, which was considered in the two case studies. For both case studies, values in the discourses were mostly identified based on Schwartz’s basic human value theory. The most prominent human value that drives both the ship-born tourism and the climate change discourse is security. Both discourses are further motivated by the conservation of the Antarctic environment and its associated ecosystems. Other values, such as power and conformity with rules were also clearly expressed in the discourses. With regard to the research questions, both case studies discussed Antarctica from two different perspectives, as a hazardous place for human activities and as a place vulnerable to any kind of changes. Conflicts in the ship-borne tourism discourse were more obvious, while the climate change discourse within the expert meeting proceeded in consensus. Value-based changes that are evident in changes in belief-systems underlying Antarctic policy-making could not be identified. This thesis argues, based on careful consideration of documents, that values play a crucial role in Antarctic policy-making at a number of different scales: individuals, political actors, and governmental levels. Values were found to be at the core of most, if not all, conflicts within the Antarctic system. Finally, this thesis provides the first understanding of the values held by the various stakeholders involved in governing and use of the Antarctic, which is crucial for further decision-making and research.

The Antarctic silverfish (Pleuragramma antarctica) is a keystone species in the continental shelf waters around the Antarctic, performing an essential role of connecting higher and lower trophic levels in the Southern Ocean ecosystem. Its early life history is dependent on the platelet ice layer found below sea ice, thus intimately intertwining its fate with that of sea ice extent. Antarctic silverfish belong to the family Nototheniidae, part of the Notothenioidei suborder whose species radiation in the Southern Ocean 24 million years ago is one of the most expansive among teleost fish. Most notothenioids inhabit a benthic niche as adults, though many experience a pelagic egg and larval phase. Antarctic silverfish are unique among notothenioids in that they are pelagic throughout their life history. Larvae develop in the platelet ice layer near the surface beneath sea ice, descending into deeper waters as they grow in size as juveniles, finally reaching their maximum depth range as adults at 400 – 700 m below the surface. While they lack a swim bladder, Antarctic silverfish manage to remain in the water column as adults by a type of paedomorphy in which they retain lipids from larval and juvenile life stages, allowing them to achieve neutral buoyancy. Despite their presence in the water column as adults, they practice a similar energy-efficient life strategy to their benthic counterparts. Their feeding strategy involves hanging in the water column and passively consuming prey. Remaining in the water column throughout their life history combined with their passive life strategy renders Antarctic silverfish especially susceptible to transport via local and circumpolar current systems. Thus, local and circumpolar current systems form the hydrographic framework in which hypotheses regarding Antarctic silverfish population connectivity must be tested. How populations of fish are defined, and the extent to which separate populations exchange individuals forms the basis of marine fish population biology. The extent to which Antarctic silverfish, which have a circumpolar distribution, represent one fully connected, panmictic population around the Antarctic continent, remains an open question. It is reasonable to presume that, given their pelagic larval phase, many species of notothenioids with a circumpolar distribution represent large, homogeneous populations. This presumption remains the null hypothesis to test when investigating population structure in notothenioids, and it is especially salient when considering the fully pelagic Antarctic silverfish. The first investigation into Antarctic silverfish population structure employed mitochondrial DNA markers on a circumpolar scale and did not find evidence to reject the null hypothesis of panmixia throughout the Southern Ocean. Intriguingly, while comparisons between regions failed to indicate differentiation, comparisons within regions between years hinted at inter-annual variation in patterns of connectivity. Genetic differentiation within the same geographic area that is lost and gained between sampling years due to variations in recruitment, mortality and hydrography is known as chaotic genetic patchiness. The extent to which chaotic genetic patchiness is relevant to understanding Antarctic silverfish population structure was further studied in a more recent investigation, restricting its geographic focus to the Antarctic Peninsula, and employing a set of highly polymorphic EST-linked microsatellite markers to understand population connectivity around the Antarctic Peninsula. Based on both its more focused regional scale and sampling scheme, as well as the use of genetic markers more adept at capturing population differentiation, this study was able to detect genetic structuring on the scale of the Antarctic Peninsula. Building upon these initial studies, this thesis aimed to characterize the circumpolar population structure of Antarctic silverfish, integrating aspects of life history and hydrography in order to describe mechanisms of connectivity between populations. The first aim was to understand the hydrography underlying life history connectivity on the scale of the Ross Sea region in order to better understand what may be occurring on the circumpolar level. Silverfish larvae were collected from areas in the Ross Sea coincident with hydrographic features hypothesized to influence their connectivity. While a microsatellite-based analysis was precluded due to the poor state of preservation of the larvae, it was possible to confirm species identification using mitochondrial sequence analysis. The genetic confirmation of species was especially important given that this study proposed a new spawning ground for silverfish in the Ross Sea based on size at collection and established growth rates from the time of hatching. Importantly, this study provided renewed support for the life history hypothesis in silverfish, emphasizing the impact of trough circulation in transporting early life stage fish from the ice shelf edge to the continental slope, where retention back towards the coast or entrainment in shelf-long currents modulates connectivity between neighboring populations of silverfish. The Ross Sea investigation was then expanded on a circumpolar scale, now carried out using a suite of highly polymorphic EST-linked microsatellite markers developed in a closely related notothenioid species and shown to successfully amplify in silverfish in a previous study. This analysis was carried out on fish collected over 25 years from six different regions: the western Ross Sea, the eastern Weddell Sea, Larsen Bay, the northern Antarctic Peninsula, the South Orkney Islands, and the western Antarctic Peninsula. The data analyzed included samples from the two previous investigations of silverfish population structure described earlier, the first using mitochondrial markers on a circumpolar scale that had not found evidence of population structuring, and the second using the same suite of microsatellite markers employed in this thesis on a regional scale around the Antarctic Peninsula. The integration of these previous datasets into the present analysis allowed for an increase in the resolving power of the previous mitochondrial marker-based study, as well as for the integration of the Antarctic Peninsular work into the greater circumpolar context. The circumpolar investigation of Antarctic silverfish population structure confirmed that the population structure of silverfish on a circumpolar scale is characterized by high levels of gene flow, and suggested that the Antarctic Slope Front and Current System (AFS) plays an integral role in connecting populations in the Southern Ocean. The importance of the AFS was evident in that reductions in gene flow were only observed in the South Orkney Islands and west Antarctic Peninsula, which were the only two areas in the study where the AFS has not been shown to arrive. This result also expanded to a circumpolar scale the earlier Ross Sea study, which had emphasized the importance of the AFS in connecting Ross Sea populations between local trough systems. It remained however, that small scale population differentiation which had been observed in the Ross Sea based on larval distributions, as well as in the eastern Weddell Sea based on the distribution of older and younger cohorts between sampling areas, was unable to be resolved using genetic techniques. Thus, the final aim of the main project of this thesis was carried out in order to resolve population structure on the regional scale, this time in the Weddell Sea, employing otolith chemistry. Analysis of trace element deposition in otolith nuclei, reflective of oceanographic conditions to which fish were exposed in early life, has been shown to delineate population structure in the Southern Ocean, in both silverfish and related notothenioids. Of the stations for which samples were available in the Weddell Sea, five stations were selected based on their locations with respect to hydrographic features hypothesized to influence population structuring in the region, in Atka Bay, Halley Bay, off of Coats Land, and west and east of the Filchner Trough. Previous studies, as well as data on biomass and abundance from the sampling expedition during which the silverfish were collected, emphasized the importance of the Filchner Trough in supporting a local population of silverfish in the eastern Weddell Sea continental shelf area. Furthermore, hydrographic data collected in the Weddell Sea emphasized the importance of warm water mass intrusion onto the continental shelf carried from the east into the Weddell Sea region by the AFS. These warm water intrusions from the AFS not only have the potential to carry fish from other regions into the Weddell Sea area, but regulate circulation patterns and the strength and directionality of coastal currents in the region, modulating local connectivity. The results of the otolith nucleus chemistry analysis revealed significant population structuring along the eastern Weddell Sea, in contrast to the structure revealed using genetics. The population structure revealed by the otolith chemistry analysis supported the importance of warm water intrusions from the AFS in transporting fish between areas, while highlighting the role of the Filchner Trough circulation in supporting a coherent population in the southeast Weddell Sea. These results emphasize the importance of the integration of multidisciplinary techniques in the context of local hydrography in addressing questions of population structure and life history connectivity in Antarctic silverfish in the Southern Ocean, and for that matter, any pelagic species inhabiting a continental shelf ecosystem.
L’antarctic silverfish (Pleuragramma antarctica) è una specie chiave nelle acque della piattaforma continentale antartica, dove svolge un ruolo essenziale nel collegare i diversi livelli trofici. La sua life history dipende, nella prima fase, dal cosiddetto “ghiaccio a placchette” (platelet ice), che si forma all’interfaccia tra l’acqua marina e lo strato di ghiaccio superficiale, legando strettamente il destino di questa specie all’estensione del ghiaccio antartico. L’antarctic silverfish appartiene alla famiglia Nototheniidae, che fa parte del sottordine dei Nototenioidei, la cui radiazione, avvenuta nell’oceano Antartico a partire da 24 milioni di anni fa, rappresenta una delle più spettacolari radiazioni adattative nei pesci teleostei. I nototenioidei comprendono, nella maggior parte dei casi, specie demersali in fase adulta, ma caratterizzate da uova e larve pelagiche; l’antarctic silverfish è unico sotto questo punto di vista perché è pelagico durante tutto il ciclo vitale. Le larve si sviluppano nello strato di platelet ice sotto il ghiaccio marino superficiale e scendono verso acque più profonde durante la maturazione, arrivando come adulti a profondità massime di 400 – 700 m. Nonostante l’assenza di vescica natatoria, l’antarctic silverfish riesce a mantenersi nella colonna d’acqua nello stadio adulto grazie a un tipo di pedomorfia caratterizzato dal mantenimento e dall’aumento dei lipidi presenti nelle fasi larvali e giovanili, che ne aumenta il potere di galleggiamento. Malgrado l’habitus pelagico da adulto, il silverfish è molto efficiente dal punto di vista energetico, possedendo una strategia alimentare simile alle controparti bentoniche, che consiste in questo caso nel galleggiare passivamente nella colonna d’acqua, consumando le prede che capitano nei paraggi, ma senza investire energia in una vera e propria ricerca attiva delle prede. Il fatto di rimanere nella colonna d’acqua durante tutto il ciclo vitale, in combinazione con la strategia di vita passiva, rende l’antarctic silverfish particolarmente suscettibile al trasporto da parte dei sistemi di correnti locali e circumpolari. Questo aspetto lo rende particolarmente interessante nel contesto della biologia di popolazione dei pesci marini, dove risulta importante identificare la presenza di diverse popolazioni e definire l’entità con cui popolazioni separate scambiano individui. In particolare, il fatto che l’antarctic silverfish, che ha una distribuzione circumpolare, presenti o meno una singola popolazione panmittica attorno al continente antartico, rimane una questione aperta. Dato che le fasi larvali sono pelagiche, è ragionevole presupporre che molte specie di nototenioidei siano organizzate in grandi popolazioni omogenee su scala geografica più o meno ampia. Questo presupposto fornisce l’ipotesi nulla da testare quando si investiga la struttura di popolazione di questo gruppo, ed è specialmente rilevante se si considera l’habitus pelagico dell’antarctic silverfish. Il primo studio della struttura genetica di popolazione dell’antarctic silverfish è stato svolto con marcatori del DNA mitocondriale; questa indagine, svolta su una scala circumpolare, non ha fornito evidenze tali da confutare l’ipotesi nulla di panmissia per l’intero oceano antartico. Tuttavia, mentre i confronti svolti tra diverse regioni non sono riusciti a dimostrare la presenza di differenziamento genetico, i confronti svolti entro regioni tra diversi anni di campionamento hanno suggerito l’esistenza di variazione inter-annuale del grado di connettività. Il differenziamento genetico tra anni di campionamento entro la stessa area geografica è riconducibile al fenomeno della chaotic genetic patchiness e può essere dovuto a variazioni nel tasso di reclutamento e mortalità e nell’idrografia. La presenza di differenziamento genetico di popolazione e di chaotic genetic patchiness nell’antarctic silverfish sono stati recentemente confermati mediante genotipizzazione di microsatelliti EST-linked in uno studio focalizzato su campioni provenienti dalla Penisola Antartica. In questo caso, l’utilizzo di marcatori genetici ipervariabili caratterizzati da un elevato potere risolutivo ha permesso di rilevare una significativa struttura genetica sulla scala regionale della Penisola Antartica. Questa tesi di dottorato mira a caratterizzare la struttura di popolazione circumpolare dell’antarctic silverfish, integrando l’informazione fornita dagli studi iniziali con nuovi campioni ed interpretando i risultati alla luce dei diversi aspetti di life history ed idrografia al fine di descrivere i meccanismi di connettività tra popolazioni. Nel primo studio prodotto nell’ambito di questa tesi di dottorato, sono stati analizzati dei campioni di larve dell’antarctic silverfish provenienti dal Mare di Ross, con l’obiettivo di legare l’idrografia locale alla connettività della specie. Lo stato di conservazione dei campioni non ha permesso di utilizzare marcatori molecolari nucleari (microsatelliti) per studiare il differenziamento tra siti geografici entro il Mare di Ross. Nonostante questo, è stato possibile sequenziare un frammento di DNA mitocondriale che ha permesso di identificare univocamente le larve come apparteneneti alla specie P. antarctica. Questo risultato è particolarmente rilevante perché conferma, grazie all’utilizzo di metodi genetici, la presenza di larve della specie P. antarctica in alcune aree del Mare di Ross che erano state precedentemente solo ipotizzate essere zone preferenziali di nursery del silverfish, sulla base di tempi di raccolta dal momento della schiusa delle uova e del tasso di crescita ipotizzato. Sulla base dell’idrografia locale, questo studio ipotizza che la circolazione legata alle depressioni del fondale sia essenziale per il trasporto delle fasi di vita iniziali dalle zone più costiere fino alla scarpata continentale, mentre l’idrografia costiera potrebbe controllare il trasporto lungo i margini della piattaforma continentale modulando la connettività tra popolazioni adiacenti. In un secondo studio prodotto nell’ambito di questa tesi di dottorato sono stati analizzati campioni raccolti nell’arco di 25 anni da sei regioni antartiche diverse: la parte ovest del Mare di Ross, la parte est del Mare di Weddell, la Baia di Larsen, la parte nord della Penisola Antartica, le Isole di South Orkney, e la parte ovest della Penisola Antartica. Questo studio su scala circumpolare è stato condotto utilizzando un pannello di 18 loci microsatellite isolati in precedenza per varie specie di nototenioidei antartici. Questi loci sono risultati polimorfici anche in P. antarctica e informativi per gli obiettivi di questa tesi di dottorato. Alcuni dei campioni inclusi in questo studio sono stati analizzati in due studi precedenti: un primo studio non aveva evidenziato segnali di differenziamento genetico a livello circumpolare (analisi di un marcatore mitocondriale) mentre un secondo studio, più recente e focalizzato sulla Penisola Antartica, aveva segnalato chaotic genetic patchiness e differenziamento genetico utilizzando lo stesso pannello di 18 microsatelliti genotipizzati in questa tesi di dottorato. Questo secondo studio ha confermato che la struttura di popolazione del silverfish sulla scala circumpolare è caratterizzato da alti livelli di flusso genico suggerendo che il sistema di correnti, in particolare l’Antarctic Slope Front and Current System (AFS), abbia un ruolo critico nel collegamento delle popolazioni nell’oceano Antartico. L’importanza del AFS è suggerita dal limitato flusso genico tra le aree ad ovest della Penisola Antartica e le South Orkneys, le due uniche zone non raggiunte dall’AFS. Questa considerazione è ulteriormente supportata dall’ipotesi che l’AFS mantenga la connettività tra depressioni del fondale anche nel Mare di Ross. Per comprendere se l’assenza di differenziamento nell’area ad est del Mare di Weddell fosse effettivamente un fatto biologico o fosse dovuta alla scarsa sensibilità dei marcatori microsatellite a piccole differenze, è stato condotto un ulteriore studio utilizzando l’analisi della chimica degli otoliti di silverfish. La quantificazione delle tracce di elementi deposti nel centro (nucleus) degli otoliti è indicativa delle condizioni chimiche oceanografiche alle quali gli individui sono stati esposti nelle fasi iniziali dello sviluppo. Questa metodologia permette di conseguenza di testare se gli individui siano stati esposti a masse d’acqua diverse nelle prime fasi di vita e di dimostrare l’esistenza di popolazioni con diversa origine. Tra i campioni disponibili per il Mare di Weddell, sono state scelte 5 aree sulla base degli aspetti idrografici che potrebbero influire sulla struttura di popolazione locale (Baia di Atka, Baia di Halley, vicino alla costa di Coats, ad est ed ovest del Filchner Trough). Dati di abbondanza e biomassa raccolti in parallelo durante in campionamento del silverfish nel Mare di Weddell avevano già evidenziato l’importanza del Filchner Trough nel sostenere la popolazione locale dell’antarctic silverfish. Inoltre, l’idrografia locale, attraverso l’intrusione di acqua più calda dall’AFS verso il Mare di Weddell, permetterebbe sia di trasportare il silverfish verso il Mare di Weddell sia di regolare direzionalità e tasso di connettività locale. In contrasto con quanto evidenziato dall’approccio genetico, le analisi di microchimica degli otoliti segnalano differenze statisticamente significative tra gruppi di individui all’interno del mare di Weddell, in particolare tra nordest e sudest del Mare di Weddell. Questi studi suggeriscono un ruolo chiave dell’idrografia sia su scala circumpolare che locale nel modulare la connettività delle popolazioni dell’antarctic silverfish. Inoltre, questa tesi di dottorato evidenzia come un approccio multidisciplinare possa chiarire questioni di connettività di popolazione proponendo una metodologia applicabile a diversi organismi sia antartici che non.

The Eastern Antarctic Dry Valley region is a polar desert, where conditions of extreme aridity, high temperature fluctuations and high irradiation levels make it one of the most extreme environments on earth. Despite the harsh environment, the soils in this region yield a wide range of bacterial and eukaryotic phylotypes in greater abundance than previously believed. In the Dry Valleys, highly localized niche communities colonise the underside of translucent quartz rocks and present macroscopic growth.

Connections between South Africa and Antarctica can be traced as far back as the 1700s when European expeditions in search of the southern continent used Cape Town (and later Simonstown) as a base of operation. This link expanded considerably after formal British acquisition of the Cape of Good Hope in 1815, yet it was not until 1926 that an actual South African policy towards the Antarctic began to materialize. Once this policy was established it continued to be characterized by procrastination as well as resistance both from within and without South Africa. The history of South Africa's Antarctic policy can be divided into five periods: first, the commencement of the policy (focusing primarily on economic interests), 1926-1939; second, the pursuit of interests through the policy (focusing on political interests), 1944- 1958; third, the entrenchment of South Africa's interests in the Antarctic (by securing South Africa's position within the Antarctic Treaty System), 1958-1960; fourth, the expansion of and foreign assault on the policy (under the auspices of the Antarctic Treaty System), 1960-1988; and fifth, the defence of and future prospects for the policy (from United Nation's calls for South Africa's exclusion from the Antarctic Treaty System), since 1982. While resistance from inside and outside the government during the first two periods resulted from inadequacies in the South African Antarctic policy itself, resistance in the final two periods has centred upon non-Antarctic issues. As South Africa has faced ever-increasing exclusion from international governmental organizations over opposition to Its apartheid policies, organizations such as the Antarctic Treaty Organization have inevitably been drawn into the debate. As a result, the Consultative Parties of the Antarctic Treaty (of which South Africa is one of the original twelve) have been forced to deal with the following question: to what extent will political issues outside the scope of the management policies of the Antarctic Treaty Organization be allowed to affect the functioning of the Antarctic Treaty System? While the Consultative Parties continue to ponder this and the fact that South Africa's Consultative Status has become the most divisive factor within the Antarctic Treaty System, no final solutions to these issues appear likely before 1991.

AbstractTwenty-nine States (the ‘Consultative Parties’), each with a substantial interest in Antarctica, collectively manage Antarctica through a system of consensus-based decisions. Traditionally, the Antarctic Treaty together with recommendations and measures adopted by the Antarctic Treaty Consultative Meetings (ATCM), the Convention on the Conservation of Antarctic Marine Living Resources (CAMLR Convention) and the Convention for the Conservation of Antarctic Seals (CCAS) form the basis of the Antarctic Treaty System. However, the Consultative Parties began to expand their environmental responsibilities in Antarctica in 1970 and agreed that they “should assume responsibility for the protection of the environment and the wise use of the Treaty area”. A major step in this regard was the addition to the Antarctic Treaty System of the Protocol on Environmental Protection to the Antarctic Treaty (PEPAT or the Protocol). Together with safeguarding free and peaceful scientific research, the Protocol incorporates the protection of the Antarctic environment into the Antarctic Treaty System. The Protocol has six annexes, with Annex VI (Liabilities Arising from Environmental Emergencies) being a product of the obligations contained in Articles 15 and 16 of the PEPAT. Specifically, Article 16 of the PEPAT states that:

The paper presents data on the lipid content of certain organs and tissues of Pleuragramma antarcticum from the Antarctic Strait (Atlantic sector of Antarctica). The obtained results on the tissue specificity of lipids and biochemical adaptations at the lipid level in this fish spe-cies, which contribute to the tolerance of the organism to influence of the extreme environ-mental factors of Antarctic ecosystems, are discussed.

The work is focused on studying bacteria associated with vascular plants in Antarctic region. Climate changes affecting the Antarctic Peninsula favor the successful colonization of ice-free lands by two Antarctic vascular plants (Deschampsia antarctica and Colobanthus quitensis). Bacteria isolated from D. antarctica collected during the 25th Ukrainian Antarctic Expedition (January-April 2020) along the Western part of the Antarctic Peninsula were studied for plant growth-promoting characteristics (nitrogen fixation, phosphate solubilization, cyclic lipopeptide production, exoprotease production, motility and carbohydrate utilization). The heterotrophy of bacterial isolated from D. antarctica and the presence of a wide range of saccharolytic enzymes for the utilization of mono- and disaccharides in studied cultures were shown. This may indicate the plasticity of metabolism and the high adaptation potential of microorganisms associated with D. antarctica. PGPT of studied bacteria were mostly presented by nitrogen-fixing ability and cyclic lipopeptides synthesis.

Considerations about steppe elements in modern Arctic and Antarctic high latitudes, about problematic sofy edoma, which was the ground for Late Pleistocene cryoarid mammoth prairies and their genetic relations to modern steppes are expounded. Taking the Antarctic hair grass (Deschampsia antarctica) Antarctic expansion into consideration, the steppe trace spreading is acknowledged for both Hemispheres high latitudes. The grass expansion in both Central Arctic and Antarctic is considered a compensation for steppe loss in their geographical zone and future potential for agricultural economy.

<p>Rothera is the main mooring location in Antarctica for research vessels of the British Antarctic Survey (BAS). The existing wharf had reached the limit of its design life. To provide mooring of the new UK polar research ship, the RRS <i>Sir David Attenborough</i>, a larger wharf structure was designed that required removal of the existing structure. This paper describes the engineering and technical challenges on providing a safe and stable structure during dismantling as well as the effects of icebergs, low temperatures and wildlife around this Antarctic research station.</p>

The Antarctic Miniature Lidar (AML) instrument has been assembled, tested, and deployed to the NOAA Clean Air Facility at the Amundsen-Scott South Pole Station. AML uses redundant commercially available, single element semiconductor lasers, operated CW, and a silicon avalanche photodiode (APD) operated in the Geiger or photon counting mode. We present preliminary lidar measurements made at both Goddard Space Flight Center, prior to deployment, and at the Clean Air Facility after installation at the South Pole Station in early February, 1995.

We built a collector to filter interplanetary dust particles (IDPs) larger than 5 µm from the clean air at the Amundsen Scott South Pole station. Our sampling strategy used long duration, continuous dry filtering of near-surface air in place of short duration, high-speed impact collection on flags flown in the stratosphere. We filtered ~107 m³ of clean Antarctic air through 20 cm diameter, 3 µm filters coupled to a suction blower of modest power consumption (5–6 kW). Our collector ran continuously for 2 years and yielded 41 filters for analyses. Based on stratospheric concentrations, we predicted that each month’s collection would provide 300–900 IDPs for analysis. We identified 19 extraterrestrial (ET) particles on the 66 cm² of filter examined, which represented ~0.5% of the exposed filter surfaces. The 11 ET particles larger than 5 µm yield about a fifth of the expected flux based on >5 µm stratospheric ET particle flux. Of the 19 ET particles identified, four were chondritic porous IDPs, seven were FeNiS beads, two were FeNi grains, and six were chondritic material with FeNiS components. Most were <10 µm in diameter and none were cluster particles. Additionally, a carbon-rich candidate particle was found to have a small ¹⁵N isotopic enrichment, supporting an ET origin. Many other candidate grains, including chondritic glasses and C-rich particles with Mg and Si and FeS grains, require further analysis to determine if they are ET. The vast majority of exposed filter surfaces remain to be examined.

This paper takes both historical and future-oriented perspectives to explore the Commission on the Conservation of Antarctic Marine Living Resources (CCAMLR) as an integral part of the Antarctic Treaty system (ATS), its accomplishments, current challenges and possible future pathways, with a focus on area-based marine management approaches including marine protected areas (MPAs).