The terrestrial arthropod fauna of the Byers Peninsula,Livingston Island,South Shetland Islands

We report the first detailed study of the terrestrial invertebrate fauna of the Byers Peninsula SSSI, Livingston Island, South Shetland Islands. Fourteen micro-arthropod taxa (10 Acari, four Collembola) and two Diptera are recorded, including the first record of the mite Edwardzetes dentifer from the maritime Antarctic. The first record of the midge Belgica antarctica from neighbouring Snow Island is also given. Population composition and density were described in samples from a wide range of terrestrial and freshwater habitats. There was no strong relationship between habitat and microarthropod species occurrence, although comparison of completely vegetated and more stony sites revealed greater population densities at the vegetated sites, and different species proportions at each. Some individual samples contained a wide range of species with none achieving numerical dominance, whilst others from superficially similar sites were dominated by one species. Dipterans were limited to a small number of lakes, streams and seepage areas, where they were sometimes abundant. Population density data and species occurrence are compared with previously published studies from the maritime Antarctic and elsewhere.     

Viruses in the plankton of freshwater and saline Antarctic lakes

1. Virus‐like particle (VLP) abundances in nine freshwater to saline lakes in the Vestfold Hills, Eastern Antarctica (68° S) were determined in December 1999. In the ultra‐oligotrophic to oligotrophic freshwater lakes, VLP abundances ranged from 1.01 to 3.28 × 10⁶ mL^–1 in the top 6 m of the water column. In the saline lakes the range was between 6.76 and 36.5 × 10⁶ mL^–1. The lowest value was found in meromictic Ace Lake and the highest value in hypersaline Lake Williams. Virus to bacteria ratios (VBR) were lowest in the freshwater lakes and highest in the saline lakes, with a maximum of 23.4 in the former and 50.3 in the latter. 2. A range of morphologies among VLP was observed, including phages with short (Podoviridae) and long tails, icosahedric viruses of up to 300 nm and star‐like particles of about 80 nm diameter. 3. In these microbially dominated ecosystems there was no correlation between VLP and either bacterial numbers or chlorophyll a. There was a significant correlation between VLP abundances and dissolved organic carbon concentration (r=0.845, P < 0.01). 4. The data suggested that viruses probably attack a spectrum of bacteria and protozoan species. Virus‐like particle numbers in the freshwater lakes were lower than values reported for lower latitude systems. Those in the saline lakes were comparable with abundances reported from other Antarctic lakes, and were higher than most values published for lower latitude lakes and many marine systems. Across the salinity spectrum from freshwater through brackish to hypersaline, VLP concentrations increased roughly in relation to increasing trophy. 5. Given that Antarctic lakes have a plankton almost entirely made up of bacteria and protists, and that VLP abundances are high, it is likely that viruses play a pivotal role in carbon cycling in these extreme ecosystems.     

Planktonic microbial assemblages and the potential effects of metazooplankton predation on the food web of lakes from the maritime Antarctica and sub-Antarctic islands

Antarctica is the continent with the harshest climate on the Earth. Antarctic lakes, however, usually presents liquid water, at least during part of the year or below the ice cover, especially those from the sub-Antarctic islands and the maritime Antarctic region where climatic conditions are less extreme. Planktonic communities in these lakes are mostly dominated by microorganisms, including bacteria and phototrophic and heterotrophic protists, and by metazooplankton, usually represented by rotifers and calanoid copepods, the latter mainly from the genus Boeckella. Here I report and discuss on studies performed during the last decade that show that there is a potential for top–down control of the structure of the planktonic microbial food web in sub-Antarctic and maritime Antarctic lakes. In some of the studied lakes, the effect of copepod grazing on protozoa, either ciliates or flagellates, depending on size of both the predator and the prey, could promote cascade effects that would be transmitted to the bacterioplankton assemblage.     

The biodiversity and ecology of Antarctic lakes: models for evolution

Antarctic lakes are characterised by simplified, truncated food webs. The lakes range from freshwater to hypersaline with a continuum of physical and chemical conditions that offer a natural laboratory in which to study evolution. Molecular studies on Antarctic lake communities are still in their infancy, but there is clear evidence from some taxonomic groups, for example the Cyanobacteria, that there is endemicity. Moreover, many of the bacteria have considerable potential as sources of novel biochemicals such as low temperature enzymes and anti-freeze proteins. Among the eukaryotic organisms survival strategies have evolved, among which dependence on mixotrophy in phytoflagellates and some ciliates is common. There is also some evidence of evolution of new species of flagellate in the marine derived saline lakes of the Vestfold Hills. Recent work on viruses in polar lakes demonstrates high abundance and high rates of infection, implying that they may play an important role in genetic exchange in these extreme environments.     

A Note on the United States and the Law of the Sea: Looking Back and Moving Forward

Since the Antarctic Treaty was negotiated in 1959, there have been substantial developments in the law of the sea. One of the most significant developments has been the recognition granted to coastal state entitlements to claim a range of offshore maritime areas. Yet, one of the principal aims of the Antarctic Treaty was to eliminate sovereignty disputes between territorial claimants, and the treaty placed limitations on the assertion of new claims. Nevertheless, most Antarctic territorial claimants have asserted some form of Antarctic maritime claim. This article particularly considers Australia's position toward maritime claims offshore the Australian Antarctic Territory (AAT). It reviews the limitations imposed by the Antarctic Treaty, the difficulties in determining baselines in Antarctica, Australia's practice in declaring Antarctic maritime claims, and the potential range of maritime boundaries that Australia may one day have to delimit with neighboring states in the Southern Ocean.     

Comparative analysis of bacterioplankton assemblages from maritime Antarctic freshwater lakes with contrasting trophic status

The bacterioplankton assemblages of eight maritime Antarctic lakes with a wide range of trophic status and geographic span (six lakes from Hope Bay, Antarctic Peninsula and two from Potter Peninsula, King George Island) were described using denaturing gradient gel electrophoresis and band sequencing during two consecutive austral summers (2003–2004). Analyses of the gels identified a total of 230 bands spread across 57 different positions. Among those bands, 14 were shared between lakes from Hope Bay and Potter Peninsula, 17 were observed only in particular lakes, and 17 were registered both years in the same lake. We successfully reamplified and sequenced 43 bands located in 36 different positions belonging to Bacteroidetes, Actinobacteria, Betaproteobacteria and Cyanobacteria. The closest matches for 63% of the sequenced bands were from Antarctic or from other cold environment clones and sequences already in the databases, suggesting the widespread dominance of microbial communities adapted to cold habitats. The results of the multivariate analyses (Cluster Analysis and CCA) indicated that the nutrient status of the lake influences the bacterioplankton assemblages. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Living on the edge – plants and global change in continental and maritime Antarctica

Antarctic terrestrial ecosystems experience some of the most extreme growth conditions on Earth and are characterized by extreme aridity and subzero temperatures. Antarctic vegetation is therefore at the physiological limits of survival and, as a consequence, even slight changes to growth conditions are likely to have a large impact, rendering Antarctic terrestrial communities sensitive to climate change. Climate change is predicted to affect the high‐latitude regions first and most severely. In recent decades, the Antarctic has undergone significant environmental change, including the largest increases in ultraviolet‐B (UV‐B; 290–320 nm) radiation levels in the world and, in the maritime region at least, significant temperature increases. This review describes the current evidence for environmental change in Antarctica, and the impacts of this change on the terrestrial vegetation. This is largely restricted to cryptogams, such as bryophytes, lichens and algae; only two vascular plant species occur in the Antarctic, both restricted to the maritime region. We review the range of ecological and physiological consequences of increasing UV‐B radiation levels, and of changes in temperature, water relations and nutrient availability. It is clear that climate change is already affecting the Antarctic terrestrial vegetation, and significant impacts are likely to continue in the future. We conclude that, in order to gain a better understanding of the complex dynamics of this important system, there is a need for more manipulative, long‐term field experiments designed to address the impacts of changes in multiple abiotic factors on the Antarctic flora.     

Molecular analysis of geographic patterns of eukaryotic diversity in Antarctic soils

We describe the application of molecular biological techniques to estimate eukaryotic diversity (primarily fungi, algae, and protists) in Antarctic soils across a latitudinal and environmental gradient between approximately 60 and 87 degrees S. The data were used to (i) test the hypothesis that diversity would decrease with increasing southerly latitude and environmental severity, as is generally claimed for "higher" faunal and plant groups, and (ii) investigate the level of endemicity displayed in different taxonomic groups. Only limited support was obtained for a systematic decrease in diversity with latitude, and then only at the level of a gross comparison between maritime (Antarctic Peninsula/Scotia Arc) and continental Antarctic sites. While the most southerly continental Antarctic site was three to four times less diverse than all maritime sites, there was no evidence for a trend of decreasing diversity across the entire range of the maritime Antarctic (60 to 72 degrees S). Rather, we found the reverse pattern, with highest diversity at sites on Alexander Island (ca. 72 degrees S), at the southern limit of the maritime Antarctic. The very limited overlap found between the eukaryotic biota of the different study sites, combined with their generally low relatedness to existing sequence databases, indicates a high level of Antarctic site isolation and possibly endemicity, a pattern not consistent with similar studies on other continents.     

Molecular Analysis of Geographic Patterns of Eukaryotic Diversity in Antarctic Soils

We describe the application of molecular biological techniques to estimate eukaryotic diversity (primarily fungi, algae, and protists) in Antarctic soils across a latitudinal and environmental gradient between approximately 60 and 87°S. The data were used to (i) test the hypothesis that diversity would decrease with increasing southerly latitude and environmental severity, as is generally claimed for “higher” faunal and plant groups, and (ii) investigate the level of endemicity displayed in different taxonomic groups. Only limited support was obtained for a systematic decrease in diversity with latitude, and then only at the level of a gross comparison between maritime (Antarctic Peninsula/Scotia Arc) and continental Antarctic sites. While the most southerly continental Antarctic site was three to four times less diverse than all maritime sites, there was no evidence for a trend of decreasing diversity across the entire range of the maritime Antarctic (60 to 72°S). Rather, we found the reverse pattern, with highest diversity at sites on Alexander Island (ca. 72°S), at the southern limit of the maritime Antarctic. The very limited overlap found between the eukaryotic biota of the different study sites, combined with their generally low relatedness to existing sequence databases, indicates a high level of Antarctic site isolation and possibly endemicity, a pattern not consistent with similar studies on other continents.     

Diversity of endophytic fungi associated with bryophyte in the maritime Antarctic (King George Island)

Bryophytes comprise one of the richest microfungal microhabitats in the Antarctic environment. The maritime Antarctic is very vulnerable to rapid environmental change caused by global warming. The aim of this study was to investigate the importance of bryophytes as a microhabitat for fungal species in the maritime Antarctic by surveying endophytic fungal diversity from several bryophytes including Andreaea sp., Barbilophozia hatcheri, Chorisodontium aciphyllum, Polytrichum alpinum, Polytrichum strictum, Sanionia uncinata, and Warnstorfia sarmentosa. We collected 13 bryophyte samples at four localities on Barton Peninsula, King George Island. In total, 31 endophytic fungi morphotypes were isolated from bryophyte tissues by a thorough surface sterilization method. Using internal transcribed spacer sequence analysis, 16 endophytic fungal strains belonging to Ascomycota (12), Basidiomycota (1), Oomycota (1), and Zygomycota (2) phyla were obtained. Our results suggest the presence of a diverse range of fungal species even in a very limited area, and those bryophytes play an important role in conserving fungal diversity in this harsh environment. Growth rate measurements at a wide range of temperatures confirmed that most of the fungal strains were both mesophilic and psychrotolerant. This is the first report of endophytic fungi in Antarctic moss tissue by fluorescence in situ hybridization.     

Ciliate biogeography in Antarctic and Arctic freshwater ecosystems: endemism or global distribution of species?

Ciliate diversity was investigated in situ in freshwater ecosystems of the maritime (South Shetland Islands, mainly Livingston Island, 63 degrees S) and continental Antarctic (Victoria Land, 75 degrees S), and the High Arctic (Svalbard, 79 degrees N). In total, 334 species from 117 genera were identified in both polar regions, i.e. 210 spp. (98 genera) in the Arctic, 120 spp. (73 genera) in the maritime and 59 spp. (41 genera) in the continental Antarctic. Forty-four species (13% of all species) were common to both Arctic and Antarctic freshwater bodies and 19 spp. to both Antarctic areas (12% of all species). Many taxa are cosmopolitans but some, e.g. Stentor and Metopus spp., are not, and over 20% of the taxa found in any one of the three areas are new to science. Cluster analysis revealed that species similarity between different biotopes (soil, moss) within a study area was higher than between similar biotopes in different regions. Distinct differences in the species composition of freshwater and terrestrial communities indicate that most limnetic ciliates are not ubiquitously distributed. These observations and the low congruence in species composition between both polar areas, within Antarctica and between high- and temperate-latitude water bodies, respectively, suggest that long-distance dispersal of limnetic ciliates is restricted and that some species have a limited geographical distribution.     

Aspects of the biology of the midge,Eretmoptera murphyi Schaeffer (Diptera: Chironomidae), introduced to Signy Island,maritime Antarctic

Summary The biology of a population of the subantarctic chironomid midge Eretmoptera murphyi Schaeffer, introduced to Signy Island in the maritime Antarctic more than 20 years ago, is described. Investment in reproduction by the parthenogenetic adult females is high, with individuals producing single egg batches containing ca. 85 eggs and having a dry weight of more than twice that of the spent female. In culture, egg development rates to hatching are increased significantly by increasing temperature from 2° to 12°C (a range covering mean summer temperatures found in the species' maritime Antarctic habitat, and natural habitat in the subantarctic). The gelatinous matrix of the egg batch forms a skin on drying, which may reduce further water loss, and allow the eggs or pre-emergence larvae to survive the short periods of desiccating conditions likely to occur in their natural habitat. The biology of E. murphyi is compared with that of the endemic maritime Antarctic species Belgica antarctica, showing much similarity. E. murphyi possesses several preadaptations which allow it to survive the harsher conditions of the maritime Antarctic.     

High viral infection rates in Antarctic and Arctic bacterioplankton

The frequency of visibly phage-infected bacterial cells (FVIB) and the average number of phages per cell [i.e. burst size (BS)] were determined in Antarctic and Arctic ultra-oligotrophic freshwater environments. Water samples were collected from two Antarctic freshwater lakes and cryoconite holes from a glacier in the Arctic. Data from this bipolar study show the highest FVIB (average 26.1%, range 5.1% to 66.7%) and the lowest BS (average 4, range 2-15) ever reported in the literature. The bacterial density is low in these ultra-oligotrophic freshwater environments but a large proportion of the bacteria are visibly infected. Our results suggest that a constant virioplankton population can be maintained in these extreme environments even though host density is low and often slow growing.     

Some aspects of iron cycling in maritime antarctic lakes

Iron occurs in extremely high concentrations in certain maritime Antarctic freshwater lakes which seasonally develop an anoxic zone. In oligotrophic Sombre Lake the data show that Fe(II) precipitates as Fe(III) oxyhydroxides which bind phosphorus and return it to the sediments. In nutrient-enriched Amos lake, significant quantities of sulphide are also produced and this binds a proportion of the released Fe(II) so reducing the ratio of total iron to phosphorus at the redox boundary where the oxyhydroxides are formed. A proportion of the sediment-released phosphorus therefore reaches the upper waters of this lake (unlike in Sombre Lake) and provides the initial nutrient source for under-ice phytoplankton development in spring. Iron-reducing bacteria have been isolated, from Sombre Lake sediments, which apparently utilise the abundant Fe(III) oxyhydroxides. From thermodynamic considerations (assuming Fe(III) is not limiting) these should outcompete sulphate reducers and methanogens (both previously reported from Sombre and Amos Lakes) and could therefore constitute an important component of the anaerobic mineralisation of organic carbon in such lakes.     

Depth distribution of euryhaline halophilic bacteria in Suribati Ike, a meromictic lake in East Antarctica

Euryhaline halophiles grow over a wide range of salinity, from <3% NaCl (seawater equivalent) to >15% NaCl and even saturation level (about 30% NaCl). Several species of euryhaline halophiles occur worldwide, especially in marine environments and also in aquatic and terrestrial habitats of the Antarctic ice-free areas. A biogeographic view of Antarctic halophiles is that their migration among lakes on land is more difficult than in marine setting. Ponds and lakes on land may thus serve as “islands” which facilitate the selection and separation of unique species. We isolated euryhaline halophiles from the saline lake, Suribati Ike, near Syowa Station and placed them into seven groups, each demonstrating a clear depth-related distribution. Six of the seven groups probably represent new species of the genera Halomonas and Marinobacter. This result suggests that Antarctic saline lakes exhibit high selectivity of unique euryhaline halophiles and possibly of other microbial groups.     

Diel patterns of photosynthate biosynthesis by phytoplankton in permanently ice-covered Antarctic lakes under continuous sunlight

Diel patterns of photosynthate biosynthesis by Antarctic freshwaterphytoplankton growing under the variable but continuous sunlightof summer were found to be similar in many respects to thosereported from other aquatic environments where light/dark periodsalternate. Lipid synthesis by freshwater phytoplankton in LakesVanda and Fryxell predominated during periods when solar radiationand photosynthesis were most intense; the inverse was generallytrue of the protein and polysaccharide fractions. The majorphotosynthetic end-products in both lakes were protein and polysaccharide,which together accounted for 60–81% of the total cellularcarbon incorporation. Less than 4% of the carbon was incorporatedinto lipid in Lake Vanda; >12% appeared in the lipid fractionin Lake Fryxell. The Lake Fryxell populations showed evidenceof photoinhibition of complete photosynthesis during ‘midday’when irradiance was most intense. I_k values, computed from thephotosynthesis irradiance relationships in Lake Fryxell, corroborateother studies suggesting that the phytoplankton populationsin permanently ice-capped Antarctic lakes are among the mostshade-adapted yet reported.     

Short-term stability of the microbial community structure in a maritime Antarctic lake

. Spatial and temporal changes in the microbial community structure in a maritime Antarctic freshwater lake were investigated over a single day/night cycle in December 1999. The community structure of key microbial planktonic groups varied with depth and this was related to both physical and chemical stratification. However, in most cases, the community structure observed at specific depths did not change over the time period studied. These results suggested short-term stability in community structure, with only some minor effects of the diel changes in irradiance on the vertical distribution of planktonic organisms. This is in marked contrast to medium- and long-term studies, which show significant changes in microbial community structure with both time and depth.     

Benthic moss pillars in Antarctic lakes

Unique pillar-like colonies of aquatic mosses, rising from cyanobacterial and algal mats, have been discovered in some freshwater lakes in the vicinity of Syowa Station (69°00′S, 39°35′E), continental Antarctica. These moss pillars are about 40 cm in diameter and up to 60 cm high and occur at the lake bottoms mainly between 3 and 5 m depth. The primary component is a species of Leptobryum, a genus unknown in the continental Antarctic terrestrial bryoflora and as an aquatic genus elsewhere in the world. Bryum pseudotriquetrum is often an associated species. In longitudinal section the pillars reveal several whitish layers formed by mineral sediment and dead cyanobacteria. It is speculated that the biomass of aquatic mosses at the bottom of many Antarctic lakes is considerably greater than that previously estimated. Accepted: 11 April 1999     

Assessing methods for collecting and transferring viable algae from Signy Island, maritime Antarctic, to the United Kingdom

. Acquisition and transfer of algae from distant polar locations to research facilities in the northern hemisphere may take several months, at which point the algae may be non-viable and in a deteriorated state. This study explores the effectiveness of 3% (w/v) Benomyl fungicide (Benlate) pre-treatments, on fungal "spoilage", viability and biochemical status of algae collected from terrestrial and freshwater habitats at Signy Island, maritime Antarctic. The results allow recommendations concerning sampling procedures and species selection for the ex-situ study of Antarctic algae to be made. The three algal taxa examined showed that although the fungicide was not necessary for successful transfer of viable specimens, it had a positive effect on viability. Prasiola crispa is suggested as a target organism for future ex-situ physiological studies.     

Evolution of Antarctic lake ecosystems

Antarctic lakes present a wide variety of physical, chemical and biological conditions, and are not always the simplified systems imagined by earlier workers. The volume of data on lakes of various ages now allows informed speculation on the evolution of the Antarctic lake ecosystem.