Biodiversity and biogeographic affiliation of Bryozoa from King George Island (Antarctica)

King George Island (KGI), which is located between the Antarctic and South American continents, may play a crucial role in the exchange of Bryozoa amongst the various Antarctic sectors and across the Polar Front. Knowledge regarding the biological diversity of this area could help us understand the evolution of the Antarctic ecosystem and its connectivity to the South American continent as well as the colonization ability of particular species. Here, we investigate the patterns of diversity and biogeographic affiliation of the cheilostome Bryozoa from KGI and the surrounding areas. Of 114 identified taxa from a depth range of 6–492 m, 26 species were reported for the first time in KGI. The most speciose genera were Camptoplites, Osthimosia, Smittina, and Cellarinella. Species richness at KGI consisted of 70% of the total bryozoans at the South Shetland Islands (SSI). Fifty-nine per cent of the bryozoans from KGI are endemic to Antarctica, which closely reflects the previously estimated endemism rate for bryozoans and other Antarctic taxa. Cluster analysis indicated that the strongest faunal links of SSI bryozoans were with Antarctic Peninsula assemblages, corresponding to the physical distance between both locations. The biogeographic similarities between SSI and South America confirm the broad trend of existing Antarctic–South American faunal links previously observed in bryozoans and many other taxa and indicate that SSI might be an important transitional zone between Antarctica and South America.     

Regional genetic diversity patterns in Antarctic hairgrass (Deschampsia antarctica Desv.)

Aim  To determine patterns in diversity of a major Antarctic plant species, including relationships of Antarctic populations with those outside the Antarctic zone.
Location  Antarctic Peninsula, Maritime Antarctica, sub-Antarctic islands, Falkland Islands and South America.
Methods  Amplified fragment length polymorphisms (AFLPs) and chloroplast sequences were used to study patterns of genetic diversity in Antarctic hairgrass ( Deschampsia antarctica Desv.) and the genetic relationships between populations over its distribution range. Thirty-eight populations were sampled from a large part of the distribution of D. antarctica , and additionally, herbarium specimens were included for areas from which we could not obtain fresh samples.
Results  A gradient in AFLP diversity was observed going from the Falklands southwards into the Antarctic. This gradient in diversity was also observed within the Antarctic Peninsula: diversity was lower further south. Diversity in the chloroplast genome of D. antarctica was low. Only three chloroplast haplotypes were found, each with a strong regional distribution.
Main conclusions  The phylogenetic construction of AFLP marker frequencies in meta-populations of D. antarctica supports a stepping-stone model of colonization, whereby gene flow mainly occurs between neighbouring populations. It is concluded that long-distance gene flow is very limited in D. antarctica . A very low diversity was found in the sub-Antarctic islands in the Indian Ocean, indicating that these populations have experienced a recent evolutionary bottleneck.     

The Bryophytes of the King George Island,Antarctica

After examining the moss collections from the King George Island collected by Dr. Wei Jiang-chun and Mr. Li Zhen-pei in 1983–1984 and 1985 separately, we find 7 species of the mosses, which belong to 4 families and 6 genera. Some of them such as the mosses of Calliergon and Drepanocladus favour moist habitats, whereas Andreaea obovata indicates the dry rocky substratum. Barbula unguiculata and Tortula ruralis could suffer non-permanent dry condition. Geographically, except Andreaea obovata and Calliergon stramineum the other mosses are almost cosmopolitans. They probably distributed to the King George Island before Antarctica drifting to the recent position, and the strong wind was also possible to blow the spores of mosses to Antarctica.     

Distribution of microphytobenthic biomass in Martel Inlet,King George Island (Antarctica)

The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island, Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005). The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m⁻², 261.7 ± 455.9 mg Phaeo m⁻²), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m⁻², 108.8 ± 73.0 mg Phaeo m⁻²) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m⁻², 58.3 ± 38.9 mg Phaeo m⁻²). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material.     

Characterization of rhizospheric bacteria isolated from Deschampsia antarctica Desv.

Deschampsia antarctica Desv. is the only gramineae capable of colonizing the Antarctic due to the region’s extreme climate and soil environment. In the present research, bacteria colonizing the rhizospheric soil of D. antarctica were isolated and characterized. The soil studies showed that D. antarctica possesses a wide spectrum of psychrotolerant bacteria with extensive and varied antibiotic resistance, as well as heavy metal tolerance. The bacterial strains isolated from the rhizosphere of D. antarctica also produced a diverse pattern of enzymes. Based on the strain identification with partial characterization of the 16S rRNA gene, the majority of the isolates correspond to different Pseudomonas species, and species of the genus Flavobacterium sp. and Arthrobacter sp. The isolated strains collected from this research constitute a unique collection for future, more detailed taxonomic analysis and physiological characterization, contributing to the search for potential biotechnological uses. These findings and others have great potential for developing new biotechnological products from Antarctic microorganisms.     

Expressed sequence tag analysis of Antarctic hairgrass Deschampsia antarctica from King George Island, Antarctica

Deschampsia antarctica is the only monocot that thrives in the tough conditions of the Antarctic region. It is an invaluable resource for the identification of genes associated with tolerance to various environmental pressures. In order to identify genes that are differentially regulated between greenhouse-grown and Antarctic field-grown plants, we initiated a detailed gene expression analysis. Antarctic plants were collected and greenhouse plants served as controls. Two different cDNA libraries were constructed with these plants. A total of 2,112 cDNA clones was sequenced and grouped into 1,199 unigene clusters consisting of 243 consensus and 956 singleton sequences. Using similarity searches against several public databases, we constructed a functional classification of the ESTs into categories such as genes related to responses to stimuli, as well as photosynthesis and metabolism. Real-time PCR analysis of various stress responsive genes revealed different patterns of regulation in the different environments, suggesting that these genes are involved in responses to specific environmental factors.     

King penguin population on Macquarie Island recovers ancient DNA diversity after heavy exploitation in historic times

Historically, king penguin populations on Macquarie Island have suffered greatly from human exploitation. Two large colonies on the island were drastically reduced to a single small colony as a result of harvesting for the blubber oil industry. However, recent conservation efforts have resulted in the king penguin population expanding in numbers and range to recolonize previous as well as new sites. Ancient DNA methods were used to estimate past genetic diversity and combined with studies of modern populations, we are now able to compare past levels of variation with extant populations on northern Macquarie Island. The ancient and modern populations are closely related and show a similar level of genetic diversity. These results suggest that the king penguin population has recovered past genetic diversity in just 80 years owing to conservation efforts, despite having seen the brink of extinction.     

The influence of landscape,climate and history on spatial genetic patterns in keystone plants (Azorella) on sub‐Antarctic islands

The distribution of genetic variation in species is governed by factors that act differently across spatial scales. To tease apart the contribution of different processes, especially at intermediate spatial scales, it is useful to study simple ecosystems such as those on sub‐Antarctic oceanic islands. In this study, we characterize spatial genetic patterns of two keystone plant species, Azorella selago on sub‐Antarctic Marion Island and Azorella macquariensis on sub‐Antarctic Macquarie Island. Although both islands experience a similar climate and have a similar vegetation structure, they differ significantly in topography and geological history. We genotyped six microsatellites for 1,149 individuals from 123 sites across Marion Island and 372 individuals from 42 sites across Macquarie Island. We tested for spatial patterns in genetic diversity, including correlation with elevation and vegetation type, and clines in different directional bearings. We also examined genetic differentiation within islands, isolation‐by‐distance with and without accounting for direction, and signals of demographic change. Marion Island was found to have a distinct northwest–southeast divide, with lower genetic diversity and more sites with a signal of population expansion in the northwest. We attribute this to asymmetric seed dispersal by the dominant northwesterly winds, and to population persistence in a southwestern refugium during the Last Glacial Maximum. No apparent spatial pattern, but greater genetic diversity and differentiation between sites, was found on Macquarie Island, which may be due to the narrow length of the island in the direction of the dominant winds and longer population persistence permitted by the lack of extensive glaciation on the island. Together, our results clearly illustrate the implications of island shape and geography, and the importance of direction‐dependent drivers, in shaping spatial genetic structure.     

Morphology and Molecular Phylogeny of Pseudocyrtohymena koreana n. g., n. sp. and Antarctic Neokeronopsis asiatica Foissner et al., 2010 (Ciliophora,Sporadotrichida), with a Brief Discussion of the Cyrtohymena Undulating Membranes Pattern

We discovered a new brackish water oxytrichid Pseudocyrtohymena koreana n. g., n. sp. in South Korea and investigated the new species on the basis of morphology, ontogenesis, and 18S rRNA gene sequences. The new genus has the 18 frontal‐ventral‐transverse cirri of typical oxytrichids with flexible body, cortical granules, Cyrtohymena undulating membranes (UM), and one left and one right marginal cirral row. Ontogenesis of the new species indicated that dorsal kinety anlage 3 stretches within the parental row without any fragmentations (Urosomoida pattern) and exclusively forms all caudal cirri. The new genus is morphologically similar to Cyrtohymena Foissner, 1989, but has the following distinctive features: (i) caudal cirri absent in dorsal kineties 1 and 2 (vs. present in Cyrtohymena); and (ii) dorsal kinety 3 nonfragmented (vs. fragmented in Cyrtohymena). Further, we collected an additional species Neokeronopsis asiatica Foissner et al. 2010, from King George Island, Antarctica, and the species shares the morphology of UM with Cyrtohymena. Herein, we describe the previously unidentified characteristics of N. asiatica (i.e., cortical granules, body flexibility, contractile vacuole, and 18S rRNA gene sequence). In addition, we obtained two 18S rRNA gene sequences from Cyrtohymena muscorum and Parasterkiella thompsoni to expand samples for phylogenetic analysis. Our 18S rRNA gene tree supports the hypothesis that the Cyrtohymena UM pattern might have evolved several times in hypotrichs (e.g., Neokeronopsidae, Oxytrichinae, and Stylonychinae).     

Leishmanicidal and antitumoral activities of endophytic fungi associated with the Antarctic angiosperms Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl.

A total of 564 isolates of endophytic fungi were recovered from the plants Deschampsia antarctica and Colobanthus quitensis collected from Antarctica. The isolates were screened against parasites Leishmania amazonensis and Trypanosoma cruzi and against the human tumour cell lines. Of the 313 fungal isolates obtained from D. antarctica and 251 from C. quitensis, 25 displayed biological activity. Nineteen extracts displayed leishmanicidal activity, and six inhibited the growth of at least one tumour cell line. These fungi belong to 19 taxa of the genera Alternaria, Antarctomyces, Cadophora, Davidiella, Helgardia, Herpotrichia, Microdochium, Oculimacula, Phaeosphaeria and one unidentified fungus. Extracts of 12 fungal isolates inhibited the proliferation of L. amazonesis at a low IC₅₀ of between 0.2 and 12.5 μg ml⁻¹. The fungus Phaeosphaeria herpotrichoides displayed only leishmanicidal activity with an IC₅₀ of 0.2 μg ml⁻¹, which is equivalent to the inhibitory value of amphotericin B. The extract of Microdochium phragmitis displayed specific cytotoxic activity against the UACC-62 cell line with an IC₅₀ value of 12.5 μg ml⁻¹. Our results indicate that the unique angiosperms living in Antarctica shelter an interesting bioactive fungal community that is able to produce antiprotozoal and antitumoral molecules. These molecules may be used to develop new leishmanicidal and anticancer drugs.     

Metagenomic analysis of microbial communities across a transect from low to highly hydrocarbon-contaminated soils in King George Island,Maritime Antarctica

Soil samples from a transect from low to highly hydrocarbon-contaminated soils were collected around the Brazilian Antarctic Station Comandante Ferraz (EACF), located at King George Island, Antarctica. Quantitative PCR (qPCR) analysis of bacterial 16S rRNA genes, 16S rRNA gene (iTag), and shotgun metagenomic sequencing were used to characterize microbial community structure and the potential for petroleum degradation by indigenous microbes. Hydrocarbon contamination did not affect bacterial abundance in EACF soils (bacterial 16S rRNA gene qPCR). However, analysis of 16S rRNA gene sequences revealed a successive change in the microbial community along the pollution gradient. Microbial richness and diversity decreased with the increase of hydrocarbon concentration in EACF soils. The abundance of Cytophaga, Methyloversatilis, Polaromonas, and Williamsia was positively correlated (p-value = <.05) with the concentration of total petroleum hydrocarbons (TPH) and/or polycyclic aromatic hydrocarbons (PAH). Annotation of metagenomic data revealed that the most abundant hydrocarbon degradation pathway in EACF soils was related to alkyl derivative-PAH degradation (mainly methylnaphthalenes) via the CYP450 enzyme family. The abundance of genes related to nitrogen fixation increased in EACF soils as the concentration of hydrocarbons increased. The results obtained here are valuable for the future of bioremediation of petroleum hydrocarbon-contaminated soils in polar environments.     

Regulation of foraging trips and costs of incubation shifts in the Antarctic petrel (Thalassoica antarctica)

In species where incubation is shared by both parents, the mate'sability to fast on the nest may constrain the time availablefor foraging. The decision to return to the nest should thereforebe a compromise between an animal's own foraging success andits mate's ability to fast on the nest. To examine how the bodyconditions of incubating Antarctic petrels, Thalassoica antarctica,influence both the length of foraging trips and incubation shifts,we experimentally handicapped females by increasing their flightcosts during a foraging trip by adding lead weights to theirlegs. Handicapped females spent more time at sea and had lowerbody conditions at arrival to the colony than controls, and,moreover, females in poor body condition at arrival to the colonyspent generally more time at sea than those with higher bodycondition. The prolonged time period spent at sea by handicappedfemales was associated with higher desertion rates than amongcontrols. The time the incubating mates fasted increased withtheir body condition at arrival to the colony, suggesting thata high body condition of the incubating bird may reduce theprobability of nest desertion. Accordingly, our results suggestthat the time spent foraging is adjusted to the body conditionsof both the foraging and incubating mate.     

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.     

Anatomical features and ultrastructure of Deschampsia antarctica (Poaceae) leaves from different growing habitats

BACKGROUND AND AIMS: The leaf anatomy and ultrastructure of Deschampsia antarctica (Poaceae) plants growing in three different habitats (a dry site in the Antarctic tundra, a wet site in a zone exposed to sea spray and a greenhouse) were investigated. The ultrastructure of the leaves of D. antarctica has not been studied before. METHODS: Semi-thin sections of the D. antarctica leaves were stained with toluidine blue and viewed using a light microscope. Ultra-thin sections stained with uranyl acetate and lead citrate were examined using a transmission electron microscope. KEY RESULTS: Plants growing in the Antarctic tundra and in a greenhouse had stronger xerophytic features than those growing at the seashore. The stress response of D. antarctica plants growing in the wet environment, exposed to high salinity and flooding, included: irregular mesophyll cells, large intercellular spaces in the parenchymatic layer, bulliform epidermal cells and vascular bundles surrounded with deformed outer and inner bundle sheaths of leaves. The highest number of sclerenchymatic fibres is characteristic of the leaves of plants growing in a greenhouse, whereas the smallest was of plants growing in a wet habitat. Stress conditions can disturb the formation of sclerenchymatic fibres. In plants growing in the Maritime Antarctic the chloroplasts of the mesophyll cells of leaves are of an irregular shape, with pockets or invaginations inside the organelles and outgrowths. Both of them make the surfaces of chloroplasts larger, and result in an increase in the amount of substances exchanged between the chloroplasts and cytoplasm or the other organelles. The leaf mesophyll cells of D. antarctica plants growing in Antarctica contain atypical structures including numerous vesicles of different sizes and concentrically arranged membranes. CONCLUSIONS: The anatomical and ultrastructural features of the leaf and their changes under stress conditions are considered in relation to the adaptations of D. antarctica to the climate conditions in the Maritime Antarctic.     

Vegetation Types,Community Species Diversity and Conservation of Southern Fildes Peninsula (King George Island,South Shetland Islands) Antarctic

The vegetation in Southern Peninsula (including Ardley Island) was classified according to the composition of species (especially dominant species), physiognomy and structure, and ecology factor, into tundra, meadow, marsh and aquatic vegetation; among which the formation and association were described. The formation and distribution of these communities were dependent on the water supply and the stability of the substrata. The paper discusses also the distributional pattern of vegetation from coast to hill top, characteristics of communities, comparative study on the species number, evenness and diversity among each formation and among different habitat, and some suggestions on vegetation conservation was also attempted.