Salinity control of the distribution of diatoms in lakes of the Bunger Hills, East Antarctica

The biogeography of Antarctic lacustrine diatoms is incompletely known due in part to the absence of information from some important ice-free regions. In the first detailed study of the diatoms of the Bunger Hills, 29 species were identified in near-edge microbial mats of lakes ranging in salinity from fresh to 77‰. Most of the species present had previously been recorded in other East Antarctic coastal oases. The distribution and relative abundance of diatoms within the Bunger Hills were strongly influenced by salinity, but other factors, notably the characteristics of lakes in the immediate area of a particular lake, also played important roles.     

Mid-Holocene skua remains from King George Island,Antarctica

Seven avian remains from Mid-Holocene strata of the southeastern coast of Potter Peninsula (King George Island: Isla 25 de Mayo, South Shetland Islands, Antarctica) are reported. They were described and assigned to the brown skua Stercorarius antarcticus lonnbergi (Aves, Laridae), a living species currently breeding in the area. The presence of penguins in the same sequence is in agreement with the current dynamics of the coastal ecosystems of Antarctica. Nowadays, penguins and skuas frequent these same environments.     

Vertical distribution of macrobenthic infauna from the shallow sublittoral zone of Admiralty Bay,King George Island,Antarctica

A 0.0625 m² mini-box corer (MBC) was used to study the vertical distribution of macrobenthos in the shallow sublittoral zone of Admiralty Bay, during the 2003/2004 summer, near the Brazilian Station Comandante Ferraz, and the Peruvian Station Machu Picchu. Sediment samples were taken from 20, 30 and 60 m, and stratified for particle-size, total organic matter (TOM) and faunal composition analysis. The most abundant taxa were Polychaeta, Oligochaeta, Amphipoda, Cumacea, Bivalvia and Gastropoda. In general, macrofauna were concentrated in the 0–4 cm layer (64% of total organisms). Correlations between sediment characteristics and faunal densities have not completely explained neither the aggregation of organisms at the surface sediment layers nor the differences in faunal composition between locations at 20 m depth. Analysis of parameters such as organic carbon, heavy metals, interstitial water, and species composition should contribute to a better understanding of the diversity patterns found in this study.     

Foraminiferida from Neogene sediments,Vestfold Hills,Antarctica

Sediment samples from several locations in the southern part of the Vestfold Hills have been examined for their foraminiferid content. Those from Early Pliocene sediments of Marine Plain immediately east of Burton Lake contain little foraminiferid evidence of marine deposition. Those from mid-late Holocene sections in and near the lakes contain good open marine faunas of species now known to be living on the continental shelf west of Cape Darnley.Foraminiferid faunas characterized by calcareous forms are most common, the most prevalent dominated by Globocassidulina crassa.The faunas examined contrast markedly with those in the present Prydz Bay which is characterized by agglutinated forms.The results, in relation to planktonic faunas, conflict with an earlier record of a diverse fauna.     

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.     

Depth distribution of photosynthetic pigments and diatoms in the sediments of a microtidal fjord

The depth distribution of photosynthetic pigments and benthic marine diatoms was investigated in late spring at three different sites on the Swedish west coast. At each site, sediment cores were taken at six depths (7–35 m) by scuba divers. It was hypothesized that (1) living benthic diatoms constitute a substantial part of the benthic microflora even at depths where the light levels are <1% of the surface irradiance, and (2) the changing light environment along the depth gradient will be reflected in (a) the composition of diatom assemblages, and (b) different pigment ratios. Sediment microalgal communities were analysed using epifluorescence microscopy (to study live cells), light microscopy and scanning electron microscopy (diatom preparations), and HPLC (photosynthetic pigments). Pigments were calculated as concentrations (mg m^–2) and as ratios relative to chlorophyll a. Hypothesis (1) was accepted. At 20 m, the irradiance was 0.2% of surface irradiance and at 7 m, 1%. Living (epifluorescent) benthic diatoms were found down to 20 m at all sites. The cell counts corroborated the diatom pigment concentrations, decreasing with depth from 7 to 25 m, levelling out between 25 and 35 m. There were significant positive correlations between chlorophyll a and living (epifluorescent) benthic diatoms and between the diatom pigment fucoxanthin and chlorophyll a. Hypothesis (2) was only partly accepted because it could not be shown that light was the main environmental factor. A principal component analysis on diatom species showed that pelagic forms characterized the deeper locations (25–35 m), and epipelic–epipsammic taxa the shallower sites (7–20 m). Redundancy analyses showed a significant relationship between diatom taxa and environmental factors – temperature, salinity, and light intensities explained 57% of diatom taxa variations.     

Influence of soil properties on the distribution of Deschampsia antarctica on King George Island, Maritime Antarctica

The extremely cold and infertile Antarctic is one of the harshest terrestrial ecosystems for the growth of vegetation, except for the grass species Deschampsia antarctica. We examined the main soil variables that determine the distribution of D. antarctica in King George Island by using Bayesian analysis of variance and regression methods. This study compared the density of D. antarctica between 2 sites; the density remained relatively stable at site 1, whereas it severely decreased in site 2 over a period of 3?years. Although site 2 showed better soil conditions for the growth of D. antarctica such as organic matter content, available phosphorus, NO₃-N, and extractable cations, its poor drainage and low soil pH may affected the survival of D. antarctica by altering nutrition availability and inhibiting root respiration. Poisson analysis of covariance showed that the early melting of snow was also an important factor in the distribution of D. antarctica. The results also showed that seabirds and mammals might have greatly influenced the distribution of the grass species in King George Island by transferring nutrients from the sea onto land; thus, changing the chemical characteristics of the soil.     

苏州河沉积物中硅藻的垂直分布与水质变化

分析了苏州河2个柱状沉积物样品中硅藻种类和丰度的垂直变化,同时采用210Pb测年法推测沉积物的沉积速率,并进行了有机质含量分析,以了解苏州河在不同年代的水质变化。结果表明,2个柱状沉积物中硅藻的优势属为小环藻属、直链藻属、舟形藻属、圆筛藻属和针杆藻属。优势种为梅尼小环藻、瞳孔舟形藻和变异直链藻。就硅藻丰度而言,总趋势是上层最多,平均4.04~25.18×104ind/g;下层其次,平均1.41~4.43×104ind/g;中层最少,平均0.91~2.30×104ind/g。硅藻种类数变化虽无明显规律,但种类最少的样品仍出现在中层,210Pb测年数据表明中层为20世纪60~80年代。相关分析表明硅藻丰度与有机质含量呈显著正相关(p<0.01))。本文结果表明,沉积物中硅藻可以反映苏州河的污染历程:20世纪40~50年代初,水质尚可,但已有富营养化现象,表现在硅藻数量和丰度均较高;50年代中后期开始出现较严重的工业污染,到20世纪70~80年代污染加重,表现在中层沉积物中硅藻种类和数量均减少;进入20世纪90年代,水质有所改善,上层沉积物中硅藻种类和数量又逐渐增多,这与90年代以后加大对苏州河治理力度有关。     

Microbial mats of twenty-six lakes from Potter Peninsula,King George Island,Antarctica

The taxonomic composition and ecology of microbial mats were investigated in 26 lentic environments of Potter Peninsula (King George Island, Antarctica) during the summer of 1995/96. These have different limnological characteristics according to the location of the basins. Among the 139 algal taxa registered, 10 are new records for Antarctica. Bacillariophyceae was the dominant class in terms of species richness, followed by the Cyanobacteria and Chlorophyceae. TWINSPAN classification was used to describe six epilithic algal assemblages; Canonical Correspondence Analysis ordination showed that soluble reactive phosphorus, phytoplanktonic chlorophyll a concentration and conductivity were the main sources for the variation in the data.     

Proteolytic anaerobic bacteria from lake sediments of Antarctica

Amongst twenty five proteolytic bacteria isolated from lake sediment samples of Antarctica, six isolates were selected based on SDS PAGE protein profile and zone of hydrolysis on casein agar at 10 degrees C. Most of the cultures were rod shaped and motile with two showing terminal bulging spores. Isolates grew between 5 degrees C to 37 degrees C and protease was induced in the late log, stationary or death phase. Isolate SPA-3 grew maximally at 10 degrees C and SPA-6 at 37 degrees C while others preferred 20 degrees C-30 degrees C for growth. The growth and protease production on casein, skimmed milk, bovine serum albumin and gelatin varied with the isolates. Acetate was the dominant volatile fatty acid (24-66% of total VFA) produced during hydrolysis of protein substrate.     

Extracellular hydrolase enzyme production by soil fungi from King George Island, Antarctica

Various microbial groups are well known to produce a range of extracellular enzymes and other secondary metabolites. However, the occurrence and importance of investment in such activities have received relatively limited attention in studies of Antarctic soil microbiota. In order to examine extracellular enzyme production in this chronically low-temperature environment, fungi were isolated from ornithogenic, pristine and human-impacted soils collected from the Fildes Peninsula, King George Island, Antarctica during the austral summer in February 2007. Twenty-eight isolates of psychrophilic and psychrotolerant fungi were obtained and screened at a culture temperature of 4°C for activity of extracellular hydrolase enzymes (amylase, cellulase, protease), using R2A agar plates supplemented with (a) starch for amylase activity, (b) carboxymethyl cellulose and trypan blue for cellulase activity or (c) skim milk for protease activity. Sixteen isolates showed activity for amylase, 23 for cellulase and 21 for protease. One isolate showed significant activity across all three enzyme types, and a further 10 isolates showed significant activity for at least two of the enzymes. No clear associations were apparent between the fungal taxa isolated and the type of source soil, or in the balance of production of different extracellular enzymes between the different soil habitats sampled. Investment in extracellular enzyme production is clearly an important element of the survival strategy of these fungi in maritime Antarctic soils.     

Meiofauna distribution in Martel Inlet, King George Island (Antarctica): sediment features versus food availability

The meiofauna density in Martel Inlet, Admiralty Bay, King George Island (Antarctica) was studied in order to better understand the spatial patterns of meiofauna distribution in shallow polar seas. Sampling was undertaken by scuba-diving at 15 m depth at 7 stations during the summers of 1996/1997 and 1997/1998. The meiofauna was dominated by nematodes (>60%), followed by copepods, nauplii and polychaetes. The mean densities found during the 2 years studied (4.09 and 3.5᎒⁶ ind. m^-2) suggest that the shallow area of Martel Inlet is characterized by higher numbers of meiofaunal organisms than are found in other ecosystems, which is in agreement with other meiofaunal studies carried out in polar areas. It may be concluded that it is mainly the sedimentary features that influence the meiofauna distribution. However, food availability must contribute to the support of the higher meiofauna densities found in the inlet.     

Morphology and diet are decoupled in nearshore notothenoids from King George Island,West Antarctica

Antarctic notothenioid fishes show wide adaptive morphological radiation, linked to habitat preferences and food composition. However, direct comparisons of phenotypic variability and feeding habits are still lacking, particularly in stages inhabiting nearshore areas. To assess these relationships, we collected juveniles and adults of the most common benthic species inhabiting shallow waters off the South Shetland Islands within a similar size range, the plunderfish Harpagifer antarcticus, the black rockcod Notothenia coriiceps, and the marbled rockcod Notothenia rossii. Individual size ranges varied from 44.0 to 98.9 mm standard length (LS) (H. antarcticus), from 95.8 to 109.3 mm LS (N. coriiceps), and from 63.0 to 113.0 mm LS (N. rossii). Notothenioid fish showed different morphospace variability, being larger for H. antarcticus than the other Notothenia species and associated with the position of the posterior end of the operculum, along with the location and relative size of the eye. The evolutionary allometry was low, but the static allometry was much higher, especially for H. antarcticus and N. rossii. The diet was mainly carnivorous, consisting of amphipods and euphausiids. Macroalgae were scarce or totally absent in the gut contents of all species. Only H. antarcticus showed an increase in the prey number and ingested prey volume with fish size. Finally, there was a significant covariation between shape changes and LS in all species (allometric effects), however, not with prey composition, probably due to the small size range or ontogenetic stage and the relative similarity (or lack of contrast) in the benthic environment that they utilized.     

Molecular diversity of microbial eukaryotes in sea water from Fildes Peninsula,King George Island,Antarctica

Data on Antarctic coastal sites remain scarce and are generally limited to microscopy; the diversity of coastal Antarctic ecosystems has long been underestimated. The diatom-dominant community in the coastal sea waters of the Fildes Peninsula has been described according to traditional protocols. Molecular diversity of microbial eukaryotes (≤20 µm) from Great Wall Cove and Ardley Cove, Fildes Peninsula, has been determined by Illumina MiSeq2000 sequencing. Inferred metabolisms of summer phytoplankton in the two coves are characterised by autotrophy and heterotrophy. The frequent occurrence of such nanoflagellates as dinoflagellates, Cryptophyta, Stramenopiles, Pyramimonas, Telonema, and Cryothecomonas is predicted to be important in these Antarctic coastal communities. Sea water exchange exists between the two coves when high tide occurs, indicating that there appears to be mixing between the microbial communities in the two coves. Cluster analysis of the microbial eukaryote composition at the phylum and genus levels reveals a conservation of the community composition between the two coves. The inner stations of Great Wall Cove represented by three shoal samples (G1, G2, and G3) are clustered closely together, surrounded by islands and formed into a semi-closed body of water. The samples from the outer stations G4 and G5 of Great Wall Cove, which are separated from the other three Great Wall stations, are more similar to the Ardley Cove samples. Sea water exchange between the outer basins might be the effect of their community compositions. The nanoplankton diversity in Great Wall Cove is richer than in Ardley Cove, according to the α-diversity index.     

Characterization and comparison of potential denitrifiers in microbial mats from King George Island,Maritime Antarctica

Cyanobacterial microbial mats are highly structured communities commonly found in Antarctic inland waters including melt streams. These benthic microbial associations comprise a large number of microorganisms with different metabolic capacities, impacting nutrient dynamics where established. The denitrification process is a feasible nitrogen loss pathway and a biological source of nitrous oxide, a potent greenhouse gas that also promotes ozone depletion. Potential denitrifiers from five microbial mats were characterized using a PCR-DGGE (denaturing gradient gel electrophoresis) approach. Molecular markers encoding for key enzymes in the denitrification process (nirK, nirS and nosZ) were used. Fingerprints were obtained for the five sampled mats and compared for two successive years. Distance analysis showed that despite the sampled year, the denitrifying genetic potential was similar between most of the sites when represented in Euclidean space. The number of dominant denitrifiers detected for each sample ranged between 6 and 18 for nirK, 4–10 for nirS and 6–17 for nosZ. The seventy-two sequenced phylotypes showed 80–98 % identity to previously reported environmental sequences from water column, sediments and soil samples. These results suggest that Antarctic microbial mats have a large denitrification potential, previously uncharacterized and composed by both site-specific and common phylotypes belonging mainly to Alpha-, Beta- and Gammaproteobacteria.     

Chitinase genes in lake sediments of Ardley Island, Antarctica

A sediment core spanning approximately 1,600 years was collected from a lake on Ardley Island, Antarctica. The sediment core had been greatly influenced by penguin guano. Using molecular methods, the chitinolytic bacterial community along the sediment core was studied over its entire length. Primers targeting conserved sequences of the catalytic domains of family 18 subgroup A chitinases detected group A chitinases from a wide taxonomic range of bacteria. Using quantitative competitive PCR (QC-PCR), chitinase gene copies in each 1-cm section of the whole sediment column were quantified. QC-PCR determination of the chitinase gene copies indicated significant correlation with phosphorus and total organic carbon concentration, suggesting a historical connection between chitinase gene copies and the amount of penguin guano input into the lake sediment. Most of the chitinase genes cloned from the historic sediment core were novel. Analysis of the chitinase gene diversity in selected sediment layers and in the fresh penguin deposits indicated frequent shifts in the chitinolytic bacterial community over time. Sequence analysis of the 16S rRNA genes of chitinolytic bacteria isolated from the lake sediment revealed that the isolates belonged to Janthinobacterium species, Stenotrophomonas species of gamma-Proteobacteria, Cytophaga species of the Cytophaga-Flexibacter-Bacteroides group, and Streptomyces and Norcardiopsis species of Actinobacteria. Chitinase gene fragments were cloned and sequenced from these cultivated chitinolytic bacteria. The phylogeny of the chitinase genes obtained from the isolates did not correspond well to that of the isolates, suggesting acquisition via horizontal gene transfer.     

Cold-active acetogenic bacteria from surficial sediments of perennially ice-covered Lake Fryxell, Antarctica

RibR is a minor cryptic flavokinase (EC 2.7.1.26) of the Gram-positive bacterium Bacillus subtilis with an unknown cellular function. The flavokinase activity appears to be localized to the N-terminal domain of the protein. Using the yeast three-hybrid system, it was shown that RibR specifically interacts in vivo with the nontranslated wild-type leader of the mRNA of the riboflavin biosynthetic operon. This interaction is lost partially when a leader containing known cis-acting deregulatory mutations in the so-called RFN element is tested. The RFN element is a sequence within the rib-leader mRNA reported to serve as a receptor for an FMN-dependent 'riboswitch'. In RibR itself, interaction was localized to the carboxy-terminate part of the protein, a segment of unknown function that does not show similarity to other proteins in the public databases. Analysis of a ribR-defective strain revealed a mild deregulation with respect to flavin (riboflavin, FMN and FAD) biosynthesis. The results indicate that the RNA-binding protein RibR may be involved in the regulation of the rib genes.     

The diversity, distribution and ecology of diatoms from Antarctic inland waters

Diatoms are abundant and diverse in many Antarctic freshwaters, with a general trend of decreasing diversity moving southwards. They form an important component of many benthic algal communities in streams and standing waters but are generally less common in the phytoplankton. Diatoms are excellent ecological indicator species and, because their remains are preserved in many sedimentary environments, there appears to be a great potential for palaeoenvironmental reconstruction and the examination of past diversity. A lack of taxonomic precision and consistency, coupled with the insufficient collection from some geographical areas, makes the estimation of the number of Antarctic diatom species problematic.