MIXOTROPHY IN THE ANTARCTIC PHYTOFLAGELLATE,PYRAMIMONAS GELIDICOLA (CHLOROPHYTA: PRASINOPHYCEAE)1

Grazing by the planktonic phytoflagellate, Pyramimonas gelidicola McFadden (Chlorophyta: Prasinophyta), and heterotrophic nanoflagellates (HNAN) in meromictic saline Ace Lake in the Vestfold Hills, eastern Antarctica was investigated in the austral summers of 1997 and 1999. Up to 47% of the P. gelidicola population ingested fluorescently labeled prey (FLP). Ingestion rates varied with depth. In January 1997 and November 1999, maximum P. gelidicola ingestion rates of 6.95 and 0.79 FLP·cell^?1·h^?1, respectively, were measured at the chemocline (6–8 m) where a deep chl maximum composed of phototrophic nanoflagellates (PNAN DCM), predominantly P. gelidicola, persisted all year. During the summers of 1997 and 1999, the grazing P. gelidicola community removed between 0.4% and approximately 16% of in situ bacterial biomass, equivalent to between 4% and>100% of in situ bacterial production. Because of their higher abundance, the community clearance rates of HNAN in Ace Lake generally exceeded those of P. gelidicola, but HNAN removed approximately only 3%–4% of bacterial biomass, equivalent to between 28% and 32% of bacterial production. Pyramimonas gelidicola growth rates were highest at the PNAN DCM concomitant with the highest ingestion rates. It is estimated that during the summer P. gelidicola can derive up to 30% of their daily carbon requirements from bacterivory at the PNAN DCM. This study confirms mixotrophy as an important strategy by which planktonic organisms can survive in extreme, polar, lacustrine ecosystems.     

Annual cycle of phytoplankton in Ace Lake,an ice covered,saline meromictic lake

The annual cycle of phytoplankton in saline, meromictic Ace Lake (68°2S.4S, 78°11.1E) in the Vestfold Hills, Antarctica, was studied from January, 1979 to January 1980. Ace Lake has permanent gradients of temperature, salinity, dissolved oxygen, and hydrogen sulphide, and is ice covered with up to 2 m of ice for 10–12 months each year. The phytoplankton community had low diversity, consisting of only four species, all flagellates — a prasinophyte Pyramimonas gelidicola McFadden et al., a cryptophyte of the genus Cryptomonas; an unidentified colourless microflagellate, and an unarmoured dinoflagellate. These were restricted to the oxic zone of the lake from the surface to 10 m.The phytoplankton had a cycle of seven months of active growth over spring and summer. Low numbers of cells survived in the water column over winter. Spring growth was initiated below the ice by increased light penetration through the ice into the lake, enhanced at the time by the removal of surface snow which accumulated on the ice over winter. Peak phytoplankton biomass production was by the shade adapted P. gelidicola and occurred at the interface of the oxic and anoxic zones where substantial available nitrogen as ammonia is found.The three dominant phytoplankton species displayed distinct vertical stratification over the oxic zone. This stratification was not static and developed over spring as the flagellates migrated to preferred light climate zones. Mean cell volume of two of the flagellates varied significantly over the year. Minimum volumes were recorded in winter and volume increased progressively over spring to reach maximum mean cell volume in summer. Mean cell volume was positively correlated with light intensity (maximum ambient PAR at the respective depth for date of sample). Low cell volume in winter may be related to winter utilization of carbohydrate reserves by slow respiration, and may represent a survival mechanism.     

The plankton community of a young, eutrophic, Antarctic saline lake

A shallow, saline lake (Rookery Lake) close to the sea and surrounded by a penguin rookery was investigated during the austral spring and summer of 1996/1997. The proximity to the sea means that the lake is likely to have been formed recently during isostatic uplift. Inputs of carbon and nutrients from the penguin rookery have rendered Rookery Lake eutrophic compared with other brackish and saline lakes in the Vestfold Hills. Chlorophyll a concentration, bacterioplankton, heterotrophic nanoflagellate and phototrophic nanoflagellate abundances were all significantly higher than in other non-enriched lakes. The high productivity created seasonal anoxia during winter and spring below ice cover. The ciliate community resembled the marine community, and was dissimilar to that seen in older saline lakes within the Vestfold Hills. Thus Rookery Lake provides valuable evidence of the impact of natural eutrophication on an Antarctic lake, as well as of the evolution of the typical microbial community which dominates the older lakes of the Vestfold Hills. Accepted: 2 May 1999     

Detection of a novel ecotype of <Emphasis Type="Italic">Pfiesteria piscicida</Emphasis> (Dinophyceae) in an Antarctic saline lake by real-time PCR

The heterotrophic dinoflagellate Pfiesteria piscicida was detected in Ace Lake in the Vestfold Hills, eastern Antarctica by using real-time PCR based on 18S rDNA sequences. Antarctic water samples collected in 2004 were tested by species-specific real-time PCR assays for the identification of P. piscicida and P. shumwayae. Positive results were shown with P. piscicida-specific real-time PCR, and PCR products were examined by sequence analysis for confirmation. A phylogenetic tree made from partial 18S rDNA sequences showed that the Antarctic clone clustered with P. piscicida. This result suggests that P. piscicida is present in the extreme conditions of an Antarctic saline lake which has not contained fish for thousands of years.     

Ace Lake: three decades of research on a meromictic,Antarctic lake

Ace Lake (Vestfold Hills, Antarctica) has been investigated since the 1970s. Its close proximity to Davis Station has allowed year-long, as well as summer only, investigations. Ace Lake is a saline meromictic (permanently stratified) lake with strong physical and chemical gradients. The lake is one of the most studied lakes in continental Antarctica. Here, we review the current knowledge of the history, the physical and chemical environment, community structure and functional dynamics of the mixolimnion, littoral benthic algal mats, the lower anoxic monimolimnion and the sediment within the monimolimnion. In common with other continental meromictic Antarctic lakes, Ace Lake possesses a truncated food web dominated by prokaryote and eukaryote microorganisms in the upper aerobic mixolimnion and an anaerobic prokaryote community in the monimolimnion, where methanogenic Archaea, sulphate-reducing and sulphur-oxidizing bacteria occur. These communities are functional in winter at subzero temperatures, when mixotrophy plays an important role in survival in dominant photosynthetic eukaryotic microorganisms in the mixolimnion. The productivity of Ace Lake is comparable to other saline lakes in the Vestfold Hills, but higher than that seen in the more southerly McMurdo Dry Valley lakes. Finally, we identify gaps in the current knowledge and avenues that demand further investigation, including comparisons with analogous lakes in the north polar region.     

E-mail: J.Laybourn-Parry@nottingham.ac.ukAnnual plankton dynamics in an Antarctic saline lake

1. The plankton dynamics of Ace Lake, a saline, meromictic basin in the Vestfold Hills, eastern Antarctica was studied between December 1995 and February 1997. 2. The lake supported two distinct plankton communities; an aerobic microbial community in the upper oxygenated mixolimnion and an anaerobic microbial community in the lower anoxic monimolimnion. 3. Phytoplankton development was limited by nitrogen availability. Soluble reactive phosphorus was never limiting. Chlorophyll a concentrations in the mixolimnion ranged between 0.3 and 4.4 μg L^??1 during the study period and a deep chlorophyll maximum persisted throughout the year below the chemo/oxycline. 4. Bacterioplankton abundance showed considerable seasonal variation related to light and substrate availability. Autotrophic bacterial abundance ranged between 0.02 and 8.94 × 10⁸ L^??1 and heterotrophic bacterial abundance between 1.26 and 72.8 × 10⁸ L^??1 throughout the water column. 5. The mixolimnion phytoplankton was dominated by phytoflagellates, in particular Pyramimonas gelidicola. P. gelidicola remained active for most of the year by virtue of its mixotrophic behaviour. Photosynthetic dinoflagellates occurred during the austral summer, but the entire population encysted for the winter. 6. Two communities of heterotrophic flagellates were apparent; a community living in the upper monimolimnion and a community living in the aerobic mixolimnion. Both exhibited different seasonal dynamics. 7. The ciliate community was dominated by the autotroph Mesodinium rubrum. The abundance of M. rubrum peaked in summer. A proportion of the population encysted during winter. Only one other ciliate, Euplotes sp., occurred regularly. 8. Two species of Metazoa occurred in the mixolimnion; a calanoid copepod (Paralabidocera antarctica) and a rotifer (Notholca sp.). However, there was no evidence of grazing pressure on the microbial community. In common with most other Antarctic lakes, Ace Lake appears to be driven by ‘bottom-up’ forces.     

Iodine distribution in an antarctic meromictic saline lake

Water samples collected from a range of depths in Ace Lake in the Vestfold Hills, Antarctica were analysed for iodine species by a polarographic method. Contrary to thermodynamic prediction, iodide was the predominant species in oxic surface waters. Total dissolved iodine was closely correlated with bacterial density down the water column. This observation and other data are used to postulate a scheme for the biological mediation of iodine distribution in the lake.     

Flagellate nutritional versatility as a key to survival in two contrasting Antarctic saline lakes

1. Seasonal patterns of grazing and photosynthesis were investigated in two saline Antarctic lakes (Highway and Ace) in the Vestfold Hills (68°S). The phototrophic nanoflagellate (PNAN) community was dominated by Pyramimonas gelidicola and two morphological forms of a cryptophyte species that occurred throughout the year. Both species were mixotrophic on bacteria, and in Highway Lake they also exploited dissolved organic carbon as determined by the uptake of fluorescently labelled dextrans. 2. Clearance rates ranged between 0.02 and 0.21 nL h^?1 cell^?1 in Ace Lake and 0.004–1.05 nL h^?1 cell^?1 in Highway Lake. On occasion cryptophyte grazing equalled that of the heterotrophic nanoflagellates (HNAN). 3. Photosynthetic rates showed similar trends in both lakes, but there were differences in chlorophyll a specific rates and photosynthetic efficiency, probably related to the meromictic characteristic of Ace Lake. Primary production was measurable in winter and peaked in summer following the maxima of mixotroph grazing. 4. The HNAN community of Highway Lake achieved clearance rates of 0.02–1.80 nL h^?1 cell^?1 and removing between 50 and 693 ng bacterial carbon L^?1 day^?1, with highest impact in winter when HNAN were most abundant. The HNAN also ingested fluorescently labelled dextrans showing a preference for 4 and 500 kDa molecules. The more diverse HNAN community of Ace Lake had lower clearance rates (0.04–0.37 nL h^?1 cell^?1) and exerted a lower grazing pressure on bacterioplankton. In Highway Lake, where the HNAN community was dominated by the choanoflagellate Diaphanoeca grandis, there was a significant correlation between mean cell volume and clearance rate. 5. The major feature was that the microbial plankton functioned throughout the year by employing nutritional versatility.     

Pigment and lipid compositions of algal and bacterial communities in Ace Lake,Vestfold Hills,Antarctica

The compositions of carotenoids, chlorophylls and lipids at four depths in Ace Lake have been determined as a means of studying the vertical zonation of species in the lake and for comparison with the lipids found in the bottom sediments. The four major species of phytoplankton found in the lake were identified by electron microscopy. The most abundant phytoplankter was Pyramimonas gelidicola McFadden (Chlorophyta, Prasinophyceae) which occurred in greatest numbers at 10 m, the base of the oxylimnion. The pigments and lipids at this depth were mainly derived from this alga. At 11 m (the top of the anoxylimnion) only traces of lipids and pigments attributable to P. gelidicola were found, indicating only limited settling of algal cells through to the anoxylimnion, at least in summer. The pigments at 11 m were dominated by bacteriochlorophylls c derived from green photosynthetic bacteria Chlorobium spp. These pigments were also abundant at 23 m suggesting the presence of intact bacterial cells which had settled out from higher in the water column. Major non-polar lipid classes in the sediments included sterols, alcohols, hydrocarbons and an unusual suite of very long-chain unsaturated ketones and esters which have not previously been reported from antarctic environments. Several novel compounds, not found previously in either sediments or organisms, are reported. These include tri- and tetra-unsaturated straight-chain C₃₉ methyl ketones and C₄₀ ethyl ketones and the methyl ester of a tetra-unsaturated straight-chain C₃₆ fatty acid. The distributions of lipids in the sediment were markedly different from those in the water column indicating extensive bacterial degradation and recycling of labile lipids.     

Grazing rates of a calanoid copepod (Paralabidocera antarctica) in a continental Antarctic lake

The presence of crustaceans in some Antarctic lakes adds a level of complexity to the food webs of these environments. The grazing pressure of the crustaceans on phytoplankton and other protists, and the role they play in controlling food web structure, has not yet been examined in any detail. This paper presents the first data on grazing pressure of crustacean zooplankton in continental Antarctic lakes. In this study the grazing rates of Paralabidocera antarctica in saline Ace Lake, Vestfold Hills, were assessed using a radio-tracer method. Clearance rates ranged from approximately 1 to 8 ml ind.⁻¹ day⁻¹, depending on developmental stage. Due to their high abundance, nauplii exhibited the highest daily carbon ingestion rates. The population cleared about 3% of the water column per day, accounting for a significant fraction of primary production. P. antarctica has a considerable impact on the carbon cycle in Ace Lake and, by inference, in the other lakes in which it occurs. Accepted: 30 October 1999     

The inshore marine fishes of the Vestfold Hills region,Antarctica

Thirteen species of fish have so far been caught in the inshore waters around the Vestfold Hills, including the Rauer Islands, in depths down to approximately 100 m. Species caught depend markedly on the type of fishing gear used, but three species are clearly dominant numerically. Pagothenia bernacchii is most abundant in the shallower (< 20 m deep) weedy and rocky habitats, while Chionodraco hamatus is dominant in the deeper (> 20 m deep) nearshore troughs and further offshore. Pagothenia borchgrevinki occupies the specialized habitat associated with sea ice and close-inshore areas, including fjords and Burton Lake.The species list from the Vestfold Hills area is similar to lists from comparable locations in East Antarctica except for the major difference that C. hamatus has not yet been recorded from such shallow waters at the other locations, while P. bernacchii and P. hansoni are much more abundant in water deeper than 20 m at those sites than at Davis.     

ROLE OF ENCYSTMENT AND EXCYSTMENT OF PERIDINIUM BIPES F. OCCULATUM (DINOPHYCEAE) IN FRESH WATER RED TIDES IN LAKE KIZAKI,JAPAN1

The encystment flux of Peridinium bipes f. occulatum (Dinophyceae) was investigated with sediment traps from 1968 to 1990 in Lake Kazki. Cysts of P. bipes were formed throughout the blooms, Encystment flux of P. bipes in the pelagic zone was usually lower than those at shallow sites, and the density of P. bipes cysts in lake sediment was higher in the shallow region than in the pelagic zone. However, in the shallower region, The concentration of P. bipes cysts varied widely, possibly due to high rates of encystment and excystment. Peridinium bipes encystment occurred between 15° and 25° C in the laboratory, with very little cyst formation below 10°C. Though cyst formation was observed in continous darkness, the rate increased with irradiance. Under continuous darkness, no excystment was observed at any temperature from 5° to 25° C. Eighty-one percent of the cysts illuminated at 105 μE m^?2 s^?1 excysted after 13 days incubation at 15° C, and lower irradiances decreased germination success. Results from laboratory experiments suggest that light is a critical factor in the germination of P. bipes cysts. Bottom depth thus can have a significant effect on germination because cysts only can excyst from depths where light is sufficient. The shallow region of the lake is thus very important as a seed bed for P. bipes during early spring. Cyst deposited in deeper waters may not ever germinate unless they are resuspended and transported to shallow areas where light reaches the bottom.     

Daphniopsis studeri (Crustacea: Cladocera) in lakes of the Vestfold Hills,Antarctica

Summary The adult sizes and reproductive capabilities of populations of the cladoceran Daphniopsis studeri Rühe from freshwater and slightly saline lakes in the Vestfold Hills, Princess Elizabeth Land were monitored during December, 1990. The population of Crooked Lake was studied in detail from July 1990–March 1991. Limited samples were also obtained from Heard Island (sub Antarctic). Obligate parthenogenesis involving the production of subitaneous eggs appears to be the case. No males occurred. The overwintering populations of continental Antarctica consist mainly of adult females containing extensive fat reserves. The main reproductive effort occurs in spring. some females produce a smaller second brood during the summer. Reproductive output increases with adult size which is related to the nutrient status of the lake and its productivity. The Heard Island populations have a higher weight to length ratio than the Vestfold populations and have a much greater reproductive output.     

Overwintering populations of Mesodinium rubrum (Ciliophora: Haptorida) in lakes of the Vestfold Hills, East Antarctica

 The autotrophic ciliate Mesodinium rubrum Lohmann was observed during winter and spring in saline lakes ranging in salinity from 2 to 78‰ in the Vestfold Hills, Antarctica. The ciliate remained active during winter, and contained chlorophyll even though the level of light available for photosynthesis was minimal. No evidence of encystment as a means of survival during winter was observed. A seasonal study in one of the lakes, Ace Lake, revealed that M. rubrum was present throughout the year at abundances ranging from 1×10⁴ to 3.5×10⁵ cells l^-1. During the winter period, when little light penetrated the lake’s ice cover, cells were most common immediately under the ice at 2 m, where cell numbers were typically 8×10⁴ cells l^-1. Received: 3 January 1996/Accepted: 21 April 1996     

Microbial community structure and biomass estimates of a methanogenic Antarctic Lake ecosystem as determined by phospholipid analyses

Phospholipid analyses were performed on water column particulate and sediment samples from Ace Lake, a meromictic lake in the Vestfold Hills, Antarctica, to estimate the viable microbial biomass and community structure in the lake. In the water column, methanogenic bacterial phospholipids were present below 17 m in depth at concentrations which converted to a biomass of between 1 and 7×10⁸ cells/liter. Methanogenic biomass in the sediment ranged from 17.7×10⁹ cells/g dry weight of sediment at the surface to 0.1×10⁹ cells/g dry weight at 2 m in depth. This relatively high methanogenic biomass implies that current microbial degradation of organic carbon in Ace Lake sediments may occur at extremely slow rates. Total microbial biomass increased from 4.4×10⁸ cells/ liter at 2 m in depth to 19.4×10⁸ cells/liter at 23 m, near the bottom of the water column. Total nonarchaebacterial biomass decreased from 4.2 ×10⁹ cells/g dry weight in the surface sediment (1/4 the biomass of methanogens) to 0.06×10⁸ cells/g dry weight at 2 m in depth in the sediment. Phospholipid fatty acid profiles showed that microeukaryotes were the major microbial group present in the oxylimnion of the lake, while bacteria dominated the lower, anoxic zone. Sulfate-reducing bacteria (SRB) comprised 25% of the microbial population at 23 m in depth in the water column particulates and were present in the surface sediment but to a lesser extent. Biomass estimates and community structure of the Ace Lake eco-system are discussed in relation to previously measured metabolic rates for this and other antarctic and temperate ecosystems. This is the first instance, to our knowledge, in which the viable biomass of methanogenic and SRB have been estimated for an antarctic microbial community.     

Meromixis in an antarctic fjord: a precursor to meromictic lakes on an isostatically rising coastline

Physico-chemical data and isotopic studies (utilising H¹⁴CO₃, H₂ ¹⁸O, ³H₂O) suggest that hypersaline meromixis in Ellis Fjord (Vestfold Hills, Antarctica) was initiated during the middle Holocene period, when hypersaline brine, excluded during the annual formation of sea-ice, gravitated in a density current to the bottom. The application of this contemporary information to the genesis of the meromictic lakes found today in the Vestfold Hills, suggest that their meromixis may have developed prior to isolation from the sea. Comparison of physico-chemical data from the meromictic basins of Ellis Fjord with that of the Vestfold Hills saline lake allows some determination of their evolutionary pathways initiated before, during and after isolation from the sea. Further evolution of each lake can be explained through the individual interaction between climate, the catchment size and basin morphology.     

Protozoan growth rates in Antarctic lakes

The growth rates of heterotrophic nanoflagellates (HNAN), mixotrophic cryptophytes, dinoflagellates and ciliates in field assemblages from Ace Lake in the Vestfold Hills (eastern Antarctica) and Lakes Fryxell and Hoare (McMurdo Dry Valleys, western Antarctica), were determined during the austral summers of 1996/1997 and 1997/1998. The response of the nanoflagellates to temperature differed between lakes in eastern and western Antarctica. In Ace Lake the available bacterial food resources had little impact on growth rate, while temperature imposed an impact, whereas in Lake Hoare increased bacterial food resources elicited an increase in growth rate. However, the incorporation of published data from across Antarctica showed that temperature had the greater effect, but that growth is probably controlled by a suite of factors not solely related to bacterial food resources and temperature. Dinoflagellates had relatively high specific growth rates (0.0057–0.384 h⁻¹), which were comparable to Antarctic lake ciliates and to dinoflagellates from warmer, lower latitude locations. Temperature did not appear to impose any significant impact on growth rates. Mixotrophic cryptophytes in Lake Hoare had lower specific growth rates than HNAN (0.0029–0.0059 h⁻¹ and 0.0056–0.0127 h⁻¹, respectively). They showed a marked seasonal variation in growth rate, which was probably related to photosynthetically active radiation under the ice at different depths in the water column. Ciliates' growth rates showed no relationship between food supply and mean cell volume, but did show a response to temperature. Specific growth rates ranged between 0.0033 and 0.150 h⁻¹ for heterotrophic ciliates, 0.0143 h⁻¹ for a mixotrophic Plagiocampa species and 0.0075 h⁻¹ for the entirely autotrophic ciliate, Mesodinium rubrum. The data indicated that the scope for growth among planktonic Protozoa living in oligotrophic, cold extreme lake ecosystems is limited. These organisms are likely to suffer prolonged physiological stress, which may account for the highly variable growth rates seen within and between Antarctic lakes. Accepted: 7 December 1999     

Life history stages of Pyramimonas tychotreta (Prasinophyceae, Chlorophyta), a marine flagellate from the Ross Sea, Antarctica

During a summer cruise to the Ross Sea (Antarctica) areas of snow‐covered sea ice were red‐coloured due to high concentrations of the recently described Pyramimonas tychotreta Daugbjerg. Light microscopy of living material revealed that the population was comprised of quadriflagellate motile cells and thick‐walled cysts. The red colour was due to large numbers of secondary carotenoid‐containing granules, positioned in the periphery of motile cells and cysts. Mature cysts also contained numerous starch grains and lipid droplets. Cells from a red‐coloured field sample turned green overnight as the secondary carotenoids disappeared when cells were placed in low light conditions. The sample then exhibited the typical grass‐green colour of motile cells observed in water samples from the area. Under reduced light motile cells showed strong positive phototaxis. The encystment process involved the asexual transformation of quadriflagellate cells into cysts. A single type of square cyst scale, with perforated floors and walls, replaced the body scales of motile cells. A marked extension, often ending in a hook was at each corner of the cyst scales. Germinating cysts produced four motile cells. Electron microscopy showed the cyst wall to be tri‐layered, with a thin, electron‐dense inner layer, a thick middle layer and a thin outer layer. Sea ice samples with dense populations of motile cells and cyst stages also contained elongate uniflagel‐late cells. These cells were covered with box scales, foot‐print scales, an underlayer of pentagonal scales, limuloid scales and flagellar hair scales identical to those present on the quadriflagellate stage. We tentatively suggest that the uniflagellate stage represents a gamete and its presence implies the occurrence of sexual reproduction. Although, fusion of gametes was not observed, a biflagellate cell with a larger volume was seen which may have been a zygote. How this stage fits into of the life history remains to be explained.     

Sediment cores from Lake Urmia (Iran) suggest the inhabitation by parthenogenetic Artemia around 5,000?years ago

In Lake Urmia area, northwestern Iran, parthenogenetic Artemia and the bisexual Artemia urmiana Günther 1890 are found to occupy different ecological niches determined by salinity. Given the fluctuations of the lake over geological times, we thus hypothesized that species identification of Artemia cysts, buried in the sediments, can provide information on lake conditions in the past. Therefore, encysted embryos of Artemia were recovered from lake sediments by augering at a site near the present shoreline. Cysts and associated plant remains from two studied levels yielded radiocarbon ages in the range 5,000–6,700 YBP. For determination of the type of Artemia, the constant synonym mutation in exon-7 of the Na/K ATPase gene was verified, and the diameter of the recovered cysts was compared with that of modern cysts from the Lake Urmia region. The results show that the cysts represent a parthenogenetic type of Artemia, whose cyst diameter is somewhat different from that of present-day local parthenogenetic Artemia. The present study firstly confirms the stability of DNA in ancient Artemia cysts for molecular analysis. Moreover, it suggests variation in Lake Urmia’s conditions over time, and based on comparison with salinity preferences of contemporary Artemia populations, it more specifically suggests that Lake Urmia was a brackish lake dominated by a parthenogenetic Artemia population in the geological period sampled. It finally illustrates how, like in the study of freshwater propagule banks, paleogenetic analysis of Artemia DNA recovered from sediment cores can be used as a tool in the paleoecological study of generally highly fluctuating saline habitats.     

Nematodes from saline and freshwater lakes of the Vestfold Hills,East Antarctica,including the description of <Emphasis Type="Italic">Hypodontolaimus antarcticus</Emphasis> sp. n.

The invertebrate fauna of many Antarctic ice-free areas, even those close to permanent research stations, can be poorly known. Here we describe some nematodes from freshwater and saline, marine-derived lakes of the Vestfold Hills, East Antarctica. The freshwater lakes contained the widespread East Antarctic endemic species, Plectus frigophilus Kirjanova, 1958. The saline lakes were inhabited by two recently described species, Halomonhystera halophila Andrássy, 2006 and Halomonhystera continentalis Andrássy, 2006, and by a new species described in this report, Hypodontolaimus antarcticus sp. n. Originally marine but now brackish Highway Lake contained a nematode fauna with both freshwater and marine-derived components. The nematode fauna of Antarctica now consists of 54 named species, 22 of which are found in East Antarctica.