Ice Communities Research Articles

Bio-optical properties of Antarctic pack ice in the early austral spring

Pack ice in the Bellingshausen Sea contained moderate to high stocks of microalgal biomass (3–10 mg Chl a m −2) spanning the range of general sea-ice microalgal microhabitats (e.g., bottom, interior and surface) during the International Polar Year (IPY) Sea Ice Mass Balance in the Antarctic (SIMBA) studies. Measurements of irradiance above and beneath the ice as well as optical properties of the microalgae therein demonstrated that absorption of photosynthetically active radiation (PAR) by particulates (microalgae and detritus) had a substantial influence on attenuation of PAR and irradiance transmission in areas with moderate snow covers (0.2–0.3 m) and more moderate effects in areas with low snow cover. Particulates contributed an estimated 25 to 90% of the attenuation coefficients for the first-year sea ice at wavelengths less than 500 nm. Strong ultraviolet radiation (UVR) absorption by particulates was prevalent in the ice habitats where solar radiation was highest—with absorption coefficients by ice algae often being as large as that of the sea ice. Strong UVR-absorption features were associated with an abundance of dinoflagellates and a general lack of diatoms—perhaps suggesting UVR may be influencing the structure of some parts of the sea-ice microbial communities in the pack ice during spring. We also evaluated the time-varying changes in the spectra of under-ice irradiances in the austral spring and showed dynamics associated with changes that could be attributed to coupled changes in the ice thickness (mass balance) and microalgal biomass. All results are indicative of radiation-induced changes in the absorption properties of the pack ice and highlight the non-linear, time-varying, bio-physical interactions operating within the Antarctic pack ice ecosystem.

Persistence of bacterial and archaeal communities in sea ice through an Arctic winter

The structure of bacterial communities in first-year spring and summer sea ice differs from that in source seawaters, suggesting selection during ice formation in autumn or taxon-specific mortality in the ice during winter. We tested these hypotheses by weekly sampling (January–March 2004) of first-year winter sea ice (Franklin Bay, Western Arctic) that experienced temperatures from −9°C to −26°C, generating community fingerprints and clone libraries for Bacteria and Archaea. Despite severe conditions and significant decreases in microbial abundance, no significant changes in richness or community structure were detected in the ice. Communities of Bacteria and Archaea in the ice, as in under-ice seawater, were dominated by SAR11 clade Alphaproteobacteria and Marine Group I Crenarchaeota, neither of which is known from later season sea ice. The bacterial ice library contained clones of Gammaproteobacteria from oligotrophic seawater clades (e.g. OM60, OM182) but no clones from gammaproteobacterial genera commonly detected in later season sea ice by similar methods (e.g. Colwellia, Psychrobacter). The only common sea ice bacterial genus detected in winter ice was Polaribacter. Overall, selection during ice formation and mortality during winter appear to play minor roles in the process of microbial succession that leads to distinctive spring and summer sea ice communities.

Viable microbes in ice: application of molecular assays to McMurdo Dry Valley lake ice communities

AbstractThe permanent ice covers of the McMurdo Dry Valley lakes, Antarctica, are colonized by a diverse microbial assemblage. We collected ice cores from Lakes Fryxell, Hoare and Bonney. Propidium monoazide (PMA) was used in combination with quantitative PCR (qPCR) and denaturing gradient gel electrophoresis (DGGE) to examine membrane integrity of prokaryotes in these extreme environments. PMA selectively penetrates cells with compromised membranes and modifies their DNA resulting in the suppression of PCR amplification. Our results based on analysis of 16S rRNA genes demonstrate that despite the hostile conditions of the Dry Valleys, the permanent ice covers of the lakes support a ‘potentially viable’ microbial community. The level of membrane integrity, as well as diversity, was higher in samples where sediment was entrapped in the ice cover. Pronounced differences in the fraction of cells with intact and compromised cell membranes were found for Lake Fryxell and east lobe of Lake Bonney, both expressed in differences in DGGE banding patterns and qPCR signal reductions. Limitations in the ability to distinguish between intact or compromised cells occurred in samples from Lake Hoare and west lobe of Lake Bonney due to low DNA template concentrations recovered from the samples.

Global distribution of cyanobacterial ecotypes in the cold biosphere

Perennially cold habitats are diminishing as a result of climate change; however, little is known of the diversity or biogeography of microbes that thrive in such environments. Here we use targeted 16S rRNA gene surveys to evaluate the global affinities of cold-dwelling cyanobacteria from lake, stream and ice communities living at the northern limit of High Arctic Canada. Pigment signature analysis by HPLC confirmed the dominance of cyanobacteria in the phototrophic communities of these High Arctic microbial mats, with associated populations of chlorophytes and chromophytes. Microscopic analysis of the cyanobacteria revealed a diverse assemblage of morphospecies grouping into orders Oscillatoriales, Nostocales and Chroococcales. The 16S rRNA gene sequences from six clone libraries grouped into a total of 24 ribotypes, with a diversity in each mat ranging from five ribotypes in ice-based communities to 14 in land-based pond communities. However, no significant differences in composition were observed between these two microbial mat systems. Based on clone-library and phylogenetic analysis, several of the High Arctic ribotypes were found to be >99% similar to Antarctic and alpine sequences, including to taxa previously considered endemic to Antarctica. Among the latter, one High Arctic sequence was found 99.8% similar to Leptolyngbya antarctica sequenced from the Larsemann Hills, Antarctica. More than 68% of all identified ribotypes at each site matched only cyanobacterial sequences from perennially cold terrestrial ecosystems, and were <97.5% similar to sequences from warmer environments. These results imply the global distribution of low-temperature cyanobacterial ecotypes throughout the cold terrestrial biosphere.

Influence of environmental factors on the development of bottom ice protist communities during the winter–spring transition

Seasonal changes in the abundance and taxonomic composition of bottom ice protists (i.e. diatoms, flagellates, and dinoflagellates) were assessed in the first-year landfast ice of Franklin Bay (Canadian Beaufort Sea) from 24 February to 20 June 2004. On each sampling day, bottom sea- ice protists were collected at sites of high (>10 cm) and low (<10 cm) snow cover. The net observed growth rates of diatoms and nanoflagellates were significantly higher during the pre-bloom (24 Feb- ruary to 25 March) than the bloom (ca. 3 April to 23 May) period under low snow cover but were not different under high snow cover. In contrast, dinoflagellates showed relatively constant net observed growth rate before and during the bloom period under both snow covers. These results indicate that the 3 protist groups responded differently to changes in the light regime during the growth period. The decline of the protist community after the bloom period was related to a combination of factors including nitrogen deficiency and melting processes. Prior to the bloom, flagellated cells, likely het- erotrophic, dominated numerically under high snow cover, whereas autotrophic protists, especially solitary diatoms, prevailed under low snow cover. During the bloom period, colonial diatoms such as Nitzschia frigida, N. promare, Navicula sp. 6, N. pelagica, and Fragilariopsis cylindrus dominated the bottom ice community irrespective of snow depth, although abundances were higher under low snow cover. The arborescent colonial N. frigida, a key species of landfast ice across circumarctic regions, was the most abundant bottom ice algal diatom throughout the entire season. During the post-bloom period, colonial and solitary diatoms declined more rapidly than nanoflagellates, suggesting that nanoflagellates, presumably heterotrophic, were better adapted to melting sea-ice conditions. Our results demonstrated that the availability of nitrate in the surface water limits the accumulation of algal biomass in the bottom horizon of Arctic landfast ice during the vernal growth season.

Biogeochemical conditions and ice algal photosynthetic parameters in Weddell Sea ice during early spring

Physical, biogeochemical and photosynthetic parameters were measured in sea ice brine and ice core bottom samples in the north-western Weddell Sea during early spring 2006. Sea ice brines collected from sackholes were characterised by cold temperatures (range −7.4 to −3.8°C), high salinities (range 61.4–118.0), and partly elevated dissolved oxygen concentrations (range 159–413 μmol kg−1) when compared to surface seawater. Nitrate (range 0.5–76.3 μmol kg−1), dissolved inorganic phosphate (range 0.2–7.0 μmol kg−1) and silicic acid (range 74–285 μmol kg−1) concentrations in sea ice brines were depleted when compared to surface seawater. In contrast, NH4+ (range 0.3–23.0 μmol kg−1) and dissolved organic carbon (range 140–707 μmol kg−1) were enriched in the sea ice brines. Ice core bottom samples exhibited moderate temperatures and brine salinities, but high algal biomass (4.9–435.5 μg Chl a l−1 brine) and silicic acid depletion. Pulse amplitude modulated fluorometry was used for the determination of the photosynthetic parameters Fv/Fm, α, rETRmax and Ek. The maximum quantum yield of photosystem II, Fv/Fm, ranged from 0.101 to 0.500 (average 0.284 ± 0.132) and 0.235 to 0.595 (average 0.368 ± 0.127) in the sea ice internal and bottom communities, respectively. The fluorometric measurements indicated medium ice algal photosynthetic activity both in the internal and bottom communities of the sea ice. An observed lack of correlation between biogeochemical and photosynthetic parameters was most likely due to temporally and spatially decoupled physical and biological processes in the sea ice brine channel system, and was also influenced by the temporal and spatial resolution of applied sampling techniques.

Temporal variation in fatty acid composition of Ulothrix zonata (Chlorophyta) from ice and benthic communities of Lake Baikal

S. Osipova, L. Dudareva, N. Bondarenko, A. Nasarova, N. Sokolova, L. Obolkina, O. Glyzina and Oleg Timoshkin. 2009. Temporal variation in fatty acid composition of Ulothrix zonata (Chlorophyta) from ice and benthic communities of Lake Baikal. Phycologia 48: 130–135. DOI: 10.2216/08-49Fatty acid (FA) composition of total lipids was compared between populations of the freshwater alga Ulothrix zonata growing in the interstitial water of the ultrapure ice cover of Lake Baikal in early spring (ice population) and on the shallow stony bottom of the lake during the ice-free season (benthic population). FA content was analysed by chromatographic mass spectrometry. Our observations over two years indicated that the FA profiles of both Baikalian ice and benthic populations of U. zonata, as are typical for other green algae, showed a high level of polyunsaturated FAs (50–70% depending on season) related to the adaptation of the alga to low temperature. Rising temperature in the algal habitat entailed a prominent drop in the proportion of monoenoic cis-7-hexadecenoic acid (from 0.8% to 3.5% in 2006). These results favour the hypothesis that monoenoic FAs play a principal role in maintaining the cellular membrane fluidity of U. zonata.

Preliminary investigation of Okhotsk Sea ice algae; taxonomic composition and photosynthetic activity

Okhotsk Sea pack ice from Shiretoko in northern Hokkaido, sampled in March 2007, contained microalgal communities dominated by the centric diatoms Thalassiosira nordenskioeldi and T. punctigera. Domination by this genus is very unusual in sea ice. Communities from nearby fast ice at Saroma-ko lagoon were dominated by Detonula conferavea and Odontella aurita. Average microalgal biomass of the Okhotsk Sea pack ice (surface and bottom) was 1.59 ± 1.09 μg chla l−1 and for fast ice (bottom only) at nearby Saroma-ko lagoon, 16.5 ± 3.2 μg l−1 (=31.1 ± 5.0 mg chla m−2). Maximum quantum yield of the Shiretoko pack ice algal communities was 0.618 ± 0.056 with species-specific data ranging between 0.211 and 0.653. These community values are amongst the highest recorded for sea ice algae. Rapid light curves (RLC) on individual cells indicated maximum relative electron transfer rates (relETR) between 20.8 and 60.6, photosynthetic efficiency values (α) between 0.31 and 0.93 and onset of saturation values (E k) between 33 and 91 μmol photons m−2 s−1. These data imply that the pack ice algal community at Shiretoko was healthy and actively photosynthesising. Maximum quantum yield of the Saroma-ko fast ice community was 0.401 ± 0.086, with values for different species between 0.361 and 0.560. RLC data from individual Saroma-ko fast ice algal cells indicated relETR between 55.3 and 60.6, α values between 0.609 and 0.816 and E k values between 74 and 91 μmol photons m−2 s−1 which are consistent with measurements in previous years.

Embryo aberrations in sea ice amphipod Gammaruswilkitzkii exposed to water soluble fraction of oil

Offshore oil and gas activities have gained momentum in the European Arctic, raising concerns of the potential impact of oil-related chemicals on the polar marine ecosystem, notably on sea ice communities. Herein, malformations on embryos of the Arctic sea ice amphipod Gammarus wilkitzkii exposed to the water soluble fraction of oil were studied. The females ranged from development stage three to nine. No differences in reproductive stage were observed among the different treatments after 30 days of exposure. Frequency of embryo aberrations was significantly higher in the high-dose compared to controls, indicating that the embryos of G. wilkitzkiii were affected by oil.

Succession of sea-ice bacterial communities in the Baltic Sea fast ice

Coastal fast ice and underlying water of the northern Baltic Sea were sampled throughout the entire ice winter from January to late March in 2002 to study the succession of bacterial biomass, secondary production and community structure. Temperature gradient gel electrophoresis (TGGE) and sequencing of TGGE fragments were applied in the community structure analysis. Chlorophyll-a and composition of autotrophic and heterotrophic assemblages were also examined. Overall succession of ice organism assemblages consisted of a low-productive stage, the main algal bloom, and a heterotrophic post-bloom situation, as typical for the study area. The most important groups of organisms in ice in terms of biomass were dinoflagellates, plasticidic flagellates, rotifers and ciliates. Ice bacteria showed a specific succession not directly dependent on the overall succession events of ice organisms. Sequenced 16S rDNA fragments were mainly affiliated to α-, β-, and γ-proteobacterial phyla and Cytophaga–Flavobacterium–Bacteroides-group, and related to sequences from cold environments, also from the Baltic Sea. Temporal clustering of the TGGE fingerprints was stronger than spatial, although lower ice and underlying water communities always clustered together, pointing to the importance of ice maturity and ice–water interactions in shaping the bacterial communities.

Responses of Microbial Communities in Arctic Sea Ice After Contamination by Crude Petroleum Oil

Microbial communities associated with Arctic fjord ice polluted with petroleum oils were investigated in this study. A winter field experiment was conducted in the Van Mijen Fjord (Svalbard) from February to June 2004, in which the ice was contaminated with a North Sea paraffinic oil. Holes were drilled in the ice and oil samples frozen into the ice at the start of the experiment. Samples, including cores of both oil-contaminated and clean ice, were collected from the field site 33, 74, and 112 days after oil application. The sampled cores were separated into three sections and processed for microbiological and chemical analyses. In the oil-contaminated cores, enumerations of total prokaryotic cells by fluorescence microscopy and colony-forming units (CFU) counts of heterotrophic prokaryotes both showed stimulation of microbial growth, while concentrations of oil-degrading prokaryotes remained at similar levels in contaminated and clean ice. Analysis of polymerase chain reaction (PCR)-amplified bacterial 16S rRNA gene fragments by denaturing gradient gel electrophoresis (DGGE) revealed that bacterial communities in oil-contaminated ice generated fewer bands than communities in clean ice, although banding patterns changed both in contaminated and clean ice during the experimental period. Microbial communities in unpolluted ice and in cores contaminated with the paraffinic oil were examined by cloning and sequence analysis. In the contaminated cores, the communities became predominated by Gammaproteobacteria related to the genera Colwellia, Marinomonas, and Glaciecola, while clean ice included more heterogeneous populations. Chemical analysis of the oil-contaminated ice cores with determinations of n-C17/Pristane and naphthalene/phenanthrene ratios indicated slow oil biodegradation in the ice, primarily in the deeper parts of the ice with low hydrocarbon concentrations.

Antarctic marine biology – two centuries of research

AbstractWhilst interest in the economic exploitation of the Southern Ocean resources dates back to the last part of the 18th century scientific research into elements of the marine ecosystem only began in the mid 19th century. As far as plankton and benthos are concerned the great exploratory voyages and expeditions laid a firm taxonomic foundation on which later work was built. The most outstanding expedition contribution was from the Discovery Investigations. Concern about uncontrolled exploitation stimulated the SCAR BIOMASS programme which in turn led to CCAMLR with its modelling programmes and top predator monitoring. Recent research on pack ice communities has been aided by dedicated ice-capable research vessels whilst unmanned photographic techniques as well as SCUBA diving and experimental research facilities in the Antarctic have encouraged major research on benthos. International collaboration, interdisciplinary research and good ideas suggest Antarctic marine biology has a bright future.

Publishing the ICES Journal of Marine Science: facing fresh challenges in a competitive environment

Publishing the ICES Journal of Marine Science: facing fresh challenges in a competitive environment

Comparison of the microalgal community within fast ice at two sites along the Ross Sea coast, Antarctica

Diverse microbial communities survive within the sea ice matrix and are integral to the energy base of the Southern Ocean. Here we describe initial findings of a four season survey (between 1999–2004) of community structure and biomass of microalgae within the sea ice and in the underlying water column at Cape Evans and Cape Hallett, in the Ross Sea, Antarctica as part of the Latitudinal Gradient Project. At Cape Evans, bottom-ice chlorophyll a levels ranged from 4.4 to 173 mg Chl a m−2. Dominant species were Nitzschia stellata, N. lecointei, and Entomoneis kjellmanii, while the proportion of Berkeleya adeliensis increased steadily during spring. Despite being obtained later in the season, the Cape Hallett data show considerably lower standing stocks of chlorophyll ranging from 0.11 to 36.8 mg Chl a m−2. This difference was attributed to a strong current, which may have ablated much of the bottom ice biomass and provided biomass to the water below. This loss of algae from the bottom of the ice may explain why the ice community contributed only 2% of the standing stock in the total water column. Dominant species at Cape Hallett were Nitzschia stellata, Fragilariopsis curta and Cylindrotheca closterium. The low biomass at Cape Hallett and the prevalence of smaller-celled diatoms in the bottom ice community indicate that the ice here is more typical of pack ice than fast ice. Further data will allow us to quantify and model the extent to which ice-driven dynamics control the structure and function of the sea ice ecosystem and to assess its resilience to changing sea ice conditions.

Microbiota within the perennial ice cover of Lake Vida, Antarctica

Lake Vida, located in the McMurdo Dry Valleys, Antarctica, is an 'ice-sealed' lake with approximately 19 m of ice covering a highly saline water column (approximately 245 ppt). The lower portions of the ice cover and the lake beneath have been isolated from the atmosphere and land for circa 2800 years. Analysis of microbial assemblages within the perennial ice cover of the lake revealed a diverse array of bacteria and eukarya. Bacterial and eukaryal denaturing gradient gel electrophoresis phylotype profile similarities were low (<59%) between all of the depths compared (five depths spanning 11 m of the ice cover), with the greatest differences occurring between surface and deep ice. The majority of bacterial 16S rRNA gene sequences in the surface ice were related to Actinobacteria (42%) while Gammaproteobacteria (52%) dominated the deep ice community. Comparisons of assemblage composition suggest differences in ice habitability and organismal origin in the upper and lower portions of ice cover. Specifically, the upper ice cover microbiota likely reflect the modern day transport and colonization of biota from the terrestrial landscape, whereas assemblages in the deeper ice are more likely to be persistent remnant biota that originated from the ancient liquid water column of the lake that froze.

Biomass, composition and activity of organism assemblages along a salinity gradient in sea ice subjected to river discharge in the Baltic Sea

A study was undertaken to examine the activity and composition of the seasonal Baltic Sea land-fast sea-ice biota along a salinity gradient in March 2003 in a coastal location in the SW coast of Finland. Using a multi-variable data set, the less well-known algal and protozoan communities, and algal and bacterial production in relation to the physical and chemical environment were investigated. Also, the first coincident measurements of bacterial production and dissolved organic matter (DOM) in a sea-ice system are reported. Communities in sea ice were clearly autotrophy-dominated with algal biomass representing 79% of the total biomass. Protozoa and rotifers made up 18% of biomass in the ice and bacteria only 3%. Highest biomasses were found in mid-transect bottom ice. Water column assemblages were clearly more heterotrophic: 39% algae, 12% bacteria and 49% for rotifers and protozoa. Few significant correlations existed between DOM and bacterial variables, reflecting the complex origin of ice DOM. Dynamics of dissolved organic carbon, nitrogen and phosphorus (DOC, DON and DOP) were also uncoupled. A functional microbial loop is likely to be present in the studied ice. Existence of an under-ice freshwater plume affects the ecosystem functioning: Under-ice water communities are influenced directly by river-water mixing, whereas the ice system seems to be more independent—the interaction mainly taking place through the formation of active bottom communities.

Spatial and seasonal heterogeneity of sea ice microbial communities in the first-year ice of Terre Adélie area (Antarctica)

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 43:95-106 (2006) - doi:10.3354/ame043095 Spatial and seasonal heterogeneity of sea ice microbial communities in the first-year ice of Terre Adélie area (Antarctica) Michel Fiala1,*, Harri Kuosa2, Elzbieta E. Kopczyńska3, Louise Oriol1, Daniel Delille1 1Observatoire Océanologique, Universite P. et M. Curie, UMR-CNRS 7621, 66651 Banyuls-sur-mer cedex, France 2Finnish Institute of Marine Research, POB 33, 00931 Helsinki, Finland 3Department of Antarctic Biology, Polish Academy of Sciences, Ustrzycka 10/12, 02 141 Warszawa, Poland *Email: mfiala@obs-banyuls.fr ABSTRACT: Spatial and temporal changes in sea ice microbial communities were investigated at 4 stations located along a south-north transect on the land-fast ice of Dumont d’Urville station area (Adélie Land, 66°40’S, 141°01’E) during the ice coverage period (April to December). A seasonal pattern was observed in microalgae, bacteria and protozoan abundance distribution. A maximum chlorophyll a concentration occurred during fall ice formation in the surface layer with the highest values at the near-shore station (100 to 215 µg l–1). A second maximum was observed before ice breaking in the bottom ice (50 to 90 µg l–1). Microalgal communities were dominated by diatoms (>86% of the total cells), mainly represented by Fragilariopsis, Nitzschia, Navicula and Pseudo-nitzschia species. Fragilariopsis curta was the dominant species during the first bloom whereas Fragilariopsis cylindrus, Nitzschia longissima and Tropidoneis sp. were the main contributors during the second bloom at the bottom ice core. Maximum protozoan abundance was recorded during the fall bloom in the surface layer with dominance of ciliates, which contributed more than 75% of total cell numbers. During this period, the maximum ciliate abundance was associated with the maximum bacteria and diatom numbers and microalgal biomass. The dramatic decrease of the ice algal biomass from south to north paralleled that of the underlying water phytoplankton available for new ice incorporation. The spatial algal biomass decrease could explain the parallel decrease in the abundance of bacteria and heterotrophic ciliates through trophic interactions. KEY WORDS: Antarctica · Land-fast ice · Microbial communities · Chlorophyll a · Nutrients Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 43, No. 1. Online publication date: May 03, 2006 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2006 Inter-Research.

Changes in Phytoplankton Biomass and Nutrient Quantities in Sea Ice as Responses to Light/Dark Manipulations during different Phases of the Baltic Winter 2003

The response of Baltic Sea ice communities to changing light climate was studied in three subsequent 3 week in situ experiments on the SW coast of Finland. The investigation covered three different winter periods, short day with low solar angles leading to limited light in the ice, late winter with deep snow cover and early spring with melting snow and increasing light availability. The experimental setup consisted of transparent (no snow) and completely darkened (heavy snow cover) plexiglass tubes in which the ice cores were incubated in situ from 1 to 2 weeks. Changes in the concentrations of inorganic nutrients (NO 3 − -–N, PO4 3−-–P, SiO4 −-–Si) and chlorophyll-a concentration in the phytoplankton community composition were recorded as responses to different light manipulations. Changes in inner ice light intensity in untreated ice as well as the temperature both in air and ice were recorded over the entire study period. Increased irradiance in late winter/early spring and during meltdown affected the chlorophyll-a amount in the sea ice. During these periods the phytoplankton community in the top layers decreased possibly as a consequence of photo-acclimation. Closer to the bottom of the ice, however, the increased inner ice light intensity induced algal growth. Complete exclusion of light stopped the algal growth in the whole ice column. Darkening the ice cores also slowed down the ice melting opposite to accelerated melting caused by increased light. The significant differences found in nutrient concentrations between the light and dark treatments were mostly explicable by changes in algal biomass. No obvious changes were observed in the phytoplankton community composition due to light manipulation, diatoms and heterotrophic flagellates dominating throughout the study period.

Composition and succession of dinoflagellates and chrysophytes in the upper fast ice of Davis Station, East Antarctica

Little is known of the wider Antarctic distribution of the upper fast ice community now comprehensively described from McMurdo Sound. We determined the fast ice protist community at Davis Station, East Antarctica and compared it with that of McMurdo Sound. As at McMurdo Sound, Davis fast ice is characterised by extreme and transitory salinities (96–2.5 psu) and temperatures (−4.5 to −0.1°C) during the spring/summer transition. Both communities are dominated by Polarella glacialis (an autotrophic dinoflagellate), chrysophytes and their life cycle stages. Furthermore, the physical parameters of brine temperature and salinity at which these successions occurred approximated those of McMurdo Sound. The high degree of similarity between the communities from the geographically disparate locations indicates that this community type has a circum-Antarctic distribution. Confirming the areal extent and seasonality of this community type will assist in future predictions of sea ice productivity.

Wind dispersal of soil invertebrates in the McMurdo Dry Valleys, Antarctica

Dispersal of soil organisms is crucial for their spatial distribution and adaptation to the prevailing conditions of the Antarctic Dry Valleys. This study investigated the possibility of wind dispersal of soil invertebrates within the dry valleys. Soil invertebrates were evaluated in (1) pockets of transported sediments to lake ice and glacier surfaces, (2) wind-transported dust particles in collection pans (Bundt pans) 100 cm above the soil surface, and (3) sediments transported closer to the surface (<50 cm) and collected in open top chambers (OTCs). Invertebrates were extracted and identified. Nematodes were identified to species and classified according to life stage and sex. Three species of nematodes were recovered and Scottnema lindsayae was the most dominant. There were more juveniles (∼71%) in the transported sediments than adults (29%). Tardigrades and rotifers were more abundant in sediments on lake and glacier surfaces while nematodes were more abundant in the dry sediment collections of Bundt pans and OTCs. The abundance of immobile (dead) nematodes in the Bundt pans and OTCs was three times greater than active (live) nematodes. Anhydrobiosis constitutes a survival mechanism that allows wind dispersal of nematodes in the McMurdo Dry Valleys. Our results show that soil invertebrates are dispersed by wind in the Dry Valleys and are viable in ice communities on lake surfaces and glaciers.