B31A-0194 0800h
Cryobiological ice core analyses in Altai Mountains, Russia
Microorganism in two shallow ice cores from the Sofiskiy Glacier (25.1m in length, taken at 3,435 m a.s.l.. in Jul, 2001) and the Belukha Glacier (20.94m in length, taken at 4,110m a.s.l. in Jul, 2001), Altai range of Russia, were examined for potential use in ice core analyses of this area. These ice cores and pit samples collected at the coring sits contained 6 types of unicellular green algal cells including 2 species of snow algae (Mesotenium.sp & Trochiscia.sp), one species of unicellular cyanobacteria, 2 species of snow fungie Chionaster nivalis Chionaster bicornis and unidentified bacteria. Vertical profiles of these microorganisms and that of Delta 18O in the snow pits (4.5m depth in Sofiskiy Glacier and 2.42m depth in Belukha Glacier) indicated their growth in the surface snow during the melting season. Biomass and species diversity of these microorganisms in the surface snow decreased with altitude, probably due to the colder condition. Biomass and species diversity in the ice cores were smaller than those in pit samples, suggesting the effects of washout and/or cell decomposition after deposition. Especially, fungus cells were very rare in the ice cores probably due to heavy cell decomposition. In both ice cores, however, seasonal cycles were still found for the snow algal biomass, though Delta 18O failed to show any clear seasonal variation, particularly at deeper part, probably due to heavy melt-water percolation. Supposing that the layers with almost no snow algae were the winter layers without melt water essential to algal growth, we estimated that Sofiskiy ice core and Belukha ice core contained about 15 and 10 annual layers, respectively. Snow algae in the ice core would be accurate boundary markers of annual layers in the ice cores of this region. Relationship between the snow algae in each annual layers and the meteorological data at the nearest meteorological station will also be discussed.
B31A-0195 0800h
Characteristics of Glacier Ecosystem and Glaciological Importance of Glacier Microorganisms
Biological activity on glaciers has been believed to be extremely limited. However, we found various biotic communities specialized to the glacier environment in various part of the world, such as Himalaya, Patagonia and Alaska. Some of these glacier hosted biotic communities including various cold-tolerant insects, annelids and copepods that were living in the glacier by feeding on algae and bacteria growing in the snow and ice. Thus, the glaciers are simple and relatively closed ecosystems sustained by the primary production in the snow and ice. Since these microorganisms growing on the glacier surface are stored in the glacial strata every year, ice-core samples contain many layers with these microorganisms. Recently, it was shown that the snow algae in the ice-core are useful for ice core dating and could be new environmental signals for the studies on past_@environment using ice cores. These microorganisms in the ice core will be important especially in the studies of ice core from the glaciers of warmer regions, in which chemical and isotopic contents are often heavily disturbed by melt water percolation. Blooms of algae and bacteria on the glacier can reduce the surface albedo and significantly affect the glacier melting. For example, the surface albedo of some Himalayan glaciers was significantly reduced by a large amount of dark-colored biogenic material (cryoconite) derived from snow algae and bacteria. It increased the melting rates of the surfaces by as much as three-fold. Thus, it was suggested that the microbial activity on the glacier could affect the mass balance and fluctuation of the glaciers.
http://www.ecology.bio.titech.ac.jp/Study/glacio_bio/G-biology-e.html
B31A-0196 0800h
Circulation Model for Subglacial Lakes.
A circulation model for Antarctic subglacial lakes is presented. This model differs from previous models used for Lake Vostok in that the momentum equations are non-hydrostatic. Consequently, the new model does not require an additional scheme to represent the thermal convection within subglacial lakes. The code uses finite volume and the SIMPLE algorithm to calculate the pressure-velocity coupling. This formulation is well established for fluid flow and heat transfer problems. Non-orthogonal, boundary fitted grids are used to capture the complex bathymetry and sloping lake-ice interface that characterise subglacial lakes. The new model uses multigrid techniques to speed up convergence of the code, which allows the use of increased resolution. Examples of how the model is applied to subglacial lakes, and their environmental implications, are presented.
B31A-0197 0800h
Large Chemical Variations in ice Formed Above Lake Vostok, Antarctica
Lake Vostok is the largest subglacial lake identified in Antarctica. It is 260 km long, 80 km wide, over 500 m deep and lies beneath $\sim$4 km of ice. It has received great scientific interest since it may provide clues to the survival of life on Earth during global glaciations, and provides an analogue for environments that may harbour life on icy planets and moons, such as Europa. Our current understanding of physical, chemical and biological conditions in the lake comes from samples of water which have refrozen to the underside of the ice sheet. Analysis of this `accreted ice' reveals large concurrent variations in the concentrations of major ions. For example, Mg^{2+}$ and SO4^{2-}$ vary by a factor of $\sim$400, Na^{+}$ and Cl^{-}$ by a factor of $\sim$40, and K^{+}$ and Ca^{2+}$ by a factor of $\sim$10. The inferred ionic content of the lake water, from which this accreted ice formed, ranges from $\sim$1 to 40 mM in terms of total dissolved anions. Clearly, these recorded ionic extremes have implications for the lake's environment, which in turn may be important to microbial life in the lake. We seek explanations for this variation by considering plausible perturbations to the lake system, possible effects of the varying environmental origin of accreted ice, and sample treatment. Specifically, these are: i) changes in lake volume in response to changes in ice sheet thickness and flow direction; ii) the sporadic contribution of saline water from a deeper-rock reservoir; iii) periodic upwelling events, bringing more concentrated waters from depth; iv) variations in the chemistry of icemelt feeding the lake; v) formation of ice near the grounding lines of a shallow embayment to the west of the main lake; vi) the effect of sampling ice crystal boundaries; and vii) post-sampling reactions with mineral particulates. The likelihood of each of these possibilities will be discussed.
B31A-0198 0800h
Deliberations on Microbial Life in the Subglacial Lake Vostok, East Antarctica
The objective was to estimate microbial contents of accretion (lake originating) ice from the Lake Vostok buried beneath 4-km thick East Antarctic ice sheet with the ultimate goal to discover microbial life in this extreme icy environment featured by no light, close to freezing point temperature, ultra-low DOC contents, and an excess of oxygen. The PCR based bacterial and archaeal 16S ribosomal RNA gene sequencing constrained by Forensic Biology and Ancient DNA research criteria was used as a main approach. Epifluorescent and confocal microscopies as well as flow cytometry were implemented. DNA study showed that the accretion ice is essentially bacteria- and archaea-free. Up to now, the only accretion ice type 1 featured by mica-clay sediments presence and namely one horizon of four studied (3607m) allowed the recovery a few bacterial phylotypes. This unexpectedly included the chemolithoautotrophic thermophile {\it Hydrogenophilus thermoluteolus} and two more unclassified phylotypes all passing numerous contaminant controls. In contrast, the deeper and cleaner accretion ice 2 (three cores) with no sediments presence and near detection limit gas contents gave no reliable signals. The microbes detected in accretion ice 1 are unbelievable to resist an excess of oxygen in the lake water body (700 - 1300 mg O$_{2}$/l). They are supposed to be thriving in rather warm anoxic sediments in deep faults at the lake bottom and sporadically flushing out along with sediments to the lake veins in a shallow depth bay due to a seismotectonic activity likely operating in the lake environment. A few geophysical and geological evidences support this scenario. In the bay the presence of mica-clay sediments, higher accretion rate due to relief rise and likely oxygen-depleted upper layer of water can provide microbes with a chance to escape the high oxygen tension by the rapid entrapment into accretion ice 1. Sediment-free accretion ice 2, which forms above a deeper part of the lake, shows no evidence for reasonable source for microbe contribution given highly oxygenated lake water environment. Microscopy and flow cytometry trials on strictly decontaminated ice samples gave supporting results. While microscopy failed to reveal cells because the local concentrations were below the detection limit, the flow cytometry succeeded in a preliminary estimate of 9 and 24 cells/ml for accretion 1 (3561m) and control glacial (2054m) ice samples, respectively. However, given the ratio contaminants to indigenous cells is about 10:1 (from PCR results), the genuine microbial contents for both accretion and glacial ice samples is expected to be as low as 1 cell/ml what practically means "sterile" conditions. Thus, the accretion ice from Lake Vostok contains the very low unevenly distributed biomass indicating that the water body (at least upper layer) should also be hosting a highly sparse life, if any. By this, the Lake Vostok for the first time could present the big natural "sterile" water body on Earth providing a unique test area for searching for life on icy moons and planets. The search for life in Lake Vostok is constrained by a high chance of forward-contamination which can be minimized by using of stringent decontamination procedures and comprehensive biological controls.
B31A-0199 0800h
Himalayan Ice Core Analyses With Snow Algae
Snow algae in a shallow ice core (7 m in length) from the Yala Glacier, Langtang region of Nepal, were examined for potential use in ice core analyses. Ice core samples taken at 5350 m a.s.l. in 1994, contained more than 7 species of snow algae. In a vertical profile of the algal biomass, 11 distinct algal layers were observed. Seasonal observation in 1996 at the coring site indicated most algal growth to occur from late spring to late summer. Pit observation in 1991, 1992 and 1994 indicated algal layer formation to take place annually. Delta $^{18}$O, chemical ions (Na$^{+}$, Cl$^{-}$, SO$_{4}$$^{2-}$, and NO$_{3}$$^{-}$) and microparticles failed to show any clear seasonal variation, particularly so at depths exceeding 2 m, possibly due to heavy melt-water percolation. Snow algae in the ice core would thus be accurate boundary markers of annual layers in the ice cores of this region. Algal biomass in each annual layer was noted to be quite closely correlated with the following two environmental indices calculated from air temperature and precipitation at Kyangjing (3,920 m a.s.l.), the village nearest the Yala Glacier: estimated mean snow cover thickness (MST) and estimated summer mass balance (SMB) ({\it n} = 6, {\it r} = -0.975, {\it P} $<$ 0.01; {\it n} = 6, {\it r} = -0.968, {\it P} $<$ 0.01, respectively). Both parameters reflect snow cover thickness on algal layers, which would be a major determinant of light available for algal growth on the glacier. The algal biomass was also found to be roughly correlated with air temperature ({\it n} = 7, {\it r} = 0.773, {\it P} $<$ 0.05) but it was not correlated with the density of particles in the layer, possible nutrient source for the snow algae. Snow algal biomass in an ice core should prove a good environmental marker for indicating summer mass balance which is important for understanding summer-accumulation-type glaciers in this region.
B31A-0200 0800h
Methanogenic Diversity in Marine Sediments at Hydrate Ridge, Oregon
Little is known about the mechanism of methanogenic degradation of acetate or the fate of hydrogen and formate in cold marine sediments, or the ability of methanogens to grow and produce methane there. We used cultivation and molecular techniques to examine the microbes that produce methane from these substrates in permanently cold, anoxic marine sediments at Hydrate Ridge, Oregon ($44\deg$35'N, $125\deg$10'W, depth 800 m). Sediment samples (15 to 35 cm deep) were collected from areas of active methane ebullition or areas where methane hydrates occurred. The samples were anoxically diluted and inoculated into enrichment media with formate, acetate, or trimethylamine as catabolic substrate. After 2 years incubation at $4\deg$C to $15\deg$C, enrichment cultures grew and produced methane. DNA was extracted from the highest dilutions that grew. The sequence data suggested that each enrichment culture contained a single strain of methanogen, and many of these sequences were dissimilar to known sequences of methanogens. This level of similarity (89 to 91% similar) suggests that these methanogens belong to novel genera. A clone library of 16S rRNA genes was also created from DNA extracted from the sediment samples. Analysis of the 16S rRNA gene libraries also revealed phylotypes that were only distantly related to cultivated organisms. The sequences of the clone library and of the enrichment cultures indicate a high degree of phylogenetic diversity among the Hydrate Ridge Archaea.
B31A-0201 0800h
Microbiological and Biogeochemical Investigations of the Accreted Ice Above Subglacial Lake Vostok, Antarctica
Subglacial Lake Vostok is located ~4 km beneath the surface of the East Antarctic ice sheet and has been isolated from the atmosphere for at least 15 million years. The lake has a surface area near 14,000 km$^{2}$ and a depth exceeding 1000 m. While the nature of the environment within Subglacial Lake Vostok remains uncertain, if a sustained microbial ecosystem is present, life in this subsurface environment operates under arguably the most extreme conditions in the biosphere (i.e., high pressure, constant cold, high oxygen concentrations, and no light). The lake represents an analogue for ecosystems that may exist in Europa's ice-covered ocean and also provides an Earthly-based model for the evaluation of technology to search for life in icy extraterrestrial subsurface environments. Concerns for environmental protection have prevented direct sampling of the lake water thus far, as a prudent sampling plan that will not contaminate this pristine environment has yet to be developed and tested. However, an ice core has been retrieved at Vostok Station in which the bottom ~85 meters consists of lake water that has accreted to the bottom of the ice sheet, providing frozen samples of water from the lakes' surface. The ice from 3539 to 3609 mbs (accretion ice I) contains visible inclusions due to accretion in the shallow embayment or western grounding line, whereas ice from 3610-3623 mbs (accretion ice II) is very clean, forming above the deep eastern basin of the main lake. Using a multifaceted protocol to monitor cellular and molecular decontamination of ice cores, we show that the microbiology and geochemistry (i.e., dissolve organic carbon, nutrients, and ions) of accretion ice is very different from the overlying glacial ice. The numbers of cells are 2- to 7-fold higher in accretion ice I than in the overlying glacial ice, and decrease with increasing depth in accretion ice II. Cell viability in accretion ice samples has been confirmed by the measurable respiration of $^{14}$C-glucose at 10$^{o}$C and recovery of bacterial isolates by enrichment culturing. Direct amplification and phylogenetic analysis of 16S rDNA sequences related to $\beta$-, $\gamma$-, and $\delta$-proteobacterial species from samples originating from the open lake basin (i.e., accretion ice II) suggest dissimilatory metal oxidation/reduction and methylotrophic metabolic lifestyles may exist. Together, these data imply a priori that Subglacial Lake Vostok is a viable ecosystem.
http://www.brent.xner.net/
B31A-0202 0800h
Environmental Framework for Vostok Core Samples of Lake Vostok
We have developed an environmental framework for interpreting the results of extensive biologic studies from the Vostok core basal ice (below 3540 m) by using new flow velocities of the ice sheet over Lake Vostok during the last glacial maximum and enhanced imaging of the shoreline topography. The ice core represents a suite of samples across the lakeshore and the lake. The oldest accretion ice in the Vostok core formed $\sim$ 56,000 years ago at accretion rates of 0.45-0.72 cm/yr at the westernmost lake shoreline. Within our new environmental framework, the ice core can be classified on the basis of water depth and relative isolation from the processes active in the main lake. Review of the basal ice studies to date, and excluding from consideration likely contaminants, the diversity of microbial taxa reflects some systematic variation with both water depth and lake environment. These results support the interpretation that some of the observed microbes are neither the product of contamination nor the result of transport of windblown surface material, but rather are a partial but accurate representation of the subglacial Lake Vostok microbial community
B31A-0203 0800h
Severe Forest Fire Impacts to Active Layers in Alaskan Permafrost
In 2004 summer season, the Boundary Fire near Fairbanks occurred and surface organic layers severely burned in widely burnt areas. The loss of the surface organic layers may cause the deepening the active layer due to unbalancing of near surface heat budget. On-the -spot investigation was conducted in Boundary Fire area as to obtain the degree of severely of fire impacts. Thermal conductivities and depth of organic layers were measured and special index is proposed for estimation of the deepening active layer in next summer season. The ratio of thermal conductivities of residual organic layer after fire and mineral soil layers is a key of determination of the thawing effect. The results are compared with the previous fire impact which occurred in 1999 at Delta Junction in central Alaska. Other data which were obtained in eastern Siberia in 2003 were applied to verify the proposed the new index by present author.
B31A-0204 0800h
The Role of the Permafrost Reservoir in the Global Carbon Budget
A high organic content is typical for all frozen sediments accumulated on permafrost, because these sediments are per se cryopreserved soils. The most interesting of these types of sediments is the frozen Pleistocene loess. It is the soil of the mammoth tundra-steppe. It covers about one million square kilometers of the north of Siberia. Carbon content of the soil is about 2%. Total carbon storage in the sediments is about 400 Gt. For many years, experiments and field measurements showed that the carbon is highly labile. The soils respire upon thawing at a rate of 3 to 20 mg C/kg/day. In the case of vast thawing of the sediments, CO$_{2}$ emission connected with this will be comparable with anthropogenic emission. Field experiments and modeling showed that the thermal flux connected with Pleistocene soil respiration upon thawing (self-heating) may provide progressive permafrost melting. It is accepted that during the Pleistocene glaciation, carbon storage in terrestrial ecosystems was reduced to about 500 Gt (0 to 1350 Gt range) . But during that time, the permafrost zone occupied all the territory north of 40-45$^{o}$ N. By making an analogy with carbon content in preserved frozen sediments in Siberia and Alaska we can suppose that terrestrial carbon storage during glaciation was 1500 to 2000 Gt higher than present assessments. The value includes carbon storage in large-scale tundra-steppe biomes; in frozen loess of Europe and the southwest of Siberia; in solifluction sediments of slopes and in alluvium; in soil, loess and peat buried under glacial sheets. Thawing of permafrost and glaciers was accompanied by oxidation of the carbon and CO$_{2}$ emission into the atmosphere. Data of the Pleistocene-Holocene dynamic of atmospheric CO$_{2}$ and $^{14}$C corresponds to the permafrost reservoir dynamic. Budget of $^{13}$ CO$_{2}$ corresponds to this dynamic only under conditions when the storage of organic carbon in the ocean during glaciation was significantly reduced.
B31A-0205 0800h
Thermokarst lake bubbling as a source of atmospheric methane (CH4) at rapid climate transitions during the last glacial period.
We propose a new hypothesis to explain the prompt increases in atmospheric methane (CH4) concentration (AMC) that accompanied rapid interglacial climate warming during the last glacial age. Understanding sources of variation in AMC is important because CH4 is a greenhouse gas with strong potential to feed back onto rapid climate change. Until now, two main hypotheses have been advanced to explain millennial scale variations in AMC as recorded in ice cores: 1) The wetland hypothesis proposes that CH4 emission from wetlands existing at the end of the glacial periods increased in response to climate warming, and 2) the `clathrate gun hypothesis' assumes that catastrophic release of methane hydrates from sea floor sediments caused rapid increases in AMC. The wetlands hypothesis is poorly constrained by a lack of data on the extent of paleo-wetlands and by the discontinuity between the fast rates of AMC rise and the slower process of wetland expansion. We propose a third hypothesis: Permafrost degradation over extensive regions of Siberia, Asia, Europe and North America resulted in the formation of thermokarst (thaw) lakes, from which high rates of ebullition (bubbling) provided an additional source of CH4 to the atmosphere. Ebullition, a mechanism of gas transport seldom quantified, constitutes 96% of CH4 emissions from modern North Siberian thermokarst lakes. Rates of CH4 ebullition along thermokarst margins of lakes are up to two orders of magnitude higher than from non-thermokarst areas of lakes. Thermokarst activity releases organic matter from permafrost soils into anaerobic lake bottoms, enhancing methane production and emission from lakes. Recognition of modern North Siberian thermokarst lakes as an additional source of atmospheric CH4 increases the current estimate of the contribution of northern aquatic ecosystems to the global atmospheric CH4 budget by 21%. Through a synthesis of paleopedological records of permafrost and thaw lake distributions, and measurements of CH4 biogeochemistry in modern thermokarst lakes, we advance the hypothesis that expansion of thermokarst lakes at the onset of interstadials constituted a major feedback to global warming during the last glacial age.