Irina N Mitskevich

Microflora in the basal strata at Antarctic ice core above the Vostok lake

The microbiological investigations of the Antarctic ice core at the Vostok station become especially important in connection with the discovery of an subglacial lake in this region. This lake is considered by the world-wide scientific community to be an important object for searching for relict forms of life on the Earth and also as a model for solving a number of problems of exobiology--for instance for development of methods to penetrate into underice sea at Europe--Jupiters satellite. For the first time the Antarctic ice core samples were taken from the horizons which correspond to the basal zone (3534-3541 m) and to the accreation ice zone (3555-3611 m) above the subglacial lake Vostok. As a result of the microbiological investigations it was shown that the total number of microbial cells have been in the same range of quantities as at the upper, younger horizons and varied from 1.3 x 10(2) up to 9.6 x 10(2) cl/ml. Some periodicity in the cell concentration and in their morphological diversity was revealed along the core. The maximal number and the greatest morphological variety were detected at horizons with the depth of 3534, 3555 and 3595 m. A drop in the cell concentration two or three times as much was found in ice layers under each of the above mentioned horizons. The discovered stratification is apparently connected with the periodicity of the lake water interactions with the basal ice layer and obviously depends on the complex natural events which took place in the geological history of our planet.

Microbiological Characterization of the Accreted Ice of Subglacial Lake Vostok, Antarctica

The accreted ice of subglacial Lake Vostok extends upward from the lake water level (a depth of 3750 m) to the bottom surface of the overlying Antarctic ice sheet. All of the accreted ice samples, taken from depths between 3541 and 3611 m, were found to contain pro- and eukaryotic microorganisms, whose number and diversity varied in different ice horizons and correlated, to a certain degree, with the occurrence of organic and inorganic impurities in a given horizon. Some biological objects found in the accreted lake ice, including bacteria, microalgae, and the pollen of higher plants, were morphologically similar to those found earlier in the glacier ice bulk. The others were not. It is suggested that the microorganisms found in the lake ice may come from different locations—the bottom layer of the glacier ice, the bedrock underlying the glacier, and the lake water.

Microbial processes of the carbon and sulfur cycles in the White Sea

The present paper contains the results of our microbiological and biogeochemical investigations carried out during a series of expeditions to the White Sea in 2002–2006. The studies were conducted in the open part of the White Sea, as well as in the Onega, Dvina, and Kandalaksha bays. In August 2006, the photosynthetic productivity in the surface water layer was low (47–145 mg C m−2 day−1). Quantitative characteristics of microbial numbers and activity of the the key microbial processes occurring in the water column of the White Sea were explored. Over the 5-year period of observations, the total number of bacterial cells in the surface layer of the water column varied from 50 to 600 thousand cells ml−1. In August 2006, bacterioplankton production (BP) was estimated to be 0.26–3.3 μg C l−1 day−1; the P/B coefficient varied from 0.22 to 0.93. The suspended organic matter had a lighter isotope composition (from −28.0 to −30.5‰) due to the predominance of terrigenous organic matter delivered by the Northern Dvina waters. The interseasonal and interannual variation coefficients for phytoplankton production and BP numbers are compared. The bacterioplankton community of the White Sea’s deep water was found to be more stable than that of the surface layer. In the surface layer of bottom sediments, methane concentration was 0.2–5.2 μl dm−3; the rate of bacterial sulfate reduction was 18–260 μg S dm−3 day−1; and the rates of methane production and oxidation were 24–123 and 6–13 nl CH4 dm−3 day−1, respectively. We demonstrated that the rates of microbial processes of the carbon and sulfur cycles occurring in the sediments of the White Sea basin were low.

Transformation of particulate organic matter at the water-bottom boundary in the Russian Arctic seas: Evidence from isotope and radioisotope data

Complex biogeochemical studies including the determination of isotopic composition of Corg in both suspended particulate matter and surface horizon (0–1 cm) of sediments (more than 260 determinations of δ13C-Corg) were carried out for five Arctic shelf seas: White, Barents, Kara, East Siberian, and Chukchi. The aim of this study is to elucidate causes that change the isotopic composition of particulate organic carbon at the water-sediment boundary. It is shown that the isotopic composition of Corg in sediments from seas with a high river runoff (White, Kara, and East Siberian) does not inherit the isotopic composition of Corg in particles precipitating from the water column, but is enriched in heavy 13C. Seas with a low river runoff (Barents and Chukchi) show insignificant difference between the value of δ13C-Corg in both suspended load and sediment because of a low content of the isotopically light allochthonous organic matter (OM) in particulates. Complex biogeochemical studies with radioisotope tracers (14CO2, 35S, and 14CH4) revealed the existence of specific microbial filter formed from heterotrophic and autotrophic organisms at the water-sediment boundary. This filter prevents the mass influx of products of OM decomposition into water column, as well as reduces the influx of a part of OM contained in the suspended particulate matter from water into sediment.

Antarctic ice sheet as an object for solving some methodological problems of exobiology

Abstract Icy formations are often found in the cosmos: there are comets nuclei, polar caps of Mars and of other planets and Europa, the Jupiters satellite covered with icy crust. Various inclusions of mineral and organic compounds have been permanently accumulated in the ice thickness which protects them from subsequent environmental influence and ensures their reliable and long-term preservation. So icy bodies are unique objects for searching microorganisms and studying ancient ecological events that occurred during formation of icy layers. Complex microbiological and glaciological investigations at Vostok station carried out during a number of years resulted in the discovery of well-preserved cells of microorganisms of different taxonomic groups, as well as plant pollen and unicellular algae in the ice sheet horizons the age of which exceeds 300,000 years. Upon incubation of some samples with radiocarbon labeled organics an evidence of the preservation of some viable microorganisms has been provided. The investigation of ice bodies in an attempt to find any possible form of microscopical life has an advantage over analogous studies of other cosmic solids because the cells of microorganisms and other inclusions can be released from the melted ice without destruction and can be studied unambiguously by different methods of microscopy.

Antarctic ice sheet as a model in search of life on other planets

Abstract This paper concerns the problem of search of life on other planets due to similarities of some conditions in polar ice caps of Earth and Mars. Viable microbes were isolated from layers of the Antarctic ice sheet that dates back about 200 000 years. Their morphological variability and gradual restoration of some physiological functions in favourable conditions were described. The relation of microbes distribution at different horizons of ice to considerable fluctuations of Earths climate in ancient geological epochs was revealed. Those fluctuations of climate brought to the sharp variations of intensity of microparticles and microbes transfer with intercontinental aerial streams to polar caps of neighbouring planets.

Microorganisms found in the basal horizons of the Antarctic glacier above Lake Vostok.

The Antarctic ice sheet, whose thickness in the central part reaches 4000 m, keeps information on the changes in the climate and composition of the Earth atmosphere over hundreds of thousands of years [1, 2]. Along with the bubbles of ancient air and particles of atmospheric dust that were brought to the surface of the glacier by the air streams, its layers also contain microorganisms, some of which retain viability after the long-term anabiosis [3].

Microbiological and biogeochemical properties of the Caspian Sea sediments and water column

The work presents the results of investigation of microbial and biogeochemical processes at the water-sediment interface in the samples of three Caspian Sea profiles obtained during the 39th cruise of RV “Rift” in May–June 2012. The decrease in suspended Corg content from the surface to the bottom resulted from the activity of aerobic heterotrophic microorganisms. Autotrophic methanogenesis occurred in anoxic water of deep-sea depressions, where methane concentrations were up to 2.2–3.75 μL CH4 L−1, which was an order of magnitude higher than in the aerobic water column (0.04–0.32 μL CH4 L−1). Methanogenesis was accompanied by a considerable decrease in δ13C of suspended Corg (−26 to −30‰). The numbers of microbial cells in the water column varied from 40 to 3200 × 103 cells mL−1. The results of microbiological and biogeochemical investigation demonstrated that, in spite of the absence of connection with the ocean and other specific features, the Caspian Sea has the characteristics of a typical marine basin.

Time machine: Ancient life on Earth and in the cosmos

The discovery more than 30 years ago of the unique superlong anabiosis phenomenon (deep sleep/dormancy) for ancient microorganisms buried in Antarctic ice deposits created the experimental and theoretical basis for the fields of cryomicrobiology and astrobiology related to searching for life or its evidence in the universe. This discovery is of special interest in light of the upcoming International Polar Year (IPY 2007–2008) and the creation of the U.S. Subglacial Antarctic Lake Environments program (http://salepo.tamu.edu/us_sale). Abysov et al. [1977, 1978] discovered superlong anabiosis for microorganisms in deep Antarctic ice cores above Lake Vostok when his group found and revived ancient microbes frozen for more than 500,000 years (Figure 1). Previously, only science fiction writers had contemplated a deep sleep/dormancy phenomenon that might allow humans to postpone their deaths by freezing and thus travel in time into the future.

Microbiological Explorations in the Northern Part of the Barents Sea in Early Winter

The total number of microorganisms and rates of microbial processes of the carbon cycle were determined in snow, sea ice, water, and seafloor sediments of the northern part of the Barents Sea from September to October, 1998. The explorations were carried out in two areas: along the transection from Franz Josef Land to Victoria Island and along the continental slope region covered with solid ice at latitude 81°–82° N and longitude 37°–39° E. At the time of study, the ice cover was represented by thick one-year old ice (up to 1.2 m), perennial ice (up to 1.85 m), and pack ice. The number of bacteria in the snow cover, sea ice, and seawater was 12 to 14, 50 to 110, and 10 to 240 × 103 cells/ml, respectively. Rates of dark CO2 assimilation, glucose utilization, and methane oxidation by bacteria were determined. The highest rate of microbial processes was found in samples of the lowermost newly formed sea ice. The lowest level of activity for all processes was observed in melted snow water. A direct relation was shown between the concentration of Corg, the bacterial biomass, and the values of δ13Corg in mixtures of melted snow and ice. The number of microorganisms and rates of microbial processes in seafloor sediments measured at the stations on the continental slope are comparable to those in the central part of the Barents Sea and the northern part of the Kara Sea.