Diatoms in bottom sediments of thermokarst lakes of the Pechora Delta

2019 ◽  
pp. 285-290
Author(s):  
Elvira A. Zinnatova, Larisa A. Frolova ◽  
Larisa A. Frolova
Keyword(s):  
Bottom Sediments ◽  
Environmental Conditions ◽  
Sources Of Information ◽  
Thermokarst Lakes ◽  
Thermokarst Lake ◽  
Fouling Organisms ◽  
Diatom Complexes

The Northern lakes are good objects for paleoclimatic reconstructions. One of the sources of information about changes in the ecosystems of lakes are diatoms. The study of diatom complexes revealed 133 taxa belonging to 49 genera, 24 families, 13 orders and 3 classes in the bottom sediments of the thermokarst lake of the Pechora Delta. Dominated by the Holarctic representatives of benthic and fouling organisms giving preference to the alkaline environmental conditions.

scholarly journals Thermokarst lake waters across the permafrost zones of western Siberia

2014 ◽  
Vol 8 (4) ◽  
pp. 1177-1193 ◽  
Author(s):  
R. M. Manasypov ◽  
O. S. Pokrovsky ◽  
S. N. Kirpotin ◽  
L. S. Shirokova
Keyword(s):  
Western Siberia ◽  
Chemical Elements ◽  
Chemical Compositions ◽  
Thermokarst Lakes ◽  
Thermokarst Lake ◽  
Surface Areas ◽  
Discontinuous Permafrost ◽  
Latitudinal Position ◽  
Hydrochemical Composition ◽  
Lake Waters

Abstract. This work describes the hydrochemical composition of thermokarst lake and pond ecosystems, which are observed in various sizes with different degrees of permafrost influence and are located in the northern part of western Siberia within the continuous and discontinuous permafrost zones. We analysed the elemental chemical composition of the lake waters relative to their surface areas (from 10 to 106 m2) and described the elemental composition of the thermokarst water body ecosystems in detail. We revealed significant correlations between the Fe, Al, dissolved organic carbon (DOC) and various chemical elements across a latitude gradient covering approximately 900 km. Several groups of chemical elements that reflect the evolution of the studied water bodies were distinguished. Combining the data for the studied latitude profile with the information available in the current literature demonstrated that the average dissolved elemental concentrations in lakes with different areas depend specifically on the latitudinal position, which is presumably linked to (1) the elements leached from frozen peat, which is the main source of the solutes in thermokarst lakes, (2) marine atmospheric aerosol depositions, particularly near the sea border and (3) short-range industrial pollution by certain metals from the largest Russian Arctic smelter. We discuss the evolution of the chemical compositions observed in thermokarst lakes during their formation and drainage and predict the effect that changing the permafrost regime in western Siberia has on the hydrochemistry of the lakes.

scholarly journals Detection and spatiotemporal analysis of methane ebullition on thermokarst lake ice using high-resolution optical aerial imagery

2016 ◽  
Vol 13 (1) ◽  
pp. 27-44 ◽  
Author(s):  
P. R. Lindgren ◽  
G. Grosse ◽  
K. M. Walter Anthony ◽  
F. J. Meyer
Keyword(s):  
Image Analysis ◽  
High Resolution ◽  
Image Acquisition ◽  
Optical Image ◽  
Aerial Imagery ◽  
Accurate Estimation ◽  
Lake Ice ◽  
Thermokarst Lakes ◽  
Thermokarst Lake ◽  
Methane Ebullition

Abstract. Thermokarst lakes are important emitters of methane, a potent greenhouse gas. However, accurate estimation of methane flux from thermokarst lakes is difficult due to their remoteness and observational challenges associated with the heterogeneous nature of ebullition. We used high-resolution (9–11 cm) snow-free aerial images of an interior Alaskan thermokarst lake acquired 2 and 4 days following freeze-up in 2011 and 2012, respectively, to detect and characterize methane ebullition seeps and to estimate whole-lake ebullition. Bubbles impeded by the lake ice sheet form distinct white patches as a function of bubbling when lake ice grows downward and around them, trapping the gas in the ice. Our aerial imagery thus captured a snapshot of bubbles trapped in lake ice during the ebullition events that occurred before the image acquisition. Image analysis showed that low-flux A- and B-type seeps are associated with low brightness patches and are statistically distinct from high-flux C-type and hotspot seeps associated with high brightness patches. Mean whole-lake ebullition based on optical image analysis in combination with bubble-trap flux measurements was estimated to be 174 ± 28 and 216 ± 33 mL gas m−2 d−1 for the years 2011 and 2012, respectively. A large number of seeps demonstrated spatiotemporal stability over our 2-year study period. A strong inverse exponential relationship (R2 >  =  0.79) was found between the percent of the surface area of lake ice covered with bubble patches and distance from the active thermokarst lake margin. Even though the narrow timing of optical image acquisition is a critical factor, with respect to both atmospheric pressure changes and snow/no-snow conditions during early lake freeze-up, our study shows that optical remote sensing is a powerful tool to map ebullition seeps on lake ice, to identify their relative strength of ebullition, and to assess their spatiotemporal variability.

scholarly journals Spatial analyses of thermokarst lakes and basins in Yedoma landscapes of the Lena Delta

2011 ◽  
Vol 5 (4) ◽  
pp. 849-867 ◽  
Author(s):  
A. Morgenstern ◽  
G. Grosse ◽  
F. Günther ◽  
I. Fedorova ◽  
L. Schirrmeister
Keyword(s):  
Spatial Analyses ◽  
Lena River ◽  
Thermokarst Lakes ◽  
Thermokarst Lake ◽  
Warming Climate ◽  
Future Potential ◽  
Lake Drainage ◽  
Carbon Balances ◽  
Lena River Delta ◽  
Ice Complex

Abstract. Distinctive periglacial landscapes have formed in late-Pleistocene ice-rich permafrost deposits (Ice Complex) of northern Yakutia, Siberia. Thermokarst lakes and thermokarst basins alternate with ice-rich Yedoma uplands. We investigate different thermokarst stages in Ice Complex deposits of the Lena River Delta using remote sensing and geoinformation techniques. The morphometry and spatial distribution of thermokarst lakes on Yedoma uplands, thermokarst lakes in basins, and thermokarst basins are analyzed, and possible dependence upon relief position and cryolithological context is considered. Of these thermokarst stages, developing thermokarst lakes on Yedoma uplands alter ice-rich permafrost the most, but occupy only 2.2% of the study area compared to 20.0% occupied by thermokarst basins. The future potential for developing large areas of thermokarst on Yedoma uplands is limited due to shrinking distances to degradational features and delta channels that foster lake drainage. Further thermokarst development in existing basins is restricted to underlying deposits that have already undergone thaw, compaction, and old carbon mobilization, and to deposits formed after initial lake drainage. Future thermokarst lake expansion is similarly limited in most of Siberia's Yedoma regions covering about 106 km2, which has to be considered for water, energy, and carbon balances under warming climate scenarios.

scholarly journals The Analytical Approach to the Competitive Strategy and the Process of its Formation

Ekonomika ◽  
1999 ◽  
Vol 48 ◽  
Author(s):  
Ramunas Časas
Keyword(s):  
Theoretical Analysis ◽  
Strategic Management ◽  
Competitive Advantage ◽  
Environmental Conditions ◽  
Competitive Strategy ◽  
Analytical Approach ◽  
Sources Of Information ◽  
Strategy Research ◽  
Company Strategy ◽  
Basic Concepts

This paper aims at taking an analytical look at the concept of competitive strategy taking into account already existing vast theoretical heritage in the strategy research. In particular, this article tries to determine and articulate basic concepts and definitions necessary for the theoretical analysis of competitive strategy and to offer an evaluation of the theories and approaches to the background of formation of competitive strategy. The main sources of information were theoretical works on strategy; strategic management, marketing, articles by researchers and practitioners working in areas related to the aforementioned ones. Reviewing and analysing the contributions of the authors in this field, in the paper the competitive strategy is called “company strategy; seeking competitive advantage”. Although the ability of the company to reach the competitive advantage may be classified as the companyspecific capability; the analysis of various theories has shown that the company can seek the competitive advantage in three distinct ways: by availing itself of unique environmental conditions, by having unique resources or by establishing the relationships and co-operating with other companies. All these concepts are closely linked together and complement each other.

scholarly journals Seasonal dynamics of organic carbon and metals in thermokarst lakes from the discontinuous permafrost zone of western Siberia

2015 ◽  
Vol 12 (2) ◽  
pp. 1975-2019
Author(s):  
R. M. Manasypov ◽  
S. N. Vorobyev ◽  
S. V. Loiko ◽  
I. V. Kritzkov ◽  
L. S. Shirokova ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Water Column ◽  
Permafrost Zone ◽  
Ice Formation ◽  
Thermokarst Lakes ◽  
Dissolved Carbon ◽  
Thermokarst Lake ◽  
Discontinuous Permafrost ◽  
Lake Waters

Abstract. Western Siberia's thermokarst (thaw) lakes extend over a territory spanning over a million km2; they are highly dynamic hydrochemical systems that receive chemical elements from the atmosphere and surrounding peat soil and vegetation, and exchange greenhouse gases with the atmosphere, delivering dissolved carbon and metals to adjacent hydrological systems. This work describes the chemical composition of ~ 130 thermokarst lakes of the size range from a few m2 to several km2, located in the discontinuous permafrost zone. Lakes were sampled during spring floods, just after the ice break (early June), the end of summer (August), the beginning of ice formation (October) and during the full freezing season in winter (February). Dissolved organic carbon (DOC) and the major and trace elements do not appreciably change their concentration with the lake size increase above 1000 m2 during all seasons. On the annual scale, the majority of dissolved elements including organic carbon increase their concentration from 30 to 500%, with a statistically significant (p < 0.05) trend from spring to winter. The maximal increase in trace element (TE) concentration occurred between spring and summer and autumn and winter. The ice formation in October included several stages: first, surface layer freezing followed by crack (fissure) formation with unfrozen water from the deeper layers spreading over the ice surface. This water was subsequently frozen and formed layered ice rich in organic matter. As a result, the DOC and metal concentrations were the highest at the beginning of the ice column and decreased from the surface to the depth. A number of elements demonstrated the accumulation, by more than a factor of 2, in the surface (0–20 cm) of the ice column relative to the rest of the ice core: Mn, Fe, Ni, Cu, Zn, As, Ba and Pb. The main consequences of discovered freeze-driven solute concentrations in thermokarst lake waters are enhanced colloidal coagulation and the removal of dissolved organic matter and associated insoluble metals from the water column to the sediments. The measured distribution coefficient of TE between amorphous organo-ferric coagulates and lake water (< 0.45 μm) were similar to those reported earlier for Fe-rich colloids and low molecular weight (< 1 kDa) fractions of thermokarst lake waters, suggesting massive co-precipitation of TE with amorphous Fe oxy(hydr)oxide stabilized by organic matter. Although the concentration of most elements is lowest in spring, this period of maximal water coverage of land creates a significant reservoir of DOC and soluble metals in the water column that can be easily mobilized to the hydrological network. The highest DOC concentration observed in the smallest (< 100 m2) water bodies in spring suggests their strongly heterotrophic status and, therefore, elevated CO2 flux from the lake surface to the atmosphere.

scholarly journals Geochemistry and Weathering Indices of Yedoma and Alas Deposits beneath Thermokarst Lakes in Central Yakutia

2021 ◽  
Vol 9 ◽  
Author(s):  
Mathias Ulrich ◽  
Loeka L. Jongejans ◽  
Guido Grosse ◽  
Birgit Schneider ◽  
Thomas Opel ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Organic Matter ◽  
Environmental Conditions ◽  
Mineral Weathering ◽  
Sediment Supply ◽  
Thermokarst Lakes ◽  
Central Yakutia ◽  
Geochemical Properties ◽  
Weathering Indices ◽  
Lake Core

Ice- and organic-rich deposits of late Pleistocene age, known as Yedoma Ice Complex (IC), are widespread across large permafrost regions in Northeast Siberia. To reconstruct Yedoma IC formation in Central Yakutia, we analyzed the geochemistry, sedimentology, and stratigraphy of thawed and frozen deposits below two thermokarst lakes in different evolutionary stages (a mature alas lake and a initial Yedoma lake) from the Yukechi site in the Lena-Aldan interfluve. We focused on inorganic geochemical characteristics and mineral weathering in two ∼17 m long sediment cores to trace syngenetic permafrost aggradation and degradation over time. Geochemical properties, element ratios, and specific weathering indices reflect varying sedimentation processes and seasonal thaw depths under variable environmental conditions. Deeper thaw during the interstadial Marine Isotope Stage (MIS) 3 enabled increasing mineral weathering and initial thermokarst processes. Sedimentological proxies reflect high transport energy and short transport paths and mainly terrestrial sediment supply. The Yedoma formation resulted from fluvial, alluvial and aeolian processes. Low mean TOC contents in both cores contrast with Yedoma deposits elsewhere. Likely, this is a result of the very low organic matter content of the source material of the Yukechi Yedoma. Pronounced cryostructures and strongly depleted pore water stable isotopes show a perennially frozen state and preserved organic matter for the lower part of the Yedoma lake core, while changing permafrost conditions, conditions promoting weathering, and strong organic matter decomposition are suggested by our proxies for its middle and upper parts. For the alas lake core, less depleted water stable isotopes reflect the influence of recent precipitation, i.e. the infiltration of rain and lake water into the unfrozen ground. The FENG, MIA(R), and ICV weathering indices have proven to be promising proxies for the identification of conditions that promote mineral weathering to different degrees in the stratigraphy of the thawed and frozen Yedoma deposits, for which we assume a rather homogeneous chemical composition of the parent material. Our study highlights that the understanding of environmental conditions during Yedoma formation and degradation processes by specific geochemical proxies is crucial for assessing the potential decomposition and preservation of the frozen and unfrozen Yedoma inventories.

Analysis of Rybinsk and Ivankovo reservoirs diatom complexes and phytoplankton associations long-term transformations

2019 ◽  
pp. 83-86
Author(s):  
Lev V. Razumovsky ◽  
Vikenty L. Razumovsky
Keyword(s):  
Bottom Sediments ◽  
Methodological Approach ◽  
Graphical Analysis ◽  
Comprehensive Analysis ◽  
Diatom Complexes

As a result of monitoring, a unified methodological approach was formulared for the ecosystems of the Ivankovsky and Rybinsk reservoirs, with comprehensive analysis of phytoplankton associations and diatom complexes from bottom sediments. In addition to traditional forms of hydrobiological analysis, the author's method of graphical analysis was applied.

Learning Disabilities and Social Environments: Kibbutz versus City Comparisons of Loneliness and Social Competence

1995 ◽  
Vol 18 (3) ◽  
pp. 519-536 ◽  
Author(s):  
Malka Margalit ◽  
Ilana Ben-Dov
Keyword(s):  
Learning Disabilities ◽  
Social Skills ◽  
Social Competence ◽  
Environmental Conditions ◽  
Peer Acceptance ◽  
Social Systems ◽  
Social Contexts ◽  
Social Environments ◽  
Sources Of Information ◽  
Regular School

In order to explore aspects of loneliness and social competence of learning disabled students in relation to specific environmental contexts, this study focused on children in two different social systems: a kibbutz and a city. The aim of the study was to investigate the social skills and loneliness patterns among 122 students with learning disabilities (LD) in self-contained special classes within regular school systems (66 kibbutz students; 56 city students) and among 120 nondisabled (nonLD) students within these same environmental conditions (69 kibbutz students; 51 city students). A four-way MANCOVA (LD/nonLD X kibbutz/city X male/female X lower/higher grades, with age as covariate) was performed for self-reported loneliness and empathy, peer-rated sociometric measures, teacher-rated social skills, and classroom adjustment as the dependent measures. LD youngsters were found to be less socially competent and more lonely than their nonLD peers in all social competence areas, and as assessed by three sources of information. When compared with LD city students, LD kibbutz students were evaluated by their teachers as demonstrating fewer maladaptive externalising behaviours, and by their peers as having more friends. Social contexts did not differentiate between the two LD groups' feeling of loneliness or rates of peer acceptance, and it can be concluded that students with LD were found to experience loneliness regardless of gender or environmental conditions.

Sign in / Sign up

Export Citation Format

Share Document