The vulnerability of Arctic shelf sediments to climate change

2015 ◽  
Vol 23 (4) ◽  
pp. 461-479 ◽  
Author(s):  
Robie W. Macdonald ◽  
Zou Zou A. Kuzyk ◽  
Sophia C. Johannessen
Keyword(s):  
Organic Carbon ◽  
Carbon Sources ◽  
The Arctic ◽  
Sedimentary Environments ◽  
Carbon Supply ◽  
Shelf Sediment ◽  
Wide Range ◽  
Metabolic Conditions ◽  
Shelf Sediments ◽  
Ocean Ecosystem

The sediments of the pan-Arctic shelves contribute an important component to the Arctic Ocean ecosystem by providing a habitat for biota (benthos), a repository for organic and inorganic non-conservative substances entering or produced within the ocean, a reactor and source of transformed substances back to the water column, and a mechanism of burial. Sediments interact with ice, ocean, and the surrounding land over a wide range of space and time scales. We discuss the vulnerability of shelf sediment to changes in (i) organic carbon sources, (ii) pathways of sediment and organic carbon supply, and (iii) physical and biogeochemical alteration (diagenesis). Sedimentary environments of the shelves and basins are likely to exhibit a wide variance in their response to global change because of their wide variation in sediment sources, processes, and metabolic conditions. In particular, the Chukchi and Barents shelves are dominated by inflowing waters from oceans to the south, whereas the interior shelves are more closely tied to terrigenous sources due to river inflow and coastal erosion.

scholarly journals Production of Poly(3-hydroxybutyrate) (P(3HB)) from Different Agroindustry Byproducts by Bacillus megaterium

2021 ◽  
Vol 11 (6) ◽  
pp. 14278-14289
Keyword(s):  
Organic Carbon ◽  
Bacillus Megaterium ◽  
Culture Media ◽  
Carbon Sources ◽  
Modern Society ◽  
Cell Biomass ◽  
Wide Range ◽  
Pha Production ◽  
Factorial Design Of Experiments ◽  
Dry Cell

The use of plastics, replacing materials such as paper and glass, has become a staple of modern society. A possible alternative is the production of biopolymers, in which case polyhydroxyalkanoates (PHAs) tend to be the most studied class. Among the PHAs, poly(3-hydroxybutyrate) (P(3HB)) is one of the most studied. Bacillus megaterium can utilize a wide range of carbon sources to produce P(3HB) and display high resistance to osmotic pressure and temperature. There are few studies regarding the viability of confectionery wastewater (CWW) and rice parboiling water (RPW) in PHA production; however, data suggests they might be successfully used as culture media for microorganisms. Cultures of B. megaterium were conducted under a 22-factorial design of experiments with different agitation and airflow conditions using mineral medium added with CWW and RPW. Under maximized conditions, it was possible to obtain 7.55 g/L of dry cell biomass, with 50.1% P(3HB) content (3.78 g/L). Kinetic parameters of the maximized culture were also assessed, with the highest productivity (0.146 g/L·h) being found after 20 h of culture. Results found in the tests indicate that CWW and RPW can be used as culture media in P(3HB) production; however further studies are necessary to fully optimize the process, as well as to find alternatives to reduce the amount of residual total organic carbon (TOC) still present in the cultures.

scholarly journals Carbon cycling on the East Siberian Arctic Shelf – a change in air-sea CO<sub>2</sub> flux induced by mineralization of terrestrial organic carbon

2017 ◽  
Author(s):  
Erik Gustafsson ◽  
Christoph Humborg ◽  
Göran Björk ◽  
Christian Stranne ◽  
Leif G. Anderson ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Organic Carbon ◽  
Carbon Cycling ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sources ◽  
Atmospheric Co2 ◽  
Arctic Shelf ◽  
The Arctic ◽  
Biogeochemical Model ◽  
Siberian Arctic

Abstract. Measurements from the SWERUS-C3 and ISSS-08 Arctic expeditions were used to calibrate and validate a new physical-biogeochemical model developed to quantify key carbon cycling processes on the East Siberian Arctic Shelf (ESAS). The model was used in a series of experimental simulations with the specific aim to investigate the pathways of terrestrial dissolved and particulate organic carbon (DOCter and POCter) supplied to the shelf. Rivers supply on average 8.5 Tg C yr−1 dissolved inorganic carbon (DIC), and further 8.5 and 1.1 Tg C yr−1 DOCter and POCter respectively. Based on observed and simulated DOC concentrations and stable isotope values (δ13CDOC) in shelf waters, we estimate that only some 20 % of the riverine DOCter is labile. According to our model results, an additional supply of approximately 14 Tg C yr−1 eroded labile POCter is however required to describe the observed stable isotope values of DIC (δ13CDIC). Degradation of riverine DOCter and POCter results in a 1.8 Tg C yr−1 reduction in the uptake of atmospheric CO2, while degradation of eroded POCter results in an additional 10 Tg C yr−1 reduction. Our calculations indicate nevertheless that the ESAS is an overall small net sink for atmospheric CO2 (1.7 Tg C yr−1). The external carbon sources are largely compensated by a net export from the shelf to the Arctic Ocean (31 Tg C yr−1), and to a smaller degree by a permanent burial in the sediments (2.7 Tg C yr−1).

scholarly journals Characterising organic carbon sources in Anthropocene affected Arctic upland lake catchments, Disko Island, West Greenland

2020 ◽  
Author(s):  
Mark A. Stevenson ◽  
Suzanne McGowan ◽  
Emma J. Pearson ◽  
George E. A. Swann ◽  
Melanie J. Leng ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Isotope Composition ◽  
Carbon Sources ◽  
Fold Increase ◽  
Arctic Lakes ◽  
Ice Age ◽  
The Arctic ◽  
Terrestrial Vegetation ◽  
Range Limit

Abstract. The Arctic is rapidly changing, disrupting biogeochemical cycles and the processing, delivery and sedimentation of carbon (C), in linked terrestrial-aquatic systems. In this investigation, we coupled a hydrogeomorphic assessment of catchment soils, sediments and plants with a recent lake sediment sequence to understand the source and quality of organic carbon present in three Arctic upland lake catchments on Disko Island, located just south of the Low-High Arctic transition zone. This varied permafrost landscape has exposed soils with less vegetation cover at higher altitudes, and all lakes received varying extent of glacial meltwater inputs. We provide improved isotope and biomarker source identifications for palaeolimnological studies in high latitude regions, where terrestrial vegetation is at or close to its northerly and altitudinal range limit. The poorly developed catchment soils lead to lake waters with low dissolved organic carbon (DOC) concentrations (≤ 1.5 mg L−1). Sedimentary Carbon / Nitrogen (C / N) ratios, the C isotope composition of organic matter (δ13Corg) and biomarker ratios (n-alkanes, n-alkanols, n-alkanoic acids and sterols) showed that sedimentary organic matter (OM) in these lakes is mostly derived from aquatic sources (algae and macrophytes). We used a 210 Pb dated sediment core to determine how carbon cycling in a lake-catchment system (Disko 2) had changed over recent centuries. Recent warming since the end of the Little Ice Age (LIA ~1860 AD), which accelerated after ca. 1950, led to melt of glacier ice and permafrost releasing nutrients and DOC to the lake, stimulating pronounced aquatic algal production, as shown by a > 10 fold increase in β-carotene, indicative of a major regime shift. Our findings highlight that in Arctic lakes with sparsely developed catchment vegetation and soils, recent Anthropocene warming results in pronounced changes to in-lake C processing and the deposition of more reactive, predominately autochthonous C, compared with extensively vegetated low Arctic systems.

scholarly journals Porewater <i>δ</i><sup>13</sup>C<sub>DOC</sub> indicates variable extent of degradation in different talik layers of coastal Alaskan thermokarst lakes

2021 ◽  
Vol 18 (7) ◽  
pp. 2241-2258
Author(s):  
Ove H. Meisel ◽  
Joshua F. Dean ◽  
Jorien E. Vonk ◽  
Lukas Wacker ◽  
Gert-Jan Reichart ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Greenhouse Gas ◽  
Carbon Isotope ◽  
Lake Sediment ◽  
Stable Carbon Isotope ◽  
The Arctic ◽  
High Porosity ◽  
Stable Carbon ◽  
Thermokarst Lakes ◽  
Wide Range

Abstract. Thermokarst lakes play an important role in permafrost environments by warming and insulating the underlying permafrost. As a result, thaw bulbs of unfrozen ground (taliks) are formed. Since these taliks remain perennially thawed, they are zones of increased degradation where microbial activity and geochemical processes can lead to increased greenhouse gas emissions from thermokarst lakes. It is not well understood though to what extent the organic carbon (OC) in different talik layers below thermokarst lakes is affected by degradation. Here, we present two transects of short sediment cores from two thermokarst lakes on the Arctic Coastal Plain of Alaska. Based on their physiochemical properties, two main talik layers were identified. A “lake sediment” is identified at the top with low density, sand, and silicon content but high porosity. Underneath, a “taberite” (former permafrost soil) of high sediment density and rich in sand but with lower porosity is identified. Loss on ignition (LOI) measurements show that the organic matter (OM) content in the lake sediment of 28±3 wt % (1σ, n=23) is considerably higher than in the underlying taberite soil with 8±6 wt % (1σ, n=35), but dissolved organic carbon (DOC) leaches from both layers in high concentrations: 40±14 mg L−1 (1σ, n=22) and 60±14 mg L−1 (1σ, n=20). Stable carbon isotope analysis of the porewater DOC (δ13CDOC) showed a relatively wide range of values from −30.74 ‰ to −27.11 ‰ with a mean of -28.57±0.92 ‰ (1σ, n=21) in the lake sediment, compared to a relatively narrow range of −27.58 ‰ to −26.76 ‰ with a mean of -27.59±0.83 ‰ (1σ, n=21) in the taberite soil (one outlier at −30.74 ‰). The opposite was observed in the soil organic carbon (SOC), with a narrow δ13CSOC range from −29.15 ‰ to −27.72 ‰ in the lake sediment (-28.56±0.36 ‰, 1σ, n=23) in comparison to a wider δ13CSOC range from −27.72 ‰ to −25.55 ‰ in the underlying taberite soil (-26.84±0.81 ‰, 1σ, n=21). The wider range of porewater δ13CDOC values in the lake sediment compared to the taberite soil, but narrower range of comparative δ13CSOC, along with the δ13C-shift from δ13CSOC to δ13CDOC indicates increased stable carbon isotope fractionation due to ongoing processes in the lake sediment. Increased degradation of the OC in the lake sediment relative to the underlying taberite is the most likely explanation for these differences in δ13CDOC values. As thermokarst lakes can be important greenhouse gas sources in the Arctic, it is important to better understand the degree of degradation in the individual talik layers as an indicator for their potential in greenhouse gas release, especially, as predicted warming of the Arctic in the coming decades will likely increase the number and extent (horizontal and vertical) of thermokarst lake taliks.

Characteristics of organic carbon in surface sediments of Laptev Sea shelf

2020 ◽  
Author(s):  
Irina Oberemok ◽  
Elena Gershelis ◽  
Andrey Grin’ko ◽  
Alexey Ruban ◽  
Elizaveta Klevantseva ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Coastal Erosion ◽  
Surface Sediments ◽  
Oxygen Index ◽  
Outer Shelf ◽  
The Arctic ◽  
Laptev Sea ◽  
Shelf Sediments ◽  
The Laptev Sea

&lt;p&gt;Accelerating coastal erosion and enhancing river sediment discharge are expected to greatly increase the delivery of terrestrial organic carbon (terrOC) to the Arctic Ocean. Remobilized terrOC may be buried in shallow or outer shelf sediments, degraded and translocated to the deeper basins, or remineralized in the water column causing a positive feedback to amplified global warming. The East Siberian Arctic Shelf (ESAS), represented by the Laptev Sea, the East Siberian Sea, and the Russian part of the Chukchi Sea, is the widest and shallowest continental shelf of the World Ocean. In the current study, we investigated surface sediment samples collected across the Laptev Sea shelf (from the coastline to the outer shelf) during the Arctic expedition onboard the Russian &lt;em&gt;R/V Academician M. Keldysh&lt;/em&gt; during fall 2018.&lt;/p&gt;&lt;p&gt;We analyzed 16 samples for bulk (TOC, &lt;em&gt;&amp;#948;&lt;/em&gt;13C) and molecular (distribution and concentration of n-alkanes and PAHs) parameters. We also performed Rock-Eval (RE) analysis in order to compare its results with the signatures provided by traditional geochemical tracers and thereby to gain new insights into the sources of organic matter in modern surface sediments. In addition, a grain-size analysis was carried out to reveal hydrodynamic control on the organic carbon transport across the studied transect. Using a combination of traditional molecular interpretations (performed in this study and published earlier) and RE parameters (Hydrogen index, Oxygen index and T&lt;sub&gt;peak&lt;/sub&gt;) we attempted to distinguish riverine input and coastal erosion and disentangle processes of terrOC degradation and its replacement with fresh/marine OC during cross-shelf transport. Overall, a strong decrease of terrigenous contribution to the sedimentary organic carbon was observed on molecular level with increasing distance from the coast. According to the RE data, intensive terrOC degradation takes place in the shallow and mid-shelf sediments which is traced by sharply increasing oxygen index. The clear correlation between OI and the clay content points toward the perception that mineral matrix do not seem to be such good protector as expected, and intensive microbial degradation of the sedimentary organic matter contained in fine particles occurs during repeated resuspension.&lt;/p&gt;&lt;p&gt;This research is supported by Russian Science Foundation, project # 19-77-00067.&lt;/p&gt;

scholarly journals Porewater δ<sup>13</sup>C<sub>DOC</sub> Indicates Variable Extent Of Degradation In Different Talik Layers Of Coastal Alaskan Thermokarst Lakes

2020 ◽  
Author(s):  
Ove H. Meisel ◽  
Joshua F. Dean ◽  
Jorien E. Vonk ◽  
Lukas Wacker ◽  
Gert-Jan Reichart ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Greenhouse Gas ◽  
Carbon Isotope ◽  
Lake Sediment ◽  
Stable Carbon Isotope ◽  
The Arctic ◽  
High Porosity ◽  
Stable Carbon ◽  
Thermokarst Lakes ◽  
Wide Range

Abstract. Thermokarst lakes play an important role in permafrost environments by warming up and insulating the underlying permafrost. As a result, thaw bulbs of unfrozen ground (taliks) are formed. Since these taliks remain perennially thawed, they are zones of increased degradation where microbial activity and geochemical processes can lead to increased greenhouse gas emissions from thermokarst lakes. It is not well understood though to what extent the organic carbon (OC) in different talik layers below thermokarst lakes is affected by degradation. Here, we present two transects of short sediment cores from two thermokarst lakes on the Arctic Coastal Plain of Alaska. Based on their physiochemical properties two main talik layers were identified. A lake sediment at the top with low density, sand and silicon content but high porosity. Underneath a deeper talik (former permafrost soil) of high sediment density and rich in sand but lower porosity. Loss on ignition (LOI) measurements show that the organic matter (OM) content in the lake sediment of 28 ± 3 wt % (1σ, n = 23) is considerably higher than in the underlying deeper talik soil with 8 ± 6 wt % (1σ, n =  35), but dissolved organic carbon (DOC) leaches from both layers in high concentrations: 40 ± 14 mg/l (1σ, n =  22) and 60 ± 14 mg/l (1σ, n = 20), respectively. Stable carbon isotope analysis of the porewater DOC (δ13CDOC) showed a relatively wide range of values from −30.74 ‰ to −27.11 ‰ with a mean of −28.57 ± 0.92 ‰ (1σ, n =  21) in the lake sediment, compared to a relatively narrow range of −27.58 ‰ to −26.76 ‰ with a mean of −27.59 ± 0.83 ‰ (1σ, n = 21) in the deeper talik soil (one outlier at −30.74 ‰). The opposite was observed in the soil organic carbon (SOC), with a narrow δ13CSOC range from −29.15 ‰ to −27.72 ‰ in the lake sediment (−28.56 ± 0.36 ‰, 1σ, n = 23) in comparison to a wider δ13CSOC range from −27.72 ‰ to 25.55 ‰ in the underlying deeper talik soil (−26.84 ± 0.81 ‰, 1σ, n = 21). The wider range of porewater δ13CDOC values in the lake sediment compared to the deeper talik soil, but narrower range of comparative δ13CSOC, along with the δ13C-shift from δ13CSOC to δ13CDOC together indicates increased stable carbon isotope fractionation due to ongoing processes in the lake sediment. Increased degradation of the OC in the lake sediment relative to the underlying deeper talik are the most likely explanation for these differences in δ13CDOC values. As thermokarst lakes can be important greenhouse gas sources in the Arctic it is important to better understand the degree of degradation in the individual talik layers as an indicator for their potential in greenhouse gas release. Especially, as predicted warming of the Arctic in the coming decades will likely increase the number and extent (horizontal and vertical) of thermokarst lake taliks.

scholarly journals Morphological and cultural studies of Septoria vignicola

2014 ◽  
Vol 19 (1) ◽  
pp. 83-89
Author(s):  
R. D. Rawal ◽  
H. S. Sohi
Keyword(s):  
Mycelial Growth ◽  
Culture Media ◽  
Agar Medium ◽  
Carbon Sources ◽  
Potassium Nitrate ◽  
Potato Dextrose Agar ◽  
Optimum Growth ◽  
Carbon Supply ◽  
Wide Range ◽  
Agar Media

Pycnidial formation starts six days after inoculation. These arę globose, dark and range between 59.28-109.20 μm in diameier. The pycnidial wall is composed of 2- 3 layers of brown cells. The pycnidiospores ooze 8 days after inoculation. They are filiform, straight to curved, hyaline, septate with 2-4 septa, ends pointed or round and 21.84-68.64 x 1.25-2.15 μm. Mycelial growth was most profuse on Czapek Dox's agar medium, whereas maximum sporulation took place on Coon's, Sabauraud's and Potato dextrose agar media. The fungus could grow over a wide range of temperature from 12- 36°C (optimum: 24 ± l°C) and showed no growth at 40°C or above. Pycnidial formation occurred at 16- 28°C with a maximum at 24 ± l°C. Out of seven carbon sources tested, sorbose was the best for growth and sporulation of <i>Septoria vignicola</i> whereas maltose was a poor source for sporulation. The fungus responded very well to the supply of carbon in culture media as no growth of the fungus could be observed when the carbon supply was with held. Aspartic acid supported optimum growth among all the organic sources tried, whereas among inorganic sources potassium nitrate was the best, last growth observed on ammonium nitrate.

A MODELING SYSTEM FOR CLIMATE CHANGE RISK ASSESSMENT, MANAGEMENT AND HEDGING IN COASTAL AREAS

2017 ◽  
Author(s):  
Sergei Soldatenko ◽  
Sergei Soldatenko ◽  
Genrikh Alekseev ◽  
Genrikh Alekseev ◽  
Alexander Danilov ◽  
...  
Keyword(s):  
Climate Change ◽  
Risk Assessment ◽  
Coastal Areas ◽  
Mitigation Strategies ◽  
System Structure ◽  
The Arctic ◽  
Risk Modeling ◽  
Wide Range ◽  
Adverse Weather ◽  
The Impact

Every aspect of human operations faces a wide range of risks, some of which can cause serious consequences. By the start of 21st century, mankind has recognized a new class of risks posed by climate change. It is obvious, that the global climate is changing, and will continue to change, in ways that affect the planning and day to day operations of businesses, government agencies and other organizations and institutions. The manifestations of climate change include but not limited to rising sea levels, increasing temperature, flooding, melting polar sea ice, adverse weather events (e.g. heatwaves, drought, and storms) and a rise in related problems (e.g. health and environmental). Assessing and managing climate risks represent one of the most challenging issues of today and for the future. The purpose of the risk modeling system discussed in this paper is to provide a framework and methodology to quantify risks caused by climate change, to facilitate estimates of the impact of climate change on various spheres of human activities and to compare eventual adaptation and risk mitigation strategies. The system integrates both physical climate system and economic models together with knowledge-based subsystem, which can help support proactive risk management. System structure and its main components are considered. Special attention is paid to climate risk assessment, management and hedging in the Arctic coastal areas.

Assimilation of various organic carbon sources by Haematococcus strains

2009 ◽  
Vol 57 (2) ◽  
pp. 231-237
Author(s):  
M. Zych ◽  
A. Stolarczyk ◽  
K. Maca ◽  
A. Banaś ◽  
K. Termińska-Pabis ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Organic Compounds ◽  
Present Experiment ◽  
Carbon Sources ◽  
Growth Conditions ◽  
Mixotrophic Growth ◽  
Naturally Occurring ◽  
Organic Carbon Sources ◽  
Secondary Carotenoids ◽  
Colour Changes

Differences in the assimilation of individual organic compounds (5 mM sugars and L-asparagine) under mixotrophic growth conditions were described for three naturally occurring Haematococcus strains.The effects of assimilation were measured by the growth intensity and size of algal cells, and the effect of colour changes in the cultures was observed. Some compounds caused the cell colouration to change from green to yellow, being the result of chlorophyll disappearance and the accumulation of yellow secondary carotenoids. In the present experiment none of the cultures turned red, thus excluding the intense accumulation of the commercially interesting carotenoid, astaxanthin.

Sign in / Sign up

Export Citation Format

Share Document