scholarly journals Degrading permafrost river catchments and their impact on Arctic Ocean nearshore processes

AMBIO ◽  
2021 ◽  
Author(s):  
Paul J. Mann ◽  
Jens Strauss ◽  
Juri Palmtag ◽  
Kelsey Dowdy ◽  
Olga Ogneva ◽  
...  
Keyword(s):  
Ecosystem Structure ◽  
Turnover Rates ◽  
Frozen Ground ◽  
Nearshore Processes ◽  
Permafrost Thaw ◽  
Nearshore Ecosystems ◽  
Degradation Rates ◽  
Ground Collapse ◽  
Future Challenges ◽  
Hydrological Cycles

AbstractArctic warming is causing ancient perennially frozen ground (permafrost) to thaw, resulting in ground collapse, and reshaping of landscapes. This threatens Arctic peoples' infrastructure, cultural sites, and land-based natural resources. Terrestrial permafrost thaw and ongoing intensification of hydrological cycles also enhance the amount and alter the type of organic carbon (OC) delivered from land to Arctic nearshore environments. These changes may affect coastal processes, food web dynamics and marine resources on which many traditional ways of life rely. Here, we examine how future projected increases in runoff and permafrost thaw from two permafrost-dominated Siberian watersheds—the Kolyma and Lena, may alter carbon turnover rates and OC distributions through river networks. We demonstrate that the unique composition of terrestrial permafrost-derived OC can cause significant increases to aquatic carbon degradation rates (20 to 60% faster rates with 1% permafrost OC). We compile results on aquatic OC degradation and examine how strengthening Arctic hydrological cycles may increase the connectivity between terrestrial landscapes and receiving nearshore ecosystems, with potential ramifications for coastal carbon budgets and ecosystem structure. To address the future challenges Arctic coastal communities will face, we argue that it will become essential to consider how nearshore ecosystems will respond to changing coastal inputs and identify how these may affect the resiliency and availability of essential food resources.

scholarly journals Degradation of permafrost carbon in the Kolyma River

2020 ◽  
Author(s):  
Kirsi Keskitalo ◽  
Lisa Bröder ◽  
Dirk Jong ◽  
Nikita Zimov ◽  
Anya Davydova ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Climate Impacts ◽  
Frozen Ground ◽  
River Bank ◽  
Permafrost Thaw ◽  
Degradation Rates ◽  
Kolyma River

<p>Soil temperatures in permafrost (i.e. perennially frozen ground) are rising globally. The increasing temperatures accelerate permafrost thaw and release of organic carbon, that has been locked in permafrost soils since the last glacial period, to the contemporary carbon cycle. The potential remineralisation of organic carbon to greenhouse gases can contribute to further climate warming. Particulate organic carbon (POC) in the Kolyma River is older than dissolved organic carbon (DOC) thus serves as a good tracer for abrupt permafrost thaw (i.e. river bank erosion and thermokarst) that dominantly releases old POC. While dissolved organic carbon (DOC) mobilised from the old Yedoma outcrops on the banks of the Kolyma River is shown to be highly labile, vulnerability of POC to biodegradation is not yet known. In this study we aim to constrain degradation rates for POC in the Kolyma River. To capture seasonal variability of the POC pool and its degradation rate the incubation was conducted both during the spring freshet and in late summer (2019 and 2018, respectively). We incubated whole-water samples over 9 to 15 days and quantified POC (and DOC) loss over time, as well as dissolved inorganic carbon (DIC). The incubation was carried out in the dark. We also tracked changes in POC composition and age with carbon isotopes (d<sup>13</sup>C-OC, d<sup>13</sup>C-DIC, ∆<sup>14</sup>C). Preliminary results from 2018 suggest a decrease in POC concentrations of up to 30 % while those of DOC decrease by up to 11 %. The rate of POC degradation is nearly three times faster than DOC though the absolute amounts of DOC are in turn higher than those of POC (< 1 mg L<sup>-1</sup> for POC and ~3 mg L<sup>-1</sup> for DOC). Furthermore, the changes in d<sup>13</sup>C of POC, DOC and DIC suggest ongoing microbial degradation and conversion of organic carbon into inorganic carbon. These first estimates show that POC degrades fairly rapidly while transported in the Kolyma River. A better understanding of POC degradation along lateral flow paths is critical for improving our knowledge of permafrost thaw and its possible climate impacts in the future.</p>

scholarly journals Lack of <sup>13</sup>C-label incorporation suggests low turnover rates of thaumarchaeal intact polar tetraether lipids in sediments from the Iceland shelf

2014 ◽  
Vol 11 (2) ◽  
pp. 201-216 ◽  
Author(s):  
S. K. Lengger ◽  
Y. A. Lipsewers ◽  
H. de Haas ◽  
J. S. Sinninghe Damsté ◽  
S. Schouten
Keyword(s):  
Marine Sediments ◽  
Dissolved Inorganic Carbon ◽  
Sediment Cores ◽  
Turnover Rates ◽  
Degradation Rates ◽  
Label Incorporation ◽  
13C Label ◽  
Sandy Sediments ◽  
Organic Rich Sediment ◽  
Complex Organic

Abstract. Thaumarchaeota are amongst the most abundant microorganisms in aquatic environments, however, their metabolism in marine sediments is still debated. Labeling studies in marine sediments have previously been undertaken, but focused on complex organic carbon substrates which Thaumarchaeota have not yet been shown to take up. In this study, we investigated the activity of Thaumarchaeota in sediments by supplying different 13C-labeled substrates which have previously been shown to be incorporated into archaeal cells in water incubations and/or enrichment cultures. We determined the incorporation of 13C-label from bicarbonate, pyruvate, glucose and amino acids into thaumarchaeal intact polar lipid-glycerol dibiphytanyl glycerol tetraethers (IPL-GDGTs) during 4–6 day incubations of marine sediment cores from three sites on the Iceland shelf. Thaumarchaeal intact polar lipids, in particular crenarchaeol, were detected at all stations and concentrations remained constant or decreased slightly upon incubation. No 13C incorporation in any IPL-GDGT was observed at stations 2 (clay-rich sediment) and 3 (organic-rich sediment). In bacterial/eukaryotic IPL-derived fatty acids at station 3, contrastingly, a large uptake of 13C label (up to + 80‰ ) was found. 13C was also respired during the experiment as shown by a substantial increase in the 13C content of the dissolved inorganic carbon. In IPL-GDGTs recovered from the sandy sediments at station 1, however, some enrichment in δ13C (1–4‰ ) was detected after incubation with bicarbonate and pyruvate. The low incorporation rates suggest a low activity of Thaumarchaeota in marine sediments and/or a low turnover rate of thaumarchaeal IPL-GDGTs due to their low degradation rates. Cell numbers and activity of sedimentary Thaumarchaeota based on IPL-GDGT measurements may thus have previously been overestimated.

scholarly journals Dikes on permafrost: predicting thaw and settlement

1970 ◽  
Vol 7 (4) ◽  
pp. 365-371 ◽  
Author(s):  
W. G. Brown ◽  
G. H. Johnston
Keyword(s):  
Heat Conduction ◽  
Reasonable Accuracy ◽  
Frozen Ground ◽  
Permafrost Thaw ◽  
Conduction Theory ◽  
Good Agreement

Prediction of permafrost thaw and settlement of dikes constructed on perennially frozen ground is important for maintenance and foundation stability. A method is developed for estimating the rates of thaw and settlement, based on simple heat conduction theory. A comparison of calculated and observed rates of thaw for dikes on ice-rich foundation soils at the Kelsey Generating Station in northern Manitoba shows good agreement and indicates that thaw and settlement rates can be predicted with reasonable accuracy.

scholarly journals Estimating RNA dynamics using one time point for one sample in a single-pulse metabolic experiment

2020 ◽  
Author(s):  
Micha Hersch ◽  
Adriano Biasini ◽  
Ana Claudia Marques ◽  
Sven Bergmann
Keyword(s):  
Single Pulse ◽  
Single Sample ◽  
Computational Time ◽  
Published Data ◽  
Data Sets ◽  
Metabolic Labeling ◽  
Turnover Rates ◽  
Computationally Efficient ◽  
Degradation Rates ◽  
Wide Scale

AbstractOver the past decade, experimental procedures such as metabolic labeling for determining RNA turnover rates at the transcriptome-wide scale have been widely adopted. Several computational methods to estimate RNA processing and degradation rates from such experiments have been suggested, but they all require several RNA sequencing samples. Here we present a method that can estimate RNA synthesis, processing and degradation rates from a single sample. To this end, we use the Zeisel model and take advantage of its analytical solution, reducing the problem to solving a univariate non-linear equation on a bounded domain. This makes our method computationally efficient, while enabling inference of rates that correlate well with previously published data sets. Using our approach on a single sample, we were able to reproduce and extend the observation that dynamic biological processes such as transcription or chromatin modifications tend to involve genes with higher metabolic rates, while stable processes such as basic metabolism involve genes with lower rates.In addition to saving experimental work and computational time, having a sample-based rate estimation has several advantages. It does not require an error-prone normalization across samples and enables the use of replicates to estimate uncertainty and perform quality control. Finally the method and theoretical results described here are general enough to be useful in other settings such as nucleotide conversion methods.

Cold truths: What does a warmer Arctic mean for carbon budgets consistent with the Paris Agreement?

2021 ◽  
Author(s):  
Rachael Treharne ◽  
Brendan Rogers ◽  
Thomas Gasser ◽  
Merritt Turetsky ◽  
Erin MacDonald ◽  
...  
Keyword(s):  
Substantial Reduction ◽  
Policy Decision ◽  
Future Climate Change ◽  
Earth System ◽  
Carbon Budgets ◽  
Frozen Ground ◽  
Linear Processes ◽  
Fire Emissions ◽  
Permafrost Thaw ◽  
Paris Climate Agreement

&lt;p&gt;Arctic regions are warming more than twice as fast as the global average. This rapid warming is expected to drive a substantial net loss of carbon to the atmosphere, particularly from the thawing of &amp;#8216;permafrost&amp;#8217;, or perennially frozen ground. However, the majority of Earth System Models do not account for permafrost or processes driving the loss of permafrost carbon. In addition, where models do consider permafrost carbon feedbacks, thaw is typically simulated as a gradual, top-down process. This ignores critical, non-linear processes - notably abrupt permafrost thaw, wildfire, and fire-induced permafrost thaw. This means that the potential for a strong positive feedback to future climate change from permafrost regions is not well understood among policy decision-makers. There is therefore an urgent need for a comprehensive and policy-relevant assessment of permafrost carbon feedbacks and their implications for the temperature goals outlined in the Paris Climate Agreement. To address this need, we built upon a reduced complexity Earth System Model and gradual permafrost thaw emulator (Gasser et. al., 2018) by incorporating abrupt thaw, fire emissions, and fire-induced thaw. Using this framework, we assessed the implications of a comprehensive representation of permafrost feedbacks for carbon budgets that constrain warming to 1.5&amp;#176;C and 2&amp;#176;C. We found that combined feedbacks - gradual thaw, abrupt thaw, and fire processes - resulted in a substantial reduction in global carbon budgets to remain below 1.5&amp;#176;C and 2&amp;#176;C.&lt;/p&gt;

scholarly journals Belowground carbon pools and dynamics in China's warm temperate and sub-tropical deciduous forests

2009 ◽  
Vol 6 (4) ◽  
pp. 6339-6369
Author(s):  
C. W. Xiao ◽  
I. A. Janssens ◽  
W. G. Sang ◽  
R. Z. Wang ◽  
Z. Q. Xie ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Deciduous Forest ◽  
Plant Litter ◽  
Deciduous Forests ◽  
Turnover Rates ◽  
Soil Microbial ◽  
Degradation Rates ◽  
Soil Carbon Stocks ◽  
Belowground Carbon ◽  
Warm Temperate

Abstract. We report the first estimates of pools and dynamics of microbes, roots, plant litter and soil organic carbon (SOC) in three dominant types of China's vast deciduous forest area: Betula platyphylla, Quercus liaotungensis, and Quercus aliena varacuteserrata. Organic matter degradation rates overshadowed litter inputs as the main determinant of the soil carbon stocks. Across the three forests, rates of litter decomposition were also indicative for turnover rates of SOC. Litter and SOC decay was faster in the sub-tropical than in the warm-temperate forests. Among the latter, SOC turnover was highest in the forest producing the higher-quality litter. Microbial biomass was, as expected, correlated with SOC content. Microbial activity, in contrast, was highest at the sub-tropical forest, despite the lower SOC availability, lower fraction of labile SOC, and lower soil microbial biomass. These results may contribute to increased understanding of controls over belowground carbon cycling in deciduous forests.

Abstract 120: Radiocarbon Birth Dating of Cerebral Arteriovenous Malformations

Stroke ◽  
2017 ◽  
Vol 48 (suppl_1) ◽  
Author(s):  
Daniel L Cooke ◽  
Meike Halberkann ◽  
Christian Matzenauer ◽  
Helen Kim ◽  
Michael Lawton ◽  
...  
Keyword(s):  
Arteriovenous Malformations ◽  
Cerebral Arteries ◽  
Equation Model ◽  
Structural Protein ◽  
Turnover Rates ◽  
Pulse Technique ◽  
Congenital Origin ◽  
Degradation Rates ◽  
Molecular Synthesis ◽  
Brain Avms

Introduction: The chronological development of brain arteriovenous malformations (AVM) is controversial. Atmospheric nuclear testing until 1963 produced a global bomb-pulse of 14 C and thus a chronometer of molecular synthesis in the entire biosphere from 1955 to the present. We isolated and dated a durable, representative structural protein from human cerebral arteries (CA) and brain AVMs. Method: Samples from cadaveric CAs or from brain AVMs from patients undergoing surgical resection were processed to ultra- purify elastin. The age of purified elastin extracted from cerebral arteries or from AVMs was measured using 14 C bomb-pulse technique. We modified a 14 C biological incorporation equation model using variable AVM formation dates and elastin formation and degradation rates. Results: A total of 62 CAs from individuals with ages ranging from 1 month to 100 years and 30 unruptured or ruptured AVMs were collected. All CAs and nearly all AVMs yielded ultra-purified elastin in sufficient amount for further 14 C birth dating. Mean age of elastin was 13.4± 11.2 years (n = 34), whereas elastin derived from AVMs was less than 5 years old (n = 15, p = 0.002). Based on 14 C content relative subject birthdate and date of tissue collection, best-fit modeling of CA and AVM elastin demonstrated turnover rates less than 2% and 25 - 50%, respectively. Amongst AVMs, those with associated aneurysms had younger elastin (p=0.007). Larger AVMs tended to have younger elastin (p=0.086) and AVM rupture was not associated with elastin age (p=0.358). Conclusions: Our data provides the first chronological evidence for the longevity of elastin in CAs, as evident based on the inclusion of bomb carbon in elastin from subjects who reached maturity prior to 1955. Importantly it also demonstrates elastin isolated from brain AVMs is contemporary and likely immature suggesting a non-congenital origin and/or rapid vascular turnover.

Monitoring and estimating drought-induced impacts on forest structure, growth, function, and ecosystem services using remote-sensing data: recent progress and future challenges

2013 ◽  
Vol 21 (2) ◽  
pp. 103-115 ◽  
Author(s):  
Yao Zhang ◽  
Changhui Peng ◽  
Weizhong Li ◽  
Xiuqin Fang ◽  
Tinglong Zhang ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Ecosystem Services ◽  
Remote Sensing Data ◽  
Growth Function ◽  
Forest Growth ◽  
Ecosystem Structure ◽  
Remotely Sensed Data ◽  
Carbon Cycles ◽  
Future Challenges ◽  
Induced Changes

Alongside global warming, droughts are expected to increase in frequency, severity, and extent in the near future, which will likely result in significant impacts on forest growth, production, structure, composition, and ecosystem services. However, due to spatial and temporal characteristics, it is difficult to monitor and assess the potential effects of droughts. Remote sensing can provide an effective way to obtain real-time conditions of forests affected by drought and offer a range of spatial and temporal insights into drought-induced changes to forest ecosystem structure, function, and services. Remote sensing is rapidly developing as more satellites are launched. In situ and remotely sensed data fusion techniques have achieved notable success in assessing drought-induced damage to forests and carbon cycles. Even so, constraints still exist when using satellite data. The objectives of this review are to (1) briefly review existing data sources and methods of remote sensing; (2) synthesize current applications and contributions of remote sensing in monitoring and estimating impacts of droughts on forest ecosystems; and (3) highlight research gaps and future challenges.

scholarly journals The life cycle of cyclotides: biosynthesis and turnover in plant cells

2020 ◽  
Vol 39 (10) ◽  
pp. 1359-1367
Author(s):  
Blazej Slazak ◽  
Tobias Haugmo ◽  
Bogna Badyra ◽  
Ulf Göransson
Keyword(s):  
Cell Culture ◽  
Storage Proteins ◽  
Production Systems ◽  
Plant Cells ◽  
Suspension Cultures ◽  
Structural Motif ◽  
Turnover Rates ◽  
Degradation Rates ◽  
Organ Tissue ◽  
Plant Families

Abstract Key message Turnover rates have implications for understanding cyclotide biology and improving plant cell culture-based production systems. Abstract Cyclotides are a family of polypeptides recognized for a broad spectrum of bioactivities. The cyclic, cystine knot structural motif imparts these peptides with resistance to temperature, chemicals and proteolysis. Cyclotides are found widely distributed across the Violaceae and in five other plant families, where their presumed biological role is host defense. Violets produce mixtures of different cyclotides that vary depending on the organ, tissue or influence of environmental factors. In the present study, we investigated the biosynthesis and turnover of cyclotides in plant cells. Viola uliginosa suspension cultures were grown in media where all nitrogen containing salts were replaced with their 15N counterparts. This approach combined with LC–MS analysis allowed to separately observe the production of 15N-labelled peptides and decomposition of 14N cyclotides present in the cells when switching the media. Additionally, we investigated changes in cyclotide content in V. odorata germinating seeds. In the suspension cultures, the degradation rates varied for individual cyclotides and the highest was noted for cyO13. Rapid increase in production of 15N peptides was observed until day 19 and subsequently, a plateau of production, indicating an equilibrium between biosynthesis and turnover. The developing seedling appeared to consume cyclotides present in the seed endosperm. We show that degradation processes shape the cyclotide pattern present in different tissues and environments. The results indicate that individual cyclotides play different roles—some in defense and others as storage proteins. The turnover of cyclotides should be accounted to improve cell culture production systems.

scholarly journals Lack of <sup>13</sup>C-label incorporation suggests low turnover rates of thaumarchaeal intact polar tetraether lipids in sediments from the Iceland Shelf

2013 ◽  
Vol 10 (8) ◽  
pp. 12807-12847
Author(s):  
S. K. Lengger ◽  
Y. A. Lipsewers ◽  
H. de Haas ◽  
J. S. Sinninghe Damsté ◽  
S. Schouten
Keyword(s):  
Marine Sediments ◽  
Dissolved Inorganic Carbon ◽  
Sediment Cores ◽  
Turnover Rates ◽  
Degradation Rates ◽  
Label Incorporation ◽  
13C Label ◽  
Sandy Sediments ◽  
Organic Rich Sediment ◽  
Complex Organic

Abstract. Thaumarchaeota are amongst the most abundant microorganisms in aquatic environments, however, their metabolism in marine sediments is still debated. Labeling studies in marine sediments have previously been undertaken, but focused on complex organic carbon substrates which Thaumarchaeota have not yet been shown to take up. In this study, we investigated the activity of Thaumarchaeota in sediments by supplying different 13C-labeled substrates which have previously been shown to be incorporated into archaeal cells in water incubations and/or enrichment cultures. We determined the incorporation of 13C-label from bicarbonate, pyruvate, glucose and amino acids into thaumarchaeal intact polar lipid-glycerol dibiphytanyl glycerol tetraethers (IPL-GDGTs) during 4–6 day incubations of marine sediment cores from three different sites on the Iceland Shelf. Thaumarchaeal intact polar lipids were detected at all stations and concentrations remained constant or decreased slightly upon incubation. No 13C incorporation in any IPL-GDGT was observed at stations 2 (clay-rich sediment) and 3 (organic-rich sediment). In bacterial/eukaryotic IPL-derived fatty acids at station 3, contrastingly, a large uptake of 13C label (up to &amp;plus;80‰) was found. 13C was also respired during the experiment as shown by a substantial increase in the 13C content of the dissolved inorganic carbon. In IPL-GDGTs recovered from the sandy sediments at station 1, however, some enrichment in 13C (1–4‰) was detected after incubation with bicarbonate and pyruvate. The low incorporation rates suggest a low activity of Thaumarchaeota in marine sediments and/or a low turnover rate of thaumarchaeal IPL-GDGTs due to their low degradation rates. Cell numbers and activity of sedimentary Thaumarchaeota based on IPL-GDGT measurements may thus have previously been overestimated.

Sign in / Sign up

Export Citation Format

Share Document