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1.
Curr Microbiol ; 79(2): 56, 2022 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-34982223

RESUMO

N2O, a greenhouse gas, is increasingly emitted from degrading permafrost mounds of palsa mires because of the global warming effects on microbial activity. In the present study, we hypothesized that N2O emission could be affected by a change in pH conditions because the collapse of acidic palsa mounds (pH 3.4-4.6) may result in contact with minerogenic ground water (pH 4.8-6.3), thereby increasing the pH. We compared the effects of pH change on N2O emission from cultures inoculated with peat suspensions. Peat samples were collected on a transect from a still intact high part to the collapsing edge of a degrading palsa mound in northwestern Finland, assuming the microbial communities could be different. We adjusted the pH of peat suspensions prepared from a collapsing palsa mound and compared the N2O emission in a pH gradient from 4.5 to 8.5. The collapsing edge had the highest N2O emission from the peat suspensions among all points on the transect under natural acidic conditions (pH 4.5). The N2O emission was reduced with a moderate rise in pH (pH 5.0-6.0) by approximately 85% compared with natural acidic level (pH 4.5). The bacterial communities in acidic cultures differed considerably from those in alkaline cultures. When pH was adjusted to alkaline conditions, N2O-emitting bacteria different from those present in acidic conditions appeared to emit N2O. The bacterial communities could be characterized by changing pH conditions after thawing and collapse of permafrost have contrasting impacts on N2O production that calls for further attention in future studies.


Assuntos
Óxido Nitroso , Pergelissolo , Concentração de Íons de Hidrogênio , Óxido Nitroso/análise , Solo , Microbiologia do Solo
2.
Sci Total Environ ; 804: 150182, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34798735

RESUMO

Understanding the evolutions of the permafrost extent and active layer thickness (ALT) in the Northern Hemisphere (NH) are critical for global carbon flux simulation, climate change prediction, and engineering risk assessment. The temporal change characteristics of the permafrost extent and ALT for the NH have not been studied. We used the Kudryavtsev method, integrating a 0.5° × 0.5° spatial resolution of air temperature, soil texture, snow depth, vegetation type, soil volume moisture content, and organic content to simulate the changes of permafrost extent and ALT in the NH from 1969 to 2018. The results indicated that permafrost extent decreased from 23.25 × 106 km2 (average from 1969 to 1973) to 21.64 × 106 km2 (average from 2014 to 2018), with a linear rate of -0.023 × 106 km2/a. Siberia had the highest degradation rate of 0.014 × 106 km2/a, followed by Alaska, Mongolian Plateau, Qinghai-Tibet Plateau, Northern Canada, and Greenland, with linear rates of -0.012 × 106, -0.005 × 106, -0.004 × 106, -0.0014 × 106, and - 0.0004× 106 km2/a, respectively. The average ALT in the NH increased at a linear rate of 0.0086 m/a. Alaska and Mongolian Plateau had the highest thickening rate of 0.024 m/a, followed by Qinghai-Tibet Plateau, Siberia, Northern Canada, and Greenland, which had linear rates of 0.009, 0.008, 0.0072, and 0.003 m/a, respectively. The uncertainty of the results could be attributed to the inaccurate forcing data and limitations of the Kudryavtsev model.


Assuntos
Pergelissolo , Mudança Climática , Solo , Temperatura , Tibet
3.
Sci Total Environ ; 807(Pt 1): 150720, 2022 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-34610405

RESUMO

Global warming in mid-latitude alpine regions results in permafrost thawing, together with greater availability of carbon and nutrients in soils and frequent freeze-thaw cycles. Yet it is unclear how these multifactorial changes will shape the 1 m-deep permafrost microbiome in the future, and how this will in turn modulate microbially-mediated feedbacks between mountain soils and climate (e.g. soil CO2 emissions). To unravel the responses of the alpine permafrost microbiome to in situ warming, we established a three-year experiment in a permafrost monitoring summit in the Alps. Specifically, we simulated conditions of warming by transplanting permafrost soils from a depth of 160 cm either to the active-layer topsoils in the north-facing slope or in the warmer south-facing slope, near the summit. qPCR-based and amplicon sequencing analyses indicated an augmented microbial abundance in the transplanted permafrost, driven by the increase in copiotrophic prokaryotic taxa (e.g. Noviherbaspirillum and Massilia) and metabolically versatile psychrotrophs (e.g. Tundrisphaera and Granulicella); which acclimatized to the changing environment and potentially benefited from substrates released upon thawing. Metabolically restricted Patescibacteria lineages vastly decreased with warming, as reflected in the loss of α-diversity in the transplanted soils. Ascomycetous sapro-pathotrophs (e.g. Tetracladium) and a few lichenized fungi (e.g. Aspicilia) expanded in the transplanted permafrost, particularly in soils transplanted to the warmer south-facing slope, replacing basidiomycetous yeasts (e.g. Glaciozyma). The transplantation-induced loosening of microbial association networks in the permafrost could potentially indicate lesser cooperative interactions between neighboring microorganisms. Broader substrate-use microbial activities measured in the transplanted permafrost could relate to altered soil C dynamics. The three-year simulated warming did not, however, enhance heterotrophic respiration, which was limited by the carbon-depleted permafrost conditions. Collectively, our quantitative findings suggest the vulnerability of the alpine permafrost microbiome to warming, which might improve predictions on microbially-modulated transformations of mountain soil ecosystems under the future climate.


Assuntos
Microbiota , Pergelissolo , Carbono , Solo , Microbiologia do Solo , Tundra
4.
Sci Total Environ ; 806(Pt 4): 150808, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34637879

RESUMO

The Arctic environment harbors a complex mosaic of mercury (Hg) and carbon (C) reservoirs, some of which are rapidly destabilizing in response to climate warming. The sources of riverine Hg across the Mackenzie River basin (MRB) are uncertain, which leads to a poor understanding of potential future release. Measurements of dissolved and particulate mercury (DHg, PHg) and carbon (DOC, POC) concentration were performed, along with analyses of Hg stable isotope ratios (incl. ∆199Hg, δ202Hg), radiocarbon content (∆14C) and optical properties of DOC of river water. Isotopic ratios of Hg revealed a closer association to terrestrial Hg reservoirs for the particulate fraction, while the dissolved fraction was more closely associated with atmospheric deposition sources of shorter turnover time. There was a positive correlation between the ∆14C-OC and riverine Hg concentration for both particulate and dissolved fractions, indicating that waters transporting older-OC (14C-depleted) also contained higher levels of Hg. In the dissolved fraction, older DOC was also associated with higher molecular weight, aromaticity and humic content, which are likely associated with higher Hg-binding potential. Riverine PHg concentration increased with turbidity and SO4 concentration. There were large contrasts in Hg concentration and OC age and quality among the mountain and lowland sectors of the MRB, which likely reflect the spatial distribution of various terrestrial Hg and OC reservoirs, including weathering of sulfate minerals, erosion and extraction of coal deposits, thawing permafrost, forest fires, peatlands, and forests. Results revealed major differences in the sources of particulate and dissolved riverine Hg, but nonetheless a common positive association with older riverine OC. These findings reveal that a complex mixture of Hg sources, supplied across the MRB, will contribute to future trends in Hg export to the Arctic Ocean under rapid environmental changes.


Assuntos
Mercúrio , Pergelissolo , Carbono , Monitoramento Ambiental , Isótopos , Mercúrio/análise , Rios
5.
Sci Total Environ ; 806(Pt 3): 151250, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34710410

RESUMO

Shallow thaw (thermokarst) lakes abundant in regions of permafrost-affected peatlands represent important sources of carbon dioxide and methane emission to the atmosphere, however the quantitative parameters of phytoplankton communities which control the C cycle in these lakes remain poorly known. This is especially true considering the roles of permafrost, hydrochemical composition of lakes, lake sizes and season as major governing factors on phytoplankton abundance and biodiversity. In this work, we quantified phytoplankton characteristics of 27 thermokarst lakes (sizes ranging from 115 m2 to 1.24 km2) sampled in spring, summer and autumn across a permafrost gradient (isolated, sporadic, discontinuous and continuous zone) in the Western Siberia Lowland (WSL). The biodiversity indices were highest during all seasons in lakes of the continuous permafrost zone and rather similar in lakes of isolated, sporadic and discontinuous permafrost zone. Considering all seasons and permafrost zones, the biomass and cell number of phytoplankton correlated with Dissolved Organic Carbon (DOC), phosphate, and some metal micro-nutrients (Ni, Zn). The strongest correlations were observed for Cyanophycea during summer, with pH, Ni, Cu, Zn, Sr, Ba (cell number) and Cu, Zn, Ba (biomass), and during autumn, with DOC, K, Cr, Cu, Zn, Ba, Cd, Pb (biomass). Using a substituting space for time approach for climate warming and permafrost thaw and suggesting a shift in permafrost boundaries northward, we foresee an increase in cell number and biomass in continuous permafrost zone in spring and summer, and a decrease in phytoplankton abundance in the discontinuous and sporadic permafrost zones. The biodiversity of phytoplankton in the continuous permafrost zone might decrease whereas in other zones, it may not exhibit any sizably change. However, in case of strong deepening of the active layer down to underlaying mineral horizons, and the release of some limiting nutrients (Si, P) due to enhanced connectivity of the lake with groundwater, the share of cyanobacteria and diatoms may increase.


Assuntos
Pergelissolo , Biodiversidade , Lagos , Nutrientes , Fitoplâncton
6.
Philos Trans A Math Phys Eng Sci ; 380(2215): 20210022, 2022 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-34865532

RESUMO

Permafrost thaw increases active layer thickness, changes landscape hydrology and influences vegetation species composition. These changes alter belowground microbial and geochemical processes, affecting production, consumption and net emission rates of climate forcing trace gases. Net carbon dioxide (CO2) and methane (CH4) fluxes determine the radiative forcing contribution from these climate-sensitive ecosystems. Permafrost peatlands may be a mosaic of dry frozen hummocks, semi-thawed or perched sphagnum dominated areas, wet permafrost-free sedge dominated sites and open water ponds. We revisited estimates of climate forcing made for 1970 and 2000 for Stordalen Mire in northern Sweden and found the trend of increasing forcing continued into 2014. The Mire continued to transition from dry permafrost to sedge and open water areas, increasing by 100% and 35%, respectively, over the 45-year period, causing the net radiative forcing of Stordalen Mire to shift from negative to positive. This trend is driven by transitioning vegetation community composition, improved estimates of annual CO2 and CH4 exchange and a 22% increase in the IPCC's 100-year global warming potential (GWP_100) value for CH4. These results indicate that discontinuous permafrost ecosystems, while still remaining a net overall sink of C, can become a positive feedback to climate change on decadal timescales. This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 2)'.


Assuntos
Pergelissolo , Dióxido de Carbono , Ecossistema , Hidrologia , Metano
7.
J Environ Sci (China) ; 113: 311-321, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34963540

RESUMO

Continuing permafrost degradation is increasing the risk of mercury (Hg) exposure in the permafrost regions on the Qinghai-Tibetan Plateau (QTP), but related studies are still limited, especially the ones on the detailed Hg migration processes in permafrost. The vertical distribution characteristics of soil Hg were investigated in three ecosystems in the Beiluhe area on the QTP, and its influencing factors and formation mechanism were investigated. The results indicate that the total soil mercury (THg) concentration in the Beiluhe area remains at an extremely low level (6.33 ± 2.45 ng/g). In the vertical profile, the THg concentration of the shallow soil layer (0-50 cm) (5.96 ± 2.22 ng/g) is significantly lower than that of the deep layer (50-400 cm) (7.44 ± 2.71 ng/g) (p < 0.05). Within the upper 50 cm, the THg concentration decreases with soil depth, and the peak THg concentration occurs at 100-300 cm on the entire profile. Although the THg concentration is slightly affected by the organic matter in the shallow soil layer, in general, the soil parent material is the dominant factor affecting the THg concentration. Intense weathering results in a low THg concentration in the shallow soil layer because the soil Hg is carried downward with the soil moisture. To a certain depth, the impermeable frozen soil layer intercepts the flow of the soil Hg, and it forms a Hg enrichment layer. This paper presents the distinctive pattern of the soil Hg distribution in the permafrost regions of the QTP.


Assuntos
Mercúrio , Pergelissolo , Ecossistema , Mercúrio/análise , Solo , Tibet
8.
Ying Yong Sheng Tai Xue Bao ; 32(12): 4237-4246, 2021 Dec.
Artigo em Chinês | MEDLINE | ID: mdl-34951264

RESUMO

Riparian wetlands in permafrost regions are critical regions for hydrological, ecological, and biochemical processes. We studied the soils of riparian and transition wetlands and analyzed physicochemical properties, stoichiometry, and microbial respiration activities (microbial biomass carbon, basal respiration, microbial entropy, and metabolic entropy) of the humus layer and diffe-rent soil layers. The results showed that the main differentiation of soil physical and chemical pro-perties in riparian forest wetlands was below 20 cm. Compared to the wetlands of transition zone, total carbon content, total nitrogen content, C/P and N/P decreased significantly with soil depth in riparian forest wetlands. These changes in soil stoichiometry were mainly caused by soil nitrogen content. Such a result meant that the transferring of nitrogen was relatively fast and that there was nitrogen limitation. The main differentiation of Na, Mg, K and Ca in soil occurred in the 30 cm layer of the transition zone and the 20 cm layer of the riparian forest wetlands. The correlations between soil Mg content and total C, total N, total P contents were significant. It meant that the soil Mg was an important element to riparian wetlands in the Great Hing'an Mountains. Microbial respiration activities of the humus layer in riparian forest wetlands and transition zone were higher than those in the other soil layers, indicating that the content of labile carbon fractions was high. The correlations between soil microbial respiration activities and soil properties, stoichiometry, nutrient elements were different in riparian wetland and transition zone. Soil total nitrogen contents were significantly correlated with soil microbial respiration activities in riparian wetland, indicating that soil microbial respiration activities were limited by nitrogen in riparian wetland of the Great Hing'an Mountains.


Assuntos
Pergelissolo , Áreas Alagadas , Carbono/análise , China , Florestas , Nitrogênio/análise , Respiração , Solo , Microbiologia do Solo
9.
PLoS One ; 16(10): e0258699, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34714842

RESUMO

We investigated the characteristics of extracellular matrix (ECM) in the soft tissue of two frozen baby woolly mammoths (Mammuthus primigenius) that died and were buried in Siberian permafrost approximately 40,000 years ago. Morphological and biochemical analyses of mammoth lung and liver demonstrated that those soft tissues were preserved at the gross anatomical and histological levels. The ultrastructure of ECM components, namely a fibrillar structure with a collagen-characteristic pattern of cross-striation, was clearly visible with transmission and scanning electron microscopy. Type I and type IV collagens were detected by immunohistochemical observation. Quantitative amino acid analysis of liver and lung tissues of the baby mammoths indicated that collagenous protein is selectively preserved in these tissues as a main protein. Type I and type III collagens were detected as major components by means of liquid chromatography-mass spectrometry analysis after digestion with trypsin. These results indicate that the triple helical collagen molecule, which is resistant to proteinase digestion, has been preserved in the soft tissues of these frozen mammoths for 40,000 years.


Assuntos
Colágeno/análise , Matriz Extracelular/ultraestrutura , Fígado/metabolismo , Pulmão/metabolismo , Mamutes/metabolismo , Animais , Cromatografia Líquida , Colágeno/genética , Colágeno Tipo I/análise , Colágeno Tipo I/genética , Colágeno Tipo IV/análise , Colágeno Tipo IV/genética , Matriz Extracelular/metabolismo , Feminino , Fósseis/ultraestrutura , Fígado/ultraestrutura , Pulmão/ultraestrutura , Espectrometria de Massas , Pergelissolo , Preservação Biológica , Análise de Sequência de Proteína , Sibéria
10.
FEMS Microbiol Ecol ; 97(10)2021 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-34468725

RESUMO

Permafrost represents a reservoir for the biodiscovery of cold-adapted proteins which are advantageous in industrial and medical settings. Comparisons between different thermo-adapted proteins can give important information for cold-adaptation bioengineering. We collected permafrost active layer samples from 34 points along a proglacial transect in southwest Greenland. We obtained a deep read coverage assembly (>164x) from nanopore and Illumina sequences for the purposes of i) analysing metagenomic and metatranscriptomic trends of the microbial community of this area, and ii) creating the Cold-Adapted Predicted Protein (CAPP) database. The community showed a similar taxonomic composition in all samples along the transect, with a solid permafrost-shaped community, rather than microbial trends typical of proglacial systems. We retrieved 69 high- and medium-quality metagenome-assembled clusters, 213 complete biosynthetic gene clusters and more than three million predicted proteins. The latter constitute the CAPP database that can provide cold-adapted protein sequence information for protein- and taxon-focused amino acid sequence modifications for the future bioengineering of cold-adapted enzymes. As an example, we focused on the enzyme polyphenol oxidase, and demonstrated how sequence variation information could inform its protein engineering.


Assuntos
Pergelissolo , Groenlândia , Metagenoma , Metagenômica , Microbiologia do Solo
11.
Ambio ; 50(11): 2104-2127, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34586591

RESUMO

A recent multidisciplinary compilation of studies on changes in the Siberian environment details how climate is changing faster than most places on Earth with exceptional warming in the north and increased aridity in the south. Impacts of these changes are rapid permafrost thaw and melt of glaciers, increased flooding, extreme weather events leading to sudden changes in biodiversity, increased forest fires, more insect pest outbreaks, and increased emissions of CO2 and methane. These trends interact with sociological changes leading to land-use change, globalisation of diets, impaired health of Arctic Peoples, and challenges for transport. Local mitigation and adaptation measures are likely to be limited by a range of public perceptions of climate change that vary according to personal background. However, Siberia has the possibility through land surface feedbacks to amplify or suppress climate change impacts at potentially global levels. Based on the diverse studies presented in this Ambio Special Issue, we suggest ways forward for more sustainable environmental research and management.


Assuntos
Ecossistema , Pergelissolo , Regiões Árticas , Mudança Climática , Camada de Gelo , Sibéria
12.
Environ Sci Technol ; 55(18): 12683-12693, 2021 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-34472853

RESUMO

Approximately 87% of the Arctic consists of low-organic carbon mineral soil, but knowledge of microbial activity in low-carbon permafrost (PF) and active layer soils remains limited. This study investigated the taxonomic composition and genetic potential of microbial communities at contrasting depths of the active layer (5, 35, and 65 cm below surface, bls) and PF (80 cm bls). We showed microbial communities in PF to be taxonomically and functionally different from those in the active layer. 16S rRNA gene sequence analysis revealed higher biodiversity in the active layer than in PF, and biodiversity decreased significantly with depth. The reconstructed 91 metagenome-assembled genomes showed that PF was dominated by heterotrophic, fermenting Bacteroidota using nitrite as their main electron acceptor. Prevalent microbes identified in the active layer belonged to bacterial taxa, gaining energy via aerobic respiration. Gene abundance in metagenomes revealed enrichment of genes encoding the plant-derived polysaccharide degradation and metabolism of nitrate and sulfate in PF, whereas genes encoding methane/ammonia oxidation, cold-shock protein, and two-component systems were generally more abundant in the active layer, particularly at 5 cm bls. The results of this study deepen our understanding of the low-carbon Arctic soil microbiome and improve prediction of the impacts of thawing PF.


Assuntos
Pergelissolo , Regiões Árticas , Canadá , Carbono , Metagenômica , RNA Ribossômico 16S/genética , Solo , Microbiologia do Solo
13.
Sci Total Environ ; 800: 149433, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34392227

RESUMO

Greenhouse gases (GHGs) released from permafrost regions may have a positive feedback to climate change, but there is much uncertainty about additional warming from the permafrost carbon cycle. One of the main reasons for this uncertainty is that the observation data of large-scale GHG concentrations are sparse, especially for areas with rapid permafrost degradation. We selected the Mongolian Plateau as the study area. We first analyzed the active layer thickness and ground temperature changes using borehole observations. Based on ground observation data, we assessed the applicability of Greenhouse Gases Observing Satellite (GOSAT) carbon dioxide (CO2) and methane (CH4) datasets. Finally, we analyzed the temporal and spatial changes in near-surface CO2 and CH4 concentrations from 2010 to 2017 and their patterns in different permafrost regions. The results showed that the Mongolian permafrost has been experiencing rapid degradation. The annual average near-surface CO2 concentration increased gradually between 2.19 ppmv/yr and 2.38 ppmv/yr, whereas the near-surface CH4 concentration increased significantly from 7.76 ppbv/yr to 8.49 ppbv/yr. There were significant seasonal variations in near-surface CO2 and CH4 concentrations for continuous, discontinuous, sporadic, and isolated permafrost zones. The continuous and discontinuous permafrost zones had lower near-surface CO2 and CH4 concentrations in summer and autumn, whereas sporadic and isolated permafrost zones had higher near-surface CO2 and CH4 concentrations in winter and spring. Our results indicated that climate warming led to rapid permafrost degradation, and carbon-based GHG concentrations also increased rapidly in Mongolia. Although, GHG concentrations increased at rates similar to the global average and many factors can account for their changes, GHG concentration in the permafrost regions merits more attention in the future because the spatiotemporal distribution has indicated a different driving force for regional warming.


Assuntos
Gases de Efeito Estufa , Pergelissolo , Dióxido de Carbono/análise , Mudança Climática , Metano/análise
14.
Appl Environ Microbiol ; 87(20): e0133921, 2021 09 28.
Artigo em Inglês | MEDLINE | ID: mdl-34347514

RESUMO

Permafrost soils store approximately twice the amount of carbon currently present in Earth's atmosphere and are acutely impacted by climate change due to the polar amplification of increasing global temperature. Many organic-rich permafrost sediments are located on large river floodplains, where river channel migration periodically erodes and redeposits the upper tens of meters of sediment. Channel migration exerts a first-order control on the geographic distribution of permafrost and floodplain stratigraphy and thus may affect microbial habitats. To examine how river channel migration in discontinuous permafrost environments affects microbial community composition, we used amplicon sequencing of the 16S rRNA gene on sediment samples from floodplain cores and exposed riverbanks along the Koyukuk River, a large tributary of the Yukon River in west-central Alaska. Microbial communities are sensitive to permafrost thaw: communities found in deep samples thawed by the river closely resembled near-surface active-layer communities in nonmetric multidimensional scaling analyses but did not resemble floodplain permafrost communities at the same depth. Microbial communities also displayed lower diversity and evenness in permafrost than in both the active layer and permafrost-free point bars recently deposited by river channel migration. Taxonomic assignments based on 16S and quantitative PCR for the methyl coenzyme M reductase functional gene demonstrated that methanogens and methanotrophs are abundant in older permafrost-bearing deposits but not in younger, nonpermafrost point bar deposits. The results suggested that river migration, which regulates the distribution of permafrost, also modulates the distribution of microbes potentially capable of producing and consuming methane on the Koyukuk River floodplain. IMPORTANCE Arctic lowlands contain large quantities of soil organic carbon that is currently sequestered in permafrost. With rising temperatures, permafrost thaw may allow this carbon to be consumed by microbial communities and released to the atmosphere as carbon dioxide or methane. We used gene sequencing to determine the microbial communities present in the floodplain of a river running through discontinuous permafrost. We found that the river's lateral movement across its floodplain influences the occurrence of certain microbial communities-in particular, methane-cycling microbes were present on the older, permafrost-bearing eroding riverbank but absent on the newly deposited river bars. Riverbank sediment had microbial communities more similar to those of the floodplain active-layer samples than permafrost samples from the same depth. Therefore, spatial patterns of river migration influence the distribution of microbial taxa relevant to the warming Arctic climate.


Assuntos
Microbiota , Pergelissolo/microbiologia , Rios/microbiologia , Alaska , Ciclo do Carbono , Movimentos da Água
15.
Glob Chang Biol ; 27(22): 5818-5830, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34390614

RESUMO

Ecosystem carbon (C) dynamics after permafrost thaw depends on more than just climate change since soil nutrient status may also impact ecosystem C balance. It has been advocated that nitrogen (N) release upon permafrost thaw could promote plant growth and thus offset soil C loss. However, compared with the widely accepted C-N interactions, little is known about the potential role of soil phosphorus (P) availability. We combined 3-year field observations along a thaw sequence (constituted by four thaw stages, i.e., non-collapse and 5, 14, and 22 years since collapse) with an in-situ fertilization experiment (included N and P additions at the level of 10 g N m-2  year-1 and 10 g P m-2  year-1 ) to evaluate ecosystem C-nutrient interactions upon permafrost thaw. We found that changes in soil P availability rather than N availability played an important role in regulating gross primary productivity and net ecosystem productivity along the thaw sequence. The fertilization experiment confirmed that P addition had stronger effects on plant growth than N addition in this permafrost ecosystem. These two lines of evidence highlight the crucial role of soil P availability in altering the trajectory of permafrost C cycle under climate warming.


Assuntos
Pergelissolo , Carbono , Ecossistema , Nitrogênio , Fósforo
16.
Glob Chang Biol ; 27(22): 5889-5906, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34462999

RESUMO

Climate change-driven permafrost thaw has a strong influence on pan-Arctic regions, via, for example, the formation of thermokarst ponds. These ponds are hotspots of microbial carbon cycling and greenhouse gas production, and efforts have been put on disentangling the role of bacteria and archaea in recycling the increasing amounts of carbon arriving to the ponds from degrading watersheds. However, despite the well-established role of fungi in carbon cycling in the terrestrial environments, the interactions between permafrost thaw and fungal communities in Arctic freshwaters have remained unknown. We integrated data from 60 ponds in Arctic hydro-ecosystems, representing a gradient of permafrost integrity and spanning over five regions, namely Alaska, Greenland, Canada, Sweden, and Western Siberia. The results revealed that differences in pH and organic matter quality and availability were linked to distinct fungal community compositions and that a large fraction of the community represented unknown fungal phyla. Results display a 16%-19% decrease in fungal diversity, assessed by beta diversity, across ponds in landscapes with more degraded permafrost. At the same time, sites with similar carbon quality shared more species, aligning a shift in species composition with the quality and availability of terrestrial dissolved organic matter. We demonstrate that the degradation of permafrost has a strong negative impact on aquatic fungal diversity, likely via interactions with the carbon pool released from ancient deposits. This is expected to have implications for carbon cycling and climate feedback loops in the rapidly warming Arctic.


Assuntos
Pergelissolo , Regiões Árticas , Ecossistema , Fungos , Lagoas
17.
Glob Chang Biol ; 27(22): 5865-5876, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34411382

RESUMO

As Arctic warming, permafrost thawing, and thermokarst development intensify, increasing evidence suggests that the frequency and magnitude of thermokarst lake drainage events are increasing. Presently, we lack a quantitative understanding of vegetation dynamics in drained lake basins, which is necessary to assess the extent to which plant growth in thawing ecosystems will offset the carbon released from permafrost. In this study, continuous satellite observations were used to detect thermokarst lake drainage events in northern Alaska over the past 20 years, and an advanced temporal segmentation and change detection algorithm allowed us to determine the year of drainage for each lake. Quantitative analysis showed that the greenness (normalized difference vegetation index [NDVI]) of tundra vegetation growing on wet and nutrient-rich lake sediments increased approximately 10 times faster than that of the peripheral vegetation. It takes approximately 5 years (4-6 years for the 25%-75% range) for the drainage lake area to reach the greenness level of the peripheral vegetation. Eventually, the NDVI values of the drained lake basins were 0.15 (or 25%) higher than those of the surrounding areas. In addition, we found less lush vegetation in the floodplain drained lake basins, possibly due to water logging. We further explored the key environmental drivers affecting vegetation dynamics in and around the drained lake basins. The results showed that our multivariate regression model well simulated the growth dynamics of the drainage lake ecosystem ( R adj 2 = . 73 , p < .001) and peripheral vegetation ( R adj 2 = . 68 , p < .001). Among climate variables, moisture variables were more influential than temperature variables, indicating that vegetation growth in this area is susceptible to water stress. Our study provides valuable information for better modeling of vegetation dynamics in thermokarst lake areas and provides new insights into Arctic greening and carbon balance studies as thermokarst lake drainage intensifies.


Assuntos
Pergelissolo , Regiões Árticas , Ecossistema , Lagos , Tundra
18.
Sci Data ; 8(1): 221, 2021 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-34413318

RESUMO

Thermokarst activity at permafrost sites releases considerable amounts of ancient carbon to the atmosphere. A large part of this carbon is released via thermokarst ponds, and fungi could be an important organismal group enabling its recycling. However, our knowledge about aquatic fungi in thermokarstic systems is extremely limited. In this study, we collected samples from five permafrost sites distributed across circumpolar Arctic and representing different stages of permafrost integrity. Surface water samples were taken from the ponds and, additionally, for most of the ponds also the detritus and sediment samples were taken. All the samples were extracted for total DNA, which was then amplified for the fungal ITS2 region of the ribosomal genes. These amplicons were sequenced using PacBio technology. Water samples were also collected to analyze the chemical conditions in the ponds, including nutrient status and the quality and quantity of dissolved organic carbon. This dataset gives a unique overview of the impact of the thawing permafrost on fungal communities and their potential role on carbon recycling.


Assuntos
Fungos/classificação , Micobioma , Pergelissolo/microbiologia , Lagoas/microbiologia , Regiões Árticas , Código de Barras de DNA Taxonômico , DNA Fúngico/genética , DNA Fúngico/isolamento & purificação , DNA Espaçador Ribossômico/genética , Congelamento , Fungos/genética , Fungos/isolamento & purificação , Lagoas/química
19.
Biomolecules ; 11(8)2021 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-34439895

RESUMO

A gene coding for a novel putative amylase, oligo-1,6-glucosidase from a psychrotrophic bacterium Exiguobacterium sibiricum from Siberian permafrost soil was cloned and expressed in Escherichia coli. The amino acid sequence of the predicted protein EsOgl and its 3D model displayed several features characteristic for the cold-active enzymes while possessing an unusually high number of proline residues in the loops-a typical feature of thermophilic enzymes. The activity of the purified recombinant protein was tested with p-nitrophenyl α-D-glucopyranoside as a substrate. The enzyme displayed a plateau-shaped temperature-activity profile with the optimum at 25 °C and a pronounced activity at low temperatures (50% of maximum activity at 5 °C). To improve the thermal stability at temperatures above 40 °C, we have introduced proline residues into four positions of EsOgl by site-directed mutagenesis according to "the proline rule". Two of the mutants, S130P and A109P demonstrated a three- and two-fold increased half-life at 45 °C. Moreover, S130P mutation led to a 60% increase in the catalytic rate constant. Combining the mutations resulted in a further increase in stability transforming the temperature-activity profile to a typical mesophilic pattern. In the most thermostable variant A109P/S130P/E176P, the half-life at 45 °C was increased from 11 min (wild-type) to 129 min.


Assuntos
Aminoácidos/química , Oligo-1,6-Glucosidase/química , Engenharia de Proteínas/métodos , Dicroísmo Circular , Clonagem Molecular , Temperatura Baixa , Biologia Computacional , Estabilidade Enzimática , Exiguobacterium/enzimologia , Glucosidases/genética , Glucosidases/metabolismo , Temperatura Alta , Concentração de Íons de Hidrogênio , Cinética , Mutagênese , Mutagênese Sítio-Dirigida , Mutação , Pergelissolo , Prolina/química , Proteínas Recombinantes/química , Temperatura
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